PURPOSE: The purpose of this study was to investigate the effects of contrast display exposure on neuronal directional and spatial frequency tuning. Neuronal responses were recorded from ninety-four neurons in cortical areas 17 and 18 in two adult cats. METHODS: A multi-channel microelectrode was implanted in cortical areas 17 and 18 of two paralyzed and anaesthetized cats. Various drifting sinusoidal grating contrast displays were presented to one of the cats' eyes in the visual field. Contour plots based on the neuronal responses to the drifting sinusoidal grating displays using various contrasts (i.e., 0.4, 0.7, and 1.0) and velocities (i.e., 4.6, 13.9, 23.1, 32.3, 41.5, 50.8, and 60.0 deg/sec) were plotted as a function of the spatial frequency and the direction associated with each velocity and contrast used. RESULTS: Five parameters were extracted from these contour plots: 1) optimum response, 2) preferred direction, 3) optimum spatial frequency, 4) directional tuning width, and 5) spatial frequency bandwidth. To determine the optimal velocity, each parameter was plotted against each of the specific display contrasts used, and a 'best fit' line was established. Response amplitudes were dependent on the type of contrast utilized; however, the spatial frequency and directional tuning properties were stable for the cortical neurons assessed. CONCLUSIONS: The results of the presentation of different contrasts on neuronal directional and spatial frequency tuning are consistent with behavioral results when medium and high contrast displays are used.
Animals ; Cats ; Contrast Sensitivity/*physiology ; Electrophysiological Phenomena ; Orientation/physiology ; Photic Stimulation/methods ; Sen ; Space Perception/physiology ; Visual Cortex/cytology/*physiology

The relationships between eye movements and head movements of the primate during gaze shifts are analyzed in detail in the present paper. Applying the mechanisms of neurophysiology to engineering domain, we have improved the robot eye-head coordination. A bionic control strategy of coordinated head-eye motion was proposed. The processes of gaze shifts are composed of an initial fast phase followed by a slow phase. In the fast phase saccade eye movements and slow head movements were combined, which cooperate to bring gaze from an initial resting position toward the new target rapidly, while in the slow phase the gaze stability and target fixation were ensured by the action of the vestibulo-ocular reflex (VOR) where the eyes and head rotate by equal amplitudes in opposite directions. A bionic gaze control model was given. The simulation results confirmed the effectiveness of the model by comparing with the results of neurophysiology experiments.
Bionics ; Eye Movements ; physiology ; Fixation, Ocular ; physiology ; Head Movements ; physiology ; Humans ; Ocular Physiological Phenomena ; Orientation ; Photic Stimulation ; Reflex, Vestibulo-Ocular ; physiology ; Saccades ; physiology

OBJECTIVEThe Muller-Lyer illusion is a visual illusion in which a horizontal shaft with an inward-pointing chevron (fins-out) affixed to each end is perceived longer than a shaft with outward-pointing chevrons (fins-in). The goal of this study was to compare the effects of experience and knowledge about the Muller-Lyer illusion on participants' perceptual precision.

METHODSParticipants were undergraduate students (n = 108) who were not familiar with the Muller-Lyer illusion prior to the experiment. The task of participants was to adjust one movable line to make it equal to the other in Muller-Lyer figure. They received ascending and descending Muller-Lyer trials in three blocks with 20 trials each. The Experimental Group received information about the Muller-Lyer illusion prior to the third block.

RESULTSFor the Experimental Group, the amount of departure in Block 3 was reduced significantly compared with previous blocks.

CONCLUSIONKnowledge about the mechanisms underlying visual illusions may play an important role in helping individuals overcome them.

Adult ; Brain ; physiology ; Cognition ; physiology ; Female ; Humans ; Illusions ; physiology ; Learning ; physiology ; Male ; Models, Neurological ; Neuropsychological Tests ; Orientation ; physiology ; Pattern Recognition, Visual ; physiology ; Photic Stimulation ; Sex Characteristics ; Visual Perception ; physiology