Neural mechanisms of smooth pursuit eye movements in schizotypy

Abstract

Patients with schizophrenia as well as individuals with high levels of schizotypy are known to have deficits in smooth pursuit eye movements (SPEM). Here, we investigated, for the first time, the neural mechanisms underlying SPEM performance in high schizotypy. Thirty-one healthy participants [N = 19 low schizotypes, N = 12 high schizotypes (HS)] underwent functional magnetic resonance imaging at 3T with concurrent oculographic recording while performing a SPEM task with sinusoidal stimuli at two velocities (0.2 and 0.4 Hz). Behaviorally, a significant interaction between schizotypy group and velocity was found for frequency of saccades during SPEM, indicating impairments in HS in the slow but not the fast condition. On the neural level, HS demonstrated lower brain activation in different regions of the occipital lobe known to be associated with early sensory and attentional processing and motion perception (V3A, middle occipital gyrus, and fusiform gyrus). This group difference in neural activation was independent of target velocity. Together, these findings replicate the observation of altered pursuit performance in highly schizotypal individuals and, for the first time, identify brain activation patterns accompanying these performance changes. These posterior activation differences are compatible with evidence of motion processing deficits from the schizophrenia literature and, therefore, suggest overlap between schizotypy and schizophrenia both on cognitive-perceptual and neurophysiological levels. However, deficits in frontal motor areas observed during pursuit in schizophrenia were not seen here, suggesting the operation of additional genetic and/or illness-related influences in the clinical disorder.

Neural effects of methylphenidate and nicotine during smooth pursuit eye movements

“…The smooth pursuit eye movement (SPEM) task requires a mechanism to track a moving object in extra-personal space without head movement and draws upon attention, motion processing and temporo-spatial prediction (Barnes, 2008). The neural correlates of the required sensorimotor feedback system are well established in both humans and non-human primates and include motion processing regions, such as area V5, and attention and prediction-related regions in frontal and parietal cortices, namely frontal, parietal and supplementary eye fields and subcortical structures such as thalamus and putamen (Lencer and Trillenberg, 2008;Meyhöfer et al, 2015;Thier and Ilg, 2005).…”

“…The SPEM paradigm was identical to the task used in Meyhöfer et al (2015). In brief, the task was presented in a block design consisting of ten pursuit blocks and nine fixation blocks.…”

“…High and low frequency block onsets were modelled in separate regressors. Fixation blocks were not modelled and formed the implicit baseline (Meyhöfer et al, 2015). The six motion regressors from the realignment procedure were entered as covariates of no interest.…”

“…The motion parameter TD was included as a covariate of no 12 interest. Task activation was obtained from the contrast pursuit>baseline and frequency activation was obtained by the contrast high>low (Meyhöfer et al, 2015).…”

“…The ROI consisted of clusters that were significantly activated during smooth pursuit. The pursuit activation ROI mask was obtained from an independent sample from a previous study who had performed the same task in the same scanner (Meyhöfer et al, 2015).…”