Recognition of halftone and contour figures under their lateralization and masking

Recognition of shape of natural objects was studied during lateralized tachistoscopic presentation and different degree of noise-like ("rain drops") masking in 15 healthy subjects. Two sets of figures were used: halftone and contour ones. In all masking conditions, the mean group data showed a significantly better recognition of contour images by the left hemisphere as compared to the right hemisphere. The probability of correct response decreased with increase in the degree of masking. Contour figures were recognized significantly better than halftone figures. Gender differences in recognition were revealed. Male subjects displayed no hemispheric preference in recognition of both types of stimuli in both masking conditions. Possible neurophysiological mechanisms and functional significance of the findings are discussed.