Akinetopsia

Disorder

• Name: Akinetopsia
• Category: Complex
• Existing deep-research providers: openai
• Existing evidence reference count in YAML: 28

Key Pathophysiology Nodes

• V5/MT motion-processing cortex dysfunction
• Left V5/MT susceptibility to acute interference
• Right-hemispheric V5/MT predominance in clinical cases
• Severity depends on surviving motion network components and stimulus speed
• Structural neurological damage to motion network
• Paroxysmal or intoxication-related cortical dysfunction
• Epileptic hyperexcitability of MT/V5 cortex
• Induced disruption from TMS or medications
• Bilateral V5/MT lesions
• Global akinetopsia with chronic course

Citation Inventory (for evidence mapping)

• (none extracted)

Akinetopsia (Motion Blindness) Pathophysiology Core Pathophysiological Mechanisms Akinetopsia – also known as motion blindness – is a rare higher visual disorder in which patients lose the ability to perceive motion, even though their visual acuity for stationary objects remains intact 1 . Fundamentally, the condition arises from disruption of the brain’s visual motion processing pathway, primarily due to damage or dysfunction in the extrastriate cortex called area V5 (also known as the middle temporal visual area, MT) 2 3 . Area V5/MT, together with the adjacent medial superior temporal area (MST), specializes in encoding the speed and direction of moving stimuli 2 . These motion-processing neurons are located near the temporo-parieto-occipital junction in each hemisphere 4 . When this region is impaired bilaterally, the brain can no longer smoothly integrate sequential visual inputs over time – instead of seeing continuous movement, the viewer perceives a series of static “freeze-frames” or jumping images of moving objects 5 6 . In effect, the normal perception of motion as fluid change is lost, confirming that the brain treats motion as a distinct component of vision processed in dedicated neural circuitry 7 . Critically, bilateral lesions to area V5/MT are classically associated with global akinetopsia, i.e. complete motion blindness across the visual field 8 9 . Seminal case studies (e.g. patient L.M.) revealed that bilateral damage to the lateral occipitotemporal cortex encompassing V5 resulted in profound motion perception loss 10 . L.M. could not perceive movement of objects except under very limited conditions (she could only detect motion in the far periphery or when object velocity was extremely slow, <10°/s) 11 12 . This indicates that slow-moving stimuli can sometimes still be perceived thanks to residual pathways, whereas faster motion fails to register. Indeed, about 10% of primary visual cortex neurons are directionselective and may partially compensate when V5 is knocked out 13 . Such surviving network components (e.g. direction-sensitive cells in V1/V2, or intact connections in one hemisphere) can mediate rudimentary motion detection for low velocities or in portions of the visual field 14 . This explains why some akinetopsic patients report perceiving very slow or small movements but not faster motion – essentially a perceptual asynchrony where slow objects are seen but anything moving quickly “disappears” or becomes imperceptible 15 . In other cases, if the lesion is unilateral (affecting V5 in only one hemisphere), patients may experience a milder deficit or hemiakinetopsia, where motion blindness is restricted to the contralateral half of the visual field 16 . However, even unilateral V5 damage can substantially degrade motion perception, especially if the dominant hemisphere’s V5 (often the right side in right-handed individuals) is affected 17 18 . Overall, the dorsal visual stream (the “where” pathway for motion and spatial processing) is the locus of pathology in akinetopsia, in contrast to the ventral stream which handles object form and color 3 . Damage to this dorsal pathway at the level of V5 effectively “cuts off” the brain’s ability to analyze dynamic visual changes, while static form perception via ventral stream remains intact 3 .

