Functional Perspectives on Memory There Are Several Kinds of Memory and Learning Memory Has Temporal Stages Short Intermediate and Long Successive Processes Capture Store and Retrieve Information in the Brain ID: 717329
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Slide1
Learning and MemorySlide2
17 Learning and Memory
Functional Perspectives on Memory
There Are Several Kinds of Memory and Learning
Memory Has Temporal Stages: Short, Intermediate, and Long
Successive Processes Capture, Store, and Retrieve Information in the Brain
Different Brain Regions Process Different Aspects of MemorySlide3
17 Learning and Memory
Neural Mechanisms of Memory
Memory Storage Requires Neuronal Remodeling
Invertebrate Nervous Systems Show Plasticity
Synaptic Plasticity Can Be Measured in Simple Hippocampal CircuitsSlide4
17 Learning and Memory
Neural Mechanisms of Memory
(
continued
)
Some Simple Learning Relies on Circuits in the Mammalian Cerebellum
In the Adult Brain, Newly Born Neurons May Aid Learning
Learning and Memory Change as We AgeSlide5
17 There Are Several Kinds of Memory and Learning
Learning
is the process of acquiring new information.
Memory
is:
The ability to store and retrieve information.
The specific information stored in the brain.Slide6
17 There Are Several Kinds of Memory and Learning
Patient H.M.
, Henry Molaison, suffered from severe epilepsy.
Because his seizures began in the temporal lobes, a decision was made to remove the anterior temporal lobes on both sides.
H.M.
’
s surgery removed the amygdala, the hippocampus, and some cortex.Slide7
Figure 17.1 Brain Tissue Removed from Henry Molaison (Patient H.M.)Slide8
17 There Are Several Kinds of Memory and Learning
Retrograde
amnesia
is the loss of memories formed before onset of
amnesia and is not uncommon after brain trauma.
Anterograde amnesia
is the inability to form memories after onset of
amnesia.
H.M. had normal short-term memory but had severe anterograde amnesia.Slide9
17 There Are Several Kinds of Memory and Learning
Damage to the hippocampus can produce memory deficits.
H.M. was able to show improvement with motor skills but could not remember performing them (i.e. he could not recall the tasks verbally.).
H.M.
’
s memory deficit was confined to describe the tasks he performed.Slide10
Figure 17.2 Henry
’
s Performance on a Mirror-Tracing TaskSlide11
17 There Are Several Kinds of Memory and Learning
Two kinds of memory:
Declarative memory
deals with
what
—facts and information acquired through learning that can be stated or described. (Things we are aware that are learned.)
Nondeclarative (procedural) memory
deals with
how
—shown by performance rather than conscious recollection.Slide12
Figure 17.3 Two Main Kinds of Memory: Declarative and NondeclarativeSlide13
17 There Are Several Kinds of Memory and Learning
Damage to other areas can also cause memory
loss.
Patient
N.A.
has amnesia due to accidental
damage
to the
left dorsal
thalamus, bilateral damage to the
mammillary bodies
(limbic structures in the hypothalamus), and
probable damage
to the
mammillothalamic
tract.
Like
Henry
Molaison
, he has short-term memory but cannot form declarative long-term memories.Slide14
Figure 17.4 The Brain Damage in Patient N.A.Slide15
17 There Are Several Kinds of Memory and Learning
Korsakoff
’
s syndrome
is a memory deficiency caused by lack of thiamine—seen in chronic alcoholism.
Patients often
confabulate
—fill in a gap in memory with a falsification which they accept as true.
Brain damage occurs in mammillary bodies and dorsomedial thalamus, similar to N.A., and to the basal frontal cortex.Slide16
17 There Are Several Kinds of Memory and Learning
Two subtypes of declarative memory:
Semantic memory
—generalized memory
Episodic memory
—detailed autobiographical memory
Patient K.C.
cannot retrieve personal (
episodic
) memory due to accidental damage to the cortex and severe shrinkage of the hippocampus and parahippocampal cortex; his semantic memory is good.Slide17
17 There Are Several Kinds of Memory and Learning
Three subtypes of nondeclarative memory:
Skill learning
—learning to perform a task requiring motor coordination.
Priming
—
repetition priming
—a change in stimulus processing due to prior exposure to the stimulus.
