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 resent 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 were 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, genialized 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. 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 with psychotic features. |
I came up with the following graphic 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 a 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.
4: Cognitive neuroscience
models highlight the fact that the separation between diagnosis and treatment
is artificial – All physicians are taught to do exhaustive evaluations or
medical problems. 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.
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 what we do clinically is
based on an 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
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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.
