NSERC
2003-2013

Psychophysical investigations of human motion and attention systems

Von Grünau, M. (Concordia University)

My proposed research deals with the study of how we perceive various kinds of motion stimuli and how attentional processes can influence this perception. In the past, I have demonstrated an intimate relationship, between the two. A new direction is to study motion perception and attention also when the observers walk or run while performing perceptual tasks. This includes analyses of eye and head movement patterns.

1. Motion & attention. It is currently accepted that motion stimuli are analyzed at various levels (cortical and sub-cortical). This implies that motion stimuli will lead to neural activity in several areas, each contributing to the overall percept. I propose to continue the study of how motion stimuli are processed concurrently at the various levels. This will be done by measuring static and dynamic motion aftereffects (MAEs; the illusory perception of motion after prolonged exposure to a moving stimulus) and their interocular transfers (IOT; adaptation and test stimuli are presented to different eyes). In particular, I will study the relationship between MAE and motion fading (a selective slowing of motion without fading of the spatial aspects of the stimulus) with the same adaptation stimuli in the same observers in order to examine whether the underlying mechanisms are the same. Luminance- and contrast-modulated stimuli will be used. As a metaphor for selective attention, properties of the ‘attentional spotlight’ (the restricted area where sensitization occurs) will be examined, with particular emphasis on the conditions for splitting of the spotlight (i.e., two spatially distinct areas of sensitization).

2. Locomotion. The approach here is based on the premise that most visual tasks outside the laboratory are performed by an actively moving observer and that vision is intimately tied to action. Observers will therefore be standing, walking or running on a treadmill while performing various visual and visuomotor tasks with stimuli presented on a large projection screen. Eye and head movement patterns will be examined with respect to compensation accuracy, spatial and temporal fixation distributions and their variation with the types of task. Tasks include object pursuit, object detection and avoidance, flow field velocity discrimination, and heading direction judgments.