Akinetopsia (from Greek akinesia 'absence of movement' and opsis 'seeing'),[1] also known as cerebral akinetopsia or motion blindness, is a term introduced by Semir Zeki to describe an extremely rare neuropsychological disorder, having only been documented in a handful of medical cases, in which a patient cannot perceive motion in their visual field, despite being able to see stationary objects without issue.
Inconspicuous akinetopsia is often described by seeing motion as a cinema reel or a multiple exposure photograph.
The akinetopsia often occurs with visual trailing (palinopsia), with afterimages being left at each frame of the motion.
LM described pouring a cup of tea or coffee difficult "because the fluid appeared to be frozen, like a glacier".
LM and other patients have also complained of having trouble following conversations, because lip movements and changing facial expressions were missed.
[2] There is an inability to see motion despite normal spatial acuity, flicker detection, stereo and color vision.
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.
[10] Inconspicuous akinetopsia can be selectively and temporarily induced using transcranial magnetic stimulation (TMS) of area V5 of the visual cortex in healthy subjects.
[10] Inconspicuous akinetopsia can be triggered by high doses of certain antidepressants[18] with vision returning to normal once the dosage is reduced.
V1 is known for its pre-processing capabilities of visual information; however, it is no longer considered the only perceptually effective gateway to the cortex.
[citation needed] In 1918, Goldstein and Gelb reported a 24-year-old male who suffered a gunshot wound in the posterior brain.
[2] Most of what is known about akinetopsia was learned from LM, a 43-year-old female admitted into the hospital October 1978 complaining of headache and vertigo.
[9] LM was diagnosed with thrombosis of the superior sagittal sinus which resulted in bilateral, symmetrical lesions posterior of the visual cortex.
[2][15] LM found no effective treatment, so she learned to avoid conditions with multiple visual motion stimuli, i.e. by not looking at or fixating them.
In addition, she estimated the distance of moving vehicles by means of sound detection in order to continue to cross the street.
Her recognition time for visual objects and words was slightly higher than the control, but not statistically significant.
[9] 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.
[9] Motion aftereffect of vertical stripes moving in a horizontal direction and a rotating spiral were tested.
[9] In 1994, several other observations of LM's capabilities were made using a stimulus with a random distribution of light squares on a dark background that moved coherently.
[12] In 2019, Heutink and colleagues described a 37-year old female patient (TD) with akinetopsia, who was admitted to Royal Dutch Visio, Centre of Expertise for blind and partially sighted people.
TD experienced problems with perceiving visual motion and also reported that bright colours and sharp contrasts made her feel sick.
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 Balint's Syndrome, hemispatial neglect or visual extinction, prosopagnosia or object agnosia.
On several behavioural tests, TD showed a specific and selective impairment of motion perception that was comparable to LM's performance.
When the blocks moved at 24 degrees per second, TD consistently reported the exact opposite direction of the actual movement.
He had difficulty watching television with significant action or movement, such as sporting events or action-filled TV shows.
[10] In 2003, a 60-year-old man complained of the inability to perceive visual motion following a traumatic brain injury, two years prior, in which a large cedar light pole fell and struck his head.
He lost his place when vertically or horizontally scanning a written document and was unable to visualize three-dimensional images from two-dimensional blueprints.