Non-specific Perceptual Organization Deficits After Traumatic Brain Injury.

Abstract

Traumatic Brain Injury (TBI) is a prevalent condition and there is limited visual perception research of this population. Here, we investigated perceptual organization changes in 15 closed head TBI outpatients (and age-matched controls) with diffuse axonal injury only (a fundamental clinical manifestation of TBI) and no other known comorbidities. Patients had normal or corrected visual acuity and differed in the time since the lesion (between 4 and 9 months). Perceptual organization was measured with the Leuven Perceptual Organization Screening Test (L-POST), a coherent motion task (CM) and the Leuven Embedded Figures Test (L-EFT). These tests were chosen to screen for deficits in different aspects of perceptual organization (L-POST), to evaluate local and global processing (L-EFT) and grouping in a dynamic set of stimuli (CM). TBI was significantly impaired compared to controls in all measures for both reaction time and accuracy, except for CM thresholds (p=0.23). Repeated measures ANOVA showed that the TBI group was similarly affected in all aspects of the L-EFT (open vs. closed figures, different number of continued elements shared by figure and ground). TBI was also similarly affected in all perceptual factors of the L-POST (perceptual grouping, figure-ground segmentation, parts in wholes, and shape discrimination). No significant correlations were found between scores and time since lesion, except for CM (r_s=-0.65), which might explain the lack of group-level differences in CM. The only scores significantly correlated to IQ were L-EFT reaction times (r_s=-0.58) and parts in wholes L-POST factor (r_s=0.62). These findings demonstrate that perceptual organization is diffusely affected in TBI and this effect has no substantial correlations with IQ. As many of the neuropsychological tests used to measure different cognitive functions involve some level of visual discrimination and perceptual organization demands, these results must be taken into account in the general neuropsychological evaluation of TBI patients.

Meeting abstract presented at VSS 2015