Influence Of Luminance And Contrast On The Responses Of Neurons In Primary Visual Cortex Of Cats

ObjectiveOur interests in this study focused on the reaction of neurons in cat primary visual cortex (VI) under different visual experience and the neural cording mechanism of luminance and contrast in the brain.MethodsWith in vivo extracellular single unit recording techniques, we tested the reaction of neurons in the primary visual cortex of adult cat under anesthesia. Visual stimuli of different luminance (5%-100%) or different contrast (5%-100%) were given to the cat. Spike rate and response latency of neurons were analyzed and tuning curves of luminance or contrast were drawn with regression analysis. C.V of spike rate and response latency was figured to compare their efficiency in the performance of neural coding. Variability of neurons was analyzed to judge the time resolution of neuronal response.ResultsThe spike rate of neurons in cat V1increased with the increasing luminance or contrast of visual stimuli and the tuning curves fit the cubic modal. The regression equation were y=4.957+2.283x-0.035x2+0.0002x3(R Square=0.374, P=0.000) for luminance and y=-0.660+1.540x-0.013x2+0.0003x3(R Square=0.452, P=0.000) for contrast, respectively. The spike rate changes sharply in low luminance or contrast (5~20%) and become relatively stable when beyond40%.The response latency of neurons in cat V1decreased with the increasing luminance or contrast of visual stimuli and the tuning curves fit the inverse modal. The regression equation were y=71.19+353.45/x (R Square=0.544,P=0.000) for luminance and y=74.22+287.58/x (R Square=0.550, P=0.000) for contrast, respectively. The response latency changes sharply in low luminance or contrast (5~20%) and become relatively stable when beyond40%.C.V of response latency is less than of spike rate, which means the latency code is more efficient than the rate code.The variability of neurons decreased with the increasing luminance or contrast of visual stimuli and the spike timing resolution is approximately5ms in cat V1.ConclusionsSpike rate and response latency can be interpreted as neural code for the information of luminance or contrast in cat V1neurons and the latency code is more efficient than the rate code. The spike rate of neurons increased and the response latency decreased with the increasing luminance or contrast of visual stimuli in cat V1. The reaction of neurons changes significantly when luminance or contrast decreased below30-40%, through which we may consider such visual information lost can be seens as abnormal visual experience. The variability of neurons decreased with the increasing luminance or contrast of visual stimuli and the spike timing resolution of neurons in cat V1is approximately5ms which is necessary for rapid processing of vision.