Physiology Ch 57 p697-709
Cerebral Cortex, Learning, and Memory
Anatomy of the Cerebral Cortex – thin layer of neurons covering surface of cerebrum; most
neurons are of 3 types: granular, fusiform, and pyramidal
1. Granular Neurons – short axons and function as interneurons transmitting signals short
distances in cortex; excitatory granular neurons secrete glutamate while inhibitory severe
GABA
a. Sensory and association areas have large concentrations of granule cells
2. Pyramidal Cells and Fusiform cells – give rise to output fibers rom cortex
a. Pyramidal cells are larger and more numerous; source of corticospinal fibers and
subcortical association fibers
-incoming sensory signals terminate in cortical layer IV while output signals leave through
cortical layers V and VI (to brainstem/cord = V, thalamus = VI)
-layers I, II, III perform most of intracortical associations, with II and III sending fibers to
adjacent areas in the cortex
Anatomical and Functional Relations of Cerebral Cortex to the Thalamus and Other Lower
Centers – connections from cortex  thalamus are in 2 directions, from cortex to thalamus and
from thalamus to cortex
-if thalamic connections are cut, functions of cortical area become lost; therefore cortex
operates in close association with the thalamus as a unit; called thalamocortical system
-all senses except for olfaction pass through the thalamus
Functions of Specific Cortical Areas – cortex pieces info together from many places, and has
areas specific to certain motor and sensory areas
-primary motor areas have direct connections with specific muscles and primary sensory areas
detect specific sensations transmitted to the brain for periphery
-secondary signals make sense out of signals from primary areas, such as the supplementary
and premotor areas + basal ganglia to provide patterns of motor activity
-secondary sensory areas interpret meanings of shape/texture, color, light intensity,
meanings of sound tones and sequence of tones
Association Areas – do not fit into rigid categories because they receive both motor and sensory
signals from cortices and subcortical structures; most important association areas are:
1. Parieto-occipitotemporal Association Area – in parietal and occipital cortex bounded by
somatosensory cortex anteriorly and visual cortex posteriorly and auditory cortex laterally;
provides meaning of signals from these sensory areas
a. Analysis of Spatial Coordinates of Body – area in post parietal cortex provides
analysis of spatial coordinates of all body parts and receives visual information from
occipital cortex and somatosensory information from ant parietal cortex
b. Area for Language Comprehension – major area is called Wenicke’s area behind
the primary auditory cortex in posterior part of superior gyrus of temporal lobe
c. Area for Initial Visual Language Processing (reading) – in the anterolateral region of
occipital lobe is a visual association area that feeds words from a book into
Wernicke’s area; called the angular gyrus area makes meaning out of visual words
d. Area for Naming Objects – lateral area of ant occipital lobe and post temporal lobe
is where naming objects takes place; learned through auditory input and physical
natures are learned through visual input
2. Prefrontal Association Area – functions in association with motor cortex to plan complex
patterns of sequences of motor movements; receives input from parieto-occipitotemporal
association area, meaning prefrontal cortex receives preanalyzed sensory information,
especially on spatial coordinates of body necessary for planning inputs
a. Out back to motor control system passes through caudate of basal ganglia-thalamic
feedback ciruit for motor planning
b. PREFRONTAL area ALSO is essential to carrying out “thought” processes in the mind
resulting from capabilities of prefrontal cortex that allow it to plan motor activities
c. Broca’s Area – provides neural circuitry for word formation; located in the posterior
lateral prefrontal cortex, partly in premotor area; plans motor patterns for
expressing individual words or phrases and works in association with Wernicke’s
i. If one language is learned first and then another, the second language is
slightly removed from the storage area of the first; if they are learned
together, then they are in the same area of the brain
3. Limbic Association Area – anterior pole of temporal lobe and in cingulate gyrus in
longitudinal fissure on each hemisphere; concerned with behavior, emotions and motivation
Area for Facial Recognition – patient with prosophenosia cannot recognize faces; occurs in
