Perceptual Learning and Individual Differences - L5 David McGonigle

What is learning?

the processes by which experiences physically change the structure of our nervous system

Types of learning, according to Carlson:

Perceptual Learning, Stimulus-Response Learning, Motor Learning

What is perceptual learning?

changes in neural circuits which help us detect a particular stimulus leading to measurable behaviour change

What is stimulus-response learning?

the association between sensory information and specific response increases

What is motor learning?

changes in neural circuits which help us respond to a stimuli

Study of Perceptual Learning in the Primary Visual Cortex (Vernier Acuity Task)

2 sets of 3 vertical lines are presented - one of the lines if offset from the other 2.

Participants have to indicate which line are aligned. - this can improve Visual Acuity

Number correct increases with time, until they change the orientation of the lines = they do not maintain the ability when they make lines horizontal

Another Study of Perceptual Learning in the Primary Visual Cortex (Texture-Discrimination Task)

Present a T or an L at a fixation point (same point) in the centre of a line pattern.

Then ask the orientation of some specific target lines. = improvement with time,

but reduces as soon as location of the target lines changes. = visual field specific learning.

4 time courses of learning:

between-day learning, within-day learning, within-day learning with no consolidation, between AND within day learning

Between-day Learning

Improvement throughout the day, and start even better the next day (after overnight consolidation) - but no improvement second day

Within-day learning

Improvement throughout the day, start where you left off the next day (no consolidation overnight)

Within-day learning, no consolidation

Improvement during the day, but do not remember any overnight (back at the start)

Within AND between day learning

IDEAL! Improvement during the first day and start even better the next day (after overnight consolidation) and then improve further.

One neural explanation for Individual Differences in Perceptual Learning (in SOMATOSENSORY CORTEX)

Levels of GABA (Gamma-Amino-Butyric-Acid) = inhibitory neurotransmitter which can decrease the size of a receptive field for a tactile task- making us more sensitive

Study of GABA levels effecting Tactile Ability (Puts et al, 2011)

Participants did a frequency discrimination task, where they were asked which of two stimuli placed on their fingers had higher frequency. They increased similarity of frequencies with every correct answer. Then measured their GABA levels using MR Spectroscopy = found higher levels of GABA in the somatosensory areas of higher performers (did NOT vary in the visual cortex - CONTROL)

What recent evidence is there that the Critical Period for the Visual Cortex may be REVERSIBLE?

After the critical period, GABAergic neurons (neurons which transmit GABA) in the visual cortex develop a PERINEURONAL NET (surrounds neurons to prevent plasticity) - HOWEVER protease enzyme could be developed to destroy the perineuronal net - they become plastic again.

Summary of Features of Perceptual Learning:

1. Can occur without participant paying attention to a stimuli

2. Often initially rapid and the slow

3. Can be retained across years

4. Tactile perceptual learning is influenced by GABA