Anosognosia for cerebral achromatopsia--a longitudinal case study.

Cerebral achromatopsia is a rare disorder of colour vision caused by bilateral damage to the occipito-temporal cortex. Patients with cerebral achromatopsia are commonly said to suffer due to their disturbed colour sense. Here, we report the case of a patient with cerebral achromatopsia who was initially unaware of his deficit, although three experiments with eye movement recordings demonstrated his severe inability to use colour information in everyday tasks. During two months, the evolution of his colour vision deficit was followed with repeated standardized colour vision tests and eye movement recordings. While his performance continuously improved, he became more and more aware of the deficit. Only after colour vision had almost normalized, his subjective colour sensation was inconspicuous again. The simultaneous occurrence of achromatopsia and the corresponding anosognosia and their parallel recovery suggest that both deficits were due to dysfunction of the same brain region. Consequently, the subjective experience of colour loss in achromatopsia may depend on the residual function of the damaged colour centre.