Learning and Plasticity

Week 9: Learning and Plasticity

patients missing one entire brain hemisphere still show intact major brain networks
however there were more connections between networks than usual
William James: plasticity is the possession of a structure weak enough to yield to an influence
brain plasticity: brain’s ability to change structure and function in response to experience
- learning something new and creating a memory physically changes the structure of the nervous system

Visual Cortex: Nature vs Nurture

critical period: maturational stage during which nervous system is sensitive to certain stimuli
- reveals the interaction between nature and nurture in development
Hubel & Wisel: learning makes physical changes to the structures in the brain

Types of Learning

stimulus response learning

classical conditioning: process by which we learn to associate stimulus and to anticipate events

operant conditioning: learning to associate behavior and its consequences (punishment or reinforcement)

the skinner box: placed rat in a box where they pressed a lever to get food dispensed as reward
positive reinforcement: adds to increase a behavior
negative reinforcement: removes to increase a behavior
positive punishment: added to decrease behavior
negative punishment: removed to decrease behavior

observational learning: watching others and then imitating
modeling: the individual performing the imitated behavior
bandura: concluded that children watch and learn from adults around them (both bad/good consequences)

motor learning

learning to perform a movement skill as result of practice
processes by which brain plans over time
Held & Hein kitten carousel:
- kittens actively explore their environment, developed normal visually guided behavior
- passively moved kittens did not, despite receiving same stimulation
damage to cerebellum compromises motor learning and coordination

Perceptual Learning

performance improvement due to practice or experience, relies on neural plasticity in sensory areas
- phonetic learning (R and L sounds)
most low level processes can be improved with practice
characteristics of perceptual learning reveal the level of the cortical hierarchy at which neural plasticity has occurred
MT (V5): motion perception in noise V3: coherent motion perception
Visual expertise area: increased FFA activity when viewing birds, cars, dogs, cats —- can make new categories
visual exercises can improve visual acuity

Relational Learning

tolman: cognitive maps, internal representation of external spaces, and we use to influence stimulus response pairings
- suggests hippocampus is the cognitive map

Mechanisms of Learning and Plasticity

Donald Hebb proposes a theory of learning based on strengthening connections between co active neurons (fire together..wire together)
before Hebb, neural communication was studies in the PNS
- PNS and motor circuits led to misunderstanding about architecture
a group of neurons that fire together in response to a specific perception or idea
Phase sequences: ordered patterns of activation underlying thought and perception (reflects temporal flow)
proposed learning rule at conceptual level: suggested how learning should work, but not known yet (functional over cellular mechanisms)

long term potentiation: persistent increase in synaptic strength after repeated stimulation
- Bliss and Lomo were recording electrical activity in the hippocampus of rabbits
- their goal was to understand how signals travel through hippocampal circuits
used a brief burst of high frequency stimulation to test the pathway
- noticed postsynaptic response became much larger, stayed larger for up to hours
- named it long term potentiation
1) repeated stimulation, 2) postsynaptic changes, 3) presynaptic changes, 4) synaptic strengthening