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Functional Neuroanatomy &
Neurological Bases of Cognition
Nigel Schofield, Consultant Clinical
Neuropsychologist May 2008
Evolutionary Development
• If you examine the brain in an
evolutionary perspective, this can
help to understand the interlinks
between form and function. The
brain can be divided anatomically
and functionally into three basic
components.
Reptilian Brain
• Corresponds to the brainstem
• Consists of the medulla, pons,
midbrain and basal ganglia
• Not only responsible for vegetative
functions but also for many volitional
behaviours directed towards individual
preservation and propagation such as
feeding, drinking and sexual
aggression.
Paleomammalian Brain
• The primitive cortex of the limbic lobe
• Subserves primitive (but distinctly
mammalian behaviours) such as
hoarding and parental care of offspring.
Neomammalian Brain
• The neocortex
• Subserves higher cognitive functioning
and speech which facilitate social
behaviour.
Lurias Work
• Simple anatomical localisation of function
does not explain cognitive and behavioural
complexity.
• Postulated three functional units
Luria’s 3 Functional Units
• Motor unit – regulates motor tone
• Sensory unit – receives, processes and
stores sensory information
• The unit for programming, regulating and
verifying action
How do the units work?
• Progression from sensation through to
symbolic function in each unit
• Primary, secondary and tertiary areas
e.g. Damage to the Visual Parts
of the Sensory Unit
• Primary areas – losses of parts of the visual
field
• Secondary areas – may lead to poor
judgement of motion, poor distance
judgement, impaired colour perception
• Tertiary areas – could lead to visual object
agnosia
e.g. Damage in the Speech
Pathways of the Motor Unit
• Primary areas – dysarthria
• Secondary areas – dysphasia
• Tertiary areas – poor speech spontaneity
Weaknesses of Luria’s Model
Does not fully explain the integration of focal
brain functions because:• Divisions between sensory and motor
neurons sometimes not clear
• Some functions exist several in
anatomically distinct areas of the brain
• There are multiple parallel functions in the
brain, not simple stepwise processes
Arousal,
Activation
Arousal,Attention,
Attention,
Activation
Arousal
Major Areas of Cognition
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•
•
•
•
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Attention and concentration
Perception
Memory
Language
Control of motor behaviour
Executive function
Attention and Concentration
Three attentional networks:• Alerting – achieving and maintaining an alert
state in preparation for incoming stimuli
• Orienting – selectively focusing on one or more
items out of many candidate ones
• Executive control – monitoring and resolving
conflicts in planning, error detection and
overcoming habitual actions
• All dependent on the brain being “aroused”
Localisation of Attentional
Networks
• Alerting – frontal and parietal cortical regions
particularly of the right hemisphere
• Orienting – parts of the superior and inferior
parietal lobe, frontal eye fields and subcortical
areas such as superior colliculus of the
midbrain, and pulvinar and reticulate nucleus
of the thalamus
• Executive control – includes midline frontal
areas(especially anterior cingulate and lateral
prefrontal cortex) and the basal ganglia
3 Compartments of Attention
Top-down modulation from prefrontal,
parietal & limbic cortices
Modality & domain specific attentional
modulations ( sounds, tactile stimuli,
colours, motion, words, spatial targets,
faces, objects, memories etc.)
Bottom-up modulation from ascending
reticular activating system
Components of the ARAS
• Reticulothalamic cortical pathway – promotes and
maintains cortical arousal by facilitating transthalamic
passage of sensory material towards the cortex.
• Transmitter specific pathways originating in the
brainstem or basal forebrain, and projecting to the
cerebral cortex – include dopaminergic projections from
the raphe nucleus & noradrenergic projections from the
locus coeruleus of the brainstem, and cholinergic &
gabaminergic pathways originating in the nucelus
basalis.
Limbic elements of attention
• Anterior cingulate cortex plays a core pivotal
role in attention – bilateral damage gives rise
to akinetic mutism
• Intralaminar nuclei of the thalamus receive
inputs from the brainstem nuclei and relay
info widely to the cortex, with a reciprocal
feedback loop from the cortex modulating
these ascending pathways via the thalamus
Cortical elements of attention
• Parietal cortex involved in sustained and
selective attention
• Dorsolateral prefrontal cortex has a key
role in divided attention
Perception
How we take
energy from
the
environment &
convert it into
a
representation
that the mind
can use
Perceptual Problems
• Visual field cuts
• Cortical blindness
• Achromatopsia – inability to discriminate
between colours (medial occipito-temporal)
• Hemianaesthesia
• Hemineglect – ? an attentional problem
• Hemispatial neglect
• Hemiakinesia
• Agnosias
• Loss of taste and/ or smell
Types of Agnosia
• Visual agnosias – inability to recognise
familiar objects e.g.