Conditioning
—the association of two stimuli or of a stimulus and a response.Slide18
Figure 17.5 Subtypes of Declarative and Nondeclarative MemorySlide19
17 Memory Has Temporal Stages: Short, Intermediate, and Long
Iconic memories
are the briefest memories and store sensory impressions that only last a few seconds.
Short-term memories
(
STM
s) usually last only for up to 30 seconds or throughout rehearsal.
Short-term memory is also known as
working memory
.Slide20
Figure 17.6 Stages of Memory FormationSlide21
17 Memory Has Temporal Stages: Short, Intermediate, and Long
Working memory can be subdivided into three components, all supervised by an
executive control
module:
Phonological loop
—contains auditory information
Visuospatial sketch pad
—holds visual impressions
Episodic buffer
—contains more integrated, sensory informationSlide22
17 Memory Has Temporal Stages: Short, Intermediate, and Long
An
intermediate-term memory
(
ITM
) outlasts a STM, but is not permanent.
Long-term memories
(
LTM
s) last for days to years.Slide23
17 Memory Has Temporal Stages: Short, Intermediate, and Long
Mechanisms differ for STM and LTM storage but are similar across species.
The
primacy effect
is the higher performance for items at the beginning of a list (LTM).
The
recency effect
shows better performance for the items at the end of a list (STM).Slide24
Figure 17.7 Serial Position Curves from Immediate-Recall Experiments (Part 1)Slide25
Figure 17.7 Serial Position Curves from Immediate-Recall Experiments (Part 2)Slide26
17 Memory Has Temporal Stages: Short, Intermediate, and Long
Long-term memory has a large capacity.
Information can also be forgotten or recalled inaccurately.Slide27
17 Successive Processes Capture, Store, and Retrieve Information in the Brain
A functional memory system incorporates three aspects:
Encoding
—sensory information is passed into short-term memory.
Consolidation
—short-term memory information is transferred into long-term storage.
Retrieval
—stored information is used.Slide28
Figure 17.8 Hypothesized Memory Processes: Encoding, Consolidation, and RetrievalSlide29
17 Successive Processes Capture, Store, and Retrieve Information in the Brain
Multiple brain regions are involved in encoding, as shown by fMRI.
For recalling pictures, the right prefrontal cortex and parahippocampal cortex in both hemispheres are activated.
For recalling words, the left prefrontal cortex and the left parahippocampal cortex are activated.Slide30
17 Successive Processes Capture, Store, and Retrieve Information in the Brain
Thus, the prefrontal cortex and parahippocampal cortex are important for consolidation.
These mechanisms reflect hemispheric specializations
(left hemisphere for language and right hemisphere for spatial ability).Slide31
17 Successive Processes Capture, Store, and Retrieve Information in the Brain
The
engram,
or
memory trace
, is the physical record of a learning experience and can be affected by other events before or after.
Each time a memory trace is activated and recalled, it is subject to changes.Slide32
17 Successive Processes Capture, Store, and Retrieve Information in the Brain
Consolidation of memory involves the hippocampus, but the hippocampal system does not store long-term memory.
LTM storage occurs in the cortex, near where the memory was first processed and held in short-term memory.Slide33
Figure 17.9 Encoding, Consolidation, and Retrieval of Declarative MemoriesSlide34
17 Successive Processes Capture, Store, and Retrieve Information in the Brain
In
posttraumatic stress disorder
(
PTSD
,
characterized as
reliving and being preoccupied by traumatic events)
, memories
produce
stress
hormones that further reinforce
the memory
.
GABA,
ACh
, and opioid transmission can also enhance memory formation in animal models.
Treatments that can block chemicals acting on the
basolateral
amygdala may alter the effect of emotion on memories.Slide35
Box 17.1 The Amygdala and MemorySlide36
17 Successive Processes Capture, Store, and Retrieve Information in the Brain
The process of retrieving information from LTM can cause memories to become unstable and susceptible to
disruption
or alteration.
Reconsolidation
is the return of a memory trace to stable long-term storage after it
’
s temporarily volatile during recall.Slide37
17 Successive Processes Capture, Store, and Retrieve Information in the Brain
Reconsolidation can distort memories.
Successive activations can deviate from original information.
New information during recall can also influence the memory trace.Slide38
17 Successive Processes Capture, Store, and Retrieve Information in the Brain
Leading questions can lead to
‘
remembering
’
events that never happened.
