Ninomiya T, Sanada TM, Ohzawa I. Contributions of excitation and suppression in shaping spatial frequency selectivity of V1 neurons as revealed by binocular measurements. J Neurophysiol 107: 2220 -2231, 2012. First published January 11, 2012 doi:10.1152/jn.00832.2010Neurons in the early visual cortex are generally highly sensitive to stimuli presented to the two eyes. However, the majority of studies on spatial and temporal aspects of neural responses were based on monocular measurements. To study neurons under more natural, i.e., binocular, conditions, we presented sinusoidal gratings of a variety of spatial frequencies (SF) dichoptically in rapid sequential flashes and analyzed the data using a binocular reverse correlation technique for neurons in cat area 17. The resulting set of data represents a frequencydomain binocular receptive field from which detailed selectivities, both monocular and binocular, could be obtained. Consistent with previous studies, the responses could generally be explained by linear summation of inputs from the two eyes. Suppressive responses were also observed and were delayed typically by 5-15 ms relative to excitatory responses. However, we have found more diverse nature of suppressive responses than those reported previously. The optimal suppressive frequency could be either higher or lower than that of the excitatory responses. The bandwidth of SF tuning of the suppressive responses was usually broader than that of the excitatory responses. Cells with lower optimal SFs for suppression tended to show high optimal SFs and sharp tuning curves. The dynamic shift of optimal SF from low to high SF was accompanied by suppression with earlier onset and higher peak SF or later onset and lower peak SF than excitation. These results suggest that the suppression plays an essential role in generating the temporal dynamics of SF selectivity.frequency-domain binocular receptive field; cat area 17; reverse correlation VISUAL INFORMATION IS SEPARATELY acquired from two retinae and is first integrated in the early visual cortex. Since Wiesel (1959, 1962) showed that many of the neurons in the early visual cortex could be activated by inputs from either eye, the nature of binocular information processing has been one of the major interests in this stage (Anzai et al. 1999a,b; Bishop et al. 1971;Cumming and DeAngelis 2001; Ohzawa and Freeman 1986a,b;Ohzawa et al. 1990Ohzawa et al. , 1996Ohzawa et al. , 1997Pettigrew et al. 1968).Previous studies performing binocular measurement have mainly been focused on its characteristics in the space domain because the response properties of neurons in the early visual cortex are generally well-described in this domain. However, neurons in this stage exhibit high selectivity for the spatial frequency (SF;Campbell et al. 1969;De Valois et al. 1982;Maffei and Fiorentini 1973), and therefore the SF domain is also useful for capturing the feature of their responses. Many previous studies have revealed the properties of monocular responses in the SF domain Jones...