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Tests Rarely Assess a Single Cognitive Domain or Function
Trail Making A
Trail Making B
etc.
etc.
Tests and the Processes they Assess
COGNITIVE PROCESS
TEST
Trail Making A
Trail Making B
Arithmetic
Symbol Search
Vocabulary
Verbal Fluency
Cognitive
Flexibility
Working
Memory
Visual
Scanning
Verbal
Retrieval
Processing
Speed
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Focal vs. Diffuse Test Patterns
• Focal
– 1-2 domains
significantly affected
– Other domains
typically WNL
– Seen in focal
neurologic process
involving area critical
to affected domains
• Diffuse
– milder deficits in
attention, concentration,
memory, processing
speed, executive
function
– Seen in diffuse
neurologic process
affecting information
processing speed and
integration
History and Deficit Pattern of
Common Conditions
Deficit
Pattern
Age at
Onset
Symptom
Onset
Time
Course
Stroke (cortical)
Focal
Late
Acute
Decline w/ recovery
Encephalitis (HSV)
Focal
Any
Acute
Decline w/ recovery
Traumatic Brain Injury
Focal
Any
Acute
Decline w/ recovery
Tumor
Focal
Any
Acute/Gradual
Variable decline
Dementia (early)
Focal
Late
Gradual
Slow decline
Epilepsy
Mixed
Early/Late
Gradual
Slow decline
Stroke (sub-cortical)
Mixed
Mid-Late
Acute/Gradual
Step-wise decline
Dementia (late)
Diffuse
Late
Gradual
Slow decline
Alcohol
Diffuse
Mid-Late
Gradual
Slow Decline
Multiple Sclerosis
Diffuse
Early-Mid
Gradual
Decline/Fluctuating
Depression
Diffuse
Any
Gradual
Fluctuating
Integrating Test Data with other
Clinical Information
• Three Important Principles
– Avoid the Fallacy of Affirming the Consequent
• because B often follows A, occurrence of B proves that
A has occurred
– Be Open Minded
• generate as many reasonable explanations for what you
see
– Apply Occam’s Razor
• “the most likely explanation for a pattern is the one that
requires the least number of unlikely events to account
for it “
Errors in Formulation
Affirming the Consequent
• Complains of memory change after MVA
• Testing - diffuse pattern (moderate-severe deficits in
attention, executive function, processing speed c/w
traumatic brain injury)
• MRI – subtle, diffuse changes in deep white matter
Additional History
• No loss of consciousness in MVA
• History of functional declines, sensory and motor
changes in year prior to MVA
• Testing 1 year later shows further declines
• Neurologic examination shows abnormal nerve
conduction consistent with multiple sclerosis
Errors in Formulation
Keeping an Open Mind
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Acute onset word-finding deficits – no recent events
History of worsening depression
Neurologic exam normal
Neuropsychological testing is normal except for
severe impairment in confrontation naming with
paraphasias
• Imaging shows multiple lesions, one in right temporal
lobe with fresh blood
Additional History
• Left-handed
• Strong family history of
– left-handedness
– early strokes
• Findings consistent with hemorrhage of genetically-based,
cavernous angioma (small tumor of vessel wall) in right,
language dominant hemisphere
• Depression is irrelevant in this context
Errors in Formulation
‘Occam’s Razor’
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54 yo. M with recent memory complaints
Neurologic exam normal
Normal neuroimaging
Family is concerned about ‘early Alzheimer’s’
Additional History
• Long-standing history of major depressive disorder
• No family history of dementia
• Trouble caring for home and finances after partner died 4 years
ago
• Recently ‘got lost’ standing in front of his house, recovered
quickly
• Continues to perform at high level at cognitively demanding job
Behavioral Geography of the
Brain
• The human brain has
– ~ 100 billion neurons in the human brain
– ~100 trillion synaptic connections
– ~3 million miles of axons in the human brain
Brain Orientation
Anterior
Posterior
Superior
Inferior
Rostral
Caudal
Dorsal
Ventral
Brain Orientation
Other definitions
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Lateral – to the side
Medial (mesial) – toward the middle
Proximal – areas of brain near to one another
Distal – areas of the brain far from one
another
• Ipsilateral – structures on same side of the
body
• Contralateral – structures on opposite sides
of body
Divisions of
the Brain
Major
Division
Subdivision
Principal
Structure
Forebrain
Telencephalon
Cerebral Cortex
Basal Ganglia
Limbic System
Diencephalon
Thalamus
Hypothalamus
Midbrain
Mesencephalon
Tectum
Tegmentum
Hindbrain
Metencephalon
Cerebellum
Pons
Myelencephalon
Medulla Oblongata
Hindbrain
• Metencephalon
– Cerebellum
• Involved in aspects of learning and coordination of skilled
or smooth movement
• Posture, walking, equilibrium
– Pons
• Links cerebellum to cerebrum, relays information from
cerebral hemispheres to cerebellum
• Role in vision, balance, auditory processing
• Mylelencephalon
– Medulla
• Regulates bp, heart rate, respiration, controls breathing,
basic muscle tone
Midbrain
• Mesencephalon
– Tectum (roof)
– Tegmentum (floor)
• Controls responses to sight
• Relay station of auditory and visual
information
• Motor control of some muscles
Forebrain
• Diencephalon
– Thalamus
– hypothalamus
• Telencephalon
– Limbic System
– Basal Ganglia
– Cerebral Cortex
Diencephalon
• Hypothalamus
– Controls aspects of motivated
(pleasure and pain) and regulatory
bx
• bodily functions, body temp, thirst,
hunger
• circadian rhythms
• “master gland” – regulation and
secretion of hormones
• Thalamus
– Gateway to cortex
– Relay center for sensory information
– Links nervous and endocrine system
Limbic system
• Groups of structures in center of brain above
brainstem
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amygdala
hippocampus
parahippocampal gyrus
cingulate gyrus
fornix
septum
olfactory bulbs
• Maintains homeostasis
• Emotional reactions needed for survival
Basal Ganglia
• Collection of subcortical nuclei in forebrain
– Caudate nucleus
– Putamen
– Globus pallidus
• Structures involved in voluntary control of
movement
• Motor planning and programming for speech
• Attention and alerting before a motor
response
Cerebral Cortex
Blumenfeld, 2002
Brain anatomy
Brain anatomy