Download BRAIN PLASTICITY Neuroplasticity

11/2/2009
BRAIN PLASTICITY
Neuroplasticity: _________________________.
Happens in at least 3 ways:
- ________________________________________
__________________
- ______________________________
- ________________________________________
Recently, it was found that “new” neurons and
glial cells are born _____________ in specific
brain regions - reorganization.
Brain plasticity occurs during:
- _______________
- _______________________
- ______________________________
DEVELOPMENT OF NERVOUS SYSTEM:
1. Neural proliferation (neurogenesis - neuronal
“birth”)
2. Migration and differentiation (neural cell
precursors travel “home” and “grow up”)
3. Axon growth and synapse formation
(growth cones and filopodia)
4. Neuron death and synaptic pruning: too
many neurons and synapses produced
- competition for neurotrophic factors (ex.,
NGF - ___________________)
1
11/2/2009
Examples of the effects of EXPERIENCE on
NEURAL DEVELOPMENT and PLASTICITY
Early visual experience
- studies of early __________________________
found deprived eye to ______ ability to activate
visual cortex
- only occurs if other eye is open, not if it is also
deprived - ____________________
- these are structural effects - ________________
- concept of _______________________________
Two eyes open
One eye shut
Environment and the cortex
- studies of rat litters separated at birth into
_______________________________________
- enriched environments produces:
- ________________
- ______________________
- __________________
- more glial cells;
- larger postsynaptic zones;
- larger protein content.
- some of these effects can be produced in adult
animals by giving them extensive maze training
2
11/2/2009
LEARNING AND MEMORY
Learning: ________________________________
_________________________________________
_________________________________________
________________________________
ability to recall or recognize previous
Memory: _________________________________
________________________________________
experience in the form of behavioral change
change.
If behavior at a later time B is different than at
earlier time A, say that learning has taken place
between time A and B
TYPES OF LEARNING:
NON-ASSOCIATIVE LEARNING: _________
_______________________________________
________________________
A. Habituation: __________________________
______________________________________
__________
B. Sensitization: __________________________
_______________________________________
___________
Marine snail “Aplysia Californica”
T il
Tail
Head
Gill-withdrawal reflex used to study habituation
and sensitization (Eric Kandel’s laboratory)
Habituation
- touch siphon repeatedly every 30 sec leads to
short-term habituation of gill-withdrawal reflex
long-term habituation if touch is
- can lead to ___________________
repeated over days
Sensitization
- one electric shock to the tail can lead to shortterm sensitization of gill-withdrawal reflex
- several electric shocks can lead to sensitization
that will be observed for weeks (long-term)
3
11/2/2009
ASSOCIATIVE LEARNING: _______________
_________________________________________
_______________
_________
A. Classical conditioning (also called Pavlovian
conditioning
process by which a neutral
____________): the
__________________________
stimulus
acquires meaning through associations
________________________________________
with
another stimulus (often a biologically
___________________
relevant stimulus)
Terminology
UCS = ____________________ (food, water, etc.)
UCR = _____________________ (salivation, etc.)
Examples: UCS - - - - - - - - - - - >
pinprick
food
sudden loud noise
airpuff
UCR
withdrawal
salivation
startle
eyeblink
CS = ________________________ (bell, light, etc.)
CR = _____________________ (salivation to bell)
so CR is the ____________ response
Development of Classical Conditioning
Example: conditioning of emotional responses Pavlov’s dog)
UCS - - - - - - - - - - - - - > UCR
(food)
(salivation)
Initially CS - - - - - - - - - - > no response
(bell - neutral stimulus)
Repeated pairings of CS + UCS - - - - - - > UCR
(bell) + (food)
(salivation)
Bell eventually comes to elicit salivation without
the presentation of food
CS - - - - - - - - - - - - - - - - > CR
(bell)
(salivation)
Note that salivation here is called conditioned
response (CR) because it is not elicited directly
by food; classical conditioning has taken place
Also conditioning of motor responses - example
of eye blink conditioning
4
11/2/2009
CLASSICAL CONDITIONING: NEURAL BASIS
Classical conditioning of emotional responses
(freezing in rats - changes in heart rate/blood
pressure or skin conductance in humans) is
learned after only a few pairings
Electric shocks produce “freezing” in rats and
changes in heart rate/skin conductance in humans
Repeatedly pair auditory stimulus (CS) with
shocks (UCS).
