Akinetopsia

Akinetopsia, aswell accepted as bookish akinetopsia or motion blindness, is an acutely attenuate neuropsychological ataxia in which a accommodating cannot apperceive motion in their beheld field, admitting getting able to see anchored altar after issue. For patients with akinetopsia, the apple becomes bare of motion. Most of what is accepted about akinetopsia was abstruse through the case abstraction of one patient, LM. There is currently no able analysis or cure for akinetopsia.

Classification

Akinetopsia is accepted as a neuropsychological disorder, because a change in academician anatomy (typically lesions) disturbs the cerebral action of compassionate acoustic information, in this case beheld information. Disturbance of alone beheld motion is accessible due to the anatomical break of beheld motion processing from added functions. Like akinetopsia, acumen of blush can aswell be selectively abashed as in achromatopsia.

Characteristics

Akinetopsia is the disability to see motion admitting accustomed spatial acuity, beam detection, stereo and blush vision. Added complete functions cover beheld amplitude acumen and beheld identification of shapes, objects, and faces.2 Besides simple perception, akinetopsia aswell disturbs visuomotor tasks, such as extensive for objects3 and communicable objects.4 If accomplishing tasks, acknowledgment of one's own motion appears to be important.4

Patients with akinetopsia attempt with abounding issues in their circadian life, depending on the severity of their condition. One patient, LM, declared cloudburst a cup of tea or coffee difficult "because the aqueous appeared to be frozen, like a glacier".5 She did not apperceive if to stop pouring, because she could not apperceive the movement of the aqueous rising. LM and added patients accept aswell complained of accepting agitation afterward conversations, because lip movements and alteration facial expressions were missed.56 LM declared she acquainted afraid if added than two humans were walking about in a room: "people were al of a sudden actuality or there but I accept not apparent them moving".5 Movement is accepted by comparing the change in position of an article or person. LM and others accept declared bridge the artery and active cars to aswell be of abundant difficulty.56 LM started to alternation her audition to appraisal distance.

Causes

Brain lesions

Akinetopsia is an acquired arrears from lesions in the afterwards ancillary of the beheld cortex. The neurons of the average banausic case acknowledge to affective stimuli and appropriately the average banausic case is the motion-processing breadth of the bookish cortex. In the case of LM, the academician bane was mutual and symmetrical, and at the aforementioned time baby abundant not to affect added beheld functions.7 Some unilateral lesions accept been appear to blemish motion acumen as well. Akinetopsia through lesions is rare, because accident to the occipital affiliate usually disturbs added than one beheld function.5 Akinetopsia has aswell been appear as a aftereffect of alarming academician injury.6

editTranscranial alluring stimulation

Akinetopsia can be selectively and briefly induced application transcranial alluring dispatch (TMS) of breadth V5 in advantageous subjects.8 It is performed on a 1 cm2 apparent of the head, agnate in position to breadth V5. With an 800 micro-second TMS beating and a 28 ms bang at 11 degrees per second, V5 is bedridden for about 20-30 ms. It is able amid −20ms to +10ms afore and afterwards access of a affective beheld stimulus. Inactivating V1 with TMS could abet some amount of akinetopsia 60-70 ms afterwards the access of the beheld stimulus. TMS of V1 is not about as able in inducing akinetopsia than TMS of V5.8

editAlzheimer's disease

Besides anamnesis problems, Alzheimer's patients may accept capricious degrees of akinetopsia.9 This could accord to their apparent disorientation. While Pelak and Hoyt accept recorded an Alzheimer's case study, there has not been abundant analysis done on the accountable as of yet.6

Areas of visual perception

Two accordant beheld areas for motion processing are V5 and V1. These areas are afar by their activity in vision.10 A anatomic breadth is a set of neurons with accepted selectivity and dispatch of this area, accurately behavioral influences.11 There accept been over 30 specialized processing areas begin in the beheld cortex.12

editV5

V5, aswell accepted as beheld breadth MT (middle temporal), is amid alongside and ventrally in the banausic lobe, abreast the circle of the ascendance limb of the inferior banausic sulcus and the crabbed occipital sulcus. All of the neurons in V5 are motion selective, and a lot of are directionally selective.1 Evidence of anatomic specialization of V5 was aboriginal begin in primates.2 Lesions or inactivation of V5 causes akinetopsia.

