Neural Correlates of Motion Perception

Motion perception is an essential visual skill which aids our navigation through the environment, allows us to identify self and object motion, and enhances our social interactions. Previous research has demonstrated an advantage for visual processing along the cardinal directions (i.e., horizontal and vertical) compared to oblique (i.e., diagonal) directions. This so called “oblique effect” has been documented in detail for orientation discrimination. The oblique effect for motion direction discrimination has received far less attention. In the present experiments, we systematically assessed the oblique effect in motion perception for motion detection and discrimination and investigated the underlying mechanisms of directional anisotropies using electroencephalography. In one experiment, participants were asked to detect coherent motion from random dot kinematograms (RDKs), and in a second experiment were asked to indicate the direction of motion from RDKs. Reaction times and accuracy were measured as well as latencies and amplitudes of event related potentials. We tested differences among these measures between (and within) cardinal and oblique motion directions. Whereas neural differences between motion directions are subtle, behavioural results show that the oblique effect is more pronounced for motion discrimination than detection. This is in line with previous studies showing that the oblique effect is highly dependent on the tasks. Results will be discussed within the context of the prevalence and relevance of motion directions in our visual environment.