people with damage on medial undersides of both occipital lobes along medioventral surfaces
Interpretive Function of Posterior Superior Temporal Lobe – “Wernicke’s Area” – are of
confluence where temporal, parietal, and occipital lobes come together is highly developed on
the dominant side of the brain (left side in most R handed people) and plays the greatest role in
comprehension of brain function that we call “intelligence”; Best known as Wernicke’s area
-damage to wernicke’s area allows person to hear well and recognize words but still unable to
arrange the words into coherent though
-electrical stimulation of this area causes highly complex thought, can bring back memories
Angular Gyrus – Interpretation of Visual Information – most inferior portion of posterior
parietal lobe behind the Wernicke’s area and into visual region
-if this area destroyed but Wernicke’s area is still intact, person can interpret auditory
experiences, but the stream of visual experiences is mainly blocked
-person can see words and know what they are, but cannot interpret meanings: dyslexia
Concept of Dominant Hemisphere – interpretive functions of Wernicke’s area and other areas
are more developed in one hemisphere than the other, called the dominant hemisphere where
the LEFT is more dominant in 95% of all people
-if left side is damaged, the right side will develop dominant characteristics
-at birth, left hemisphere is slightly larger, and it begins to be used to a greater extent, so the
rate of learning in that hemisphere first increases rapidly
-in remaining 5% of people, they are usually codominant
-Broca’s area is far laterally in the intermediate frontal lobe always on the dominant side
-motor areas for controlling hands are also on dominant side
-dominant side receives sensory information from both hemispheres (sensory/motor regions)
that transfers over via the corpus callosum
Role of Language in Function of Wenicke’s Area and in Intellectual Functions – we first store
the words from a book before the visual images; sensory area of language interpretation is the
Wernicke’s area and is closely associated with both primary and secondary hearing areas of
temporal lobe
Functions of Parieto-Occipitotemporal Cortex in Nondominant Hemisphere – destroying
Wernicke’s area in dominant hemisphere causes person to lose intellectual function of
language: reading, math operations, and ability to think through logical problems
-NONdominant hemisphere important for interpreting music, nonverbal visual experiences,
spatial relations between person and surroundings, body language, and intonations of voices
Higher Intellectual Functions of Prefrontal Association Areas – patients who have undergone a
prefrontal lobotomy found relief from severe psychotic depression: also these mental changes
1. Patients lost ability to solve complex problems
2. Unable to string together sequential tasks to reach complex goals
3. Unable to learn to do several parallel tasks at the same time
4. Level of aggressiveness was decreased, lost ambition
5. Social responses often inappropriate, loss of morals and little reticence in relation to sex
and excretion
6. Could still talk and comprehend language, but unable to carry on long trains of thought
and moods changed from sweetness to rage
7. Patients could still perform motor functions, but often without purpose
-Decreased aggressiveness and Inappropriate Social Responses result from loss of ventral frontal
lobes on underside of brain (limbic association cortex)
-Inability to progress toward goals or to carry through sequential thoughts due to loss of
prefrontal cortices – people really distracted
Elaboration of Thought, Prognostication, Higher Intellectual Areas – Working Memory – ability
of prefrontal cortex to keep track of many bits of information simultaneously and recall
information is called the brain’s “working memory” and could explain higher intelligence
-by combining all temporary bits of working memory, we have the ability to prognosticate, plan
for the future, delay action in response to incoming sensory signal, consider consequences of
motor actions, solve complex problems, diagnose diseases, control activities with moral laws
Function of Brain in Communication – Language Input and Output – two aspects of
communication: the SENSORY aspect (language input) and MOTOR (language output)
Sensory Aspects of Communication – loss of auditory areas is called auditory receptor aphasia
and visual receptor aphasia (word deafness and word blindness)
Wenicke’s Aphasia and Global Aphasia – can understand words but unable to interpret the