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Schematic of the human visual pathways in the brain. The dorsal pathway (blue dashed line, running through occipital to parietal regions) is responsible for motion and spatial processing (“where”), whereas the ventral pathway (green dashed line, into the temporal lobe) handles object identity and form (“what”). Visual information from primary visual cortex (V1, Brodmann area 17) is distributed into these two streams. Area V5 (MT) is a key node in the dorsal stream (highlighted at the temporo-parietal junction) dedicated to detecting object motion 19 . Lesions of V5 in the dorsal stream cause akinetopsia, the inability to perceive motion. 19 3 Beyond the cortical anatomy, various pathophysiological insults can disrupt the motion-perception network. The most common mechanism is structural damage: ischemic stroke in the posterior cerebral artery territory or traumatic brain injury can infarct or shear the cortical tissue in V5/MST, abolishing motion processing 20 21 . Neurodegenerative changes can also target the dorsal visual areas – for instance, patients with the posterior cortical atrophy variant of Alzheimer’s disease (AD) have progressive atrophy in occipito-parietal regions and can develop akinetopsia corresponding to the degree of cortical damage 22 23 . In such cases, the molecular pathology of AD (amyloid-β plaques and tau neurofibrillary tangles accumulating in visual association cortex) underlies a gradual loss of motion processing neurons 24 . Another mechanistic category is transient functional suppression of V5 activity, as seen in epileptic seizures or drug effects. For example, focal epileptic discharges in the right temporal or parietal cortex can propagate and inhibit bilateral MT/V5 function (possibly via aberrant network inhibition through the corpus callosum), leading to temporary full-field motion blindness until the seizure activity resolves 25 26 . One case report described a 68-year-old woman whose complex partial seizures in the right frontotemporal region caused daily episodes where her vision “froze” and lost color, like a black-and-white photograph; imaging confirmed hyperactivity in frontal regions and suppressed blood flow in bilateral occipital motion areas during these episodes 25 27 . Treatment with anti-epileptic medication completely abolished the akinetopsia in this patient, highlighting that the motion blindness was due to reversible cortical dysfunction rather than permanent damage 28 . Similarly, pharmacological suppression of motion pathways has been documented: the antidepressant nefazodone (a serotonergic drug) at high doses can induce reversible akinetopsia, with patients describing a “bizarre derangement” of vision where moving objects appeared as a sequence of freeze-frame images 6 . This drug effect is thought to reflect selective impairment of neural signaling in the dorsal stream (perhaps via serotonin receptors or downstream cortical circuits), again indicating how critical intact cortical network function is for motion perception 6 . In summary, regardless

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of trigger, the core pathophysiology of akinetopsia is the disruption of neural activity in the MT/V5 network, which prevents the normal integration of visual snapshots into a fluid temporal continuum. If the impairment is bilateral and permanent (e.g. a bilateral cortical lesion), the motion blindness is global and enduring 9 . If the disruption is partial, unilateral, or transient (e.g. a small lesion, one hemisphere, or an episodic suppression), the deficit may be incomplete, affecting only part of the visual field or only certain conditions (fast motion, low light, etc.), and in some cases may improve if the underlying cause is treated 29 30 .

Key Molecular and Cellular Players • Genes/Proteins: Notably, no single gene mutation has been identified as a direct cause of akinetopsia – it is usually an acquired cortical syndrome rather than a familial genetic disorder. Instead, genetic factors play an indirect role via underlying diseases. For example, in rare instances akinetopsia occurs in Alzheimer’s disease or other dementias; here, genes like APP (Amyloid precursor protein, HGNC:620) or PSEN1 (HGNC:9508) that drive AD pathology could be considered contributory in that they lead to cortical degeneration 22 . (Tsai and Mendez (2009) reported akinetopsia in a patient with the posterior cortical atrophy form of AD 22 .) However, these genes are not specific to motion processing. Likewise, risk genes for stroke (e.g. those affecting lipid metabolism or coagulation) might predispose to the brain infarcts that cause akinetopsia, but no akinetopsia-specific gene is known. At the protein level, the molecular pathologies underlying neurodegeneration (such as amyloid-β and tau protein aggregates in AD, or prion protein in CJD) can damage the visual motion cortex 24 31 . In Creutzfeldt-Jakob disease (prion disease), for instance, rapid accumulation of misfolded prion protein (PrP^Sc) in the occipital lobes has caused Alice-in-Wonderland-like visual disturbances including akinetopsia 31 . Another protein of interest is serotonin (5-HT) receptors in the cortex – while not a disease protein per se, modulation of 5-HT signaling by drugs can induce akinetopsia (nefazodone is a potent 5-HT_2A antagonist/SSRI that disrupted motion vision 6 ). This suggests that normal neurotransmitter receptor function in MT/V5 neurons is crucial for motion integration. Additionally, signal-transduction proteins involved in cortical plasticity and connectivity (for example, those in glutamatergic synapses or myelin maintenance) may influence how the brain compensates for or manifests motion blindness, although specific candidates are not established in current literature (no OMIM genes are linked to akinetopsia as of now). • Chemical Entities: Several chemicals and drugs have been implicated in akinetopsia, either as triggers or in experimental settings. Nefazodone (an antidepressant in the phenylpiperazine class) is the best-documented; toxicity of this drug caused selective motion perception impairment in multiple reports 6 . Patients described it as if their vision turned into a stroboscopic slideshow, an effect that resolved after the drug was discontinued 6 . Other SSRIs and psychiatric medications have occasionally been reported to cause similar motion-processing disturbances (likely via serotonergic or other neuromodulatory pathways in visual cortex) 6 . Recreational hallucinogens are also notable: LSD and related substances can produce persistent visual perceptual disorders (Hallucinogen Persisting Perception Disorder, HPPD) that include altered motion perception, such as trailing after-images or a sensation of time slowing 32 33 . These phenomena overlap with akinetopsia-like symptoms (e.g. illusory slow motion), presumably because hallucinogens disrupt the normal firing and synchronization of motion-sensitive cortical neurons via 5-HT_2A receptor agonism. In general, any neurotoxic or intoxicant exposure that affects the occipital or parietal cortices could, in theory, induce motion blindness. For instance, antiepileptic drugs or migraine

