Title 1 Dim - light sensitivity of cells in the awake cat ’ s lateral geniculate and medial 2 interlaminar nuclei : a correlation with behavior 3 4

26 27 Contrast thresholds of cells in the dorsal lateral geniculate (LGNd) and medial 28 interlaminar (MIN) nuclei of awake cats were measured for scotopic and mesopic vision 29 with drifting sine gratings (1/8, 2 and 4 cpd; 4 Hz temporal frequency). Thresholds for 30 mean firing rate (F0) and temporally-modulated responses (F1) were derived with ROC 31 analyses and compared to behavioral measures of Kang et al. (2009). Behavioral 32 sensitivity was predicted by the neural responses of the most sensitive combinations of 33 cell class and response mode: Y-cell F1 responses for 1/8 cpd, X-cell F1 responses for 2 34 cpd, and Y-cell F0 responses for 4 cpd. All previous estimates of neural scotopic 35 increment thresholds in animal models have fallen between Weber’s law (proportional to 36 retinal illuminance) and the deVries-Rose law (proportional to the square root of 37 illuminance). However, psychophysical experiments suggest that under appropriate 38 conditions human scotopic vision follows the deVries-Rose law. If behavioral sensitivity 39 is assumed to be determined by the most sensitive class of cells, this discrepancy is 40 resolved. In scotopic conditions, OFF-center Y cells were the most sensitive, and these 41 followed the deVries-Rose law fairly closely. MIN Y cells were, on average, 0.25 log 42 units more sensitive than LGNd Y cells in scotopic conditions, supporting a previous 43 proposal that the MIN is a specialization of the carnivore for dim-light vision. We 44 conclude that both physiologically and behaviorally, cat and human scotopic vision are 45 fundamentally similar, including adherence to the deVries-Rose law for detection of 46 Gabor functions. 47 48