Note on Visual and Figural Aftereffects in the Brain Damaged

Abstract

concepts may be applied. He suggests that the arrival in the visual cortex of nerve impulses resulting from a visual stimulus establishes electromotive forces, which set up potentials in the cortical tissue, causing polarization of the cell masses. The resulting stare of electrotonus opposes further flow of such current. Where the initial ease of transmission or conductivity is greatest, this process (satiation) will be most marked. When visual stimulation ends, a process of depolarization occurs, leading to the brief appearance of a negative reverse image. Thus, where conductivity is greatest, satiation will be maximum and the reverse image of the spiral will be seen. Where conductivity is lowest, polarization, electrotonus, and satiation will be minimal; depolariza[ion will be less intense; and the reversal effect of the spiral will be less likely to appear. The notion that brain injury is associated with a change in cortical conductivity has been advanced by Klein and Krech (Z), who discuss particularly the effect of the distortion of a secondarily introduced figure by a preceding percept. They postulate that Ss with low basal conductivity in the central nervous system become satiated more slowly and recover from satiation leu quickly. Thus, if brain damage is associated with low conductivity, distortion of a second percept by residuals of the preceding percept will be more marked. Also, the spontaneous type of aftereffect will be less marked, as our finding indicates.