The Semantic Memory of Physicians - and More...

 

I have the somewhat grandiose plan to model psychiatric diagnosis based on the cognition of a physician rather than focusing on the externals.  By the externals I mean classification systems and critiques of classification systems.  At a later date – I might try to comment on how this approach compares with AI.  For now, I will try to keep it focused on human diagnosticians.  I have an interest in this is because I have made and witnessed incredible diagnoses and treatments by physicians and psychiatrists who I have been affiliated with. I don’t think there has been much of a focus on the process.  A secondary consideration is that cognitive neuroscience is a neglected subject in psychiatry and I hope to make the point that should change. I would go as far as suggesting that cognitive neuroscience should be taught to all psychiatrists more urgently than focusing on another DSM.    

Since the early 1970s, memory functions are divided along various lines clinically and functionally. The first division is long term memory and working memory (also called short term memory).  On the long-term side there is a further division to declarative and procedural memory.  Declarative memory is divided into episodic and semantic memory.  Episodic memory is the ability to recall discrete events.  Semantic memory can have a number of graded definitions.  A minimalist definition is factual knowledge independent of the source (7). A definition more informed by recent research in cognitive psychology: “General (encyclopedic) knowledge as well as schematic representations of events distilled from lifelong experiences, retrieved independently from their original spatial or temporal context” (9).  The authors in that case give examples of knowing who wrote the book “1984” and what generally happens at a birthday party.  That naturally raises the question how does all of this freestanding knowledge occur in the first place?  And also – does that imply a connection to episodic memory? In other words, does semantic memory occur when the context surrounding episodic memory is forgotten?

In the case of physicians there is a very long list of formative experiences across the course of one’s career.  The ability to recall them often assists in making diagnoses and provides an advantage over a physician who has not experienced that event.  Semantic memory is about concepts, words, and their relationship independent of a specific event or experience.  It typically consists of a collection of general facts and word meanings.  For example, it would include facts that apples can be red, green, or yellow and what a mechanic does.

Anyone familiar with cognitive screening examinations has probably asked questions focused on semantic memory.  Naming, word similarities, verbal fluency by word generation, general knowledge questions, are all examples. 

The semantic memory of a physician will contain many unique concepts and they will vary based on experience and exposure to clinical scenarios.  The general categories can be described as the following:

1:  Meaningful prior experiences – even though episodic memory stores specific events at specific intervals, semantic memory contains the specific meaning.  In the case of psychiatry an example would be seeing the effects of CMV encephalitis in a major university transplant unit and a decade later seeing similar behavior and consulting on a case in a general community hospital for similar findings.  That similarity triggers non-analytic hypothesis generation.

2:  Prototypes - the patterns noted in the above example can be averaged over a group of patients and those averages can be consolidated into prototypes.  In the above case a psychiatrist may have seen many cases of encephalitis and many cases of meningitis resulting in encephalitis and meningitis prototypes.  Similar prototypes may exist for all major neurological, medical, and psychiatric condition that they have encountered.  Note that the prototype differs from diagnostic criteria (the typical focus) because it is recall of all of the relevant and in many cases unique clinical features that were experienced.

3:  Specific patient memories (exemplars) – all physicians recall specific patients.  These memories are important for non-analytical reasoning like pattern matching.

4:  Knowledge Encapsulation – medicine like most professions is based on a system of graduated learning.  Basic science transitions rapidly into clinical medicine and then into clinical practice and lifelong learning.  At each stage prior knowledge is reorganized in a more efficient way.  In this case – general biomedical knowledge from basic science is organized under higher level concepts. 

An example in one of the references is a person with an infection who is experiencing progressive physiological problems.  At the medical student/basic science level the analysis might proceed from the basic science level and pathophysiology first.  At the clinician level the relevant pathophysiology is organized as sepsis and that provides a more immediate pathway for intervention.  The encapsulation encompasses and efficiently organizes the lower-level information.  At the same time experts must retain a significant amount of that earlier information.  

5:  Illness Scripts – are mental representations of diseases containing three different dimensions.  The first is enabling conditions like risk factors, demographics, predisposition, and context.  The second is fault or underlying pathophysiology.  The third is consequences including signs, symptoms, lab findings, and course or natural history.  Experts have a significant collection of these features.   

One of the questions in this area is what kind of illness script do physicians have?  Should they all be from their particular specialty or should these scripts encompass the totality of their training?  Some authors suggest that the pathophysiological mechanisms from basic science needs to be retained for true expertise – so my conclusion is that the illness scripts from the entirety of a physicians training probably remain relevant.

This is important in psychiatry because the general pathophysiology important in today’s environment was probably not taught is any detail in medical school and most conditions that are not secondary to medical conditions or the effects of drugs do not easily lend themselves to physiological explanations.  I would suggest that medical stability, generalized seizures and seizure variants, increased intracranial pressure, meningitis, encephalitis, cerebral localization, cerebellar dysfunction, peripheral neuropathies, coma, confusion/stupor/delirium, intoxication, and cranial nerve deficits are some of the illness scripts that every psychiatrist must have.

6:  Semantic Qualifiers - every physician has a lexicon of semantic qualifiers acquired in both medical school and post graduate training. They include anatomic descriptions (areas, more specific locations), pathological descriptions, disease course descriptions, and many others. Framing clinical scenarios with these qualifiers is often all that is needed to acquire associations to the disease of interest.

7:   Base rates and Context – experts by way of their clinical practice have an intuitive grasp of the base rates of various clinical conditions and how they typically present in their practice.  These rates of presentations and findings are integrated with the other features of semantic memory (disease scripts, patterns, etc) for more analysis and hypothesis generation.

These features of semantic memory are of course models of brain function for the most part determined by experimental models in cognitive psychology. Examples include testing for specific functions and seeing how those modelled functions vary among trainees and experts at various stages of development. 

Apart from the descriptive approaches used in many studies on physicians at various levels of training are there any more general models that could apply?  Cognitive neuroscience and cognitive psychology offer a more complete model of memory and knowledge structures as well as the underlying biology.  The lead figure for this post is a case in point and has the potential to consolidate many of the descriptions under a more comprehensive model based on experimental validation.

