[Phosphenes elicited by subcortical stimulation in man].

Electrical stimulation of a point in the visual pathway can evoke a visual sensation which is called a phosphene. The phosphenes elicited by intracerebral stimulation were investigated in twenty-three subjects. One hundred and seven phosphenes were reported and all of them appeared in the visual field contralateral to the side of stimulation. The exception was a single case where a diffuse flashing sensation appeared in the whole visual field. Thirteen patients reported white phosphenes and nine patients reported coloured phosphenes. In the medial area (10-15 mm from the midline) of the occipital lobe, stimuli above the calcarine fissure resulted in phosphenes in the lower quadrant of the visual field. In the lateral area (16-32 mm from the midline), however, stimuli above the level of the calcarine fissure tended to produce phosphenes in the upper quadrant. These findings appear to conflict with traditional concept of the physiological anatomy of the visual pathway in man. The possible mechanism of this phenomenon produced by intracerebral stimulation is discussed in relation to the phosphenes produced by cortical stimulation.