| Summary: | 碩士 === 國立臺灣大學 === 心理學研究所 === 106 === Previous studies have shown that black-dominant neurons outnumber white-dominant neurons in the primary visual cortex in many species. The black-over-white bias may serve as the neural substrate for better and faster processing of black than white objects. One possible neural mechanism for the ample black preference is through recurrent connections in the superficial layer of V1 — the black-dominant signal is more sustained for the multiunit activity of superficial layer than for the local field potential of input layer. Based on the finding, we hypothesized that the strength of synchronous firing among black-dominant neurons should be stronger than that among white-dominant neurons. Here we used a multi-electrode matrix to simultaneously record from multiple neurons in different cortical layers of macaque V1. The receptive field measured with white noise (a binary stimuli generated by m-sequence) by reverse correlation was used to determine a cell’s response bias (dominated by positive or negative contrast stimuli). We quantified the strength of synchronous firing of a cell pair as the peak amplitude minus the baseline amplitude of the cross-correlogram. The correlation strength was negatively correlated with the distance between two cells. The correlation strength between black-dominant cells was stronger than that of white-dominant cells, especially the cell pairs from the input to the superficial layer. These results might provide evidence for another mechanism, the unequal feedforward projection from input layer, might also be critical for generating the stronger black bias in V1 superficial layer. Moreover, the strength of the synchronous firing was also modulated by the spatial property of stimulus. In comparison with white noise, correlation strength was higher and the peak width of the cross-correlogram was broader when cells were stimulated by Hartley gratings (stimuli with high spatial correlation). These results are evidence for the stronger recurrent activity evoked by Hartley gratings. Overall, our results supported both feed forward and recurrent hypotheses that largely amplify the black signal in the superficial layer of V1.
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