Chapter 14: Learning and Memory Flashcards
How do we learn and remember?
connecting learning and memory
dissociating memory circuits
neural systems underlying explicit and implicit memories
structural basis of brain plasticity
recovery from brain injury
What are types of experiences that change the brain?
development, culture, preferences, coping
learning is common to these experiences
What is neuroplasticity?
the nervous system’s potential for physical or chemical change, which enhances its adaptability
What is learning?
a relatively permanent change in an organism’s behavior as a result of experience
What is memory?
the ability to recall or recognize previous experience
a mental representation of a previous experience
corresponds to a physical trace (engram) in the brain, most likely involving synapses
What is Pavlovian conditioning?
learning achieved when a neutral stimulus (such as a tone) comes to elicit a response after its repeated pairing with some event (such as delivery of food)
also called classical conditioning or respondent conditioning
What is an conditioned stimulus (CS)?
in Pavlovian conditioning, an originally neutral stimulus that triggers a conditioned response (CR) after association with an unconditioned stimulus
What is an unconditioned stimulus (UCS)?
a stimulus that naturally and automatically (unconditionally) triggers an unconditioned response (UCR)
What is an unconditioned response (UCR)?
unlearned, naturally occurring response to an unconditioned stimulus (UCS), such as salivation when food is in the mouth
What is a conditioned response (CR)?
in Pavlovian conditioning, the learned response to a formerly neutral conditioned stimulus
What is the eyeblink conditioning experiment?
a tone (CS) is associated with a painless puff of air (UCS) to a participant’s eye
blinking is a normal reaction (UCR) to a puff of air
learning has occurred when blinking is a response to the CS alone (CR)
What is operant conditioning?
learning procedure in which the consequences (such as obtaining a reward) of a particular behavior (such as pressing a bar) increase or decrease the probability of the behavior occurring again
also called instrumental conditioning
What was Thorndike’s puzzle box?
a cat gradually learned that its actions had consequences
on the initial trial, the cat touched the releasing mechanism only by chance as it restlessly paced inside the box
the cat learned that something it had done opened the door, and it tended to repeat its behaviors from just before the door opened
What is implicit memory?
unconscious memory
subjects demonstrate knowledge, such as a skill, conditioned response, or recalling events on prompting, but cannot explicitly retrieve the information
What is explicit memory?
conscious memory
subjects can retrieve an item and indicate that they know the retrieved item is the correct one
What is the pursuit-rotor task?
people with amnesia, a partial or total loss of memory, perform at normal on tests on implicit memory
presented with the same task a week later, both controls and amnesiacs take less time to perform it
amnesiacs fail to recall having performed the task before
What is declarative memory?
ability to recount what one knows, to detail the time, place, and circumstances of events; often lost in amnesia
same thing as explicit memory
What is procedural memory?
ability to recall a movement sequence or how to perform some act or behavior
same thing as implicit memory
How is implicit information processed?
implicit information is processed in a bottom-up, or data-driven, manner
information is encoded in the same way it was perceived
How is explicit information processed?
explicit information is processed in a top-down, or conceptually driven, manner
the subject recognizes the information before it is encoded
How are implicit and explicit tasks encoded in memory?
in implicit tasks, the person has a passive role, whereas in explicit tasks, the person has an active role
What is priming?
using a stimulus to sensitize the nervous system to a later presentation of the same or a similar stimulus, often used to measure implicit memory
What is short term memory?
few minutes
information is held in memory only briefly, then discarded; involves the frontal lobes
What is long term memory?
indefinite duration
information is held in memory indefinitely, perhaps for a lifetime; involves the temporal lobe
How is memory stored?
information from different sensory modalities (e.g. vision, audition) is processed and stored in different neural areas
What is episodic memory?
autobiographical memory for events pegged to specific place and time contexts
What is episodic amnesia?
inability to recall any personal experience
associated with frontal lobe injury or reduced blood flow to the frontal lobes
frontal loves may allow us to mentally travel through our past
What is highly superior autobiographical memory (HSAM)?
