Visual-Spatial and Temporal Integration in Patients with Hypothyroidism

Thyroid hormones play an essential role in brain functioning not only during development, but also in adult life. A link between visuospatial abilities and thyroid hormones has already been established. However, it is unclear whether this link is related to the changes in visual information processing, whether the ventral or the dorsal streams are more affected, or the interaction of the two pathways is impaired. The present study aimed to evaluate the effect of hypothyroidism on the visuospatial abilities related to the ventral and dorsal visual pathways using behavioral tasks. Twenty-six newly diagnosed hypothyroid patients and 26 euthyroid controls took part in the study. They had to determine whether the virtual center of radial Glass patterns (GPs) was shifted to the left or right of the screen center, or to discriminate between radial and concentric GPs with varying coherence. Three different conditions were applied: static and two dynamic flicker conditions with a limited lifetime of the dot pairs. The results show that the coherence thresholds were higher in the static condition and the center location task for both groups. The hypothyroid group had higher thresholds in discriminating the radial from the concentric patterns in the dynamic flicker conditions. The proportion of correct responses was lower in the hypothyroid group for patterns with the centers shifted to the right and for concentric compared to the radial patterns. The control group showed decreased performance in localizing the pattern centers shifted to the left. The findings imply that hypothyroidism leads to subtle changes in integrating spatiotemporal information that might be related to deficient processing in the ventral system and the reallocation of spatial attention under cognitive load.