The oblique effect revealed by optical imaging in primary visual cortex of cats

The oblique effect is a ubiquitous visual psychological effect. To explore its underlying neural basis, we quantitatively analyzed the proportion and response amplitude of the cardinal preferred areas and the oblique preferred areas in a fairly large region of the primary visual cortex of cats, using optical imaging based on intrinsic signals. The results show that cardinal preferred areas were larger than oblique preferred areas, with a mean difference of 4.7%. Overall, the responses evoked by cardinal stimuli were generally greater than those by oblique stimuli. The present work provides an explanation for the differences in electrophysiological results reported for this issue, and gives a new insight into the neural basis of the oblique effect.