thought that is expressed, resulting from damage to Wernicke’s area
-when lesion in Wernicke’s area is widespread and extends into angular gyrus, temporal love,
and sylvian fissure person is likely to be demented completely; called global aphasia
Motor aspects of Communication – speech involves formation of thoughts and choice of words,
and then motor control used for vocalization
Loss of Broca’s Area Causes Motor Aphasia – if person knows what to say but cannot make
vocal system emit words, it is called motor aphasia resulting from damage to Brocas area in the
prefrontal and premotor facial region of cerebral cortex
Articulation – muscular movements of mouth, tongue, larynx, vocal cords; timing of each to
produce sequential sounds; controlled by motor cortex, cerebellum, basal ganglia, and sensory
cortex
Summary – reception in primary auditory area  interpretation of words in Wernicke’s area 
determination of thoughts and words to be spoken  transmission of signals from Wernicke’s
area to Broca’s area by way of arcuate fasciculus  activation of skilled motor programs for
word formation  transmission of signals to motor cortex to control speech muscles
Function of Corpus Callosum and Anterior Commissure to Transfer Thoughts, Memories,
Training, and Other Info Between 2 Hemispheres – corpus callosum connects two cerebral
hemispheres except for the amygdala, where interconnected fibers pass through anterior
commissure
-destruction of corpus callosum does not produce severe brain deficits; one function of corpus
callosum is to make information from one hemisphere available to the other hemisphere
1. Cutting corpus callosum blocks transfer of info from Wernickes area of dominant
hemisphere to motor cortex on opposite side, causing loss of control over voluntary
muscle functions contralaterally
2. Cutting corpus callosum prevents transfer of somatic/visual info from right hemisphere
into Wernicke’s area in dominant hemisphere and cannot be used for decision making
3. Cutting corpus callosum causes 2 entirely separate conscious brain portions causing
brain to do things without knowing the other did it
4. Effect is different when emotional response triggered on right side, causing effect in left
side as well, so a connection still existed through the anterior commissure
Thoughts, Consciousness, Memory – Destruction of cortex does not prevent person from having
thoughts, but it does reduce the depth of thoughts and degree of awareness
-thought results form a pattern of stimulation of many parts of nervous system at the same
time, involving cortex, thalamus, limbic system, and upper reticular formation of brain stem; this
is called the holistic theory of thoughts
-limbic, thalamus, reticular formation generates pleasure, displeasure, pain, comfort,
and crude sensations
-consciousness is a continuous stream of awareness
Memory – Roles of Synaptic Facilitation and Inhibition – memories are stored in the brain by
changing basic sensitivity of synaptic transmission between neurons as a result of previous
neural activity; new pathways are called memory traces and can be selectively activated to
reproduce memories
-memories are more often due to negative experiences rather than positive
-brain ignores information that is of no consequence, called inhibition of synaptic pathways,
resulting in habituation, a type of negative memory
-incoming information that causes important consequences such as pain or pleasure, brain
stores this as positive memory due to memory sensitization
Classification of Memories – short term memory (seconds or minutes), intermediate long-term
memory (days/weeks), and long-term memory (lifetime)
-memories are classified according to type of information stored:
1. Declarative Memory – memory of details of an integrative thought, such as of an important
experience: surroundings, memory of time relationships, causes of experience, meaning of
experience, and deductions left in person’s mind
2. Skill Memory – motor activities of body
Short-Term Memory – typicfied by memory of 7-10 digits of phone number for a few seconds or
minutes, caused by circuits of reverberating neurons
-also could be caused by presynaptic facilitation or inhibition using interneurons
Intermediate Long-Term Memory – may last for many minutes to weeks and lost unless
memory traces are activated enough to become permanent
Memory Based on Chemical Changes in Presynaptic Terminal or Postsynaptic Neuronal
Membrane – you have two synaptic terminals; one is from a sensory input neuron and
terminates on neuron that is to be stimulated, called the sensory terminal. The other is a
