RESUMEN
In primates, inspection of a visual scene is typically interrupted by frequent gaze shifts, occurring at an average rate of three to five times per second. Perceptually, these gaze shifts are accompanied by a compression of visual space toward the saccade target, which may be attributed to an oculomotor signal that transiently influences visual processing. While previous studies of compression have focused exclusively on saccadic eye movements made with the head artificially immobilized, many brain structures involved in saccade generation also encode combined eye-head gaze shifts. Thus, in order to understand the interaction between gaze motor and visual signals, we studied perception during eye-head gaze shifts and found a powerful compression of visual space that was spatially directed toward the intended gaze (and not the eye movement) target location. This perceptual compression was nearly constant in duration across gaze shift amplitudes, suggesting that the signal that triggers compression is largely independent of the size and kinematics of the gaze shift. The spatial pattern of results could be captured by a model that involves interactions, on a logarithmic map of visual space, between two loci of neural activity that encode the gaze shift vector and visual stimulus position relative to the fovea.
Asunto(s)
Modelos Neurológicos , Movimientos Sacádicos/fisiología , Percepción Espacial/fisiología , Colículos Superiores/fisiología , Visión Binocular/fisiología , Animales , Fenómenos Biomecánicos/fisiología , Fijación Ocular/fisiología , Fóvea Central/fisiología , Cabeza , Humanos , Inmovilización/métodos , Masculino , Estimulación Luminosa/métodos , Primates , Desempeño Psicomotor/fisiologíaRESUMEN
Our ability to explore our surroundings requires a combination of high-resolution vision and frequent rotations of the visual axis toward objects of interest. Such gaze shifts are themselves a source of powerful retinal stimulation, and so the visual system appears to have evolved mechanisms to maintain perceptual stability during movements of the eyes in space. The mechanisms underlying this perceptual stability can be probed in the laboratory by briefly presenting a stimulus around the time of a saccadic eye movement and asking subjects to report its position. Under such conditions, there is a systematic misperception of the probes toward the saccade end point. This perisaccadic compression of visual space has been the subject of much research, but few studies have attempted to relate it to specific brain mechanisms. Here, we show that the magnitude of perceptual compression for a wide variety of probe stimuli and saccade amplitudes is quantitatively predicted by a simple heuristic model based on the geometry of retinotopic representations in the primate brain. Specifically, we propose that perisaccadic compression is determined by the distance between the probe and saccade end point on a map that has a logarithmic representation of visual space, similar to those found in numerous cortical and subcortical visual structures. Under this assumption, the psychophysical data on perisaccadic compression can be appreciated intuitively by imagining that, around the time of a saccade, the brain confounds nearby oculomotor and sensory signals while attempting to localize the position of objects in visual space.