Akinetopsia
Encyclopedia
Akinetopsia, also known as cerebral akinetopsia or motion blindness, is an extremely rare neuropsychological disorder in which a patient cannot perceive motion in their visual field, despite being able to see stationary objects without issue. For patients with akinetopsia, the world becomes devoid of motion. Most of what is known about akinetopsia was learned through the case study of one patient, LM. There is currently no effective treatment or cure for akinetopsia.
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Patients with akinetopsia struggle with many issues in their day-to-day life, depending on the severity of their condition. One patient, LM, described pouring a cup of tea or coffee difficult "because the fluid appeared to be frozen, like a glacier". She did not know when to stop pouring, because she could not perceive the movement of the fluid rising. LM and other patients have also complained of having trouble following conversations, because lip movements and changing facial expressions were missed. LM stated she felt insecure when more than two people were walking around in a room: "people were suddenly here or there but I have not seen them moving". Movement is inferred by comparing the change in position of an object or person. LM and others have described crossing the street and driving cars to also be of great difficulty. LM started to train her hearing to estimate distance.
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(TMS) of area V5 in healthy subjects. It is performed on a 1 cm2 surface of the head, corresponding in position to area V5. With an 800 micro-second TMS pulse and a 28 ms stimulus at 11 degrees per second, V5 is incapacitated for about 20-30 ms. It is effective between −20ms to +10ms before and after onset of a moving visual stimulus. Inactivating V1 with TMS could induce some degree of akinetopsia 60-70 ms after the onset of the visual stimulus. TMS of V1 is not nearly as effective in inducing akinetopsia than TMS of V5.
patients may have varying degrees of akinetopsia. This could contribute to their marked disorientation. While Pelak and Hoyt have recorded an Alzheimer's case study, there has not been much research done on the subject as of yet.
have damage to V1, but because V5 is intact, they can still sense motion. Inactivating V1 limits motion vision, but does not stop it completely.
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. LM was diagnosed with thrombosis
of the superior sagittal sinus which resulted in bilateral, symmetrical lesions posterior of the visual cortex. These lesions were verified by PET and MRI in 1994. LM had minimal motion perception that was preserved as perhaps a function of V1, as a function of a "higher" order visual cortical area, or some functional sparing of V5.
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. She developed very efficient coping strategies to do this and nevertheless lived her life. In addition, she estimated the distance of moving vehicles by means of sound detection in order to continue to cross the street.
LM was tested in three areas against a 24-year-old female subject with normal vision:
Visual functions other than movement vision
LM had no evidence of a color discrimination deficit in either center or periphery of visual fields. Her recognition time for visual objects and words was slightly higher than the control, but not statistically significant. There was no restriction in her visual field and no scotoma.
Disturbance of movement vision
LM's 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. However she knew the object had changed in position, she knew the size of the cube, and she could correctly judge the distance of the cube in relation to other nearby objects.
Inner and outer visual fields
Detection of movement in the inner and outer visual fields was tested. Within her inner visual field, LM could detect some motion, with horizontal motion more easily distinguished than vertical motion. In her peripheral visual field, the patient was never able to detect any direction of movement. LM's ability to judge velocities was also tested. LM underestimated velocities over 12 deg/s.
Motion aftereffect and Phi phenomenon
Motion aftereffect
of vertical stripes moving in a horizontal direction and a rotating spiral were tested. She was able to detect motion in both patterns, but reported motion aftereffect in only 3 of the 10 trials for the stripes, and no effect for the rotating spiral. She also never reported any impression of motion in depth of the spiral. In Phi phenomenon
two circular spots of light appear alternating. It appears that the spot moves from one location to the other. Under no combination of conditions did the patient report any apparent movement. She always reported two independent light spots.
Visually guided pursuit eye and finger movements
LM was to follow the path of a wire mounted onto a board with her right index finger. The test was performed under purely tactile (blindfolded), purely visual (glass over the board), or tactile-visual condition. The patient performed best in the purely tactile condition and very poorly in the visual condition. She did not benefit from the visual information in the tactile-visual condition either. The patient reported that the difficulty was between her finger and her eyes. She could not follow her finger with her eyes if she moved her finger too fast.
Additional experiments
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. With this stimulus, LM could always determine the axis of motion (vertical, horizontal), but not always the direction. If a few static squares were added to the moving display, identification of direction fell to chance, but identification of the axis of motion was still accurate. If a few squares were moving opposite and orthogonal to the predominant direction, her performance on both direction and axis fell to chance. She was also unable to identify motion in oblique directions, such as 45, 135, 225, and 315 degrees, and always gave answers in cardinal directions, 0, 90, 180, and 270 degrees.
(mild simultanagnosia, optic ataxia, and optic apraxia).
