Peripheral and central contributions to psychophysical spatial interactions.

This chapter is concerned with the functions of some neural structures involved in vision. It does not cover all aspects of vision nor all the neural structures that may be involved in vision. It is limited to a consideration of a portion of the visual system called the geniculocortical system. For the purposes of this chapter, the geniculocortical system is defined as: (1) the peripheral receptor apparatus (retina); (2) the thalamic region receiving input from the retina and (3) the region of cerebral cortex receiving a direct input from the thalamus (cf. Chapters 5 and 7).

Vision: Geniculocortical System

Periodic oscillation of a luminance grating imaged upon the peripheral retina reduces the threshold visibility of a foveally presented test spot. This new effect has been named the “jerk effect”.

Foveal inhibition and facilitation caused by remote grating jerks: Interaction between long-range and short-range effects

Receptive fields of 262 pulvinar neurons were studied. Receptive fields of 142 of these neurons were studied in detail with the aid of a stationary spot of light, flashing in different parts of the receptive field. Depending on responses to presentation of the stationary stimulus the neurons were divided into six groups. The first group included neurons with on-off responses to photic stimulation (44 of 142), the second group neurons with off responses only (42 of 142). In cells of the third group (19 of 142) an on response only was recorded in all structures of the receptive field tested. Neurons of the fourth group (eight of 142) had a receptive field of similar structure to that of the simple receptive fields of neurons in cortical area 17. The fifth group (10 of 142) included neurons with a receptive field of concentric structure, the sixth (19 of 142) consisted of neurons with receptive fields with multiple discharge centers. The structure of the receptive field of these neurons was mosaic, with an irregular distribution of exciting and “silent” zones. The mean response latency of the pulvinar neurons was 40–70 msec. Responses of neurons with shorter (20 msec) and longer (130–160 msec) latent periods also were recorded.

A. Fiorentini

Papers

Retino-geniculate convergence and the analysis of contrast.