‘
Recovered memories
’
and
‘
guided imagery
’
can have false information implanted into the recollection.Slide39
Figure 17.10 Are
“
Recovered
”
Memories Reliable?Slide40
17 Different Brain Regions Process Different Aspects of Memory
Testing declarative memories in monkeys:
Delayed non-matching-to-sample task
—a test of
object recognition memory
, where the subject must choose the object that was
not
seen previously.Slide41
Figure 17.11 The Delayed Non-Matching-to-Sample TaskSlide42
17 Different Brain Regions Process Different Aspects of Memory
Medial temporal lobe damage causes impairment on the delayed nonmatching-to-sample task.
The amygdala is not necessary for declarative memory tasks.
The hippocampus (in conjunction with the entorhinal, parahippocampal) and perirhinal cortices, is important for these tasks.Slide43
Figure 17.12 Memory Performance after Medial Temporal Lobe LesionsSlide44
17 Different Brain Regions Process Different Aspects of Memory
Imaging studies confirm the importance of medial temporal (hippocampal) and diencephalic regions in forming long-term memories.
Both are activated during encoding and retrieval, but long-term storage depends on the cortex.Slide45
17 Different Brain Regions Process Different Aspects of Memory
Episodic
and
semantic
memories are processed in different areas.
Episodic
(autobiographical) memories cause greater activation of the right frontal and temporal lobes.Slide46
Figure 17.13 My Story versus Your StorySlide47
17 Different Brain Regions Process Different Aspects of Memory
Early research indicated that animals form a
cognitive map
—a mental representation of spatial relationships.
Latent learning
is when acquisition has taken place but has not been demonstrated in performance tasks.Slide48
Figure 17.14 Biological Psychologists at WorkSlide49
17 Different Brain Regions Process Different Aspects of Memory
The hippocampus is also important in spatial learning.
It contains
place cells
that become active when in, or moving toward, a particular location.
Place cells remap when a rodent is placed in a new environment.Slide50
17 Different Brain Regions Process Different Aspects of Memory
Grid cells
and
border cells
are neurons that fire when animal is at an intersection and at the perimeter of an abstract grid map, respectively.Slide51
17 Different Brain Regions Process Different Aspects of Memory
In rats,
place cells
in the hippocampus are more active as the animal moves toward a particular location.
In monkeys,
spatial view cells
in the hippocampus respond to what the animal is looking at. Slide52
17 Different Brain Regions Process Different Aspects of Memory
Comparisons of behaviors and brain anatomy show that increased demand for spatial memory results in increased hippocampal size (relative to the rest of the brain) in mammals and birds.
In food-storing species of birds, the hippocampus is larger but only if used to retrieve stored food.Slide53
Figure 6.6 Food Storing in Birds as Related to Hippocampal SizeSlide54
17 Different Brain Regions Process Different Aspects of Memory
Spatial memory and hippocampal size can change within the life span.
In some species, there can be sex differences in spatial memory, depending on behavior.
Polygynous male meadow voles travel further (to find females) and have a larger hippocampus than female meadow voles or males of monogamous pine voles.Slide55
Figure 17.15 Sex, Memory, and Hippocampal SizeSlide56
17 Different Brain Regions Process Different Aspects of Memory
Imaging studies help to understand learning and nondeclarative memory for different skills:
Sensorimotor skills
, such as mirror-tracing.
Perceptual skills
—learning to read mirror-reversed text.
Cognitive skills
—planning and problem solving.
All three of these depend on functional basal ganglia; the motor cortex and cerebellum are also important for some skills.Slide57
17 Different Brain Regions Process Different Aspects of Memory
Imaging studies of repetition priming show
reduced
bilateral activity in the occipitotemporal cortex, related to perceptual priming.
Perceptual priming reflects prior processing of the
form
of the stimulus.
Conceptual priming (priming based on word
meaning
) is associated with reduced activation of the left frontal cortex.Slide58
17 Different Brain Regions Process Different Aspects of Memory
Imaging of conditioned responses can show changes in activity.
PET scans made during eye-blink tests show increased activity in several brain regions, but not all may be essential.
Patients with unilateral cerebellar damage can acquire the conditioned eye-blink response only on the intact side.Slide59
17 Different Brain Regions Process Different Aspects of Memory
Different brain regions are involved with different attributes of working memories such as space, time, or sensory perception.
