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Cerebral Cortex, Intellectual Functions of the Brain, Learning, and Memory.
1. UNIT XI
- Dr Dipti Magan
Cerebral Cortex, Intellectual Functions of
the Brain, Learning, and Memory
2. OBJECTIVES
The students should be able to:
Describe the various forms of memory
Identify the parts of the brain involved in memory
processing and storage
Define synaptic plasticity, long-term potentiation
(LTP), long-term depression (LTD), habituation, and
sensitization, and their roles in learning and memory
3. Physiologic Anatomy of Cerebral Cortex
• Each area of the cortex is connected to a specific part of
the thalamus
• When thalamic connection is lost cortical function stops
• All sensory pathways pass through the thalamus with the
exception of the olfactory tract
6. Dominant and Non-Dominant Hemisphere
• Wernicke area more developed in one hemisphere,
responsible for verbal symbolism and related intelligence.
• 95% of population has a left dominant hemisphere.
• Wernicke area can be as much as 50% larger in the
dominant hemisphere.
7. Dominant and Non-Dominant Hemisphere (Cont.)
• Damage to dominant Wernicke area leads to
dementia
• Non-dominant side related to other forms of
sensory intelligence (music, sensory feelings)
8. Intellectual Functions of the Prefrontal Association Area
• Responsible for calling forth stored information and using it
to obtain a goal
• Responsible for concerted thinking in a logical sequence
– damage causes an inability to keep tract of simultaneous
bits of information, easily distracted
9. Intellectual Functions of the Prefrontal Association Area (Cont.)
• Elaboration of thought
– prognosticate, plan, consider consequences of motor
actions before they are performed. correlate widely
divergent information, control one’s activities
10. Function of the Brain in Communication
“For millions of years
mankind lived just like the animals.
Then something happened which unleashed the
power of our imagination. We learned to talk.”
Pink Floyd
11. 1. Primary auditory
area recognition of the
sound as a word
2. Interpretation of
the word and the
thought that the word
expresses in Wernicke
area
3. Formation of the
word that expresses a
particular thought
4. Transmission via the
arcuate fasciculus to
Broca area
5. Activation of motor
programs in Broca area for
control of word formation
6. Transmission of signals to motor
cortex to control speech muscles
Pathways for Auditory Communication
12. Pathways for Visual Communication
1. Receive the visual input in
primary visual area
2. Processing of the visual
information in the parietal-
temporal-occipital association
cortex, the angular gyrus
region
3. Visual input reaches full
level of interpretation in
Wernicke area
4. Then to Broca area for motor
formation of the word
5. Transmission of signals to motor
cortex to control speech muscles
13. Sensory Aspects of Communication
Destruction of the
visual and auditory
association areas
results in an inability
to understand the
written or spoken word
Wernicke aphasia
14. Motor Aspects of Communication
• Speech involves two things
– formation in the mind of thoughts to be expressed and the
choice of words
– motor control of vocalization and the act of vocalization
• Formation of word, thought and choice of words is function of
Wernicke area
• Broca area controls the motor coordination required for
speech
15. Function of the Corpus Callosum
• Connects the two hemispheres and allows transfer of
information
• Interruption of these fibers can lead to bizarre types of
anomalies
– dominant hemisphere understands spoken word.