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medications that alter cortical excitability might precipitate transient akinetopsia in some susceptible individuals, though such cases are extremely rare. On the other hand, anti-seizure medications like carbamazepine can treat akinetopsia when seizures are the cause – one patient with akinetopsia from epileptic seizures due to a parietal AVM had complete symptom resolution on carbamazepine therapy 34 . This underscores that chemical agents can both precipitate and remedy motion blindness, depending on whether they disrupt or restore the neural balance in motion pathways. • Cell Types: The primary cells affected in akinetopsia are neurons of the visual cortex, especially the large excitatory pyramidal neurons in area V5/MT that normally respond to moving visual stimuli (corresponding roughly to layer 4B and 6 output neurons in MT, which project to other cortical areas and to subcortical structures) 2 . These cortical neurons (often characterized functionally by direction-selective receptive fields) are the ones that fail to function when V5 is lesioned or suppressed. Interneurons (such as GABAergic inhibitory neurons) in the motion cortex may also be involved: for example, excessive inhibition or excitation of local circuits (as in seizures or drug effects) can shut down the coordinated activity of V5 pyramidal cells 27 . In addition, neurons upstream and downstream of V5 play roles – the retinal magnocellular ganglion cells (large retinal neurons that detect motion and project to the lateral geniculate nucleus) provide the initial input to the motion pathway. These feed into thalamic relay neurons in the lateral geniculate nucleus (LGN) and then into primary visual cortical neurons (V1), which in turn project to V5 35 36 . While akinetopsia primarily reflects cortical dysfunction, damage to any neurons in this chain (e.g. LGN cells in a thalamic stroke, or the V1–V5 projection neurons in white matter) could interrupt the motion signal flow. Notably, MST neurons (in the medial superior temporal area) are another cell population of interest – they process more complex motion (optic flow, rotation, expansion) and often work in tandem with MT neurons 2 . If MST is also damaged (it lies adjacent to MT), patients might experience additional motion disturbances such as loss of optic flow perception (e.g., an inability to perceive the general movement of the visual scene during self-motion) 37 . In summary, the critical cell types in akinetopsia are the cortical neurons of the dorsal visual stream (both excitatory and inhibitory) that collectively encode moving visual information. Glial cells can be indirectly involved as well – for instance, in demyelinating disease or trauma, oligodendrocytes and astroglia might be damaged, leading to impaired support for the neurons in motion pathways. However, the defining cellular event is the dysfunction or loss of the motion-sensitive neurons themselves, which results in the breakdown of motion perception. • Anatomical Locations: The anatomical locus of akinetopsia is the visual association cortex in the posterior cerebrum – specifically the region of the lateral occipital lobe extending into the inferior parietal and temporal lobes where area V5/MT resides 4 3 . In terms of neuroanatomy, this corresponds to the temporoparietooccipital junction (often on the banks of the lateral occipitotemporal sulcus) and is part of Brodmann areas 19/37. Both hemispheres contain a V5 area; the right hemisphere V5 is thought to be functionally dominant for motion perception in many individuals 17 . Damage to the right occipitoparietal region is especially common in reported cases 20 21 . Bilateral lesions (involving V5 on both sides) typically produce the full syndrome, whereas unilateral right-side lesions can produce motion blindness that may or may not generalize beyond the contralateral visual field 16 38 . Other brain regions that are part of the motion perception network include V1 (primary visual cortex in the occipital lobe, Brodmann 17), V2/V3 (secondary visual areas in occipital cortex), MST (often considered part of the dorsal stream in the parietal lobe), and even the cerebellum (which has connections for visual motion tracking and eye