At levels B and C in the diagram we see a perceptual episode being processed from the left to the right in the diagram.  The activated or instantiated schema is a template for extracting relevant features and repressing irrelevant features.  In the diagram circles represent general concepts and squares are action scripts. Gist in the case of the model is a representation of a single episode where much of the detailed information is removed.  The overall sequence at level B depicts how a schema serves to form semantic type memory (gists) and at the same time can be altered or accommodated by new information.

Level A in the diagram illustrates what is known about the localization of these processes largely from human fMRI and preclinical studies.  Memory schemas are stored in various sites including the retrosplenial cortex (RSPL), middle and superior temporal gyrus (MTG/STG), anterior temporal lobe (ATL), and temporoparietal junction (TPJ).  These sites are bound per the diagram to the ventromedial prefrontal cortex (vmPFC).    Solid lines are context sensitive associative pathways biased by the vmPFC. Broken lines in the diagram represent context irrelevant associations that are not activated or inhibited.

How might all of this model work for psychiatry?  In general physicians are seeing a lot of patients in their training and practice.  In the course of that work - schemas are developed for diagnoses, signs, symptoms, and situations.  Here is a comparison of two scenarios that all psychiatrists are trained to recognize acute encephalitis and bipolar disorder, manic with psychotic features. 

	Encephalitis	Bipolar disorder, manic with psychosis
Schema	Acute illness, acute altered mental status, fever, seizures, focal neurological deficits, CSF/MRI abnormalities	Acute illness, euphoria/irritability/anger, hyperactivity, functional impairment, psychosis, temporal pattern, exclusion features
Subschema	Predisposing factors, pathophysiology patterns, temporal pattern	Euphoric expansive Irritable dysphoric Spontaneous v. precipitated
Gist	Acute confusion + fever + temporal lobe MRI changes = treat as HSV until proven otherwise" "Young woman + new psychosis + movement disorder = think anti-NMDAR, look for teratoma" "Summer encephalitis + flaccid paralysis = arboviral, likely West Nile" “Immunocompromised man with acute agitation = think CMV encephalitis	Episodic psychosis +/- mood changes (diagnosis gist) Mood stabilizer + antipsychotic (treatment gist) Severe postpartum psychosis = think bipolar disorder, manic with psychotic features Catatonia – think bipolar disorder, manic/depressed/mixed with psychotic features.

 

I came up with the following graphic (click to enlarge) based on the descriptive categories and the cognitive neuroscience model of Gilboa and Marlatte (12).  From left to right – the  “heterogenous construct supported by clinical utility” characterization is probably the most charitable one from philosophers.  Others like “this disorder does not exist” or “this disorder is not real” are two additional examples.  The central semantic memory category includes investigations and models of diagnostic reasoning conducted largely on medical students and physicians.  The cognitive neuroscience model contains schema and I have attempted to show how the concepts and actions map from the semantic memory to the schema model.  In both the semantic memory and cognitive neuroscience model, although the focus is memory the conceptualizations are really knowledge structures emphasizing a dynamic role for the schema in incorporating features of reality – in this case patient encounters. The cognitive neuroscience and semantic memory models also map on to brain anatomy – with a more comprehensive map for the cognitive neuroscience model as illustrated in the figure at the top.

What have I learned about this so far:

1:  The pattern matching of yesterday is more complicated today – I taught a course in diagnosis and diagnostic reasoning for 15 years into the early part of this century.  Pattern matching and pattern completion was a big part of that course.  The patterns were fairly simple and involved visual diagnoses (diabetic retinopathy, rashes) comparing physicians at various levels of training.  The most dynamic aspect was the implication that experts were better at matching incomplete patterns than novices.  Today’s conceptualizations of knowledge structures and schemas contain concepts, actions, and dynamically alter what is retained in memory and what is not. 

2:  There are clear implications for psychiatric diagnosis -   the DSM classification and all of the criteria do not capture the reality of medical and psychiatric diagnoses.  There is a qualifier in the manual that it is not a substitute for experience but that is never defined.  That reason becomes a lot clearer looking these cognitive models.  Classification systems attempt to operationalize the diagnostic reasoning of a physician by averaging a verbal description of those events.  I don’t think that is possible and I will cite a couple of examples.

Example 1:  A psychotherapist refers a 27-year-old woman to a psychiatrist because of concerns that she has histrionic personality disorder.  She has not been able to make progress in therapy.  The psychiatrist seeing the patient knows within minutes that she is manic.

Example 2:  An intern is presenting the history of a 68-year-old man to his psychiatric attending.  The patient is extremely depressed to the point that he believes that he is cursed based on a trivial event that occurred in his childhood. Within the first 5 minutes the attending realizes that the patient is delusional and communicates that to the intern. The intern acknowledges that this is true and wonders how he failed to make that diagnosis.

Both cases highlight that knowledge of a classification system is not enough.  The psychotherapist and the intern both know the DSM and use it regularly. They have both had didactics in classification of mental disorders.  The only difference is that the psychiatrist in both cases has experienced cases of the disorder and had knowledge structures and schema to make the diagnosis.  Written descriptions of schema and knowledge structures are an incomplete approach to diagnostic reasoning. 

3: Classifications artificially separate actions from concepts – any reading of the DSM gives the impression that “this is the universe of psychiatric disorders – in order to function as a psychiatrist, pick one and then come up with a treatment plan.”  This is problematic at two levels.  First, if the cognitive neuroscience model of memories and knowledge structures is correct – a classification system is operating at a sublevel that averages features.  It is blind to the overall gist that despite this averaging no two people are alike.  Second, it removes action features that are necessary to function as a physician.  That would include top level schemas like “This patient is medically unstable and requires medical or surgical care first” or “This is a life-threatening problem that requires a safe and closely monitored environment." Some will argue that is not the goal of classification.  I would argue that many consider classification to be a diagnosis and in order for it to function that way – it needs to include action items in addition to a general rule out of causative intoxication states and medical problems. The DSM as it exists is classification without diagnosis.

4:  Cognitive neuroscience models highlight the fact that the separation between diagnosis and treatment is artificial.  All physicians are taught to do exhaustive evaluations of medical problems.  That is the initial step in a career.  It is also critical to learn when that exhaustive process needs to be immediately interrupted to focus on a more acute problem. I can still recall seeing a 7-year-old boy who have been hit by a car while playing in the street. He was alert but had significant abdominal pain.  The car bumper struck him just below his left rib cage.  It took me less than 5 minutes to determine that he had an acute abdomen and call the trauma surgeons. That non-linear process happens frequently in acute care psychiatry and in outpatient psychiatry with patients in crisis who need verbal interventions to assist in the diagnostic and treatment process.  