Memory tasks assess the contributions of each brain region.Slide60
17 Different Brain Regions Process Different Aspects of Memory
The eight-arm radial maze is used to test
spatial
location memory.
Rats must recognize and enter an arm that they have entered recently to receive a reward.
Only lesions of the hippocampus produce a deficit in this predominantly spatial task.Slide61
Figure 17.16 Tests of Specific Attributes of Memory (Part 1)Slide62
17 Different Brain Regions Process Different Aspects of Memory
In a memory
test of
motor
behavior, the animal must remember whether it made a left or right turn previously.
If it turns the same way as before, it receives a reward.
Only animals with lesions to the caudate nucleus showed deficits.Slide63
Figure 17.16 Tests of Specific Attributes of Memory (Part 2)Slide64
17 Different Brain Regions Process Different Aspects of Memory
Sensory perception
can be measured by the object recognition task.
Rats must identify which stimulus in a pair is novel.
This task depends on the extrastriate cortex.Slide65
Figure 17.16 Tests of Specific Attributes of Memory (Part 3)Slide66
17 Different Brain Regions Process Different Aspects of Memory
Interim summary of brain regions involved in learning and memory:
Many brain regions are involved.
Different forms of memory are mediated by at least partly different mechanisms and brain structures.
The same brain structure may be involved in many forms of learning.Slide67
Figure 17.17 Brain Regions Involved in Different Kinds of Learning and MemorySlide68
17 Neural Mechanisms of Memory Storage
Molecular, synaptic, and cellular events store information in the nervous system.
New learning and memory formation can involve new neurons, new synapses, or changes in synapses in response to biochemical signals.
Neuroplasticity
(or
neural plasticity
) is the ability of neurons and neural circuits to be remodeled by experience or the environment.Slide69
17 Memory Storage Requires Neuronal Remodeling
Sherrington speculated that alterations in
synapses
were the basis for learning.
Synaptic changes can be measured physiologically, and may be presynaptic, postsynaptic, or both.
Changes include increased neurotransmitter release and/or a greater effect due to changes in neurotransmitter-receptor interactions.Slide70
Figure 17.18 Synaptic Changes That May Store Memories (Part 1)Slide71
17 Memory Storage Requires Neuronal Remodeling
Changes in the rate of
inactivation
of transmitter would also increase effects.
Inputs from other neurons might increase or decrease neurotransmitter release.Slide72
17 Memory Storage Requires Neuronal Remodeling
Structural changes at the synapse may provide long-term storage.
New synapses could form or some could be eliminated with training.
Training might also lead to synaptic reorganization.Slide73
Figure 17.18 Synaptic Changes That May Store Memories (Part 2)Slide74
Figure 17.18 Synaptic Changes That May Store Memories (Part 3)Slide75
Figure 17.18 Synaptic Changes That May Store Memories (Part 4)Slide76
17 Memory Storage Requires Neuronal Remodeling
Lab animals living in a complex environment demonstrated biochemical and anatomical brain changes from those living in simpler environments.
Three housing conditions:
Standard condition
(
SC
)
Impoverished
(or
isolated
)
condition
(
IC
)
Enriched condition
(
EC
)Slide77
Figure 17.19 Experimental Environments to Test the Effects of Enrichment on Learning and Brain MeasuresSlide78
17 Memory Storage Requires Neuronal Remodeling
Animals housed in EC, compared to those in IC, developed:
heavier, thicker cortex;
enhanced cholinergic activity;
More dendritic branches (especially on
basal dendrites
near the cell body), with more dendritic spines suggesting more synapses.Slide79
Figure 17.20 Measurement of Dendritic Branching (Part 1)Slide80
Figure 17.20 Measurement of Dendritic Branching (Part 2)Slide81
Figure 17.20 Measurement of Dendritic Branching (Part 3)Slide82
17 Invertebrate Nervous Systems Show Plasticity
Aplysia
is used to study plastic synaptic changes in neural circuits.
The advantages of
Aplysia
:
Has fewer nerve cells
Can create detailed circuit maps for particular behaviors—little variation between individualsSlide83
17 Invertebrate Nervous Systems Show Plasticity
Invertebrates demonstrate
nonassociative learning
which involves a single stimulus presented once or repeated.
Three types of nonassociative learning:
Habituation
—a decreased response to repeated presentations of a stimulus.
Dishabituation
—restoration of response amplitude after habituation.