– Prosopagnosia – inability to recognise faces
– Agnostic alexia – inability to read
– Colour agnosia – inability to retrieve colour
information e.g. what colour are bananas
– Object agnosia – inability to name objects
– Simultiagnosia – inability to recognise a whole
image although individual details are
recognised
• Auditory agnosia – an inability to recognise
auditory stimuli
- Auditory/verbal information agnosia – an
inability to hear words
- Auditory agnosia – inability to hear
environmental sounds e.g. car starting or dog
barking
- Receptive amusia – inability to hear music
• Somatosensory agnosia (Astereognosis or tactile
agnosia)
- Difficulty perceiving objects by touch
Object recog, understanding & naming
Functions
Discrimination of
shape, colour, location
Perceptual classification
Knowledge of objects
Store of names
Object
Consequence of impairment
Visual analysis
Apperceptual agnosia
Object recog.
Associative agnosia
(modality specific)
Semantic system
Associative agnosia
(non-modality specific)
Lexicon
Anomia & paraphasias
Spoken name
Apperceptive vs Associative Agnosia
Basic High-level Naming Semantic
visual perceptual
&
knowledge
proc analysis
identific.
Apperc.
/
x
x
/
Assoc.
/
/
x
x/
Prosopagnosia
Face
Visual analysis
Expression, lip reading,
Feature matching
Semantic system
Face-recognition units
****
Voice, gait
etc.
Knowledge of person
Lexicon of names
Spoken name
Topographical Disorientation
• Egocentric disorientation – an inability to represent
the location of objects relative to self (often seen in
conjunction with features of Balints syndrome – due
to bilateral posterior parietal damage
• Landmark agnosia – an inability to recognise salient
environmental stimuli (buildings etc) – a form of
associative agnosia due to lingual gyrus (basal
occipital) damage
• Anterograde spatial disorientation – an inability to
create “new maps” or representaions of the
environment – due to damage to the right
parahippocampal gyrus
Memory Taxonomy
Cortical
Network
Memory
Basic Neuroanatomy of Memory
A) Subcortical structures
• Basal ganglia and cerebellum – Procedural
memory. Caudate nucleus involved particularly
with habit formation (unconscious learning)
• Thalamus – Temporal sequencing information.
Also supplementary role to medial temporal lobes
in new learning
• Basal forebrain – The binding together of different
modal components in episodic memory
B. Cortical structures
• Hippocampus – Acquisition of new factual
knowledge
• Primary association cortex – Visual, auditory and
somatosensory data
• Non-medial temporal – Retrieval of previously
learned material e.g. autobiographical info, names,
faces
• Ventromedial frontal lobes – Memory traces
linking facts and emotion
• Dorsolateral frontal lobes – Recency and
frequency memory. Working memory
Limbic System Elements of
Episodic Memory
Cingulate cortex
Frontal Lobe
Fornix
Retrosplenial Cortex
Thalamus
Anterior mediodorsal
Mamillary body
Basal forebrain
Amygdala
Hippocampus
Entorhinal cortex
Semantic Memory
Pre-motor cortex
Sensorimotor cortex
Touch
Action
Words
Perisylvian cortex
Semantic
Representation
Sound
Occipeto-temporal
parietal junction
Motion
Middle temporal gyrus
Anterior temporal cortex
Posterior temporal/inferior
parietal cortex
Colour
Shape
Posterior ventral occipetal
temporal cortex
Language Areas of the Brain
Language Functions
• Phonology – production & comprehension of
appropriately sequenced speech sounds
(phonemes) – left superior temporal lobe and
anterior insula
• Semantics –Assignment of meaning to words and
production of linguistically appropriate
individual words – Anterior and inferior
temporal lobe (semantic representations) and
Wernicke’s area (mapping sound to underlying
representations)
• Syntax – Assembly of strings of words
into sentences using pronouns,
prepositions, tenses etc. – Broca’s area
• Prosody – Fine tuning by intonation,
cadence etc – Left anterior hemisphere
and basal ganglia & Emotional
expression – Right hemisphere
Characteristics of Different Types of Aphasia
Type
Fluent Repetition Comprehension Naming Right-sided Sensory
hemiplegia deficits
Broca
Wernicke
Conduction
Global
Transcortical
sensory
Transcortical
motor
Transcortical
mixed
Anomia
no
yes
yes
no
yes
poor
poor
poor
poor
good
good
poor
good
poor
poor
poor
poor
poor
poor
poor
yes
no
no
yes
some
few
some
some
yes
yes
no
good
good
poor
some
no
no
good
poor
poor
some
yes
yes
good
good
poor
no
no
Disorders of Reading
• Peripheral dyslexias - Preserved oral and written
spelling, and ability to identify words spelt out aloud
coupled with
(a) ability to write, but unable to read other than
letter by letter (alexia without agraphia) – left