5:  Psychotherapy – there are recent perspectives on how cognitive psychology applies to the psychotherapeutic process at both the psychological and biological levels using these models.  Basically, maladaptive schemas are confronted and modified during the therapy.  There is some empirical evidence that this may happen particularly in the area of positive and negative self-schemas.  Much of this literature draws on existing cognitive behavioral therapy.  That leads to a question of what is the difference between a therapy focused on a cognition or an isolated memory compared with a schema focused therapy?

At the highest level of analysis memory focused therapies generally involve isolated autobiographical memories and schema focused therapies are about knowledge structures abstracted across multiple events that involve emotion, cognition, and behavior.  In theory the schema focused therapies may be useful in cases where the memory focused therapy is not effective, but a competing consideration is that schemas can be entrenched and difficult to change.  The memory focused therapy could be considered a bottom-up type of approach and the schema focused a top-down approach. 

6:  Criticisms – Criticizing the DSM as a diagnostic system is a cottage industry in the US and the UK.  As we approach a new version of the DSM expect most media sites to start months and even years of criticism. Practically everybody does it rarely discussing their motivations, understanding, and the limitations of their proposed system if they have one.  If diagnostic reasoning is a complex process consistent with the cognitive neuroscience models and requires direct experience, criticism of the manual rings hollow.  It is equivalent to reading about things that might exist and proclaiming you are an expert.  Psychiatrists with criticisms are also limited if they have insufficient experience in the areas they are criticizing.  Psychiatrists with the broadest experience will produce the best criticism. If you are criticizing a list of diagnostic criteria in a classification system in isolation – that is exactly what you are doing.  It is trivial compared with an actual diagnosis by a trained and experienced psychiatrist.        

This brief focus on the cognitive neuroscience of diagnosis should highlight that psychiatric education and practice is seriously lagging in this knowledge base.  If we are taking the “diagnosis” in DSM seriously it has to be modified to include this important brain science.  All of the current competing models face the same criticism.  A diagnosis by a physician is much more than typed criteria attempting to capture a dynamic process.  Secondly, psychiatry needs modern approaches to the mind. Approaches that correlate with neurobiology and have a clear empirical basis. Much of the DSM claims a sketchy atheoretical basis that should no longer be acceptable when powerful explanatory theories may exist.  Philosophy is no substitute.  Finally, we must find a way to implement these across all of our training programs and practitioners.  We should be devoting as many resources to integrating cognitive neuroscience into psychiatry as we do modifying the DSM.

And that should be the first step.  What does a DSM looked like with cognitive neuroscience baked in?  The answer goes a lot farther than “dimensions”.      

   

George Dawson, MD, DFAPA

 

 

References:

 

1:  Norman G, Young M, Brooks L. Non-analytical models of clinical reasoning: the role of experience. Med Educ. 2007 Dec;41(12):1140-5. doi: 10.1111/j.1365-2923.2007.02914.x. Epub 2007 Nov 13. PMID: 18004990.

2:  Brush JE Jr, Sherbino J, Norman GR. Diagnostic reasoning in cardiovascular medicine. BMJ. 2022 Jan 5;376:e064389. doi: 10.1136/bmj-2021-064389. PMID: 34987062.

3:  Custers EJ. Thirty years of illness scripts: Theoretical origins and practical applications. Med Teach. 2015 May;37(5):457-62. doi: 10.3109/0142159X.2014.956052. Epub 2014 Sep 2. PMID: 25180878.

4:  Koufidis C, Manninen K, Nieminen J, Wohlin M, Silén C. Unravelling the polyphony in clinical reasoning research in medical education. J Eval Clin Pract. 2021 Apr;27(2):438-450. doi: 10.1111/jep.13432. Epub 2020 Jun 22. PMID: 32573080.

 5:  Binder JR, Desai RH, Graves WW, Conant LL. Where is the semantic system? A critical review and meta-analysis of 120 functional neuroimaging studies. Cereb Cortex. 2009 Dec;19(12):2767-96. doi: 10.1093/cercor/bhp055. Epub 2009 Mar 27. PMID: 19329570; PMCID: PMC2774390.

6:  Duff MC, Covington NV, Hilverman C, Cohen NJ. Semantic Memory and the Hippocampus: Revisiting, Reaffirming, and Extending the Reach of Their Critical Relationship. Front Hum Neurosci. 2020 Jan 24;13:471. doi: 10.3389/fnhum.2019.00471. PMID: 32038203; PMCID: PMC6993580.

7:  Insaustu R, Amaral DG. Hippocampal Formation. In: Mai JK, Paxinos G (eds) The Human Nervous System, 3^rd ed.  Elsevier, London, 2012: p. 933.

8:  Mazoué A, Gaultier A, Rocher L, Deruet AL, Vercelletto M, Boutoleau-Bretonnière C. Does a rabbit have feathers or fur? Development of a 42-item semantic memory test (SMT-42). J Clin Exp Neuropsychol. 2022 Sep;44(7):514-531. doi: 10.1080/13803395.2022.2133088. PMID: 36269845.

9:  Renoult L, Irish M, Moscovitch M, Rugg MD. From Knowing to Remembering: The Semantic-Episodic Distinction. Trends Cogn Sci. 2019 Dec;23(12):1041-1057. doi: 10.1016/j.tics.2019.09.008. Epub 2019 Oct 28. PMID: 31672430.

10:  Brown TI, Rissman J, Chow TE, Uncapher MR, Wagner AD. Differential Medial Temporal Lobe and Parietal Cortical Contributions to Real-world Autobiographical Episodic and Autobiographical Semantic Memory. Sci Rep. 2018 Apr 18;8(1):6190. doi: 10.1038/s41598-018-24549-y. PMID: 29670138; PMCID: PMC5906442.

11:  Teghil A, Bonavita A, Procida F, Giove F, Boccia M. Temporal Organization of Episodic and Experience-near Semantic Autobiographical Memories: Neural Correlates and Context-dependent Connectivity. J Cogn Neurosci. 2022 Nov 1;34(12):2256-2274. doi: 10.1162/jocn_a_01906. PMID: 36007071.

