Abstract
Although there have been several documented cases of dissociations between colour perception and imagery, we present here what may be the first evidence for a selective deficit in colour working memory and imagery, affecting only particular hues. At the time of testing, our patient, QP, was a 36-year old woman who had experienced a brief period of achromatopsia following a severe concussion at age 17. Although her colour perception gradually normalized, she has experienced persisting problems with memory for colour, and colour imagery. During the present assessment, we verified that QP's estimated verbal intelligence was in the high-average range, and that her immediate and delayed recall of both verbal and visual form information (faces, designs) was also in the high-average range. Performance on tests of spatial span and spatial imagery was well within normal limits, and short-term memory for visual texture was also intact. Despite performing normally on tests of colour naming and discrimination, when recalling colours after an 8 s delay she scored below the 95% confidence interval for red, but not blue, hues. Similarly, in a test requiring her to visualize named objects and compare their colours, QP's reaction times exceeded the 95% confidence limit when the objects' hues were reddish, but not bluish. Together, these data suggest that QP's deficit does not simply reflect a general problem with maintaining visually-encoded information in working memory, or with generating a visual image within a working memory buffer. Instead, the present data suggest that, just as category-specific recognition impairments indicate separation in the neural representations of different categories of objects (e.g., living vs. nonliving) within the temporal lobe, QP's particular colour-specific impairment suggests that different colour categories may be represented separately in the brain.