Neuroscience of learning Flashcards
Model system: rats
leading model organism
similar nervous system to humans
x - Don’t have folds
Model system: Aplysia Sea Slug
20,000 large neurons - colour coded
easy to study natural defence reflex
X- invertebrates distantly related o humans
Levels of learning in the brain
gross structural level
neural pathway level
neuron level
synapse level
Gross structural level in humans
Reversal learning- ^ orbitofrontal cortex and ^ medial prefrontal cortex (MRI scans)
Motor learning (juggling)- pre and post scans - structure change in temporal and parietal - changes reversed after learning ceased
Gross structural level in animals
Rodents- hippocampal lesions decrease spatial learning and conditioned fear response
primates- frontal lobectomies impair reversal learning
timing of lesions important a must occur shortly after conditioning not before
Neural pathway in sea slugs
Gill withdrawal
Directly- sensory neurons in back to motor neuron to gill withdraw
Indirectly- via relay neuron in the tail sensory relay sensory motor
sensory neurons stimulated with microelectrode (identify exact neuron)
strengthen correlational evidence of associative learning
Neural pathway in stimulus generalization
CS (associative) excite any sensory and motor neurons. Different CS will excite some sensory neurons therefore some motor neurons but not all
Support for neurons as web rather then chain
Neural pathway in Habituation
can occur without sensory neurons. Only need motor neurons (rules out sensory adaptation) and fatigue as motor stimulation resumes to normal after a break
(results mirror behavioural studies)
neural pathway in imprinting
birds neural pathway connecting the visual wulst (processes visual cues) and telencephalon (stores visual inputs as memory) (discovered by neural tracing)
humans don’t have these
Pavlovian conditioning strengthens pathway but only during a short time window
Making new neural pathways
Rhesus macaques - map neural pathways before learning task then map after. New neural pathways are created
neural pathway and avoidance
chick eat bead covered in chemicals found in grapes. Denser neurons with more synapses
Limits of neuroscience
animals without nervous system can learn
nerve net (jellyfish) van habituate but not capable of associative learning
slime mould can learn (no nerve network)
Synapse level
changes in synapses underlie learning
Hebb’s rule
Any two cells that are repeatedly active at the same time will tend to become ‘associated,’ so that activity in one facilitates activity in the other
part of synaptic level
long term potentiation
The process of strengthening a synapse when one neuron repeatedly fires and excites another. This is also synonymous with the ‘Hebbian synapse’.
Part of synaptic level
LTP in the vertebrate hippocampus
Bliss and lomo- implanted electrodes into rabbit brain to activate neural pathway (perforant path) stimulating and recording electrode needed. Establish baseline of pulses.
test high frequency pulse (simulation of learning) wait a few months and then activate with low frequency pulse. Hippocampus results in far greater activity.
Associative LTP
weakly firing neurons can over time through their associations with strongly firing neurons make other neurons fire
Long term depression
Synapses become WEAKER with INFREQUENT activation
stops neurons firing by LTP to make way for new info
Neuroplasticity
The brain’s ability to change its structure and function in response to the environment, through flexible (plastic) changes in neuron presence and activity
including gross brain structure, neural pathways and structure and synapses.
Neuroplasticity gives rise to learning through
LTP- Strengthening existing synapses
Neurogenesis- Formation of new neurons
Synaptogenesis- Formation of new synaptic connections
Neuroplasticity and fear learning
synaptic changes in the prefrontal regions cortex of mice change over development.
less synaptic plasticity during adolescence leads to blunted regulation of fear extinction
Neurogenesis across life
peaks at age 2
lose half our hippocampal neurons between puberty and adulthood
Hippocampus one of few brain regions where in adulthood new neurons continue to be formed and this process is important in learning and memory
Use it or lose it
neurons die if don’t engage in active successful learning experiences
half of all new hippocampal cells die within weeks but learning retains more cells
learning recuse cells around 1-2 weeks old but not younger or older
pruning occurs when unused neural connections are discarded
increased neuronal cell survival has been linked to associative learning (surprise)
Learning in the ageing brain
healthy ageing associated with:
reduced neurogenesis
altered gross structure of hippocampus and prefrontal cortex
altered calcium levels and gene expression leads to impaired LTP
less dendritic branching and spine density
thickened stumpy dendrites indicate where learning has become fixed