Classification
Akinetopsia is known as a neuropsychological disorder, because a change in brain structure (typically lesions) disturbs the psychological process of understanding sensory information, in this case visual information. Disturbance of only visual motion is possible due to the anatomical separation of visual motion processing from other functions. Like akinetopsia, perception of color can also be selectively disturbed as in achromatopsiaAchromatopsia
Achromatopsia , is a medical syndrome that exhibits symptoms relating to at least five separate individual disorders. Although the term may refer to acquired disorders such as color agnosia and cerebral achromatopsia, it typically refers to an autosomal recessive congenital color vision disorder,...
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Characteristics
Akinetopsia is the inability to see motion despite normal spatial acuity, flicker detection, stereo and color vision. 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 one's own motion appears to be important.Patients with akinetopsia struggle with many issues in their day-to-day life, depending on the severity of their condition. One patient, LM, described pouring a cup of tea or coffee difficult "because the fluid appeared to be frozen, like a glacier". She did not know when to stop pouring, because she could not perceive the movement of the fluid rising. LM and other patients have also complained of having trouble following conversations, because lip movements and changing facial expressions were missed. LM stated she felt insecure when more than two people were walking around in a room: "people were suddenly here or there but I have not seen them moving". Movement is inferred by comparing the change in position of an object or person. LM and others have described crossing the street and driving cars to also be of great difficulty. LM started to train her hearing to estimate distance.
Brain lesions
Akinetopsia is an acquired deficit from lesions in the posterior side of the visual cortex. 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 injuryTraumatic brain injury
Traumatic brain injury , also known as intracranial injury, occurs when an external force traumatically injures the brain. TBI can be classified based on severity, mechanism , or other features...
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Transcranial magnetic stimulation
Akinetopsia can be selectively and temporarily induced using transcranial magnetic stimulationTranscranial magnetic stimulation
Transcranial magnetic stimulation is a noninvasive method to cause depolarization or hyperpolarization in the neurons of the brain...
(TMS) of area V5 in healthy subjects. It is performed on a 1 cm2 surface of the head, corresponding in position to area V5. With an 800 micro-second TMS pulse and a 28 ms stimulus at 11 degrees per second, V5 is incapacitated for about 20-30 ms. It is effective between −20ms to +10ms before and after onset of a moving visual stimulus. Inactivating V1 with TMS could induce some degree of akinetopsia 60-70 ms after the onset of the visual stimulus. TMS of V1 is not nearly as effective in inducing akinetopsia than TMS of V5.
Alzheimer's disease
Besides memory problems, Alzheimer'sAlzheimer's disease
Alzheimer's disease also known in medical literature as Alzheimer disease is the most common form of dementia. There is no cure for the disease, which worsens as it progresses, and eventually leads to death...
patients may have varying degrees of akinetopsia. This could contribute to their marked disorientation. While Pelak and Hoyt have recorded an Alzheimer's case study, there has not been much research done on the subject as of yet.
Areas of visual perception
Two relevant visual areas for motion processing are V5 and V1. These areas are separated by their function in vision. A functional area is a set of neurons with common selectivity and stimulation of this area, specifically behavioral influences. There have been over 30 specialized processing areas found in the visual cortex.V5
V5, also known as visual area MT (middle temporal), is located laterally and ventrally in the temporal lobe, near the intersection of the ascending limb of the inferior temporal sulcus and the lateral occipital sulcus. All of the neurons in V5 are motion selective, and most are directionally selective. Evidence of functional specialization of V5 was first found in primates. Lesions or inactivation of V5 causes akinetopsia.V1
V1, also known as the primary visual cortex, is located in Brodmann area 17. 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. Motion information can reach V5 without passing through V1 and a return input from V5 to V1 is not required for seeing simple visual motion. Motion related signals arrive at V1 (60-70ms) and V5 (<30ms) at different times, with V5 acting independently of V1. Patients with blindsightBlindsight
Blindsight is a phenomenon in which people who are perceptually blind in a certain area of their visual field demonstrate some response to visual stimuli...
have damage to V1, but because V5 is intact, they can still sense motion. Inactivating V1 limits motion vision, but does not stop it completely.
Ventral and dorsal streams
Another thought on visual brain organization is the theory of streams for spatial vision, the ventral stream for perception and the dorsal stream for action. Since LM has impairment in both perception and action (such as grasping and catching actions), it has been suggested that V5 provides input to both perception and action processing streams.Potzl and Redlich's patient
In 1911, Potzl and Redlich reported a 58-year-old female patient with bilateral damage to her posterior brain. She described motion as if the object remained stationary but appeared at different successive positions. Additionally, she also lost a significant amount of her visual field and had nominal aphasiaNominal aphasia
Nominal aphasia is a severe problem with recalling words or names.Dysnomia refers to a less severe form of this word-recall dysfunction. Learning disabilities caused by name-recall problems are usually diagnosed as dysnomia rather than anomia.- Overview :Anomic aphasia is a type of aphasia...
