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.
Other intact functions include visual space perception and visual identification of shapes, objects, and faces. Besides simple perception, akinetopsia also disturbs visuomotor tasks, such as reaching for objects and catching objects. When doing tasks, feedback of ones own motion appears to be important. Causes
Brain lesions
Akinetopsia may be an acquired deficit from lesions in the posterior side of the visual cortex. Lesions more often cause gross akinetopsia. The neurons of the middle temporal cortex respond to moving stimuli and hence the middle temporal cortex is the motion-processing area of the cerebral cortex. In the case of LM, the brain lesion was bilateral and symmetrical, and at the same time small enough not to affect other visual functions. Some unilateral lesions have been reported to impair motion perception as well. Akinetopsia through lesions is rare, because damage to the occipital lobe usually disturbs more than one visual function. Akinetopsia has also been reported as a result of traumatic brain injury. Transcranial magnetic stimulation
Inconspicuous akinetopsia can be selectively and temporarily induced using transcranial magnetic stimulation (TMS) of area V5 of the visual cortex in healthy subjects. It is performed on a 1 cm² surface of the head, corresponding in position to area V5. With an 800-microsecond TMS pulse and a 28 ms stimulus at 11 degrees per second, V5 is incapacitated for about 20–30 ms. It is effective between −20 ms and +10 ms before and after onset of a moving visual stimulus.