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movements) 39 . For instance, some research suggests the cerebellum contributes to smooth pursuit eye movements and motion prediction; lesions there might compound motion perception deficits 39 . Anatomically, any lesion encompassing the posterior visual pathways – including the optic radiations and white matter tracts that connect V1 to V5 – can effectively cause akinetopsia by disconnecting critical areas. Cases of posterior cortical atrophy in degenerative disease demonstrate widespread atrophy in the occipito-temporal-parietal junction bilaterally 40 . Meanwhile, functional causes like seizures may not have a visible lesion, but neuroimaging (e.g. SPECT, fMRI) shows abnormal activity in frontal or temporal regions and reduced activity in occipital motion areas during episodes 41 . In summary, the key anatomical substrate of akinetopsia is the MT+/V5 complex in the lateral occipital cortex (UBERON:0002910), with contributions from connected areas in the parietal lobe (UBERON:0001384), occipital lobe (UBERON:0000955), and thalamus (LGN, UBERON:0002111) that together form the dorsal visual stream 39 . Damage to this network at any point can impair the brain’s representation of visual motion.

Disrupted Biological Processes (GO Terms) Several biological processes are perturbed in akinetopsia, corresponding to the breakdown of normal visual and neural functions: • Visual motion perception (GO:0007601 – visual perception): By definition, the process of detecting and interpreting moving visual stimuli is disrupted. Normally, the retina-to-cortex pathway encodes motion via temporal changes in light patterns, which the brain interprets as object movement 19 . In akinetopsia, this process fails – the integration of sequential visual inputs over time is impaired, so the perception of motion cannot emerge from the visual stream 5 6 . This can be seen as a failure of the neural computation of velocity and direction, which is a specialized visual process subserved by area V5/MT neurons. Essentially, the sensory processing of dynamic visual stimuli is selectively lost, even though processing of static visual features (shape, color) remains intact. • Dorsal stream signal transmission and integration: The dorsal visual pathway normally carries signals related to motion and spatial location from V1 through V5 to the parietal lobe 19 42 . In akinetopsia, the biological process of transmitting this information and integrating it into a coherent percept is disrupted. This involves processes like axon-mediated conduction of visual information (from occipital to parietal cortex) and synaptic transmission between motion-processing neurons. For instance, neurons in V1 encode simple motion components and relay to V5, where more complex motion integration (different speeds, directions) occurs; if those synapses or axonal pathways are damaged, the process fails. Neuronal network synchronization in the beta/gamma range – often important for binding visual features across time – may also be affected, preventing the brain from “binding” successive frames into motion. In summary, any biological process involved in the detection, relaying, or integration of moving visual signals is a candidate for disruption. This includes photoreceptor and retinal ganglion cell responses to moving stimuli, thalamocortical relay of transient signals, and especially cortical integration of temporally changing signals in the dorsal stream. • Neurotransmitter signaling and cortical excitability: Underlying the loss of motion perception is often an imbalance or loss of normal neural signaling. In cases of drug-induced or seizure-related akinetopsia, the process of neurotransmission in visual cortex is transiently altered. For example, serotonin-modulating drugs interfering with cortical 5-HT receptors suggest that monoaminergic