12:  Gilboa A, Marlatte H. Neurobiology of Schemas and Schema-Mediated Memory. Trends Cogn Sci. 2017 Aug;21(8):618-631. doi: 10.1016/j.tics.2017.04.013. Epub 2017 May 24. PMID: 28551107.

13:  Reyna VF, Edelson S, Hayes B, Garavito D. Supporting Health and Medical Decision Making: Findings and Insights from Fuzzy-Trace Theory. Med Decis Making. 2022 Aug;42(6):741-754. doi: 10.1177/0272989X221105473. Epub 2022 Jun 23. PMID: 35735225; PMCID: PMC9283268.

14:  Wilhelms EA, Fraenkel L, Reyna VF. Effects of Probabilities, Adverse Outcomes, and Status Quo on Perceived Riskiness of Medications: Testing Explanatory Hypotheses Concerning Gist, Worry, and Numeracy. Appl Cogn Psychol. 2018 Nov-Dec;32(6):714-726. doi: 10.1002/acp.3448. Epub 2018 Sep 1. PMID: 30686857; PMCID: PMC6345391.

15:  Hawke LD, Provencher MD, Parikh SV. Schema therapy for bipolar disorder: a conceptual model and future directions. J Affect Disord. 2013 May 15;148(1):118-22. doi: 10.1016/j.jad.2012.10.034. Epub 2012 Dec 4. PMID: 23218898.

16:  Lane RD, Ryan L, Nadel L, Greenberg L. Memory reconsolidation, emotional arousal, and the process of change in psychotherapy: New insights from brain science. Behav Brain Sci. 2015;38:e1. doi: 10.1017/S0140525X14000041. Epub 2014 May 15. PMID: 24827452.

Graphics Credit:

1:  The lead graphic as noted is from Cell Press and reference #12.  It is reproduced here with permission from Elsevier and this is their acknowledgement:

Reprinted from Trends in Cognitive Sciences, August 21(8), Gilboa A, Marlatte H. Neurobiology of Schemas and Schema-Mediated Memory, p. 618., Copyright 2017, with permission from Elsevier.  License 6278000229455, May 29, 2026 

2:  Second graphic was made by me using Microsoft Visio.

Supplementary 1:  Nobel Laureate and Psychiatrist Eric Kandel noted the importance of cognitive neuroscience years ago and this was a quote from his book:  The Age of Insight.

 

Medical Reasoning vs. A Diagnostic Manual

 

I taught a course on medical decision making and how not to mistake a physical illness for a psychiatric disorder from about 1990 to 2002. The main theorists at the time were all internists – Stephen Pauker, Jerome Kassirer, Richard Kopelman, David Eddy, and Harold Sox.  I read their papers and attended their courses.  State-of-the-art in those days involved extensive differential diagnosis, Bayesian analysis, and an awareness of an extensive list of potential cognitive biases. I had been impressed with the need for pattern matching and pattern completion and incorporated all those elements into my course.  I eventually pared it down to about 9 sections in the lecture notes illustrated with case vignettes.

My original emphasis was to recognize that there are several considerations when assessing the medical aspects of psychiatric care.  The first is the medical stability of the patient.  Can they be cared for on a psychiatric unit or do their medical needs require medicine or in some cases surgery?  Do they need referral to a generalist of specialist?  This is more complicated than it sounds because the patient is there seeing a psychiatrist for what is supposed to be a psychiatric problem.  But that presentation is complicated by several factors including most patients have no primary care physician and no routine health care maintenance. Many will come into the emergency department concerned about a medical problem but get sent to psychiatry. In that situation, people still get all of the acute medical illnesses including heart attacks, strokes, asthma attacks, pulmonary emboli, seizures, pneumonia, meningitis, encephalitis, and acute cholecystitis to name a few.  Many exhibit non-specific behaviors like agitation, crying out, aggression, or unresponsiveness that can be due to either a psychiatric disorder or a medical problem.    

The second is a psychiatric presentation of a physical illness in a communicating patient. The classic presentations involve brain pathology that is infection, inflammatory, vascular, trauma, or neurodegenerative.  Systemic endocrinopathies and inflammatory disorders are a close second. 

Finally, there is the patient with a clear psychiatric disorder who has intercurrent illness that is or is not known.  Examples that I have seen many times include current or new onset diabetes mellitus, profound anemia usually secondary to an upper or lower GI bleed, dermatology conditions that have often been neglected, symptomatic nutritional deficiencies (B12, folate, D), sexually transmitted diseases, complications of substance use like cirrhosis, and various acute and chronic infectious diseases.

Given that large population with diverse medical and psychiatric problems as well as diverse presentations that can include denying any physical problems – I typically reviewed how the diagnoses occurred.  Pattern matching was the fastest.  The physician has seen a physical finding, lab, behavior, etc – many times before, knows what it is, diagnoses it and treats it.  A good example is a rash.  Dermatologists are rash experts and can correctly classify rashes and marginal cases much faster than primary care physicians (4).  The same is true for diabetic retinopathy and ophthalmologists (5).  Until you have seen a person with severe mania or catatonia, neuroleptic malignant syndrome, or serotonin syndrome it is less likely that you can diagnose the conditions by reading criteria in a book.  Patterns are important for all medical specialists.

On the other end of the spectrum is the contemplative side of diagnosis.  There are several possible diagnoses, and it takes additional data, thought, and reasoning to come to a final diagnosis. Every medical student does this in their initial internal medicine rotation.  There is encouragement to produce a list of many diagnoses that might account for the presentation – but even as the case is being recorded or presented that list rapidly narrows to the apparent diagnosis.

In psychiatry, it may take much more data and collateral information to make a specific diagnosis at the initial presentation.  First episode psychosis (FEP) is a case in point. It is very important to determine what the symptoms onset was like and whether there were any associated mood symptoms or substance use problems. The patient may not be able to describe the phenomenology and depending on the circumstances treatment may be initiated while the diagnostic process is ongoing.  Teaching about the diagnostic process, we would spend time discussing what that might look like combined with a recursive approach to the patient and an awareness of cognitive and emotional biases.  I provided several examples of non-psychiatric physicians making errors due to emotional biases.

Since my course, the literature on medical decision making has changed to some degree.  There is some literature that addresses expertise in general at both the level of cognitive psychology (1) and neurobiology (2).  The general approaches have been to analyze expertise and diagnostic reasoning from the perspective of typical domains (cognitive, perceptual, motor) or to look at a general model and how that has developed over the years.

