Chapter 14 Flashcards
Learning
Relatively permanent change in an organisms behaviour as a result of experience
Memory
Ability to recall or recognize previous experience
Engram
Physical trace of a memory in the brain
Classical conditioning (Pavlovian)
Neutral stimulus comes to elicit a response after its repeated pairing with some event
Eye-blink conditioning
Tone is the conditioned stimulus that comes to elicit an eye blink
Air puff is the unconditioned stimulus and blinking in response to the airpuff is the unconditioned response
Blinking in response tp the tone is the conditioned response
Eye-blink conditioning is mediated by the ____
Cerebellum
Fear conditioning
Unpleasant stimulus is used to elicit an emotional response
Tone presented before a shock comes to elicit a fear response without the shock
Fear conditioning is mediated by the_______
Amygdala
Operant conditioning (instrumental conditioning)
Learning in which the consequences of a particular behaviour increase or decrease the probability of the behaviour occurring again
Reinforcement and punishment
Not localized to any brain circuit
Thorndike and operant conditioning
Cat had to press a lever to get out of a box in order to eat a fish
Reward of the fish reinforced the behaviour
Skinner and operant conditioning
Reinforcement to train rats to press bars to obtain food
Implicit memory
Unconscious awareness
Demonstrate knowledge on prompting but cannot directly retrieve the information
Priming
Exposure to a stimulus influences a response to a later stimulus
Implicit
Explicit memory
Conscious memory
Can retrieve a memory and indicate they know the retrieved item Is correct
Declarative memory
Specific contents of experiences that can be verbally recalled
Procedural memory
Ability to perform a task and recall a movement sequence
Encoding
Information is changed into a form that can be stored in the brain
Appears to involve modification of synapses, changes in gene expression, modification of proteins
Encoding of implicit information
Encoded similar to how to is perceived
Bottom up
Person plays a passive role
Encoding of explicit memory
Depends on conceptually driven processing
Top down
Reorganizing information
Individual plays an active role
Storing semantic memories
Studies show a network of 7 left-hemisphere regions involved
Similar to the default network, appears the semantic processing makes up a large component of cognitive activity during passive states
Episodic memory
Autobiographical memory, part of explicit memory
Record of events, our presence and role
Key regions of episodic memory
Ventromedial prefrontal cortex
Hippocampus
Pathways between the two
Loss of episodic memory (K.C)
Cognitive abilities and short-term memory intact but could not recall personally experienced events from his entire life
Highly superior autobiographical memory
Virtually complete recall for events in their lives beginning around age 10
Increased grey matter in temporal and parietal lobes
Increased fibre projections between temporal and frontal lobes
Dissociating explicit memory (Patient H.M.)
Removal of anterior hippocampus, amygdala, adjacent cortex
Severe anterograde amnesia- could not recall anything that happened since the surgery
Past memory and implicit memory intact
Disconnecting implicit memory (Patient J.K.)
Basal ganglia dysfunction
Memory disturbances related to tasks he had performed his whole life
3 medial temporal areas involved in explicit memories
Entorhinal cortex
Parahippocampal cortex
Perirhinal cortex
Perirhinal cortex
Receives input from the visual ventral stream
For visual object memory
Parahippocampal cortex
Receives input from the parietal visual regions
For visuospatial memory
Entorhinal cortex
Receives projections from the perirhinal and parahippocampal regions
Integrative memory functions
The hippocampus and spatial memory
Visuospatial memory for places
Selective hippocampal injury= deficits in spatial memory and difficulty with visuospatial learning
Perirhinal lesions in monkeys
Impaired at visual-recognition tasks
Parahippocampal lesions in monkeys
Impaired at object-position taks
Place cells
Discharge when in a spatial location regardless of orientation
In the hippocampus
Head direction cells
Discharge when head points in a particular direction
In the hippocampus
Grid cells
Discharge at many locations
form a virtual grid invariant to changes in direction, movement, or speed
In the entorhinal cortex
Reciprocal connections for explicit memory
The temporal lobe pathway is reciprocal: neocortex to the entorhinal cortex back to the neocortex
Keeps the sensory experience alive in the brain so the neural record outlasts the experience
Keeps the neocortex appraised of the information being processed in the medial temporal regions
Frontal lobe’s role in memory
Short term memory
Delayed response task
A monkey is shown 2 lights, it must choose the one in the same position as the cue shown earlier
Delayed-alternation task
Monkey is shown 2 lights must choose the one not in the same location as the cue shown earlier
Delayed matching to sample task
A monkey is shown a green light, then a red and a green light
It must choose the green light
Korsakoff syndrome
Explicit memory disturbance from chronic alcohol abuse, kills cells in he medial diencephalon and thalamus
Consolidation for explicit memories
Memories move from hippocampus to diffuse neocortical regions
The hippocampus consolidates new memories
Distributed reinstatement theory
An explicit learning episode produces a stored memory representation that is strong in the hippocampus and weak elsewhere
The memory is replayed after the learning leading to enhanced representations outside the hippocampus
Reconsolidation
Whenever a memory is played in the mind it is open to further consolidation
Restabilizing a memory trace
Memories are changeable
Neural circuit for implicit memories
The basal ganglia receive input from the entire neocortex-only one direction, unconscious
Sends projections to the ventral thalamus and the premotor cortex
Substantia nigra indirectly involved through dopamine projections
Why are implicit memories unconscious?