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modulation of visual areas is involved in motion processing 6 . Similarly, seizures point to disrupted ion channel activity and excitatory/inhibitory balance in the cortical networks: the process of maintaining normal excitability (via GABAergic inhibition and glutamatergic excitation) is perturbed, leading to a functional inhibition of motion processing neurons 27 . In stroke or TBI, the relevant processes are more degenerative or acute – ischemic cell death, excitotoxicity, and inflammation in the affected cortex. The moment-to-moment biological process of synaptic plasticity is also relevant: normally, if one pathway is damaged, the brain might adapt via plastic changes. There is evidence that residual motion perception can occur via alternate pathways (e.g. pulvinar or collicular inputs to V5, or neuroplastic reorganization) 13 43 . Thus, processes like cortical reorganization and visual learning come into play in long-term adaptation, although in most documented cases true recovery of motion vision is minimal once V5 is destroyed. • Visual sensory processing in related domains: Often, akinetopsia may co-occur with or be distinguished from disruptions in other visual processes. For example, some patients also experience achromatopsia (loss of color perception) if area V4 (ventral stream) is co-damaged 41 . Others have palinopsia or visual trailing if cortical processing of after-images is affected (as in HPPD). These indicate that processes such as color perception (GO:0007602) or visual short-term memory of stimuli could be secondarily involved depending on lesion extent. However, pure akinetopsia is specifically the selective disruption of motion analysis processes in the brain’s visual system, making it a unique disturbance of an otherwise intact visual modality. In terms of formal ontology, akinetopsia entails abnormality of motion perception (HP:0032692) and falls under agnosia (loss of a specific perception). It highlights how specific neural processing pathways (here, the visual motion pathway) can be selectively impaired, illustrating a dissociation in the biological processes of vision.

Cellular and Subcellular Components Involved On the cellular level, the pathology is rooted in cortical gray matter, where the cell bodies and dendrites of motion-sensitive neurons reside. Within area V5/MT of the cortex, the synapses and neuronal dendritic arbors are crucial sites of information processing – this is where incoming signals from V1/V2 are received and integrated. In akinetopsia due to structural lesions, these synaptic connections and cell bodies are destroyed or rendered non-functional. For instance, an ischemic infarct will cause neuronal cell death in layers of V5, and the loss of those neurons’ cell membranes and organelles (such as their mitochondria and synaptic vesicle machinery) means the local circuit is broken. The synaptic cleft is a particularly important subcellular site: in drug-induced akinetopsia, it is at synapses (e.g. serotonin synapses onto cortical neurons) that neurotransmission is altered, effectively silencing the postsynaptic response in the motion pathway 6 . Thus, receptors on the neuronal membrane (for glutamate, GABA, serotonin, etc.) are key molecular components whose function (or blockade) can dictate whether motion signals are transmitted or not. Additionally, the white matter tracts and axon fibers connecting visual processing areas are critical cellular components. The myelinated axons from V1 projecting to V5 (and from V5 to parietal cortex) form part of the visual processing circuit. Damage to these axons – for example, diffuse axonal injury in trauma or demyelination in multiple sclerosis – can disconnect the pathway. In such cases, the nodes of Ranvier and oligodendrocyte-myelin units along these axons are indirectly involved in the pathophysiology: if conduction fails, motion information cannot reach the cortical neurons even if those neurons are intact. In

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one reported case of traumatic brain injury, the patient developed akinetopsia with evidence of posterior white matter atrophy, suggesting the connectivity was disrupted 40 . At the subcellular level, visual cortical neurons rely on calcium signaling and action potential generation in their axon hillocks to fire in response to motion stimuli. Any disruption in ion channel function (for instance, due to hypoxia in stroke or abnormal depolarization in seizures) can affect the cellular excitability of these neurons. Also, synaptic plasticity mechanisms (like long-term potentiation in visual cortex) could be relevant to how motion perception might recover or not; if the subcellular machinery for synaptic strengthening (receptors, second messenger systems) is compromised, the network cannot rewire effectively. In summary, the key cellular components in akinetopsia include the neuronal cell bodies in area V5, their dendrites and synapses (the sites of input integration, located in cortical layer I–IV synaptic zones), and the axons/white matter that connect motion-processing neurons to upstream and downstream areas. The extracellular environment in the visual cortex is also a factor – for example, adequate cerebral blood flow in the occipital lobe is necessary to support these cells, and ischemia (lack of blood supply) swiftly deranges the ionic homeostasis in the extracellular space, leading to neuronal death. Thus, components such as cerebral blood vessels (capillaries of the visual cortex) are indirectly part of the pathophysiology in vascular cases. Ultimately, however, it is the loss of functional synaptic networks in the cortical motion area that underlies the clinical manifestation of akinetopsia.