A dual processing model (3) is generally considered the best current representation of clinical reasoning and decision making.  In this model, there is a fast automatic, heuristic, and unconscious system called Type 1 and a slower conscious, analytical, and effortful system called Type 2.  Additional properties are indicated in the following table.

Parameter	Type 1	Type 2
Speed	Fast, automatic, unconscious/preconscious, little effort	Slow, deliberate, analytical, varying degrees of effort
Control	Minimum control, similar to automatic associations in everyday life except more focused	Control over thought process and direction
Systems and Processing	Pattern recognition and completion, implicit learning, access to long term memory	Working memory and manipulation of data in working memory, planning and reasoning based on that data
Memory Systems	Long term memory	Short term and working memory
Localization	-Orbitofrontal cortex (OFC) -Basal ganglia (caudate, putamen) -Insula -Anterior cingulate cortex -Amygdala -Hippocampus	-Dorsolateral prefrontal cortex (DLPFC) -Left inferior frontal gyrus -Middle frontal gyrus -Inferior parietal lobule -Precuneus -Hippocampus

 A clinical example of Type 1 reasoning is when a trained clinician recognizes a classic presentation of a medical illness, diagnosis, or finding.  An example I frequently use is when one of my Infectious Disease attendings who was an expert in Streptococcal infections recognized characteristic rash from across the room on a patient we were consulted for a different problem.  He made the diagnosis within seconds and told us how it could be confirmed.  In studies of the process the orbitofrontal cortex and limbic connections are activated.  Training is a critical element, especially seeing a maximum number of patterns and their variations.  Although the characterization is that this is a fast and automatic process, there is some room for deliberation.  For example, recognizing or attempting to classify equivocal cases without classic presentations. 

Type 2 reasoning is considered more of the typical process of differential diagnosis.  The findings are compared, analyzed, and accepted or rejected based on additional data and clinical judgment. This process is thought to localize in dorsolateral prefrontal cortex (DLPFC) the home of the working memory where data can be maintained and analyzed.  The left inferior frontal gyrus contributes to rule-based reasoning and hypothesis testing.  A clinical example from my experience is the case of the agitated stuporous patient.  These cases require a great deal of caution because they are most likely to represent a serious or life-threatening illness.  It requires a clinician who knows how to examine patients with stupor or coma and rapidly makes sense of the history and findings. It is a problem that can rarely be solved by Type 1 reasoning alone due to a fairly non-specific presentation.  Some of the critical points for hypothesis testing will be signs of increased intracranial pressure, purposeful response to painful stimuli, eye movements, reflex and musculoskeletal exam abnormalities, signs of infection, and meningeal signs.

The interaction between Type 1 and Type 2 systems is not necessarily sequential but it can be with the Type 1 system matching patterns that lead to hypothesis generation.  There is some evidence that in most clinical situations most of the diagnoses occur with Type 1 reasoning.  Experts can operate at the level of Type 1 reasoning due to extensive experience.  There is not necessarily a hard separation based on the properties in the table. Some hypothesis testing can occur at both levels.  Both systems are commonly grounded in both the limbic system and the hippocampus.

The human brain is capable of parallel distributed processing of data or information.  This means that there are many processing areas in the brain that are interconnected and they can all be working at once.  The modern conceptualization is brain networks that are active processing areas connected by white matter tracts widely distributed through the brain.  

That brings me to my model of diagnostic reasoning (see lead graphic and click to enlarge).  It is based on the course I taught, neuroanatomy and neurology, and what I have observed clinically. When I was talking about pattern matching 20 years ago based on my observations and reading studies in dermatology, ophthalmology, radiology, and pathology – the term seemed to fade rapidly from the diagnostic reasoning literature.  It was revived somewhat by the more recent focus on AI and comparison of that modality to humans.

There was a lull in Bayesian analysis after the invention of computerized programs like Quick Medical Reference (QMR) and Iliad.  They were designed to facilitate medical diagnoses by providing an exhaustive list of findings and their probabilities. These were 20^th century personal computer programs and not AI.  A study of these and 2 additional programs suggests that the programs got 52-71% of 105 diagnostic cases correct with 19-37% being the mean portion of correct diagnoses (6). Despite those figures the programs provided an additional 2 diagnoses per case that experts considered as relevant.  The authors recommended that the programs be used only by physicians who could include the relevant and exclude the irrelevant information provided by the programs.  The programs were discontinued without further modification or updates.  

That is the 8-mile-high view.  I plan to do a deeper dive into the neuroanatomy and neurophysiology.  But the clear reality of the situation is the ability to make a psychiatric diagnosis resides in the brain of a psychiatrist and not a classification manual or a checklist.   Manuals and checklists are crude approximations of some of the cognitive features that psychiatric experts possess.  Like all experts – skill will vary based on practice, exposure, and interest because of the effects on these brain systems.  But we are well past the point of equating what a psychiatrist does to a crude manual.  A manual never saved or treated anyone.  Further – the diagnostic reasoning process emphasizes elements that are important for education and training. It seems that in the past decades there has been a preoccupation with evidence-based research rather than the evidence itself. It does not do the physician or patient any good to be in a situation where that physician is unable to communicate with a person who is in a critical state and has no idea how to assess that problem.  Rearranging diagnostic criteria in a manual for the ninth or tenth time does not get you there.   

 

George Dawson, MD, DFAPA

Supplementary 1:   Before anyone says the diagram is too complex - it is a general diagram for any human diagnostician.  The main modifications for physicians and psychiatrists are the interactive aspects that include empathic comments, formulations, and numerous verbal interventions that other diagnosticians may not need to use.  The specifics about how these memory systems interact are not known at this point - I will be researching that over the next several months.  I borrowed the superposition concept from quantum mechanics - even though there are no wave functions for memory.         

 References:

.

1:  Bilalić M.  The Neuroscience of Expertise.  Cambridge University Press. Cambridge, United Kingdom. 2017.

2:  Maguire EA, Gadian DG, Johnsrude IS, Good CD, Ashburner J,  Frackowiak RSJ, Frith CD. 2000. Navigation-related structural change in the hippocampi of taxi drivers. Proc Natl Acad Sci USA 97:4398–4403.

