Credit: Amy Center

A vivid perception of color is evoked by spoken words (“seven” is blue, for instance) in people with a condition called 'colored-hearing synesthesia'. This percept is associated with activity in an area of the brain that responds to color vision, report Julia Nunn and colleagues on page 371 of this issue. Because other visual areas are not activated, these results suggest that a conscious perception of color can be created by activation of the brain's 'color center' alone.

In a control experiment, normal subjects did not show activity in the color center in response to spoken words, even after they had been extensively trained to visualize particular colors in association with those words. The authors conclude that synesthesia is much more like a color hallucination than color imagery. Synesthesia may also have a genetic basis, as it runs in families and is strongly sex-linked (six times more common in women). The authors speculate that this condition may result from developmental errors in the formation or retraction of connections between auditory cortex and visual cortex.