people display virtually complete recall for events in their lives, usually beginning around age 10
many can describe any episode, including the day of the week and the date
increased gray matter in the temporal and parietal lobes
increased size in the fiber projection between the temporal and frontal lobes
still vulnerable to distortions
What did Karl Lashley study regarding memory circuits?
searched in vain for the neural circuits underlying memories
severity of memory disturbance related to size, not location, of injury
What was discovered through the bilateral medial temporal lobe resection of H.M.?
seizures originated in the region of the amygdala, hippocampal formation, and associated subcortical structures, so Scoville removed them bilaterally
following surgery, H.M. had severe amnesia, lacking any explicit memory
he could not recall anything that happened after the surgery
despite this deficit, H.M. had an above-average IQ, performed well on perceptual tests, and could recall events from his childhood
H.M.’s performance on implicit memory tests was left intact
What is the parahippocampal cortex?
receives connections from the parietal cortex
believed to take part in visuospatial processing
What is the perirhinal cortex?
receives connections from the visual regions of the ventral stream
believed to take part in visual object memory
What is the entorhinal cortex?
located on the medial temporal lobe surface
provides a major route for neocortical input to the hippocampal formation
often degenerates in Alzheimer disease
What is visuospatial memory?
using visual information to identify an object’s location in space
laboratory animals and human patients with selective hippocampal injury have severe deficits in various forms of spatial memory
monkeys with hippocampal lesions have difficulty learning the location of objects
What does the hippocampus and spatial memory look like in animals?
animals with especially good spatial memory should have bigger hippocampi than do species with poorer spatial memories
the hippocampal formation in food-storing birds and rodents is larger than that of birds and rodents that do not store food
What are the three classes of spatial cells in the rat and mouse hippocampus?
place cells
head direction cells
grid cells
What are place cells in the rat and mouse hippocampus?
discharge when rats are in a spatial location regardless of orientation (hippocampus)
What are head direction cells in the rat and mouse hippocampus?
cells discharge whenever a rat’s head points in a particular direction
What are grid cells in the rat and mouse hippocampus?
discharge at many locations, forming a virtual grid invariant to changes in the rat’s direction, movement, or speed (entorhinal cortex)
How are connections for explicit memory in the temporal lobe pathway reciprocal?
connections from the neocortex run to the entorhinal cortex and then back to the neocortex
signals from the medial temporal regions to the cortical sensory regions keep the sensory experience alive in the brain, the neural record outlasts the actual experience
pathway back to the neocortex means it is kept apprised of the information being processed in medial temporal regions
What is the relationship between the frontal lobe and short term memory?
the frontal love appears to participate in many forms of short-term memory
all sensory systems project to the frontal lobes
during tasks in which monkeys must keep information in short-term memory over a delay, certain cells in the frontal cortex will fire throughout the delay (animals that have not learned the task show no such cell activity)
What is Korsakoff syndrome?
permanent loss of the ability to learn new information (anterograde amnesia) and to retrieve old information (retrograde amnesia)
caused by diencephalic damage from chronic alcoholism or malnutrition that produces a vitamin B1 deficiency
80% of these patients show loss of frontal lobe cells
What is the explicit memory circuit?
sensory/motor AREAS –> temporal regions –> medial thalamus & prefrontal cortex
temporal lobe/pfc are central to LTM formation
PFC central for ST explicit memories and recency of events
How does the hippocampus consolidate memory?
in consolidation, or stabilizing a memory trace after learning, memories move from the hippocampus to diffuse regions in the neocortex
once memories move, hippocampal involvement is no longer needed
What is distributed reinstatement theory?
a learning episode rapidly produces a stored memory representation that is strong in the hippocampus but weak elsewhere
the memory is replayed on the time scale of hours or days after learning, leading to enhanced representation outside the hippocampus
What is reconsolidation?
restabilizing a memory trace after the memory is revisited
whenever a memory is replayed in the mind, it is open to further consolidation
new information is constantly being integrated into existing memory networks
it is possible to erase negative memories by using amnesic agents when the memory is revisited (e.g. in PTSD)
What is the proposed neural circuit for explicit memory?