Sensitization
—prior strong stimulation increases response to most stimuli.Slide84
17 Invertebrate Nervous Systems Show Plasticity
Habituation is studied in
Aplysia
.
Squirts of water on its siphon causes it to retract its gill.
After repeated squirts, the animal retracts the gills less; it has learned that the water poses no danger.Slide85
Figure 17.21 The Sea Slug
AplysiaSlide86
17 Invertebrate Nervous Systems Show Plasticity
The habituation is caused by synaptic changes between the sensory cell in the siphon and the motoneuron that retracts the gill.
Less transmitter released in the synapse results in less retraction.Slide87
Figure 17.22 Synaptic Plasticity Underlying Habituation in
Aplysia
(Part 1)Slide88
17 Invertebrate Nervous Systems Show Plasticity
Over several days, the animal habituates faster, representing long-term habituation.
The number of synapses between the sensory cell and the motoneuron is reduced. Slide89
Figure 17.22 Synaptic Plasticity Underlying Habituation in
Aplysia
(Part 2)Slide90
17 Synaptic Plasticity Can Be Measured in Simple Hippocampal Circuits
Hebb proposed that when two neurons are repeatedly activated together, their synaptic connection will become stronger.
Cell assemblies
—ensembles of neurons— linked via
Hebbian synapses
could store memory traces.
Hebb
’
s idea was supported when researchers used
tetanus
(a brief increase of electrical stimulation that triggers thousands of axon potentials) on the hippocampus.Slide91
17 Synaptic Plasticity Can Be Measured in Simple Hippocampal Circuits
Long-term potentiation
(
LTP
)—a stable and enduring increase in the effectiveness of synapses.
A weakening of synaptic efficacy—termed
long-term depression
—can also encode information.Slide92
Figure 17.23 Long-Term Potentiation Occurs in the Hippocampus (Part 1)Slide93
17 Synaptic Plasticity Can Be Measured in Simple Hippocampal Circuits
Synapses in LTP behave like Hebbian synapses:
Tetanus drives repeated firing.
Postsynaptic targets fire repeatedly due to the stimulation.
Synapses are stronger than before.Slide94
17 Synaptic Plasticity Can Be Measured in Simple Hippocampal Circuits
LTP can be generated in conscious and freely behaving animals, in anesthetized animals, and in tissue slices and that LTP is evident in a variety of invertebrate and vertebrate species.
LTP can also last for weeks or more.
Superficially, LTP appears to have the hallmarks of a cellular mechanism of memory.Slide95
17 Synaptic Plasticity Can Be Measured in Simple Hippocampal Circuits
LTP occurs at several sites in the
hippocampal formation
—formed by the
hippocampus
, the
dentate gyrus
and the
subiculum
(also called
subicular complex
or
hippocampal gyrus
).
The hippocampus has regions called
CA1
,
CA2
, and
CA3
(CA=Cornus Ammon which means Ammon
’
s Horn). Slide96
Figure 17.23 Long-Term Potentiation Occurs in the Hippocampus (Part 2)Slide97
17 Synaptic Plasticity Can Be Measured in Simple Hippocampal Circuits
The CA1 region has two kinds of glutamate receptors:
NMDA receptors
(after its selective ligand,
N
-
m
ethyl-
D
-
a
spartate
)
AMPA receptors
(which bind the glutamate agonist AMPA)Slide98
17 Synaptic Plasticity Can Be Measured in Simple Hippocampal Circuits
Glutamate first activates AMPA receptors.
NMDA receptors do not respond until enough AMPA receptors are stimulated, and the neuron is partially depolarized.Slide99
17 Synaptic Plasticity Can Be Measured in Simple Hippocampal Circuits
NMDA receptors at rest have a magnesium ion (Mg
2+
) block on their calcium (Ca
2+
) channels.
After partial depolarization, the block is removed, and the NMDA receptor allows Ca
2+
to enter in response to glutamate.Slide100
Figure 17.24 Roles of the NMDA and AMPA Receptors in the Induction of LTP in the CA1 Region (Part 1)Slide101
Figure 17.24 Roles of the NMDA and AMPA Receptors in the Induction of LTP in the CA1 Region (Part 2)Slide102
17 Synaptic Plasticity Can Be Measured in Simple Hippocampal Circuits
The large Ca
2+
influx activates certain
protein kinases
—enzymes that add phosphate groups to protein molecules.
