Comment on "visual system's view of acoustic space".

Abstract

MORRELL1 has presented “evidence of a rigorous spatial specificity in the acoustical projection to visual neurones”. He observed that “along the horizontal meridian, the acoustical receptive fields were arranged in as orderly and systematic a way as the receptive fields for vision”. The acoustical receptive fields were mapped onto visual receptive fields “having the same horizontal boundaries as the corresponding visual receptive field(s)” (Fig. 4, ref. 1). The superposition of the visual and auditory receptive fields is difficult to understand if one takes into account that the eyes move within their orbits. What happens to this superposition if, for instance, the eyes are turned 10° to the left side whereas the head remains in its original position? Three different results are conceivable: (1) The visual receptive field is shifted 10° to the left and thus keeps its position with reference to retinal coordinates. The auditory receptive field remains at its original position. In this situation there would be a dissociation between the position of the visual and the auditory receptive fields. (2) Both the visual and the auditory receptive fields are shifted 10° to the left, that is, the visual system would “control” the position of the receptive fields of the auditory system. (3) Both the visual and the auditory receptive fields remain at their original position, that is, the position of the visual receptive fields is remapped in order to coincide with the position of the auditory receptive fields, and thus with head coordinates. The outcome of an experiment investigating these possibilities cannot be anticipated, and the results might differ between an anaesthetized and an unanaesthetized preparation. It seems, therefore, that the data do not yet establish clearly that there is a “rigorous spatial specificity in the acoustical projection to visual neurones”.