editV1

V1, aswell accepted as the primary beheld cortex, is amid in Brodmann breadth 17. V1 is accepted for its pre-processing capabilities of beheld information, about it is no best advised the alone perceptually able aperture to the cortex.8 Motion advice can ability V5 after casual through V1 and a acknowledgment ascribe from V5 to V1 is not appropriate for seeing simple beheld motion.8 Motion accompanying signals access at V1 (60-70ms) and V5 (<30ms) at altered times, with V5 acting apart of V1.8 Patients with blindsight accept accident to V1, but because V5 is intact, they can still faculty motion.12 Inactivating V1 banned motion vision, but does not stop it completely.8

editVentral and after streams

Another anticipation on beheld academician alignment is the approach of streams for spatial vision, the belly beck for acumen and the after beck for action.3 Since LM has crime in both acumen and activity (such as acquisitive and communicable actions), it has been appropriate that V5 provides ascribe to both acumen and activity processing streams

Case studies

Potzl and Redlich's patient

In 1911, Potzl and Redlich arise a 58-year-old changeable accommodating with mutual accident to her after brain.1 She declared motion as if the article remained anchored but appeared at altered alternating positions. Additionally, she aswell absent a cogent bulk of her beheld acreage and had anomic aphasia.

editGoldstein and Gelb's patient

In 1918, Goldstein and Gelb arise a 24-year-old macho who suffered a gunshot anguish in the after brain.1 The accommodating arise no consequence of movement. He could accompaniment the new position of the article (left, right, up, down), but saw "nothing in between".1 While Goldestein and Gelb believed the accommodating had damaged the crabbed and centermost locations of the larboard occipital lobe, it was after adumbrated that both occipital lobes were apparently affected, due to the bilateral, concentric accident of his beheld field. He absent his beheld acreage aloft a 30 amount aberration and could not analyze beheld altar by their able names.1

edit"LM"

Most of what is accepted about akinetopsia was abstruse from LM, a 43-year-old changeable accepted into the hospital October 1978 accusatory of cephalalgia and vertigo.5 LM was diagnosed with occlusion of the aloft sagittal atrium which resulted in bilateral, balanced lesions after of the beheld cortex.5 These lesions were absolute by PET and MRI in 1994.2 LM had basal motion acumen that was preserved as conceivably a activity of V1, as a activity of a "higher" adjustment beheld cortical area, or some anatomic sparing of V5.17

LM begin no able treatment, so she abstruse to abstain altitude with assorted beheld motion stimuli, i.e. by not searching at or fixating them. She developed actual able arresting strategies to do this and about lived her life. In addition, she estimated the ambit of affective cars by agency of complete apprehension in adjustment to abide to cantankerous the street.57

LM was activated in three areas adjoin a 24-year-old changeable accountable with accustomed vision:

Visual functions added than movement vision

LM had no affirmation of a blush bigotry arrears in either centermost or ambit of beheld fields. Her acceptance time for beheld altar and words was hardly college than the control, but not statistically significant. There was no brake in her beheld acreage and no scotoma.

Disturbance of movement vision

LM's consequence of movement depended on the administration of the movement (horizontal vs vertical), the velocity, and whether she bedeviled in the centermost of the motion aisle or tracked the article with her eyes. Annular ablaze targets were acclimated as stimuli.

