TD experienced problems with perceiving visual motion and also reported that bright colours and sharp contrasts made her feel sick. TD also had problems perceiving objects that were more than ± 5 meters away from her. Although TD had some impairments of lower visual functions, these could not explain the problems she experienced with regard to motion perception. Neuropsychological assessment revealed no evidence of Balints Syndrome, hemispatial neglect or visual extinction, prosopagnosia or object agnosia. There was some evidence for impaired spatial processing. On several behavioural tests, TD showed a specific and selective impairment of motion perception that was comparable to LMs performance.TDs ability to determine the direction of movement was tested using a task in which small grey blocks all moved in the same direction with the same speed against a black background. The blocks could move in four directions: right to left, left to right, upward and downward. Speed of movement was varied from 2, 4.5, 9, 15 and 24 degrees per second. Speed and direction were varied randomly across trials. TD had perfect perception of motion direction at speed up to 9 degrees per second. When speed of targets was above 9 degrees per second, TDs performance dropped dramatically to 50% correct at a speed of 15 degrees per second and 0% correct at 24 degrees per second. When the blocks moved at 24 degrees per second, TD consistently reported the exact opposite direction of the actual movement. Pelak and Hoyts Alzheimers patient
In 2000, a 70-year-old man presented with akinetopsia.
There was no restriction in her visual field and no scotoma. Disturbance of movement vision
LMs impression of movement depended on the direction of the movement (horizontal vs vertical), the velocity, and whether she fixated in the center of the motion path or tracked the object with her eyes. Circular light targets were used as stimuli.In studies, LM reported some impression of horizontal movement at a speed of 14 degrees of her predetermined visual field per second (deg/s) while fixating in the middle of the motion path, with difficulty seeing motion both below and above this velocity. When allowed to track the moving spot, she had some horizontal movement vision up to 18 deg/s. For vertical movement, the patient could only see motion below 10 deg/s fixated or 13 deg/s when tracking the target. The patient described her perceptual experience for stimulus velocities higher than 18 and 13 deg/s, respectively as "one light spot left or right" or "one light spot up or down" and "sometimes at successive positions in between", but never as motion. Motion in depth
To determine perception of motion in depth, studies were done in which the experimenter moved a black painted wooden cube on a tabletop either towards the patient or away in line of sight. After 20 trials at 3 or 6 deg/s, the patient had no clear impression of movement.