SELECTIVE AND INVARIANT SENSITIVITY TO CROSSES AND CORNERS IN CAT STRIATE NEURONS

Many neurons (56/174, or 32.2%) studied in the cat striate cortex (are a 17) increased significantly (by 3.3 times on average) their response s under stimulation by cruciform or corner figures of specific or non- specific shape and orientation flashing in receptive field as compared with single light bar of preferred orientation. Most of these neurons (71.4%) were found to be highly selective to both the shape (the angl e between the figure's lines) and orientation of these figures. In the neuronal selection studied we have also found all possible types of i nvariance of the cross and corner tuning to orientation and/or shape o f these figures. We found neurons with selectivity to the form of the figures and invariance to their orientation and, on the contrary, unit s invariant to shape but selective to orientation. Some cells were fou nd invariant to both the form and orientation of the cruciform or corn er figure but highly sensitive to appearance of any such figure in the receptive held. Two main hypotheses about the mechanisms of selective sensitivity to crosses and angles can be considered. They are as foll ows: an excitatory convergence of two units with different preferred o rientations, and intracortical inhibitory interactions. The cells with double orientation tuning for a single bar are found relatively rarel y (about 20%), thus making the first suggestion the most unlikely. Thi s circumstance is of special importance since it provides evidence aga inst the hierarchic formation of the higher-order cortical units from a set of lower-order cells that is still under discussion.(8) The unit s with high sensitivity to cross or corner seem to be ideally suitable for their selection, rather than to serve as classical orientation de tectors only. (C) 1998 IBRO. Published by Elsevier Science Ltd.