- temporal lobe structures
- frontal lobe structures
- medial thalamus
- basal forebrain - activating systems
What is the proposed neural circuit for implicit memory?
basal ganglia
ventral thalamus
substantia nigra
premotor cortex
What does the basal ganglia do in the neural circuit for implicit memories?
basal ganglia receive input from the entire neocortex and send projections first to the ventral thalamus and then to the premotor cortex
basal ganglia also receive widely and densely distributed projection from dopamine-producing cells in the substantia nigra
dopamine appears necessary for basal ganglia circuits to function and may indirectly participate in implicit memory formation
What is the unconscious nature of implicit memory?
Mishkin believes that implicit memories are unconscious because the connections between the basal ganglia and cortex are unidirectional
basal ganglia receive information from the cortex but do not project back to the cortex
for memories to be conscious, there must be feedback to the cortex
the medial temporal lobe projects back to the cortex, so explicit memories are conscious
What is emotional memory?
memory for the affective properties of stimuli or events
can be implicit or explicit
amygdala is critical for emotional memory
damage to the amygdala abolishes emotional memory but has little effect on implicit or explicit memory
we tend to remember emotionally arousing experiences vividly
emotionally driven neurochemical and hormonal activating systems (probably cholinergic and noradrenergic) stimulate the amygdala
What does the amygdala do in the neural circuit for implicit memories?
the amygdala has close connections with medial temporal cortical structures as well as with the rest of the cortex
Where does the amygdala send projections to in the neural circuit for implicit memory?
brainstem structures that control autonomic responses such as blood pressure and heart rate
the hypothalamus, which control hormonal system
periaqueductal gray matter (PAG), which affects pain perception
the basal ganglia, to tap into the implicit memory system
What is the structural basis of memory?
at the neural level, memory is associated with changes that take place at the synapse
the synapse is where one neuron influences another neuron
How do we find the neural correlated of memory?
determine how synaptic changes are correlated with memory in the mammalian brain
localize the synaptic changes to specific neural pathways
analyze the nature of the synaptic changes themselves
What is associative learning?
linkage of two or more unrelated stimuli to elicit a behavioral response
neurons that fire together, wire together
What is long-term potentiation (LTP)?
in response to stimulation at a synapse, changed amplitude of an excitatory postsynaptic potential that lasts for hours to days or longer
plays a part in associative learning
a strong burst of electrical stimulation applied to the presynaptic neuron produces an increase in the amplitude of the EPSP in the postsynaptic neuron
What is field potential?
EPSPs from many neurons; recorded with extracellular electrodes
What must happen for an EPSP to increase in size?
more neurotransmitter must be released from the presynaptic membrane
postsynaptic membrane must become more sensitive to the same amount of transmitter
What is long-term depression (LTD)?
decrease in EPSP size
if LTP is a mechanism for forming memories, perhaps LTD is a mechanism for clearing out old memories
What are the two types of receptors that glutamate acts on in the postsynaptic membrane?
AMPA (alpha-amino-3-hydroxy-5-methylisoxazole-4-proprionic acid) normally responds to glutamate
NMDA (N-methyl-D-aspartate) doubly gated channels, normally blocked by magnesium (Mg2+) ions
What two events must occur together for NMDA receptors to open?
depolarization of postsynaptic membrane, which displaces Mg2+ from pore (strong electrical stimulus)
activation by glutamate from the presynaptic neuron (weak electrical stimulus)
strong and weak stimuli have been paired
What happens after NMDA receptors open and Ca2+ enters the postsynaptic neuron?
increased responsiveness of AMPA receptors to glutamate
formation of new AMPA receptors
retrograde messengers that trigger more glutamate release from presynaptic neuron
What neural processes underlie the persistent long-term changes of learning?
