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   [page 16 of handout]

Lueck, C.J., Zeki, S., Friston, K.J., Deiber, M-P., Cope, P., Cunningham, V.J., Lammertsma, A.A., Kennard, C. and Frackowiak, R.S.J. (1989) The colour centre in the cerebral cortex of man. Nature, 340, 386-9.

Early this century suggestions for a colour centre in the human brain were dismissed. It has now been shown that there is an area specialized for colour (V4) in macaque monkeys. Also visual deficits in patients with lesions in similar places suggest that there is an equivalent specialization in humans.

In this study PET was used with normal human subjects: 3 male volunteers, 2 of whom were left-handed.

They were presented with an abstract display of coloured squares and rectangles (a “Mondrian”) on a monitor occupying the central 40o of the visual field: on control trials the display was identical but compose of grays isoluminant with the colours (isoluminance was gauged by alternating gratings and adjusting the grays until the perception of motion ceased.

Ss moved their eyes back and forward across a central line (5o).

Complex PET methods: Ss inhaled radioactive CO2 for 2 min: radioactive H2O was produced in the lungs and monitored in arterial blood.

Each S had 6 trials:

1&6 = eyes shut;
2&5= colour;
3&4=gray

Each scan lasted 3.5 min with 15 min between trials (half- life is 2.1 minutes), with head in fixed position.

Results (special stats for small n)
No difference (colour-gray) in V1 (striate: V2 same). Just one area with large colour-grey difference . which was in the place expected, in region of lingual and fusiform gyri. “We presume this is the homologue of V4 in the monkey”.

V1 had 14% increase for both stimuli, over eyes closed.
Colour area had 13% increase for colour cf gray.


Unexpected results

1. There was a small (3-5%) increase in the “motion area” (V5) on both colour and gray trials. A 4th S was tested with moving stimuli and showed a bigger increase in this area, and thus the increase in the original Ss may have been due to the eye movements.

2. In all Ss activity in the colour area was greater in the left hemisphere.

3. There was no major change in activity in the areas of the temporal lobe to which V4 projects. They suggest this may be because the task did not require any memory or experience.

 

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