Cerebral Achromatopsia in Monkeys

Abstract

In human cerebral achromatopsia, extrastriate cortical damage produces a severe or complete loss of colour vision, with relative sparing of non-chromatic vision. The critical lesion appears to be in a medial occipito-temporal area, occupying the lingual and caudal fusiform gyri; positron emission tomography has shown that this cortical region is one of several activated in normal human observers during colour vision tasks. Attempts to find an analogous 'colour centre' in the cortex of monkeys have not been successful. In particular, ablation of cortical area V4, sometimes thought on physiological grounds to be more involved in wavelength and colour coding than any other visual cortical area, produces only mild impairments in colour discrimination. In the present study we tested the colour vision of monkeys after cortical ablations that mainly or entirely spared area V4. One group of monkeys (group AT) received ablations in the temporal lobe anterior to area V4, and a second group (group MOT) received ablations in a medial occipito-temporal area roughly corresponding in cranial location to the lesion that produces human cerebral achromatopsia. The animals in group MOT showed no impairment of their colour vision. Group AT, in contrast, had a severe impairment in chromatic vision, with a relative sparing of non-chromatic vision. Their behaviour was indistinguishable from that of a human patient with total cerebral achromatopsia who had been tested on the same tasks. These results show that area V4 in macaque monkeys is not analogous, and probably not homologous, to the human colour centre. Instead, they suggest that the area of the monkey's brain corresponding to the colour area in the human brain is in the temporal cortex, anterior to area V4.

Achromatopsia, color vision, and cortex

“…The percentage of color selective cells in V4 now appears little different from that in adjacent areas [48], and other investigators have emphasized its role in spatial vision [49]. Furthermore, lesions anterior and ventral to V4 in the monkey inferior temporal lobe do result in color impairments [50,51], consistent with the increased activation shown in these regions when monkeys perform color discriminations during neuroimaging [52]. Some features of the neuronal population in area V4 are consistent with a role in some aspects of color processing, notably color constancy.…”

Neuroimaging Weighs In: Humans Meet Macaques in “Primate” Visual Cortex

“…1) (Hadjikhani et al, 1998;Tootell and Hadjikhani, 2001). Furthermore, lesions including macaque TEO/TE do produce significant deficits of color vision (macaque achromatopsia) (Heywood and Cowey, 1987;Heywood et al, 1988Heywood et al, , 1992Heywood et al, , 1995. Neuroimaging (Takechi et al, 1997;Vanduffel et al, 1997;Nelissen et al, 2003) and single unit (Komatsu et al, 1992;Komatsu and Ideura, 1993;Missal et al, 1997) studies also reveal colorrelated activity in these same macaque regions.…”

Distribution of colour‐selective activity in the monkey inferior temporal cortex revealed by functional magnetic resonance imaging

“…In the cortex, colour information is further processed along the ventral visual pathway, through the primary visual cortex (V1) (Lennie et al, 1990;Hanazawa et al, 2000;Johnson et al, 2001;Conway et al, 2002;Solomon et al, 2004), area V2 (Gegenfurtner et al, 1996) and area V4 (Schein & Desimone, 1990;Kusunoki et al, 2006) and finally reached to the IT cortex. Lesion studies have shown that bilateral ablation of the IT cortex disrupts colour discrimination (Horel, 1994;Heywood et al, 1995;Buckley et al, 1997;Huxlin et al, 2000) although ablation of V4 does not (Heywood et al, 1992;Heywood et al, 1995), and this suggests that the IT cortex plays a key role in colour vision. Moreover, single cell recording studies have shown that there are many colour-selective neurons in the IT cortex, and that some of them have selectivities for various hues and degrees of saturation (Komatsu et al, 1992;Koida & Komatsu, 2007;Matsumora et al, 2008;Yasuda et al, 2009).…”