Comparison of the Retinotopic Organization of the Visual Wulst in Nocturnal and Diurnal Raptors, with a Note on the Evolution of Frontal Vision

Abstract

Anatomical studies by KARTEN and his coworkers (1), more recent physiological recording experiments (PETTIGREW and KONISHI (2,3)), and behavioral studies (e.g., see FOX, this volume), all indicate that the visual Wu1st of birds is analogous in its visual processing capabilities to the striate cortex of mammals. Similarities in function between the two structures include the following: (1) Both have laminar organization with monocular information from both eyes arriving in the granular layers (cf. KARTEN, et al., (1), and PETTIGREW and KONISHI (2,3) with HUBEL and WIESEl14)); (2) Binocular convergence of excitatory information in both systems occurs here first (PETTIGREW and KONISHI (2, 3, 5), versus HUBEL and WIESEL (6, 7, 8)); (3) In both structures, binocular excitatory convergence appears to occur at the same level of processing as the elaboration of orientation selective neurons, since the monocular, thalamic afferents have concentrically-organized receptive fields which contrast with the orientation-selective receptive fields of the binocular cortical neurons (cf. PETTIGREW and KONISHI (2,3), with HUBEL and WIESEL (7, 8)); (4) Both structures are primarily concerned with binocular visual processing and neurons are found in each structure which appear to be selectively tuned to stereoscopic depth cues (e.g., cf. PETTIGREW and KONISHI (2,3) with PETTIGREW, NIKARA and BISHOP (9)). This last point is controversial with respect to the monkey because of the technical difficulties involved in the control of the relevant stimuli which, based on psychophysical considerations, may have the order of seconds of arc in primates. Note however that there are now positive reports of disparity-selective neurons in monkey striate cortex (FISCHER and POGGIO (10)) to balance the earlier negative one (HUBEL and WIESEL (11)); (5) The functioning of both is sensitive to visual experience in the neonatal period (PETTIGREW and KONISHI (3); HUBEL and WIESEL (11)).