Inversion of Perceived Direction of Motion Caused by Spatial Undersampling in Two Children with Periventricular Leukomalacia

Abstract

Abstract& We report here two cases of two young diplegic patients with cystic periventricular leukomalacia who systematically, and with high sensitivity, perceive translational motion of a random-dot display in the opposite direction. The apparent inversion was specific for translation motion: Rotation and expansion motion were perceived correctly, with normal sensitivity. It was also specific for random-dot patterns, not occurring with gratings. For the one patient that we were able to test extensively, contrast sensitivity for static stimuli was normal, but was very low for direction discrimination at high spatial frequencies and all temporal frequencies. His optokinetic nystagmus movements were normal but he was unable to track a single translating target, indicating a perceptual origin of the tracking deficit. The severe deficit for motion perception was also evident in the seminatural situation of a driving simulation video game. The perceptual deficit for translational motion was reinforced by functional magnetic resonance imaging studies. Translational motion elicited no response in the MT complex, although it did produce a strong response in many visual areas when contrasted with blank stimuli. However, radial and rotational motion produced a normal pattern of activation in a subregion of the MT complex. These data reinforce the existent evidence for independent cortical processing for translational, and circular or radial flow motion, and further suggest that the two systems have different vulnerability and plasticity to prenatal damage. They also highlight the complexity of visual motion perception, and how the delicate balance of neural activity can lead to paradoxical effects such as consistent misperception of the direction of motion. We advance a possible explanation of a reduced spatial sampling of the motion stimuli and report a simple model that simulates well the experimental results. &

BOLD Response Selective to Flow-Motion in Very Young Infants

“…Timing of arrival of spike input to cortex is crucial for motion perception. Jitter in temporal delay of the order of milliseconds is sufficient to disrupt or even invert motion [ 77 ]; disorganization of input spike trains or high levels of noise may be sufficient to impede the formation of direction selectivity at the cortical level. As input motion signals become more reliable and organized, the cortex may be capable of developing the complex neuronal circuitry for direction selectivity and trajectory integration only within a very limited time window.…”

Cerebral Visual Impairment in Children

“…Impaired motion perception is common in children born before 34 weeks, and is more marked in those who manifest periventricular white matter lesions (Guzzetta et al 2009 ). Specifi c aspects of motion perception can be defi cient, for example the perception of linear motion, while other aspects, such as seeing radial and circular motion may be intact in children with evidence of periventricular white matter pathology ( Morrone et al 2008). Children born extremely prematurely may also have diffi culties with motion-defi ned form processing, but may in addition exhibit problems with visual search, stereopsis, and with visuo-spatial tasks (construction, mental rotation) (Jacobson et al 2006 ).…”

Dorsal Stream Dysfunction in Children. A Review and an Approach to Diagnosis and Management

“…The authors suggested that there may therefore be different developmental requirements for establishment of different neural processes (such as the requirement of precise timing of neural signals) rather than differential vulnerability of different anatomical regions and proposed that extrastriate mechanisms develop in parallel but the dorsal stream has a greater vulnerability to early neurological impairment. Recent work by Morrone et al [78] reported two cases of diplegic children with PVL who both perceived translational motion of a random-dot display in the opposite direction. Circular and radial motion perception was normal, reinforcing the idea that translational motion is processed in a separate area.…”