One protein kinase is CaMKII (calcium-calmodulin kinase II) which affects AMPA receptors in several ways:
Causes more AMPA receptors to be produced and inserted in the postsynaptic membrane.Slide103
17 Synaptic Plasticity Can Be Measured in Simple Hippocampal Circuits
CaMKII:
Moves existing nearby AMPA receptors into the active synapse.
Increases conductance of Na
+
and K
+
ions in membrane-bound AMPA receptors.
These effects all increase the synaptic sensitivity to glutamate.Slide104
Figure 17.24 Roles of the NMDA and AMPA Receptors in the Induction of LTP in the CA1 Region (Part 3)Slide105
17 Synaptic Plasticity Can Be Measured in Simple Hippocampal Circuits
The activated protein kinases also trigger protein synthesis.
Kinases activate
CREB
—
c
AMP
r
esponsive
e
lement-
b
inding protein
.Slide106
17 Synaptic Plasticity Can Be Measured in Simple Hippocampal Circuits
CREB binds to
cAMP responsive elements
in DNA promoter regions.
CREB changes the transcription rate of genes.
The regulated genes then produce proteins that affect synaptic function and contribute to LTP.Slide107
Figure 17.25 Steps in the Neurochemical Cascade during the Induction of LTPSlide108
17 Synaptic Plasticity Can Be Measured in Simple Hippocampal Circuits
Strong stimulation of a postsynaptic cell releases a
retrograde messenger
, often a diffusible gas like carbon monoxide (CO) or nitric oxide (NO) or
that travels across the synapse and alters function in the
presynaptic
neuron.
More glutamate is released and the synapse is strengthened.Slide109
17 Synaptic Plasticity Can Be Measured in Simple Hippocampal Circuits
LTP can occur without NMDA receptor activation.
There is evidence that LTP may be one part of learning and memory formation:
Correlational observations
—time course of LTP is similar to that of memory formation.Slide110
17 Synaptic Plasticity Can Be Measured in Simple Hippocampal Circuits
Somatic intervention experiments
— pharmacological treatments that block LTP impair learning.
Behavioral intervention experiments
— training an animal in a memory task can induce LTP.Slide111
17 Some Simple Learning Relies on Circuits in the Mammalian Cerebellum
Associative learning
involves relations between events.
In
instrumental conditioning
—or
operant conditioning
—an association is made between:
Behavior (the instrumental response).
The consequences of the behavior (the reward).Slide112
Figure 17.26 Two Types of Conditioning (Part 1)Slide113
17 Some Simple Learning Relies on Circuits in the Mammalian Cerebellum
In
classical conditioning
—
Pavlovian conditioning
—a neutral stimulus is paired with another stimulus that elicits a response.
Eventually, the neutral stimulus by itself will elicit the response.Slide114
Figure 17.26 Two Types of Conditioning (Part 2)Slide115
17 Some Simple Learning Relies on Circuits in the Mammalian Cerebellum
Researchers use the eye-blink reflex to study neural circuits in mammals.
An air puff is preceded by an acoustic tone; conditioned animals will blink when just the tone is heard.
A circuit in the cerebellum is necessary for this reflex.Slide116
Figure 17.27 Functioning of the Neural Circuit for Conditioning of the Eye-Blink Reflex (Part 1)Slide117
Figure 17.27 Functioning of the Neural Circuit for Conditioning of the Eye-Blink Reflex (Part 2)Slide118
Figure 17.27 Functioning of the Neural Circuit for Conditioning of the Eye-Blink Reflex (Part 3)Slide119
17 Some Simple Learning Relies on Circuits in the Mammalian Cerebellum
The trigeminal (V) pathway that carries information about the corneal stimulation (the US) to the cranial motor nuclei also sends axons to the brainstem (specifically a structure called the
inferior olive
).
These brainstem neurons, in turn, send axons called
climbing fibers
to synapse on cerebellar neurons in a region called the
interpositus nucleus
.Slide120
17 Some Simple Learning Relies on Circuits in the Mammalian Cerebellum
Blocking GABA in interpositus nucleus stops the behavioral response.
The cerebellum is also important in conditioning of emotions and cognitive learning, as shown by humans with cerebellar damage.Slide121
17 In the Adult Brain, Newly Born Neurons May Aid Learning
Neurogenesis
, or birth of new neurons, occurs mainly in the dentate gyrus in adult mammals.
