Stability of simple – complex classification with contrast and 2 extra - classical receptive field modulation in macaque V 1

39 A key property of neurons in primary visual cortex (V1) is the distinction between simple 40 and complex cells. Recent reports in cat visual cortex indicate the categorization of simple 41 and complex can change depending on stimulus conditions. We investigated the stability of 42 the simple/complex classification with changes in drive produced by either contrast or 43 modulation by the extra-classical receptive field (eCRF). These two conditions were reported 44 to increase the proportion of simple cells in cat cortex. The ratio of the modulation depth of 45 the response (F1) to the elevation of response (F0) to a drifting grating (F1/F0 ratio) was 46 used as the measure of simple/complex. The majority V1 complex cells remained classified 47 as complex with decreasing contrast. Near contrast threshold an equal proportion of simple 48 and complex cells changed their classification. The F1/F0 ratio was stable between optimal 49 and large stimulus areas even for those neurons that showed strong eCRF suppression. 50 There was no discernable overall affect of surrounding spatial context on the F1/F0 ratio. 51 Simple – complex cell classification is relatively stable across a range of stimulus drives, 52 either produced by contrast or eCRF suppression. 53 54 55