Role of input factors in visual-field asymmetries

This paper examines the implications of lateral tachistoscopic presentation of information for the processing efficiency of the intact cerebral hemispheres. Considering that the understanding of the processes underlying the particular competences of each hemisphere may require, as a preliminary step, the specification of the characteristics of the input on which the brain operates, anatomical, physiological, and psychophysical consequences of briefly stimulating the retinal periphery for the representation of information in the brain are outlined, with special reference to the spatial-frequency spectral composition of the stimuli. Retinal eccentricity and brief exposure duration converge to making the representation of information qualitatively different from the information that the brain normally operates on, which constrains the interpretation of findings with respect to the normal functions of the cerebral hemispheres. A review and discussion of empirical findings relevant to these issues suggest that manipulation of procedural variables may differentially affect the processing efficiency of the cerebral hemispheres and indicate that a given pattern of visual-field asymmetry may be overdetermined by a multitude of variables interacting in complex ways.