- the auditory CS come to elicit freezing and
changes in heart rate/skin conductances
- the ________________________ to produce
classical conditioning of emotional responses
Classical conditioning of motor responses, such as
eyeblink in response to puffs of air is learned only
after 100s of pairings of an auditory stimulus with
puffs of air
- the _______________ is necessary to produce
classical conditioning of motor responses
B. Instrumental Conditioning (also called _______
______________): _________________________
________________________________________
__________________________________
Terminology:
Discriminative stimulus (SD): _______________
cue that triggers the
___________________________________
motor response (ex.
(ex sight of a lever bar).
bar)
reinforcers (ex. food,
Favorable outcome: positive
________________________
water, etc) or termination of negative reinforcers
__________________________________________
(termination of pain, isolation, etc).
_____________________________
5
11/2/2009
Example of instrumental conditioning: Cats
have to learn to press a lever in order to obtain
palatable food (Thorndike’s experiment)
Neural Basis of Instrumental Conditioning:
- _____________________________ necessary for
instrumental motor response learning
- ________________________________________
_______ necessary for “detection” of reinforcer.
HUMAN MEMORY
The various stages of memory:
Sensory registers (high capacity, low duration)
I. _______________
With Attention II. Short-term
_________________
memory (low capacity & duration)
With Consolidation III Long-term
III.
________________
memory (high capacity & duration)
Retrieval - recall and recognition
Implicit memory (similar to _________________):
__________________________________________
___________________________
Examples: - mirror drawing tasks
- playing video games
- riding a bicycle
- word associates (define fall after
different stories)
Explicit memory (similar to _________________):
________________________________
Two types - _______________ (time and places)
- _________ (facts and knowledge)
6
11/2/2009
NEUROBIOLOGICAL BASES OF MEMORY
Karl Lashley (1920’s - 1950’s) and the search for
the “engram” or memory trace: _________
__________________
He derived two principles from his studies:
- ______________________= memories stored
diffusely all over neocortex
- _______________________= neocortex all over
the brain plays an equal role in memory storage
What was wrong with these interpretations?
- task difficulty;
- different “learning” systems/strategy used to
solve problems.
Donald Hebb (early 1950
1950’s)
s) and ______________
of short-term memories into long-term memories
via ________________________________
- cell assemblies: ________________________
- reverberation: __________________________
_______________________________
____________
LESSONS FROM HUMAN AMNESIAS
Amnesia: _________________
Retrograde amnesia: forget events _______ brain
trauma
Anterograde amnesia: forget events _____ brain
trauma
The beginnings of Explicit Memory mechanisms
Case of H.M.: ____________________________
______________ because of severe epilepsy
(removal of enthorinal and perirhinal cortex,
part of amygdala and most of hippocampus)
H.M. experienced:
1. No loss of intelligence (IQ)
2. Mild retrograde amnesia
3 Devastating
3.
D
i anterograde
d amnesia
i
What we learned from H.M.:
short- & long-term memory processes
1. Supports
________________________________________
of explicit vs. implicit memory
2. Existence
____________________________________
of consolidation process
3. Existence
________________________________
view of diffuse memory process
4. Challenges
_____________________________________
discrete brain regions in memory
5. Implicates
_______________________________________
7
11/2/2009
Implicit memories: various forms of implicit
knowledge.
Amygdala: _______________________________
Cerebellum: _______________________________
Basal ganglia: _____________________________
__________________________
8