HEADING DETECTION USING MOTION TEMPLATES AND EYE VELOCITY GAIN FIELDS

Eye or head rotation would influence perceived heading direction if it were coded by cells tuned only to retinal flow patterns that correspo nd to linear self-movement. We propose a model for heading detection b ased on motion templates that are also Gaussian-tuned to the amount of rotational flow. Such retinal flow templates allow explicit use of ex tra-retinal signals to create templates tuned to head-centric flow as seen by the stationary eye. Our model predicts an intermediate layer o f 'eye velocity gain fields' in which 'rate-coded' eye velocity is mul tiplied with responses of templates sensitive to specific retinal how patterns. By combination of the activities of one retinal how template and many units with an eye velocity gain held, a new type of unit app ears: its preferred retinal flow changes dynamically in accordance wit h the eye rotation velocity. This unit's activity becomes thereby appr oximately invariant to the amount of eye rotation. The units with eye velocity gain fields form the motion-analogue of the units with eye po sition gain fields found in area 7a, which according to our general ap proach, are needed to transform position from retino-centric to head-c entric coordinates. The rotation-tuned templates can also provide rate -coded visual estimates of eye rotation to allow a pure visual compens ation for rotational flow. Our model is consistent with psychophysical data that indicate a role for extra-retinal as well as visual rotatio n signals in the correct perception of heading. (C) 1998 Elsevier Scie nce Ltd. All rights reserved.