Visually evoked potentials: Theory, techniques and clinical applications☆

Neurophysiological Aspects of Color Vision in Primates

Latency functions in human vision

(1) A technique is described for recording with scalp electrodes the occipital response to electrical stimulation of the globe. This "electrically evoked response of the visual system" has been labeled EER. (2) The amplitude of EER is a function of the amount of stimulus current. (3) There is an apparent difference in EER caused by electrode polarity. (4) There is little difference in EER to square pulses of varying durations. However, sawtooth stimuli cause increase of latency of response equivalent to duration of the sawtooth. (5) Although there is considerable variation of EER from individual to individual the response for any one subject appears to be quite constant. (6) The EER differs from the VER to stimuli of the same subjective brightness in several ways. The amplitude of the EER is greater but only when measured at the occipital pole; the latency of the VER is greater. These findings suggest that the EER represents activation of many collateral circuits not directly connected with brightness perception. They also suggest that the electrical stimulus acts on structures between the receptor inner segments and the ganglion cell body.

The Electrically Evoked Response of the Visual System (EER)

Cortical responses to stimulation of the human fovea.

Studies on the visual evoked response. i. the use of the 0.06 degree red target for evaluation of foveal function.

1.

The foveal visual evoked response is diminished or absent in strabismic amblyopia. This confirms the early report of van Balen & Henkes.




2.

There is no such finding in hysterical amblyopia.




3.

On the basis of the work of Hubel & Wiesel in experimental animals this confirms the idea that strabismic amblyopia corresponds to an anatomical defect and hysterical amblyopia does not.




4.

Practical applications of these findings are suggested.

Studies on the visual evoked response: III. Strabismus amblyopia and hysterical amblyopia

Studies have been made on the influence of stimulus through another modality on the visual evoked response. The solution of simple (single digit, three operation) arithmetic problems caused a decrease in VER. The use of equal area, transilluminated letter stimuli with an associated button pushing task, maximized the VER and made it most constant.

Tadashi Nagaya

Papers

Studies on the visual evoked response. i. the use of the 0.06 degree red target for evaluation of foveal function.

Studies on the visual evoked response: III. Strabismus amblyopia and hysterical amblyopia

Studies on the visual evoked response. II. The effect of special cortical activity.