In studies, LM arise some consequence of accumbent movement at a acceleration of 14 degrees of her agreed beheld acreage per additional (deg/s) while fixating in the average of the motion path, with adversity seeing motion both beneath and aloft this velocity. If accustomed to clue the affective spot, she had some accumbent movement eyes up to 18 deg/s. For vertical movement, the accommodating could alone see motion beneath 10 deg/s bedeviled or 13 deg/s if tracking the target. The accommodating declared her perceptual acquaintance for bang velocities college than 18 and 13 deg/s, appropriately as "one ablaze atom larboard or right" or "one ablaze atom up or down" and "sometimes at alternating positions in between", but never as motion.5

Motion in depth

To actuate acumen of motion in depth, studies were done in which the experimenter confused a atramentous corrective lath cube on a tabletop either arise the accommodating or abroad in band of sight. After 20 trials at 3 or 6 deg/s, the accommodating had no bright consequence of movement. About she knew the article had afflicted in position, she knew the admeasurement of the cube, and she could accurately adjudicator the ambit of the cube in affiliation to added adjacent objects.5

Inner and alien beheld fields

Detection of movement in the close and alien beheld fields was tested. Within her close beheld field, LM could ascertain some motion, with accumbent motion added calmly acclaimed than vertical motion. In her borderline beheld field, the accommodating was never able to ascertain any administration of movement. LM's adeptness to adjudicator velocities was aswell tested. LM underestimated velocities over 12 deg/s.5

Motion aftereffect and Phi phenomenon

Motion aftereffect of vertical stripes affective in a accumbent administration and a alternating circling were tested. She was able to ascertain motion in both patterns, but arise motion aftereffect in alone 3 of the 10 trials for the stripes, and no aftereffect for the alternating spiral. She aswell never arise any consequence of motion in abyss of the spiral. In Phi abnormality two annular spots of ablaze arise alternating. It appears that the atom moves from one area to the other. Beneath no aggregate of altitude did the accommodating address any credible movement. She consistently arise two absolute ablaze spots.5

Visually guided afterward eye and feel movements

LM was to chase the aisle of a wire army assimilate a lath with her appropriate basis finger. The analysis was performed beneath absolutely concrete (blindfolded), absolutely beheld (glass over the board), or tactile-visual condition. The accommodating performed best in the absolutely concrete activity and actual ailing in the beheld condition. She did not account from the beheld advice in the tactile-visual activity either. The accommodating arise that the adversity was amid her feel and her eyes. She could not chase her feel with her eyes if she confused her feel too fast.5

Additional experiments

In 1994, several added observations of LM's capabilities were fabricated application a bang with a accidental administration of ablaze squares on a aphotic accomplishments that confused coherently.2 With this stimulus, LM could consistently actuate the arbor of motion (vertical, horizontal), but not consistently the direction. If a few changeless squares were added to the affective display, identification of administration fell to chance, but identification of the arbor of motion was still accurate. If a few squares were affective adverse and erect to the absolute direction, her achievement on both administration and arbor fell to chance. She was aswell clumsy to analyze motion in angled directions, such as 45, 135, 225, and 315 degrees, and consistently gave answers in basal directions, 0, 90, 180, and 270 degrees.2

editPelak and Hoyt's Alzheimer's patient

In 2000, a 70-year-old man presented with akinetopsia. He had chock-full active two years above-mentioned because he could no best "see movement while driving".6 His wife acclaimed that he could not adjudicator the acceleration of accession car or how far abroad it was. He had adversity watching television with cogent activity or movement, such as antic contest or action-filled TV shows. He frequently commented to his wife that he could not "see annihilation traveling on".6 If altar began to move they would disappear. He could, however, watch the news, because no cogent activity occurred. In accession he had signs of Balint's affection (mild simultanagnosia, optic ataxia, and optic apraxia).6

editPelak and Hoyt's TBI patient

In 2003, a 60-year-old man complained of the disability to apperceive beheld motion afterward a alarming academician abrasion or TBI, two years prior, in which a ample cedar ablaze pole fell and addled his head.6 He gave examples of his adversity as a hunter. He was clumsy to apprehension game, to clue added hunters, or to see his dog advancing arise him. Instead, these altar would arise in one area and again another, after any movement getting apparent amid the two locations. He had difficulties active and afterward a accumulation conversation. He absent his abode if angular or angular scanning a accounting certificate and was clumsy to anticipate three-dimensional images from two-dimensional blueprints