Disease Progression and Course Akinetopsia can manifest with different time-courses depending on its underlying cause: • Sudden Onset with Static Deficit: In cases of acute brain injury – such as a stroke (infarction/ hemorrhage) or head trauma affecting the occipitoparietal region – akinetopsia often has an abrupt onset. The patient may suddenly notice motion blindness immediately after the neurological event. For example, a person who suffers a bilateral occipital lobe stroke can awaken to find that moving objects are no longer perceivable 20 . In these cases, the deficit is immediate and often permanent. There is typically a single-stage progression: initial loss of motion vision followed by little recovery. Follow-ups of patient L.M. and similar cases years later have shown essentially no improvement in motion perception, indicating that once cortical neurons are destroyed, the brain rarely regains motion vision (short of hypothetical future therapies) 44 . Thus, for vascular or traumatic causes, the disease progression is characterized by an acute onset and a chronic stable deficit. One systematic review found that over half of reported akinetopsia cases had continuous, unremitting symptoms lasting ≥6 months after onset 45 . This chronicity is especially true for bilateral lesions, which virtually always resulted in long-term or permanent motion blindness 46 . • Gradual Onset and Progressive Worsening: When akinetopsia is due to an underlying neurodegenerative process, the symptom may develop insidiously and worsen over time. In the context of Alzheimer’s disease (particularly the posterior cortical atrophy subtype) or other cortical degenerations, patients might initially have subtle difficulty tracking moving objects or may get disoriented by moving scenes. Over months to years, as atrophy in the dorsal visual stream progresses, the motion perception deficit can become more pronounced 22 47 . For instance, an AD patient might go from mild trouble in judging moving cars to an inability to see motion at all in later disease stages. This progressive course mirrors the progression of the neurodegenerative disease

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itself – motion blindness may be one of several visual-spatial deficits that accumulate. Notably, in a 2024 case report, a patient with brain metastases in the parietal lobes developed akinetopsia that likely worsened as the metastatic lesions grew, until treatment was given 48 . These scenarios underscore that when the pathology is progressive, akinetopsia can worsen over time, potentially going from partial (e.g. only fast motion affected) to complete motion blindness. However, because akinetopsia is rare, data on its progression in degenerative disease are limited to individual cases. • Transient or Episodic Course: Akinetopsia can also present as brief episodes that come and go, particularly in non-structural causes like epileptic activity or drug effects. In focal seizures involving the visual areas, patients may experience transient motion blindness lasting seconds to minutes, often with a clear start and end corresponding to seizure activity 25 49 . These episodes may recur until the seizure focus is controlled. In the case of the 68-year-old with daily akinetopsia episodes due to epilepsy, her “motion freezes” would recur frequently but each episode was temporary, and once anti-epileptic medication prevented the seizures, the akinetopsia ceased entirely 28 . Migraine auras are another possible cause of transient akinetopsia – in the context of Alice in Wonderland syndrome (often migraine-related), patients can have brief spells of motion distortion that resolve spontaneously as the migraine passes 50 . Similarly, drug-induced akinetopsia tends to be reversible and linked to dosing. Patients on high-dose nefazodone developed motion blindness that improved upon drug withdrawal over days 6 51 . Hallucinogen persisting perception disorder (HPPD) may cause more chronic lingering symptoms, but these too can fluctuate in intensity and sometimes gradually improve with abstinence and time. Thus, in paroxysmal or toxic etiologies, the course can be intermittent or self-limited. In terms of distinct stages, akinetopsia itself does not have well-defined phases like “early, middle, late” as some diseases do. Instead, the staging often reflects the underlying disorder. For example, if caused by Alzheimer’s, one could correlate akinetopsia’s severity with the mild vs. moderate vs. advanced stages of dementia. If caused by a stroke, one might consider an acute stage (with possible partial recovery in weeks after as swelling reduces) followed by a chronic stage. A unique scenario was reported by Maeda (2019) in which a “fresh” occipital infarct caused akinetopsia that completely resolved after prompt treatment with antiplatelet agents 52 . This implies that in very acute stages of a stroke (before permanent damage sets in), there might be a reversible stage of cortical dysfunction. Generally, though, once neurons are lost, the condition enters a stable chronic phase. About half of documented cases were noted to have progressive or continuous symptoms, whereas a smaller fraction had transient or sporadic episodes 53 . This heterogeneity in course is a hallmark of akinetopsia’s dependence on diverse etiologies. Clinically, it means that the prognosis (whether motion vision can return) hinges on the cause: removal of a cause (treating a seizure, stopping a drug, reperfusing an ischemic penumbra) can lead to improvement, but if the cause is an irreversible lesion or ongoing degeneration, akinetopsia will likely persist or worsen 54 .