Ca2+ enters postsynaptic neuron and activates a second messenger (e.g. cyclic AMP)
cAMP alters gene expression in nucleus, which physically alters synapse, structural changes in the synapse (dendritic spines), formation or loss of synapses
How does the brain modify existing circuits?
neurons change their structure in response to their changing experiences
changes in the number of dendrites can be used to infer synaptic changes, more dendrites provide more connections
new synapses can form between neurons that are already connected or between neurons that were not previously connected
What is the evidence of the brain creating novel circuits?
predominant view prior to the mid-1990s, the mammalian brain does not make new neurons in adulthood
there is evidence that neurogenesis does occur in the mammalian brain: olfactory bulb, hippocampal formation, and possibly neocortex
reason for neurogenesis still unclear
What is raising rats in enriched enclosures associated with?
increased brain weight
more dendrites
more astrocytes
more blood capillaries
more synapses per neuron
increased mitochondrial volume (marker of greater metabolic activity)
How did Chang and Greenough (1982) manipulate experience experimentally?
placed patches over one eye of each rat so that the contralateral hemisphere was deprived of visual input
trained rats on a maze
the visual cortex of the trained hemisphere (the one that received input from the eye without the patch) had more extensive dendrites
How did Nudo and colleagues (1997) manipulate experience experimentally?
had monkeys retrieve food from small or large food wells
small wells required dexterous movements of one or two fingers, whereas the monkeys could put their entire hand in the large wells
the digit representation on the motor cortex was larger for animals that had to retrieve food from the smaller wells
What is an example of life experiences altering dendritic morphology?
career word processors have greater differences between finger and trunk neurons than do salesperson
What is the epigenetic of memory?
specific sites in the DNA of neurons involved in specific memories might exist in either a methylated or nonmethylated state
fear conditioning is associated with rapid methylation, but if methylation was blocked, there was no memory
epigenetic mechanisms mediate synaptic plasticity broadly, especially in learning and memory
What is the relationship between hormones and plasticity?
high levels of estrogen: more dendritic spines in the hippocampus
low levels of estrogen: more dendritic spines in neocortex but fewer in hippocampus
low levels of testosterone: more dendritic spines in neocortex
What are glucocorticoids?
released from the adrenal cortex in times of stress
steady levels of glucocorticoids that are seen with prolonged stress may be neurotoxic
glucocorticoids can kill hippocampal cells
What is nerve growth factor?
neurotrophic factor that stimulates neurons to grow dendrites and synapses and in some cases promotes the survival of neurons
What is the brain-derived neurotrophic factor (BDNF)?
may enhance plastic changes, such as the growth of dendrites and synapses
increased levels when animals learn to solve problems
What is behavioral sensitization?
escalating behavioral response to the repeated administration of a psychomotor stimulant
sensitization is associated with an increased number of receptors, synapses, and dendrites
drug exposure alters brain response to experience
What are the guiding principles of brain plasticity?
behavioral change reflects brain change
all nervous systems are plastic in the same general way
plastic changes are age specific
prenatal events can influence brain plasticity throughout life
plastic changes are brain-region dependent
experience-dependent changes interact (metaplasticity)
plasticity has pros and cons
What are the three possible ways to recover from brain injury?
learn new ways to solve problems
recognize the brain to do more with less
generate new neurons to produce new circuits
What is the three-legged cat solution to brain injury?
when a cat loses a leg, it usually can compensate, not by growing a new leg but rather by learning how to walk with only three legs
the same ability to compensate is also present in humans
a person who loses a certain ability, such as being able to write with the right hand, may be able to compensate by learning to write with the left hand
What is the new-circuit solution to brain injury?
in response to injury, the brain can form new connections and do more with less
the amount of recovery is increased significantly if the person also engages in some form of intervention
behavioral therapy: speech or physiotherapy
pharmacological therapy: nerve growth factor, amphetamine