3:  Norman GR, Monteiro SD, Sherbino J, Ilgen JS, Schmidt HG, Mamede S. The Causes of Errors in Clinical Reasoning: Cognitive Biases, Knowledge Deficits, and Dual Process Thinking. Acad Med. 2017 Jan;92(1):23-30. doi: 10.1097/ACM.0000000000001421. PMID: 27782919.

4:  Federman DG, Concato J, Kirsner RS. Comparison of dermatologic diagnoses by primary care practitioners and dermatologists. A review of the literature. Arch Fam Med. 1999 Mar-Apr;8(2):170-2. doi: 10.1001/archfami.8.2.170. PMID: 10101989

5:  Sussman EJ, Tsiaras WG, Soper KA. Diagnosis of Diabetic Eye Disease. JAMA. 1982;247(23):3231–3234. doi:10.1001/jama.1982.03320480047025

6:  Berner ES, Webster GD, Shugerman AA, Jackson JR, Algina J, Baker AL, Ball EV, Cobbs CG, Dennis VW, Frenkel EP, et al. Performance of four computer-based diagnostic systems. N Engl J Med. 1994 Jun 23;330(25):1792-6. doi: 10.1056/NEJM199406233302506. PMID: 8190157.

How Physicians Think

One of the more interesting aspects of my career has been contemplating how physicians make decisions on both the diagnostic and therapeutic side. Early in my career there was an explosion of activity in this area. Much of it had to do with internal medicine. There were computerized programs that were designed to assist physician decision-making. There were also entire courses taught at the CME level by experts in the field. At the time those experts included Jerome Kassirer, Stephen Pauker, Harold Sox, Richard Kopelman, Alvan Feinstein, and others.  The New England Journal of Medicine has a long-standing feature entitled Case Records of the Massachusetts General Hospital that showcases both diagnostic reasoning and the associated clinicopathological correlates. They added additional articles and a long standing feature on diagnostic decision making. After studying the subject area for about 10 years, I started to teach my own version to 3^rd and 4^th year medical students. It was focused on not mistaking a medical disorder for a psychiatric one.  It included a complete review of cognitive errors in that setting and how to prevent them. I taught that course for about 10 years.

There are a lot of ideas about psychiatrists and how they may or may not diagnose and treat medical disorders. Systematic biases affect the administrative and environmental systems where psychiatrists work.  Many psychiatrists are very comfortable at the interface of internal medicine or neurology and psychiatry. The most common bias about psychiatrists is that other medical conditions need to be “ruled out” before the patient is referred to a psychiatrist. From a psychiatric perspective the real day-to-day problems include inadequate assessment due to an inability to communicate with the patient and considerable medical comorbidity. Psychiatrists who work in those problem areas need to be competent in recognizing new medical diagnoses and making sure that their prescribed treatment does not adversely affect a person with pre-existing medical disorder.

Against that backdrop I decided to read 2 relatively new books. Both of them have the same title “How Doctors Think”. One book was written by Jerome Groopman, MD hematologist-oncologist by clinical specialty. The other book is written by Kathyrn Montgomery, PhD – a professor of Bioethics, Humanities, and Medicine. As might be expected from the writers’ qualifications Groopman is writing more from the standard perspective of a physician with an intense interest in medical decision making and Montgomery is describing the clinical process and analyzing it from the unique perspective of philosophy and the humanities. It follows that even though the titles are the same these are two very different books.

Groopman’s approach is to use a case-based style of looking at medical decision-making from the perspective of several clinicians-including his own work. The mistakes that occur are teaching moments and are explained from the perspective of heuristics or common cognitive biases. It is the approach I used in my course on preventing cognitive errors associated with psychiatric diagnoses. To cite one example, he describes an athletic forest ranger in his forties. The kind of a guy an internist might say: “I am not worried about his heart – he does his own stress test every day.”  He noticed increasing chest discomfort for a few days without any associated cardiopulmonary symptoms. He presented for an assessment on a day when the pain did not go away. He was seen and thoroughly examined.  There were no physical symptoms, exam findings, or laboratory finding to suggest a cardiac problem and he was released from the emergency department.  He returned a few days later with a myocardial infarction.  Discussions with the attending physician indicate that there were two issues associated with the missed diagnosis of cardiac chest pain – the generally healthy appearance of the patient and a lack of any positive tests indicating coronary artery disease.  Groopman discusses it from the perspective of representativeness bias (p 44) or being affected by a prototype – in this case the patient’s apparent level of fitness and attributing the chest pain to musculoskeletal pain rather than pain of cardiac origin. 

This case also allowed for a discussion of attribution errors especially if the patient fits a negative stereotype.  In the next case, a 70 yr old patient with alcohol use presents with and enlarged nodular liver on exam.  The presumptive diagnosis is alcoholic cirrhosis and the team’s plan was to discharge him back home as soon as possible. Closer examination confirmed that the patient was not drinking that much and searching for other causes of liver disease resulted in a diagnosis of Wilson’s disease.  For most of the book, Groopman uses this technique to illustrate substantial errors, the kind of cognitive bias that it reflects, and corrective action. The reality of “making mistakes on living people” comes though.

He recognized the importance of pattern matching and pattern recognition in clinical practice. There is an initial conversation with a physician that collapses pattern recognition to stereotypes and their associated shortcomings.  He elaborates on the concept and quotes a cognitive scientist to illustrate that pattern recognition may not require any conscious reasoning at all.  An expert can arrive at a diagnosis in about 20 seconds that may take a medical student or resident 30 minutes. Experts begin collecting information about the patient on contact and are immediately considering diagnostic possibilities. I have personally had this experience many times, typically for acute neurological syndromes (strokes, cerebral edema, encephalitis, meningitis) in patients who were referred for me to see in a hospital setting. Pattern matching clearly occurs in the diagnostic process, but it is more difficult to write about and discuss than verbal reasoning.

A major strength of the book is a fairly detailed look at uncertainty in medicine. The diagnoses are not etched in stone and no outcomes are guaranteed based on the accuracy of the diagnosis or not. He introduces a pediatric cardiologist who advances the argument that most of his cases are novel and that there are no set guidelines for what he treats. Even more complicated is that fact that what may appear to be sound science-based treatments like closing an atrial septal defect with a 2:1 shunt in kids it can be an illusion.  Many of those children do well without the surgery and many have had unnecessary surgery. The cardiologist also points out that study of this kind of problem is impossible because of the length of time it would take to do a randomized study.