Phenotypic Manifestations and Clinical Correlates Akinetopsia’s defining phenotype is an inability to perceive motion in the visual field, despite otherwise normal vision. Patients experience the visual world in a fundamentally altered way: moving objects do not produce the normal sensation of movement. Instead, many patients describe it as seeing the world in a series of static images or “snapshots.” For example, a moving person may appear first in one location, then a split-second later in another, without any fluid intermediate movement – “people were suddenly here or there but I have not seen them moving,” as one patient vividly reported 55 . This can be likened to a flickering strobe-light effect or an old cinematic reel where only every few frames are visible 5 56 .

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Another common description is “freeze-frame vision”: objects in motion look like they momentarily freeze in one position, then jump to the next position 6 . In one case, a patient said moving objects became a trial of “freeze-frame images,” as if reality was a broken video feed 6 . Some patients also report the impression that objects vanish once they start moving – an object that is perfectly visible when still will seem to disappear or turn invisible as soon as it moves beyond a slow drift 57 . This “vanishing object” phenomenon is essentially the extreme of motion blindness: the brain only registers the object when stationary, failing to register it during movement. The clinical manifestations profoundly affect daily life. Visual tracking of moving targets becomes difficult or impossible, so activities like following a conversation in sign language, watching sports, or noting the position of cars while crossing the street are very challenging 56 . Patients often cannot pour liquids properly because the stream of liquid appears frozen – one classic report noted that a patient saw the tea in a cup “pile up like a glacier” because she could not see it flowing, risking overflow. Driving is typically unsafe because the person cannot judge moving traffic or pedestrians 58 . Even walking in a crowd is hazardous; patients frequently bump into moving people because they only realize someone is in front of them when it’s too late 59 . Balance and gait can be affected as well – one patient felt uncomfortable walking and maintaining posture, likely because the optic flow of the environment (which normally informs balance) was not perceived 59 . Reaching for moving objects is impaired; for instance, an akinetopsic individual will struggle to catch a ball or even reach for a moving target like a swinging door, since they lose track of where the target is in mid-motion 60 . These deficits highlight the role of continuous motion feedback in coordination. Despite the dramatic motion deficit, other visual functions are often intact. Patients can recognize faces, read, discern colors (unless a co-lesion causes achromatopsia), and perceive fine details of stationary objects normally 61 62 . This dissociation – motion vs form – is the hallmark of akinetopsia as a selective visual agnosia. However, depending on the extent of brain injury, akinetopsia can co-occur with other visual syndromes. For example, in the context of Balint syndrome (bilateral parietal lesions), one might see akinetopsia alongside simultanagnosia (inability to perceive multiple objects at once) and optic ataxia, since all are dorsal stream functions. In Alzheimer’s or PCA, patients might have elements of visual neglect or other visuo-spatial confusion in addition to motion blindness 22 . One AD case with akinetopsia also had left hemifield neglect, indicating a broader parietal dysfunction 22 . In epileptic akinetopsia, episodes often included achromatopsia (loss of color) concurrently 41 , since the seizures affected area V4 as well as V5. These combinations show that phenotypes can blend if lesions span multiple visual areas. Psychologically, akinetopsia is disorienting and can be anxiety-provoking. Patients remain aware of the deficit – unlike some stroke deficits where insight is lost, motion-blind patients typically know that their perception is abnormal 63 64 . They often develop coping strategies, such as relying more on auditory cues or touch to detect motion. For instance, they might listen for approaching objects that they cannot see moving, or physically touch a pouring container to sense vibrations of liquid movement. Some patients report consciously “training” their hearing to judge distance and movement, effectively substituting auditory motion cues for visual ones 65 . Still, many everyday tasks become impractical. Watching television or movies (which rely on perceiving motion from frame sequences) may be confusing or unpleasant. Some patients withdraw from driving or outdoor activities due to fear of accidents. Quality-of-life surveys specific to akinetopsia are not well-studied (the condition is too rare), but anecdotal reports underscore a significant impact on independence and safety 5 66 .