presynaptic ending that lies on surface of the sensory terminal, called the facilitator terminal
-when sensory terminal is stimulated repeatedly, without facilitation signal, signal is at first
great, but becomes less and less intense with repeated stimulation, called habituation
-if facilitator signal is excited at same time as sensory terminal, ease of transmission is easier
-noxious stimulus causes memory pathway through sensory terminal to become
facilitated
Molecular Mechanism of Intermediate Memory
Mechanism for Habituation – results from progressive closure of Ca channels through terminal
membrane
Mechanism for Facilitation – believed to be:
1. stimulation of facilitator presynaptic terminal at same time as sensory terminal causes
serotonin release at facilitator synapse on surface of sensory terminal
2. serotonin causes activation adenylyl cyclase to form cAMP inside sensory presynaptic
terminal
3. cAMP activates protein kinase that causes phosphorylation of a protein that is part of K
channels in sensory synaptic terminal membrane, which blocks K conductance; blockage
can last for weeks
4. Lack of K conductance causes greatly prolonged action potential in synaptic terminal
because flow of potassium out of terminal is necessary for recovery
5. Prolonged action potential causes prolonged activation of Ca channels allowing
neurotransmitter release by synapse and facilitating neuron
Long-Term Memory – distinction between intermediate memory is one degree, resulting from
structural changes instead of chemical changes at the synapses to enhance or suppress signal
conduction
Structural Changes in Synapses for Long-Term Memory –
1. increase in vesicle release sites for secretion of transmitter
2. increase in number of transmitter vesicles released
3. increase in number of presynaptic terminals
4. changes in structures of dendritic spines that permit stronger signals
Number of Neurons and Their Connectivities Often Change Significantly During Learning – in
first years of life, brain produced large excessof neurons o send branches everywhere; if axon
fails to connect to something, it will die
-thus, a number of neuronal connections is determined by nerve growth factors released
reteogradely from stimulated cells; this is a type of learning
Consolidation of Memory – for short-term memory to be converted to long-term memory, it
must be consolidated by memory being activated repeatedly to cause chemical, physical, and
anatomical changes allowing memory to be stored as a long-term memory
-requires 5-10 minutes for minimal consolidation or an hour for strong consolidation
Rehearsal Enhances the Transference of Short-Term Memory into Long-Term Memory –
rehearsing the same material over and over accelerates and potentiates degree of transfer
between short term and long term memory
New Memories are Codified During Consolidation – during consolidation, new memories are
codified into different classes of information, where similar types of info are pulled from
memory storage bins and used to help process new information
-new memory is processed by being compared to old information and stored in association with
other memories of the same type
Hippocampus Promotes Storage of Memories – Anterograde Amnesia After Hippocampal
Lesions – hippocampus is most medial portion of temporal lobe cortex, where it folds medially
underneath brain and up into lower, inside surface of lateral ventricle
-removal of hippocampi doesn’t affect memories already stored, but prevents new verbal and
symbolic memories from being stored in long-term memory (unable to establish new
memories), called anterograde amnesia; motor memory stays fine
-hippocampi are most important output pathways from reward and punishment areas of limbic
system
-sensory stimuli or thoughts causing pain or aversion excite limbic punishment centers
-the reward or punishment may play a role in deciding whether memory is worth
keeping
Retrograde Amnesia – Inability to Recall Memories from the Past – distant memories have
been rehearsed many times so that memory traces are deeply engrained and widespread in
brain
-with hippocampal lesions, some degree of retrograde amnesia occurs along with anterograde
amnesia, suggesting that they are related
-thalamus may play a role in helping people search memory storehouses and read out memories
Hippocampi are Not Important in Reflexive Learning – people with lesions do not have
difficulty learning physical skills that do not involve verbalization or symbolic intelligence, and
people can still do reflexive learning requiring repetitive tasks over and over rather on symbolic
rehearsing