Visual responses of neurones in the second visual area of flying foxes (Pteropus poliocephalus) after lesions of striate cortex.

1. The first (V1) and second (V2) cortical visual areas exist in all mammals. However, the functional relationship between these areas varies between species. While in monkeys the responses of V2 cells depend on inputs from V1, in all non-primates studied so far V2 cells largely retain responsiveness to photic stimuli after destruction of V1. 2. We studied the visual responsiveness of neurones in V2 of flying foxes after total or partial lesions of the primary visual cortex (V1). The main finding was that visual responses can be evoked in the region of V2 corresponding, in visuotopic co-ordinates, to the lesioned portion of V1 ('lesion projection zone'; LPZ). 3. The visuotopic organization of V2 was not altered by V1 lesions. 4. The proportion of neurones with strong visual responses was significantly lower within the LPZs (31.5 %) than outside these zones, or in non-lesioned control hemispheres ( > 70 %). LPZ cells showed weak direction and orientation bias, and responded consistently only at low spatial and temporal frequencies. 5. The data demonstrate that the functional relationship between V1 and V2 of flying foxes resembles that observed in non-primate mammals. This observation contrasts with the 'primate-like' characteristics of the flying fox visual system reported by previous studies.