Another major strength is advice to patients about how to keep the doctor they are seeing thinking about their case.  Numerous examples are given ranging from seeing large number of healthy patients where abnormalities are rare to seeing patients with real problems who have been stereotyped for one reason or another. Groopman is very specific in coaching prospective patients in how to overcome some of the associated biases.  This advice centers on the fact that biological systems are complex and don’t necessarily support logical deductions.  The astute doctor needs to be systematic, evaluate the data for themselves including the elicitation or more history, and question their first impressions. The patient aware of these limitations can ask the correct questions along the way to assist their physician in staying on track. He advises the patient to express their concern about the worst-case scenario to get that out there for discussion and to keep their doctor focused.  The patient is informed of how their history, review of systems and exam may need to be repeated along with some tests that have been previously done. The physician may have to ignore common aphorisms or maxims that are designed to focus on common problems and consider the complex – like more than one diagnosis being suggested. Business management of the medical encounter is seen to impair and obstruct this interactive process.

Groopman’s book is very good both as a guide to patients and a review for physicians who have been educated in diagnostic thinking. In the body of the book technical jargon is avoided and the case scenarios thoroughly explained. There is an excellent list of references and annotations for each chapter at the end of the book. 

How Doctors Think by Kathryn Montgomery takes the unexpected form of a philosophical argument against medicine as a science. She qualifies her criticism by being very clear that she is considering Newtonian or positivist science and not biological science. She recognizes several features of biological science that make it an integral part of medicine, but also not at all like the criteria for science that she sets as the premise for her argument. This is problematic at two levels. First, deterministic and reductionist physicists like Sabine Hossenfelder are very clear that everything is reducible to known subatomic particles and that particles in a brain are deterministic.

“Biology can be reduced to chemistry, chemistry can be reduced to atomic physics, and atoms are made of elementary particles like electrons, quarks, and gluons.” (5)

So for at least some scientists – reductionism is not a problem and the boundaries are not very clear between physical science, biology, and medicine.  Second, it is now known that biological organisms have a wide array of stochastic mechanisms that by virtue of their own nature produce apparently random results. With that range of possibilities, it is not very clear if the standards of physical science are that much different than the biological science necessary for medicine.

Montgomery makes the argument about science and the damage that the idea of medicine as science does to both medicine and its practitioners at several levels.  First, she describes science in medical training. Medical students encounter the basic science curriculum in the first two years of medical school. It is not physical science but biological sciences relevant to understanding pathophysiology, pharmacology, and epidemiology/evidence-based medicine.  She suggests this exposure to science is less relevant as the student transitions to a clinician with adequate clinical judgment – almost to the point that the basic science is an afterthought. This aspect of training is also used to point out that medical students are not being trained as scientists and the remainder of their formal education is spent learning clinical judgement.  At places she describes the preclinical years as fairly bleak period of memorization peripherally related to clinical development.  Second, the uncertainty of biology and medicine is part of her argument.  She extends the argument from the patient side to the side of the doctor. Patients want and need certainty and therefore they want doctors who are schooled in the best possible science who can provide it. Patients want an answer and all they get is statistics. Third, she suggests that the moral and habitual practice of medicine although dependent on human biology and the associated technical advances is not really science.  Physicians are taught to practice medicine and the don’t question “the status of its knowledge” (p. 191). She describes medical practice as a set of rational procedures that are shared with many other professions in the humanities and social sciences.  Fourth, the notion of medicine as a science is “clinically useful” in that it reassures the patients that physicians are engaged in a rational process like they were taught in science classes rather than a contextual, interpretive, narrative process used by non-scientists.  She cites numerous examples of maxims and aphorisms used in medicine to guide this process like Peabody’s famous: “The secret of the care of the patient is in caring for the patient.” 

 Montgomery’s writing is as sophisticated as you might expect from a bioethics professor with a doctorate in English and extensive exposure to medical training. Her critique depends a lot on verbal reasoning and the application of that model to numerous disciplines. Philosophical critiques of medicine and psychiatry that I have responded to in the past are typically presented as arguments with the premises being set by the author. As I read through these arguments being repeated across chapters there were clear points of disagreement.  Here is a short list:

1:  The argument about medicine not being a physical science – that is a good starting point if you want to be able to attack the scientific aspects of medicine, but does anyone really accept that premise? No physical science is taught in the basic science years of medicine.  The basic sciences are focused on human anatomy and physiology. An associated argument is that biological sciences have no overriding laws like physics and that is given as further evidence that medicine is not a science. There is an entire range of science within the basic science of medicine that cannot be explained by physical science but it is necessary for clinical medicine and innovation in medicine.  Finally science is a process that is subject to ongoing verification. That is as true for biological science as it is for physical sciences. While there appear to not be as many absolutes for biology progress is undeniable even within the boundaries of medicine.

2:  Uncertainty in biological systems and medicine - the author makes it seem like defining medicine as a science gives the false impression of certainty. I don’t think that certainty is misrepresented or minimized in clinical medicine.  Every physician I know experiences the uncertainty during informed consent and prognosis discussions. It is built into surgical consent forms and in situations involving medical treatment or testing – the discussions are even more complex. In a typical day, I will advise patients on side effects that occur at rates varying from 4 out of 10 patients to 1 out of 50,000 and tell them what to look for and when to call me.  I have had patients tell me after those discussions that they would prefer not to take a medication or do the recommended testing. I will also discuss life threatening problems with patients, and let them know I cannot predict outcomes but can advise them on how to reduce risk. The only way medicine can practiced is by having appropriate informed consent discussions that fully acknowledge uncertainty and the associated biological heterogeneity.  From the patient side, everyone has a friend, acquaintance, or family member who was healthy until the day there were not. The uncertainty of physical health and medical outcomes at that point are widely known by the general public.

An additional and lesser known aspect of the effect of uncertainty on physician behavior is encouraging the correct answer or treatment as soon as possible. Montgomery attributes some of this to the moral dimension of the physician-patient relationship and doing the right thing for the patient.  But a critical part of uncertainty is that physicians eventually learn to project their decisions out into the future. Those projections are all taken into account in developing the current treatment plan. The outcome of an idealized plan can be viewed as the direct result of the uncertainties involved.  