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In clinical examination, there is no standard “motion perception test” in routine neuro-ophthalmic exams, but certain observations can be made. A simple bedside test is to throw a ball to the patient; an akinetopsic patient will have trouble catching it because they lose sight of it in mid-flight 67 . They may also struggle to estimate the speed of a moving finger or cannot accurately report a moving object’s trajectory. Interestingly, some patients can detect very slow movement (as noted), so if an object is moved slowly enough, they might see it, but once it exceeds a threshold speed, it “disappears.” This threshold phenomenon was documented in patient L.M. (>~10°/s movement could not be perceived) 12 . Another nuance: because primary visual cortex is intact, patients with akinetopsia still have the reflexive responses to motion, such as optokinetic nystagmus (OKN) or blindsight for motion. In Riddoch syndrome (the complement of akinetopsia), cortically blind patients can detect motion without conscious vision; in akinetopsia, conscious motion perception is gone, but there might be subcortical reflexes like dodging an oncoming object without “seeing” it move – although this is not well-documented and likely minimal. In summary, the phenotype of akinetopsia is selective motion blindness: patients cannot smoothly perceive moving objects, leading to a world experienced in disjointed visual episodes. They maintain normal recognition of stationary scenes, which helps distinguish akinetopsia from general vision loss. The core symptom – “life in stop-motion” – can range from mild (trouble with fast motion or crowded movement) to severe (complete inability to see any motion). This rare syndrome dramatically illustrates the modular organization of the visual brain: it proves that one can lose the “movie” of vision while keeping the “pictures.” Each major manifestation, from freeze-frame vision to vanishing moving objects, ties back to the underlying pathophysiology in area V5 and the dorsal visual stream. Clinicians must be aware that a patient reporting “I can see things until they move” is describing this unique phenotype, and it usually signals an injury to the visual motion network 68 69 . Early recognition is important, as treatable causes (like drug toxicity or seizures) should be addressed promptly to restore normal motion vision 54 . Evidence: The association of akinetopsia with bilateral V5 lesions was first documented by Zihl et al. (1983) and Zeki (1991) 70 71 . More recent analyses, such as a 2025 systematic review by Browne et al. (PMID: 39996018), confirm that damage to the MT/V5 complex is the central finding in all cases of motion blindness 72 3 . Neuroimaging and stimulation studies support this: transcranial magnetic stimulation over area V5 can transiently induce akinetopsia 73 , and functional MRI shows MT activation correlating with motion perception. Case reports like Horton & Trobe 1999 (PMID: 10577552) demonstrated druginduced akinetopsia with detailed patient descriptions 6 , and Sakurai et al. 2013 (PMID: 24926238) showed an example of epileptic akinetopsia with resolution on treatment 49 28 . Pelak & Hoyt 2005 described akinetopsia in Alzheimer’s disease, linking it to posterior cortical atrophy on MRI 40 . These and other reports form a body of evidence that underpins our understanding of the pathophysiology and clinical features of akinetopsia, illustrating the crucial role of area V5/MT in visual motion processing and how its dysfunction leads to the fascinating phenomenon of motion blindness. 2 6

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Life in stop motion: a review of akinetopsia - PMC

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https://pmc.ncbi.nlm.nih.gov/articles/PMC12225072/ 2

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Akinetopsia: a systematic review on visual

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3

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Akinetopsia - EyeWiki

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