Date Presented 04/06/19
Although frequently overlooked, children with cerebral palsy may have a visual dysfunction that can impact their occupational performance. Our brain imaging results show that these children have weaker activity in the V5 visual cortices, and this aberrant activity is linked with their altered perception of visual motion. These results highlight a possible neurophysiological nexus of the visual dysfunction and identify a neurologic target for improved occupational performance.
Primary Author and Speaker: Jacy VerMaas-Hannan
Contributing Authors: James Gehringer, Tony Wilson
Faculty Advisor: Max Kurz
BACKGROUND/AIM: Up to 80% of children with CP have some form of vision or visual perceptual impairment (Fazzi et al., 2012). Despite the high incidence of visual dysfunction, these problems are frequently overlooked, misdiagnosed, and not addressed clinically. This is especially salient considering that visual perception may impact mobility, participation in activities, and social interactions (Philip & Dutton, 2014). Previously we revealed that children with CP have uncharacteristic neural oscillations in the occipital and V5 cortical areas during a visuomotor knee target matching task (Kurz, Proskovec, Gehringer, Heinrichs-Graham, & Wilson, 2017). These altered cortical oscillations appear to be linked with the motor execution errors seen in the children with CP. Cortical processing in V5 is necessary for tracking movement and performing reliable visuomotor transformations in everyday activities. Although the role of V5 is well recognized, the activity of the V5 cortical area in children with CP has not been directly examined. The aim of this study was to more directly examine the neural oscillatory responses in the V5 cortices in a cohort of children with CP.
METHODS: Twenty-one children with CP (Age: 16.1 ± 4.4 yrs.; 13 males, MACS levels I-IV) and twenty-one typically developing (TD) children (Age: 14.0 ± 2.0 yrs; 12 males) participated in this study. Magnetoencephalography and advanced beamforming methods were used to image the neural oscillations in the V5 cortices as the children viewed a random array of black dots that moved coherently in either the horizontal or vertical direction. The children pushed a button each time the direction of the visual stimulus changed from horizontal to vertical. Accuracy in identifying a directional change and the reaction time to identify the change were used as proxy measures for visual perception.
RESULTS: The children with CP were less accurate in identifying a change in the direction of the moving visual stimulus (P = 0.002) and had slower reaction times (P < 0.001). There was a negative correlation between accuracy and the reaction time (r = -0.71, P < 0.001), implying that the children with slower reaction times were also less accurate in perceiving a change in the visual stimulus. Compared with the TD children, the children with CP had significantly weaker beta event related desynchronization (ERD) within the V5 cortical area (P = 0.005). We also identified a positive correlation between the strength of the beta ERD and reaction time (r = 0.40, P = 0.012). This suggests that a weaker V5 cortical activity was associated with the child taking longer to perceive a change in the visual stimulus.
CONCLUSIONS/SIGNIFICANCE: This study is the first to directly show that children with CP have aberrant activity in the V5 cortices when processing a moving visual stimulus. Our findings suggest that stronger neural oscillations in the V5 cortices may reflect the integration of updated visual information needed for occupational performance. These results are significant because they provide neurophysiological evidence that individuals with CP have differences in visual perception that occupational therapists might not recognize or be factoring into their intervention plan. This neurological marker can be used to aid the development of comprehensive assessments and may be a viable metric for gauging intervention effectiveness.
References
Fazzi, E., Signorini, S. G., La Piana, R., Bertone, C., Misefari, W., Galli, J., … Bianchi, P. E. (2012). Neuro-ophthalmological disorders in cerebral palsy: Ophthalmological, oculomotor, and visual aspects. Developmental Medicine and Child Neurology, 54(8), 730–736. https://doi.org/10.1111/j.1469-8749.2012.04324.x
Kurz, M. J., Proskovec, A. L., Gehringer, J. E., Heinrichs-Graham, E., & Wilson, T. W. (2017). Children with cerebral palsy have altered oscillatory activity in the motor and visual cortices during a knee motor task. NeuroImage: Clinical, 15(February), 298–305. https://doi.org/10.1016/j.nicl.2017.05.008
Philip, S. S., & Dutton, G. N. (2014). Identifying and characterising cerebral visual impairment in children: A review. Clinical and Experimental Optometry, 97(3), 196–208. https://doi.org/10.1111/cxo.12155