medial occipital lobe
(b) errors reading left-hand or initial parts of words
(neglect dyslexia) – Right hemisphere lesions
•
Central linguistic dyslexias – linguistically based,
invariably affect oral spelling
(a) Breakdown of whole word (lexical) reading,
difficulty with irregularly spelt words,
phonologically plausible errors (surface dyslexia)
– left tempero-parietal damage
(b) Loss of sound-based (phonological) reading,
semantic errors, difficulty with function and
abstract words, inability to read non-words (deep
dyslexia) – extensive left hemisphere damage
Disorders of Spelling
• Dyspraxic dysgraphia – oral spelling intact,
defective copying – dominant parietal or frontal
lobe
• Neglect dyspraxia – wide left margin or misspelling of initial part of words. Other neglect
phenomena usually also preseent – Right
hemisphere lesions
• Lexical (surface) dysgraphia – breakdown of
lexical route for spelling, so
• difficulty spelling irregular words,
phonologically plausible errors – left temperoparietal damage
• Deep dysgraphia – breakdown of sound route
for spelling , so semantic errors, unable to spell
unfamiliar or non-words, better concrete than
abstract spelling – extensive left hemisphere
damage
Control of Movement
Apraxia
• Limb kinetic apraxia – breakdown of fine motor
organisation of finger movements, so find it hard to copy
meaningless hand movements, mimic proper gestures or
use real objects flawlessly – Basal ganglia damage,
supplementary motor area damage
• Ideomotor apraxia – unable to carry out motor acts to
command, but often can do so spontaneously. Difficulty
with selection, sequencing, spatial orientation and
movements in meaningless and meaningful gestures, and
demonstrating imaginary use of objects dominant lobe.
Perf. improves with imitation, and real object use Inferior parietal and prefrontal damage. Callosal lesions
can impair performance of one limb (usually the left)
• Ideational or conceptual apraxia – inability to
carry out a complex sequence of co-ordinated
movements even though each separate
component of the sequence can be successfully
performed. Inability to mime use of objects, or
to even use the real objects. Thus possibly a
disorder of semantic memory. – Left temporal
lobe damage
• Orobuccal apraxia – difficulty performing
learned, skilled movements of face, lips, tongue,
cheeks, larynx and pharynx on command –
Inferior frontal region and insula, so commonly
seen in Broca’s aphasia patinets
Frontal Executive Function
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Abstract conceptual ability
Set shifting/mental flexibility
Inhibitory control
Problem solving and strategy formulation
Planning
Self-monitoring
Initiation
Sequencing of behaviour
Decision making
Temporal-order judgements
Personality, esp. drive, motivation & inhibition
Social behaviour, incl. theory of mind
Important core functions
• Controlling acquisition of new memories
• Divergent thinking – choosing different
ways of approaching a situation
• Environmental control of behaviour –
using cues and information from the
environment to direct, control or change
personal behaviour.
• Directing interpersonal behaviour
Acquisition Deficits
• Impaired working memory
• Poor associative learning – difficulty
associating varying facets of memory about
facts or events, thus finding it hard to make
use of external cues to direct behaviour
Divergent Thinking Deficits
• Loss of spontaneous behaviour – e.g. speaking and
verbal fluency decreased; decreased ability to
produce graphic designs or doodling; reduced
behavioural output shown by lethargy, inability to
initiate
• Impaired strategy formulation and planning,
especially in response to novel situations
• Poor abstract thinking e.g. concept formation
Deficits in Environmental
Control of Behaviour
• Ability to inhibit responses is impaired, so
perseverative on tasks
• Breaking rules and taking risks
• Unable to follow instructions
• Gambling
• Poor error perception
• Amotivation and apathy
Impaired Interpersonal
Behaviours
• Inappropriate social and sexual behaviour,
or altered behaviours in comparison to
premorbid patterns.
• Pseudodepression
• Pseudopsychopathy
Brains are not absolutely
hard-wired – as shown by
these fMRI images of
regional activation in
different people doing a
Stroop task – some overlap
of dorsolateral and medial
frontal lobe, inferior
parietal lobule and occipital
cortex plus significant other
variability. There are also
gender differences that can
account for better gender
performance on different
tasks e.g. on spatial working
memory tasks men have
more frontal and less
occipital activation, women