plasticity in learning Flashcards
What happens in brain follwing deafferentation?
Extensive changes in cortical maps follow long-term
deafferentation
What happens after deaffetenation of the homunculus?
After
deafferentation of a
part of the
‘homonculus’, the
neurones in that
area respond to
sensory stimuli
applied to sensory
surfaces that are
represented
adjacent to the
deafferented cortex
on the homonculus.
Why do phantom limbs occur?
The cortex that loses its afferent input gets inputs now from
adjacent cortical areas!
How can phantom pain be cured?
Phantom limb pain and cure with a mirror:
shows visual inputs to the somatosensory system!
visual inputs that trick the brain.
What do eye laser lesion studies show?
You can got to the corresponding areas in the two eyes. Record from binocualr cells. You can’t get stimulation from lesioned eye.
corresponding receptive fields respond to stimuli projected to adjacent zone. Similar to phantom limb phenomenon.
What happens after 1-2 hours after a lesion and then 5-6 hours after a lesion? What does it demonstrate?
There is an eccentric response with cells near the area of lesion showing up but are not yet responsive. After 5-6 hours, there are responses recorded after visual stimuli have been applied demonstrating cortical reorganisation.
what are Stages of the response to a partial loss of input to the
topographically-arranged representations in sensory
cortex? What is the source of the input to give the capacity for ectopic fields?
Stage 1 (immediate to hours) : unmasking of inputs that were already there esp in relation to the lateral connections.
Stage 2: (hours to days) refining and strengthening of synaptic connectiions of these unmasked responsiveness.
Stage 3: (weeks to months) weeks to months: axonal sprouting, dendritic remodelling
What are these changes such phantom limb for?
Think about visual illusions and visual
illusions happen because we are actually tricking the brain.
And visual illusions actually hijack our normal visual-neural mechanisms to make you see things which are which are
not really there
the same way this what you are
seeing in the phantom limb and his op sub fields.
Maybe something else, maybe maybe an expression of something else,
which is probably necessary and useful.
What could that be?
Increasing perceptual learning or filling in phenomenon
Example of Filling in phenomenon?
Pupil blindspot. We fill in information so we don’t really have breaks in our vision.
So, filling in missing information
from areas such as the blind spot
may be one function of such lateral
connections.
2 instances of lateral connections?
Filling in phenomenon
perceptual learning
Examples of perceptual learning?
‘Practice makes perfect”. In most tasks, repetition leads to improved
performance.. E.g.,
* Discrimination of two very similar directions of motion (Ball & Sekuler,
1982).
* Discrimination of gratings (Fiorentini & Berardi, 1980)
* Texture discrimination (Karni & Sagi, 1991)
* Streoacuity with some random dot kinematograms (Ramachandran &
Braddick, 1973).
What things get better at practice?
No, it’s not just the it’s not just the motor
coordination, sensory motor coordination and you get your better skills
better, but your **perception gets better **when you repeatedly do
something.
Why does brain retain some pasticity?
*Perceptual learning may be one of the reasons that the primary sensory
cortices preserve some potential for plasticity, which otherwise may be a
handicap in the adult
Where does perceptual learning occur most?
*Perceptual learning is in most cases specific to the retinal location of the
stimulus, thus leading to the idea that it occurs early along the visual
pathway, probably in area V1.
What can it be influenced by?
However, perceptual learning is also influenced by top-down processes
such as attention and spatial integration across different co-ordinate frames
(Zhang & Li, PNAS, 2010).