– non-dominant hemisphere understands written word
and can elicit motor response without dominant side
knowing why response was performed
16. Learning and Memory
• ‘Learning’ is acquisition of the information
or
in other words learning is knowledge
acquisition, representation, and organization
• ‘Memory’ is the retention and storage of the
information
17. Thoughts and Memory
• Neural mechanism for thought is not known
• Most likely a specific pattern of simultaneous neural activity in
many brain areas
• Destruction of cerebral cortex does not prevent one from
thinking
– however, depth of thought and level of awareness may be
less
18. Memory
• Change in the capability of synaptic transmission from neuron
to neuron as a result of prior stimulation
• Memory trace is a specific pattern or pathway of signal
transmission
• Once established they can be activated by the thinking mind to
reproduce the pattern and thus the memory
19. 3 Types of Memory
• Immediate memory
– lasts for seconds or minutes
• Short-term memory
– lasts for days to weeks
• Long-term memory
– lasts for years or for a lifetime
20. Mechanism of Memory
• Immediate memory may result from synaptic potentiation
through the accumulation of calcium in the presynaptic
membrane
– would promote neurotransmitter release
• Short-term memory may result from a temporary physical or
chemical change in the pre- or postsynaptic membrane
21. Cellular Basis for Memory
• Repetitive stimulation causes a progressive decline in
sensitivity called habituation
• Results from progressive decline in the number of active
calcium channels
• Less calcium entry less transmitter released
• Stimulation of facilitator terminal prevents habituation
22. Molecular basis for memory (Cont.)
Transmitter activates G protein
which in turn activates
adenylate cyclase resulting in
an increase in cAMP
cAMP activates a protein kinase
that phosphorylates a
component of the K+ channel
blocking its activity
This prolongs the action
potential which increases
transmitter release
23. Long-Term Memory
• Results from a structural change in the synapse
• Increase in the area for vesicular release therefore, more
transmitter is released
• During periods of inactivity the area decreases in size
• Enlargement of the release site area results from synthesis of
release site proteins
24. Consolidation of Memory
• Converting immediate into short and long-term memory
• Results from chemical, physical and anatomical changes in
the synapse
• Requires time
• Interruption of the process by electrical shock or by
anesthesia will prevent memory development
• Rehearsal enhances consolidation
25. Brain centers for memory
Hippocampus is critical for long-term memory
Damage causes inability to form new verbal or symbolic
long-term memory
anterograde amnesia
Hippocampus is involved in determining which sensory
experiences are important and which do not require
attention.
26. Brain Centers and Memory (cont.)
• Thalamic structures are important for recalling memories
• Damage to thalamus causes retrograde amnesia or the inability
to recall stored experiences
• Thalamus scans the cortex for the area and the circuit for the
stored memory
30. Explicit memory
- factual knowledge about people, places, and things
- It is divided into semantic memory for facts (eg, words,
rules, and language) and episodic memory for events
Explicit memories that are initially required for activities
such as riding a bicycle can become implicit once the
task is thoroughly learned
31. Implicit memory
-training reflexive motor or perceptual skills and is subdivided
into four types:
1. Priming: facilitation of the recognition of words or objects
by prior exposure to them
- dependent on the neocortex
- an example of priming is the improved recall of a
word when presented with the first few letters of it
2. Procedural memory includes-
- skills and habits, which, once acquired, become
unconscious and automatic
- is processed in the striatum
32. 3. Associative learning relates to-
- classical and operant conditioning in which one
learns about the relationship between one
stimulus and another
- is dependent on the amygdala for its
emotional responses and the cerebellum for the
motor responses
4. Non-associative learning includes-
- habituation and sensitization
-dependent on various reflex pathways
Implicit memory (cont.)
33. ASSIOCIATIVE LEARNING: CONDITIONED REFLEXES
A classic example of associative learning is a
conditioned reflex
A conditioned reflex- reflex response to a
stimulus that previously elicited little or no
response, acquired by repeatedly pairing the
stimulus with another stimulus that normally
does produce the response
Pavlov’s classic experiments (later slides)
34. In the present experiment:
the meat placed in the mouth was the
unconditioned stimulus (US)
the stimulus that normally produces a
particular innate response
(USR=unconditioned response)
The conditioned stimulus (CS) was the bell
ringing
After the CS and US had been paired a
sufficient number of times, the CS produced
the response originally evoked only by the
US
The CS had to precede the US
An immense number of somatic, visceral,
and other neural changes can be made to
occur as conditioned reflex responses
40. SYNAPTIC PLASTICITY & LEARNING
Short- and long-term changes in synaptic function--
result of the history of discharge at a synapse
Synaptic conduction can be strengthened or weakened
on the basis of past experience
These changes are of great interest because they
represent forms of learning and memory--can be
presynaptic or postsynaptic in location
44. Production of LTP in Schaffer collaterals in the hippocampus
1. Glutamate (Glu) released from the presynaptic neuron binds to AMPA and NMDA receptors in the membrane of
the postsynaptic neuron
2. The depolarization triggered by activation of the AMPA receptors relieves the Mg2+ block in the NMDA receptor
channel, and Ca2+ enters the neuron with Na+
3. The increase in cytoplasmic Ca2+ activates Ca2+/calmodulin kinase, protein kinase C, and tyrosine kinase which
together induce LTP
4. The Ca2+/calmodulin kinase II phosphorylates the AMPA receptors, increasing their conductance, and moves
more AMPA receptors into the synaptic cell membrane from cytoplasmic storage sites
5. In addition, once LTF is induced, a chemical signal (possibly nitric oxide, NO) is released by the postsynaptic
neuron and passes retrogradely to the presynaptic neuron, producing a long-term increase in the quantal release
of glutamate
Steps of LTP Induction
