Abstract
Tree shrews (Tupaia) possess dichromatic color vision based on short wavelength sensitive (SWS) and long wavelength sensitive (LWS) cones. Deep red-light-rearing (RLR) selectively deprives SWS cones, and produces differential stimulation of color and luminance pathways. After months of subsequent housing in white light, RLR shrews show poorer color discrimination (Petry & Kelly 1991) coupled with enhanced high temporal frequency vision (Callahan & Petry 1995). Retinal ganglion cells of RLR shrews also are tuned to higher temporal frequencies (Lu & Petry, 2002) indicating an initial retinal locus. To address how this atypical high frequency information is processed and represented in V1, where many signals have been shown to correlate with perception, we compare two-photon imaging with single-unit recordings of receptive field properties. Normally-reared tree shrews and RLR tree shrews (reared from birth to 8-wks of age in deep red light then housed in standard white light) were studied. Two-photon calcium imaging: the fluorescence of identified cells in V1 layers II/III was computed in response to achromatic 0.2-0.4 c/deg sine-wave gratings drifting at 0.5-32Hz. Extracellular recordings were obtained using tungsten microelectrodes from single neurons in V1 layers II/III, IV and V. Flashing Gaussian spots, drifting achromatic sine-wave gratings, random-dot kinematograms, and sparse noise stimuli were used. Taken together, results of the imaging and single-unit recordings revealed V1 neurons in RLR shrews that exhibited higher, and lower, temporal frequency preferences than controls. Furthermore, RLR changed the stimulus selectivity profile of layer IV neurons. This suggests that temporal filtering mechanisms in cortex are susceptible to modification during early post-natal development by other inputs (e.g., color pathways), likely by competitive interactions at earlier levels of processing. These findings strengthen the evidence for an enhancement of temporal vision (paired with deficit in color vision) in RLR shrews that can be perceived and used in their behavior.
Meeting abstract presented at VSS 2016