Neurogenesis and neuronal survival can be enhanced by exercise, environmental enrichment, and memory tasks.
Reproductive hormones and experience are also an influence.Slide122
Figure 17.28 Neurogenesis in the Dentate GyrusSlide123
17 In the Adult Brain, Newly Born Neurons May Aid Learning
In some studies, neurogenesis has been implicated in hippocampus-dependent learning.
Conditional knockout
mice, with neurogenesis selectively turned off in specific tissues in adults, showed impaired spatial learning but were otherwise normal.Slide124
17 In the Adult Brain, Newly Born Neurons May Aid Learning
G
enetic
manipulations
can increase
the survival of newly generated neurons in the dentate, resulting in
improved
performance.
These
animals showed enhanced hippocampal LTP
, which
was expected since younger neurons display greater synaptic
plasticity.Slide125
17 In the Adult Brain, Newly Born Neurons May Aid Learning
Adult neurogenesis is also seen in the olfactory bulb.
Activation of newly generated neurons in the olfactory bulb enhances olfactory learning and memory.Slide126
17 Learning and Memory Change as We Age
With age, we tend to show some memory impairment in tasks of conscious recollection that:
require effort, and
rely primarily on internal generation of the memory rather than on external cues.
We also experience some decreases in spatial memory and navigational skills.Slide127
17 Learning and Memory Change as We Age
Some causes of memory problems in old age:
Impairments of coding and retrieval— less cortical activation in some tasks.
Loss of neurons and/or neural connections; some parts of the brain lose a larger proportion of volume.Slide128
Figure 17.29 Active Brain Regions during Encoding and Retrieval Tasks in Young and Old PeopleSlide129
17 Learning and Memory Change as We Age
Deterioration of cholinergic pathways—the
septal complex
and the
nucleus basalis of Meynert
(
NBM
) provide cholinergic input to the hippocampus and cortex.
Cholinergic pathways to the cortex are lost in Alzheimer
’
s disease.
Enhancing cholinergic transmission helps with memory tasks.Slide130
17 Learning and Memory Change as We Age
Nootropics
are a class of drugs that enhance cognitive function.
Cholinesterase inhibitors result can have a positive effect on memory and cognition.
Ampakines
, which act via glutamate receptors, work to improve LTP in the hippocampus. Slide131
17 Learning and Memory Change as We Age
One particular protein kinase—PKMζ (ζ is zeta)—is needed for long-term maintenance of both hippocampal LTP and cortical memory traces.
Highly selective memory enhancing drugs could be developed in the near future.Slide132
17 Learning and Memory Change as We Age
Lifestyle factors can help reduce cognitive decline:
Living in a favorable environment
Involvement in complex and intellectually stimulating activities
Having a partner of high cognitive statusSlide133
17 The Cutting Edge: Artificial Activation of an Engram
Mice were placed in two contexts:
Context A—placed in a box with a white plastic floor in a dimly lit room with black walls and a faint smell of almonds; these mice explored the chamber and showed no signs of being afraid.
Context B—classically conditioned to a tone with electrical shock; these mice learned to freeze to the tone.Slide134
17 The Cutting Edge: Artificial Activation of an Engram
These mice had also been genetically modified so that whenever neurons in the dentate gyrus (DG) of the hippocampus were active, they would start producing channelrhodopsin, a protein that would excite those cells, and only those cells, when exposed to blue light.Slide135
Figure 17.31 Artificial Activation of an Engram (Part 1)Slide136
17 The Cutting Edge: Artificial Activation of an Engram
Activity of the subset of DG neurons with channelrhodopsin was responsible for the mice finding context B frightening.
Reactivating those neurons caused the mice to freeze in fear, even when they were in a completely different context.Slide137
Figure 17.31 Artificial Activation of an Engram (Part 2)Slide138
17 The Cutting Edge: Artificial Activation of an Engram
Turning the light off again caused the animals to resume activity, indicating that they remained unafraid of context A.
It wasn
’
t just that light-induced activation of any random set of DG neurons induced fear, because when blue light reactivated DG neurons that had been active in a third (nonfearful) context, C, the animals did not freeze.Slide139
Figure 17.31 Artificial Activation of an Engram (Part 3)Slide140
Figure 17.31 Artificial Activation of an Engram (Part 4)