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Goldstein and Gelb's patient
In 1918, Goldstein and Gelb reported a 24-year-old male who suffered a gunshot wound in the posterior brain. The patient reported no impression of movement. He could state the new position of the object (left, right, up, down), but saw "nothing in between". While Goldestein and Gelb believed the patient had damaged the lateral and medial parts of the left occipital lobe, it was later indicated that both occipital lobes were probably affected, due to the bilateral, concentric loss of his visual field. He lost his visual field beyond a 30 degree eccentricity and could not identify visual objects by their proper names.Leibold Gisela (LM)
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 vertigoVertigo (medical)
Vertigo is a type of dizziness, where there is a feeling of motion when one is stationary. The symptoms are due to a dysfunction of the vestibular system in the inner ear...
. LM was diagnosed with thrombosis
Thrombosis
Thrombosis is the formation of a blood clot inside a blood vessel, obstructing the flow of blood through the circulatory system. When a blood vessel is injured, the body uses platelets and fibrin to form a blood clot to prevent blood loss...
of the superior sagittal sinus which resulted in bilateral, symmetrical lesions posterior of the visual cortex. These lesions were verified by PET and MRI in 1994. LM had minimal motion perception that was preserved as perhaps a function of V1, as a function of a "higher" order visual cortical area, or some functional sparing of V5.
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. She developed very efficient coping strategies to do this and nevertheless lived her life. In addition, she estimated the distance of moving vehicles by means of sound detection in order to continue to cross the street.
LM was tested in three areas against a 24-year-old female subject with normal vision:
Visual functions other than movement vision
LM had no evidence of a color discrimination deficit in either center or periphery of visual fields. Her recognition time for visual objects and words was slightly higher than the control, but not statistically significant. There was no restriction in her visual field and no scotoma.
Disturbance of movement vision
LM's 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. However she knew the object had changed in position, she knew the size of the cube, and she could correctly judge the distance of the cube in relation to other nearby objects.
Inner and outer visual fields
Detection of movement in the inner and outer visual fields was tested. Within her inner visual field, LM could detect some motion, with horizontal motion more easily distinguished than vertical motion. In her peripheral visual field, the patient was never able to detect any direction of movement. LM's ability to judge velocities was also tested. LM underestimated velocities over 12 deg/s.
Motion aftereffect and Phi phenomenon
Motion aftereffect
Motion aftereffect
The motion after-effect is a visual illusion experienced after viewing a moving visual stimulus for a time with stationary eyes, and then fixating a stationary stimulus. The stationary stimulus appears to move in the opposite direction to the original stimulus...
of vertical stripes moving in a horizontal direction and a rotating spiral were tested. She was able to detect motion in both patterns, but reported motion aftereffect in only 3 of the 10 trials for the stripes, and no effect for the rotating spiral. She also never reported any impression of motion in depth of the spiral. In Phi phenomenon
Phi phenomenon
The phi phenomenon is an optical illusion defined by Max Wertheimer in the Gestalt psychology in 1912, in which the persistence of vision formed a part of the base of the theory of the cinema, applied by Hugo Münsterberg in 1916....
two circular spots of light appear alternating. It appears that the spot moves from one location to the other. Under no combination of conditions did the patient report any apparent movement. She always reported two independent light spots.
Visually guided pursuit eye and finger movements
LM was to follow the path of a wire mounted onto a board with her right index finger. The test was performed under purely tactile (blindfolded), purely visual (glass over the board), or tactile-visual condition. The patient performed best in the purely tactile condition and very poorly in the visual condition. She did not benefit from the visual information in the tactile-visual condition either. The patient reported that the difficulty was between her finger and her eyes. She could not follow her finger with her eyes if she moved her finger too fast.
Additional experiments
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. With this stimulus, LM could always determine the axis of motion (vertical, horizontal), but not always the direction. If a few static squares were added to the moving display, identification of direction fell to chance, but identification of the axis of motion was still accurate. If a few squares were moving opposite and orthogonal to the predominant direction, her performance on both direction and axis fell to chance. She was also unable to identify motion in oblique directions, such as 45, 135, 225, and 315 degrees, and always gave answers in cardinal directions, 0, 90, 180, and 270 degrees.
Pelak and Hoyt's Alzheimer's patient
In 2000, a 70-year-old man presented with akinetopsia. He had stopped driving two years prior because he could no longer "see movement while driving". His wife noted that he could not judge the speed of another car or how far away it was. He had difficulty watching television with significant action or movement, such as sporting events or action-filled TV shows. He frequently commented to his wife that he could not "see anything going on". When objects began to move they would disappear. He could, however, watch the news, because no significant action occurred. In addition he had signs of Balint's syndromeBalint's syndrome
Bálint's syndrome is an uncommon and incompletely understood triad of severe neuropsychological impairments: inability to perceive the visual field as a whole , difficulty in fixating the eyes , and inability to move the hand to a specific object by using vision...
(mild simultanagnosia, optic ataxia, and optic apraxia).