SPATIAL INTEGRATION IN COHERENT MOTION DETECTION AND IN THE MOVEMENT AFTEREFFECT

Sensitivity characteristics and spatial integration properties of the motion-detection system are compared with those of the system responsi ble for the movement aftereffect (MAE), elicited by the same stimulus. This provides new information about the mechanisms involved in MAE ge neration. A screen was divided into a chequerboard where the squares w ere filled with random-pixel arrays moving in opposite directions. Cha nging the size of the squares produced drastic changes in the percept during the adaptation phase and in the MAE during the test phase. One striking new phenomenon that is described is 'structure from MAE'. The results indicate that the receptive fields of units involved in elici ting the MAE are larger than the receptive-field sizes of units involv ed in detection and segregation of motion components in the stimulus. Furthermore, the results suggest that the receptive fields contributin g to the MAE are involved in complex interactions in which different l ocal motion directions are integrated in pattern-specific ways.