Recovery from achromatopsia and prosopagnosia is not reflected by corresponding changes in the response to color or faces in human visual cortex

Abstract

A 17 year old male (JJ) presented with a complete loss of vision following head trauma. Over 5 days, JJ recovered acuity, but revealed a specific deficit in color vision (achromatopsia). Structural MRI scans revealed no obvious lesion. 10 days after injury, JJ was tested with a battery of visual tests that showed: improving, but still abnormal color discrimination, normal stereopsis, normal motion discrimination and normal visual acuity. Tests of face perception showed that he also had a selective deficit in the ability to recognize familiar faces (prosopagnosia), but normal recognition for objects and places. 20 days after injury, color vision had improved, but he remained densely prosopagnosic. JJ was then tested weekly to map recovery of function. Over this period, color vision improved, but he was unable to recognize faces. Additional MRI scans failed to show any structural abnormality. 4 months after his initial loss of vision, JJ showed a sudden recovery in his perception for color and faces. Throughout his recovery, fMRI was used to measure responses in his visual cortex. JJ showed normal visual field maps, including an intact hemifield representation in V4. His responses to color in V1 and V4 showed no clear signs of change over time. We were also able to localize face-selective regions, such as the OFA, FFA and STS, which showed a normal response to facial identity. In sum, we found no changes in these functional measures of color and face processing from pre- to post-recovery. These results show that specific deficits in visual perception can exist without an identifiable lesion and in the absence of changes to conventional measures of functional response. This suggests that the responses of these regions may be necessary, but not sufficient for the normal recognition of color and faces.

Meeting abstract presented at VSS 2012