3:  Physician detachment is a likely consequence of characterizing medicine as a science – At points Montgomery makes the point that physician can emotionally protect themselves by assuming the detached rationality of science. It follows that abandoning medicine as a science would result in a more realistic emotional connection with patients. She has a detailed discussion of the physician-patient relationship being more as a friend or a neighbor.  She concludes that neighborliness has a number of virtues to recommend it as the relationship for the 21^st century. Two concepts from psychiatry are omitted from this discussion – empathy and boundaries. Empathy is a technical skill that is typically taught to physicians in their first interviewing courses in the first year of medical school.  It is a technical skill that allows for a more complete understanding of the patient’s emotional and cognitive predicament. In my experience what patients are looking for is a physician who understands them. That is generally not available from a friend or neighbor.  The basic boundary issue is that it is very difficult to provide care to a person who is emotionally involved with the physician. There are degrees of involvement, but any degree is important. A physician who is empathic, had a clear awareness of the relevant boundaries, and has a solid alliance with the patient is far from detached.  But I would not see them as neighborly or a friend.  The physicians job is the be in a position where they can provide the best possible medical advice. That can only happens from a neutral position where they can give a patient the same advice they would give anybody else.  That also does not mean that physicians are not emotionally affect when bad things happen to their patients or when their patients die.

4:  Do ancient Greek concepts still apply? – The author uses Aristotelian definitions of episteme and phronesis several times throughout the text. Episteme is scientific reasoning and phronesis is practical reasoning.  Aristotle’s view was that since there are no “fixed and invariable answers” to questions about health, every question must be considered an individual case.  In those cases, practical reasoning that considers context and additional factors or phronesis applies.  That allows the author to compare medicine to a number of social science disciplines that use the same kind of reasoning.  The question needs to be asked: “What would Aristotle conclude today?”  In ancient Greece there were basically no good medical treatments and medical theory was extremely primitive. Over the intervening centuries medicine has become a lot less imperfect. Uncertainty clearly exists, but the scientific advances are undeniable.  It is possible to say today that there are now fixed and invariable answers to large populations of people. Medicine has always been a collection of probability statements – but those probabilities in terms of successful outcomes have significantly improved.  One the corollaries of  Aristotle’s work is that there can be “no science of individuals” and yet the current goal is individualized or personalized medicine.

5:  Is science relevant to clinicians on a day-to-day basis? -  I think that it is.  I have certainly spent hours and even entire weekends researching patient related problems to find the best solution to a problem and to be absolutely sure that my recommended course of treatment would not harm the patient. All of that reading was basic or clinical science.  On the same day that I received Montgomery’s book, I got my weekly copy of the New England Journal of Medicine.  I have been a subscriber since my first year of medical school based on the recommendation of my biochemistry professor. Our biochemistry class was designed around research seminars where we read and critiqued basic science research. There was also the assumption that you were reading the text cover to cover and attending all of the lectures.  He encouraged all of us to keep up on the science of medicine by continuing to read the NEJM and in retrospect it was a great idea.  In that edition I turned to the Case records of the MGH (6): An 81-Year-Old Man with Cough, Fever, and Shortness of Breath. It was a detailed discussion by an Internist about the presentation and differential diagnosis of the problem. And there on page 2336 was a diagram of the ventilation perfusion mismatch that occurs with a pulmonary embolism and acute respiratory distress syndrome. I have seen this science at the bedside in many clinical settings.  

The clinical competency of pattern matching, pattern recognition, and pattern completion is left out of Montgomery’s description of how doctors think and it is an important omission.  It is a good example of non-verbal and unconscious reasoning that can be a critical part of the process. The answer to the question: “Is this patient critically ill?” and the triage that follows depends on it.  Pattern matching is also experience dependent with experts in their respective fields being able to more rapidly diagnose and classify problems that physicians who are not experts. Biases affecting verbal reasoning can negatively impact the diagnostic process, but so can the lack of experience in seeing patterns of illness and an inadequate number of cases in a particular specialty.

I consider both of these books to be good reads, especially if you are a physician and have had no exposure to thinking about the diagnostic process.  Both authors have their own ideas about what occurs and there is a lot of overlap. Both authors have the goal of stimulating discussion and analysis of how physicians think and educating the general public about it. Physicians will probably find Groopman a faster and more relatable text. Physicians may find the references and vocabulary used in Montgomery to be less recognizable. I would encourage any physician who is responding to initiatives to change the medical curriculum or critique it to read Montgomery’s book and work through her criticisms.  Both books have excellent references and annotations listed by the chapter for further reading. Non-physicians especially patients who are working with physicians on difficult problems may benefit from Groopman’s tips on how to keep those conversations focused and relevant.  As a psychiatrist who is sensitive to attacks (even philosophical ones) from many places – you may find my criticism of Montgomery’s work to be too rigorous. I tried to keep that criticism down to a level that could be contained in a blog post.  I encourage a reading of her book and formulating your own opinions. It is an excellent scholarly work.

Finally, the area of expertise in medicine and the associated clinical judgment of experts is still a current research topic.  The research has gone from basic experiments about who can properly diagnose a rash or diabetic retinopathy to a clear look at brain systems responding during that process. Those changes have occurred over the past 30 years. At the descriptive level it remains important to be aware of the possible cognitive biases and what can be done to overcome them.

 

George Dawson, MD, DFAPA

 

References:

1:  Groopman J.  How Doctors Think. Houghton Mifflin Company, New York, 2008.

2:  Montgomery K.  How Doctors Think. Oxford University Press, New York, 2006.

3:  Kassirer JP, Kopelman RI.  Learning Clinical Reasoning. Williams and Wilkens, Baltimore, 1991.

4:  Sox HC, Blat MA, Higgins MC, Marton KI.  Medical Decision Making. Butterworths, Boston, 1988.

5:  Hossenfelder S.  The End of Reductionism Could Be Nigh. Or Not.  Nautilus June 18,2021 (accessed on June 18, 2021) https://nautil.us/blog/the-end-of-reductionism-could-be-nigh-or-not

6:  Hibbert KA, Goiffon RJ, Fogerty AE. Case 18-2021: An 81-Year-Old Man with Cough, Fever, and Shortness of Breath. N Engl J Med. 2021 Jun 17;384(24):2332-2340. doi: 10.1056/NEJMcpc2100283. PMID: 34133863.