PSY260H1 Lecture Notes - Lecture 4: Perceptual Learning, Southwest Ohio Regional Transit Authority, Entorhinal Cortex
Sensitization:
Increase in the strength or occurrence of a behaviour due to exposure to an arousing or noxious
stimulus This is the opposite of habituation.An example of a task where you can measure
sensitization is an acoustic task. So lets say you play a sound and it reacts to the sound and then
an unpleasant physical stimulus which does not hurt the animal (longterm) but is painful short
term is introduced. So the next time (test 2) when you play this sound there will be a much
stronger acoustic startle response than the first time. (Refer to graph on slide)
• Initial habituation to settle animals to a stable baseline • Foot shock applied at dashed line to
red group only • Sensitization: increased responding to startle stimulus after shock
So the read group is the only one receiving an aversive stimuli (shock to the foot).So the next
time you measure the response to the exact same sound only the red group will show a stronger
response because the green group will continue along the green curve.so in the same way that
habituation is equibitous so is sensitization. There is a set of common characteristics which all
species show in sensitiziation.• Spontaneous recovery, short- and long-term forms • Noxious
(painful) stimuli work better than weak • More generalization, less stimulus specificity• Can
develop with just a single noxious (INTENSE BUT NOT NECESSAIRLY NEGATIVE)
stimulus• A mechanism to increase responses to stimuli that are important for general purposes:
habituation is not generalized but sensitization is.
You can develop sensitization with just one noxious stimuli but with habituation you need many
applications of the stimuli for response development.This is because evolutionarily we need to
learn quickly with negative/dangerous stimuli. Graph on the next page is very helpful (Refer to
it) —Habituation vs. Sensitization
Sensitization in Aplysia Gentle touch to siphon,
produces gill withdrawal• Aversive shock to tail (next time you touch any of its sensory areas
you are going to get an aversive reaction) but it reverses quickly. It can become long lasting if
you keep giving it aversive shocks to the tail.• Next touch, much longer withdrawal duration •
Recovers quickly, but becomes long-lasting with multiple sessions
. How? (videographic description in your audio recording)
. Aplysia has huge huge neurons and they take out neurons (forgot which ones) and put
them in a vat and form a mini brain and see what happens when memory formation
occurs in this mini brain. Over time, there are new synaptic connection growth so even if
there is a break of shocks you still remember.
. Mechanisms of Sensitization in Aplysia Error in the textbook —— Refer to slide.
They misname a motor neuron as a sensory neuron (obviously the one responsible
for the gill muscles). • Tail-shock activates interneurons that release serotonin • The
serotonin modulates sensory neurons to release more transmitter (glutamate —
responsible for heightened response) on next activation • In long-term sensitization, new
sensory-motor synapses are added These are short term changes but if you do it over and
over and over you will develop new sensory synapses over time.
.
Action potential slide is next. Pretty graph with many colours.
(if for some reason u need to review this cry and then go to recording)
Aplysia Sensitization
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PSY260H1 Full Course Notes
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