SynesthesiaFunctional and Magnetic Resonance

Imaging: Activation of V4/V8

J.A. Nunn, L.J. Gregory, M. Brammer, S.C.R. Williams, D.M. Parslow, M.J. Morgan, R.G. Morris,

E.T. Bullmore, S. Baron-Cohen, & J.A. Gray

By Cecylia Witkowski

What is Synesthesia?

Synesthesia occurs when one sensory modality triggers another

A common synonym for Synesthesia is “Coloured Hearing”

Picture the number two in your mind

2how most people see

the number 2

2how people with

synesthesia see it

The Experiments

Three experiments conducted Experiment 1

› 30 blocks of single spoken words (abstract and concrete) were alternated with single pure tones over a course of 5 min

› Synesthetes were asked to describe the colour they experienced after each word This data was used for experiment 3

The Experiments Experiment 2

› This was a control to see whether the presentation of words along with images of colour (Mondrians) would activate the same brain areas as synesthetes

The Experiments

Experiment 3 Non-synesthetes would learn the word-

colour combinations that synesthetes described

They were required to predict and imagine the colours associated with the words

Also required to re-test to obtain 100% accuracy

The Results

Both the synesthetes and non-synesthetes displayed activation in all brain regions EXCEPT for the V4/V8 region› V4/V8 regions are gathered to be

responsible for coloured vision Even in Experiment 3, V4/V8 regions in

non-synesthetes were not activated

fMRI Results

Discussion

V4/V8 regions are still under much investigation for their absolute function and their relation to synesthesia

Despite training non-synesthetes, there was still no activation of V4/V8 regions› V4/V8 regions specific only to synesthetes?

Discussion

Due to activation, synesthetic colour experience is that of colour perception rather than imagery

There was no left V4/V8 activation in response to colours› Competition between normal colour

perception and synesthetic perception

Thoughts

Very well laid out Had methodical approach to riddle out

whether just association can procure ‘synesthesia-like’ effects

Interesting results› Synesthetes had regions activated that

don’t in normal people Usage of fMRI and PET scans to obtain

accurate results

Strengths & Limitations

Effectively used controls to determine synesthete and non-synesthete activations

Limited number of participants› 13 synesthetes › 27 controls› All female

Further Research

More participants› Variation in gender (not just females)

Vary in testing such that controls would see a word in colour, then repeated again without colour and test to see whether association will occur

Questions