Transcript 10 Learning and Plasticity

Introduction to Psychology
Learning and Plasticity
Prof. Jan Lauwereyns
[email protected]
Development: Formation of the neural tube
Embryo: flat disk with 3 layers of cells,
endoderm, mesoderm, ectoderm
Neural plate
Fluid-filled tube,
will become the
ventricular system
Cerebral cortex
(Telencephalon)
Limbic structures
Basal ganglia
Forebrain
Thalamus
(Diencephalon)
Midbrain
(Mesencephalon)
Hypothalamus
Tectum
(Substantia nigra,
Superior colliculus,…)
Cerebellum
(Metencephalon)
Pons
Hindbrain
(Myelencephalon)
Medulla
Figure 5.3
Growth and Development of Neurons
• Proliferation (Neurogenesis):
cells in ventricles divide
Some stay as stem cells
Some become primitive neurons and glia
that go to new destinations
Many more are created than survive…
•Migration:
cells follow chemical path toward final destination
Specific locations based on chemical gradient
Chemical pathfinding
• Differentiation
Axons and dendrites are formed while migrating
Cells begin to express particular genes and cells
acquire the distinctive appearance of neurons
characteristic of that region.
•Cell Death
Apoptosis: programmed cell death;
occurs when synapses are inactive
•Synaptic rearrangement
at Birth
6 Years Old
14 Years Old
Plasticity
• To some extent brain development is hardwired but brains also show plasticity:
• Synaptic connections can be strengthened or
weakened depending on use:
– High use = strengthened
– Low use = weakened
• Learning leads to brain plasticity
Critical Periods in Development
• Critical periods are sensitive periods when
certain important psychological processes are
developing most rapidly.
• Disturbances during these periods might alter
the development of these processes in critical
ways.
Example of Critical Periods in Development:
Effects of deprivation in the first year of life on
the development of visual cortex
Neural plasticity
After selective training of middle digits,
the cortical map is reorganized
with stronger representation
for the trained digits
Emerging field of BMI
Brain-Machine Interface
[ TH : Tyrosine Hydroxylase ]
Ontogeny: Development of the individual based on the
individual’s history. This is the typical subject
matter of learning theorists. Nurture
Phylogeny: Development of the species – evolutionary
history. Behaviour that occurs without personal
experience may well derive from species experience.
Nature
Ontogeny: Development of the individual based on the
individual’s history. This is the typical subject
matter of learning theorists. Nurture
Phylogeny: Development of the species – evolutionary
history. Behaviour that occurs without personal
experience may well derive from species experience.
Nature
Matt Ridley, Nature via Nurture
Non-Learned Behaviors
• Simple Reflexes:
Reflect point-to-point
processing and the developed nervous
system mechanisms.
• Complex behavioural adaptions and chains
– Tropisms (kineses and taxes)
– Fixed Action patterns
– Repeated sequences
Learned Behaviours
Non-associative learning
Pavlovian or Classical Conditioning
Operant or Instrumental Conditioning
Non-associative learning
• Does not involve association of 2 or more
events or stimuli
• Sensitization : increase in responsiveness
Generalized, following an aversive stimulus
• Habituation: decrease in responsiveness
Stimulus-specific
Classical or Pavlovian Conditioning
learning stimulus-stimulus relations
conditioned reflexes
FOUR basic elements:
UNCONDITIONED STIMULUS (US)
UNCONDITIONED RESPONSE (UR)
CONDITIONED STIMULUS (CS)
CONDITIONED RESPONSE (CR)
The key event is the co-occurrence of the pre and post synaptic
neurons.
Neurons that fire together wire together
while
neurons that are out of sync lose their link.