Because the connection from the cortex to the basal ganglia flows only one direction
Most of the neocortex receives no direct information from the basal ganglia
Neural circuit for emotional memories
Unique in that it involves the amygdala- mediates fear conditioning
Damage to amygdala abolishes emotional memory but has little effect on other types of memory
4 locations the amygdala sends projections to
Brainstem structures that control autonomic responses
Hypothalamus- hormones
Periaqueductal grey matter- pain perception
Enteric nervous system
Long-term potentiation
Long lasting increase in synaptic effectiveness after a high-frequency stimulation
More neurotransmitter released or the postsynaptic membrane becomes more sensitive
Increase in EPSP
Long-term depression
Long lasting decrease in synaptic effectiveness after low frequency electrical stimulation
Possible mechanism for cleaning out old memories
2 predictions about LTP and memory
When animals learn problems we should see enhanced LTP in the recruited pathways
LTP should produce enduring changes in synaptic morphology that resemble those seen in memory
AMPA receptors
Normally mediate responses produced when glutamate is released
NMDA receptors
Do not usually respond to glutamate because they are blocked my magnesium
Open if the postsynaptic membrane is depolarized which displaces the magnesium and the receptors are activated by glutamate
Synaptic change- modifying existing circuits
Changes in dendrites- more dendrites=more connections
Additional contacts between neurons already connected or contacts with a new neuron
New axon terminals
Formation of synapses along axons
Synaptic change- creating novel circuits
The adult brain is capable of generating new neurons
Enhances brain plasticity
May underly learning and memory as experience seems to increase the generation of new neurons
Benefits of enriched experience
Housing animals in environments providing sensory or motor experience enhanced later learning
Increase in brain weight independent of body weight
Experiment placing a patch over one eye of a rat then training them in a maze
Neurons in the visual cortex of the trained hemisphere (opposite of the eye able to see) had more extensive dendrites
Experience-dependent change in humans (Wernicke’s area and education)
Studies found relationship between dendrite size in Wernicke’s area and level of education
More dendritic branches when college-educated
Epigenetic explanation of why memories remain stable when cells are constantly undergoing molecular turnover
Specific sites in the DNA of neurons involved in memory may exist in methylated or non-methylated states
Epigenetic mechanisms mediate synaptic plasticity
Gonadal hormones and plasticity
Establish differences in cortical neurons
Continue to influence structure and behaviour in adulthood
Changes in estrogen levels on brain structure
Alters structures of the neurons and astrocytes in the neocortex and hippocampus
Decline in estrogen- greater synapses in the neocortex and less in the hippocampus
Stress hormones and plasticity
Pituitary produces adrenocorticotropic hormone which stimulates the adrenal cortex to produce glucocorticoids
With prolonged stress can kill hippocampal cells
Neurotrophic factors
Chemical compounds that signal stem cells to develop into neurons or glia, or reorganize neural circuits
Nerve growth factor
Stimulates growth of dendrites and synapses
Brain-derived neurotrophic factor (BDNF)
Increases when animals solve problems
Enhances plastic changes like the growth of dendrites and synapses
Behavioural sensitization
Progressive increase in behavioural actions in response to repeated administration of a drug
Memory for a particular drug, similar structural changes to other forms of learning - more receptors, more synapses
Localized to certain areas- nucleus accumbent
Three-legged cat solution to recovery from brain injury
Simplest solution
Cat loses leg, learns to compensate by walking on 3 legs
the behaviour changed to compensate
New-circuit solution to recovering from brain injury
The brain forms new connections to overcome losses
Behavioural therapy and recovery from brain injury
Therapy increases brain activity which facilitates neural changes
New-circuits
Pharmacological intervention and recovery from brain injury
Drugs to influence brain plasticity (eg nerve growth factor)
Neural growth needs to occur in brain regions that can influence a lost function
New circuits
Electrical stimulation and deep brain stimulation and recovery from brain injury
Electrical stimulation directly increases activity in the remaining parts of damaged networks
DBT puts the brain in a more plastic state for other rehab therapies
New circuits
