Background: Measures of the coherence of electroencephalography (EEG) time-series recorded at spatially distant points on the scalp are often used by researchers to characterize the dynamic interactions of brain regions. In dense-array EEG recordings, one or more electrode signals often contain prominent artifact necessitating replacement of the recorded data with an estimated signal using interpolation from data in valid recordings from the surrounding electrodes. Typically the signal estimation is carried out using spherical spline interpolation (SSI; Perrin et al., 1989); however, it is shown that this can introduce an erroneous increase in coherence between signals because the estimated signal is derived from elements in common recordings from other electrode sites. Although SSI performance depends on three SSI parameters, including interpolation order m, the Legendre polynomial order n, and regularization parameter λ, clear guidelines on how to optimally choose parameters have yet to be established for ensuring the temporal features of interpolated signals are accurate.

There is accruing evidence of spontaneous dyskinesia in individuals with schizophrenia that is independent of medication exposure. Dyskinetic motor behavior is also present in individuals who are at high risk of schizophrenia and appears to have prognostic value for the development of psychosis. Nonetheless, it remains unclear whether dyskinesia is present in first-degree relatives of individuals with schizophrenia and thus associated with genetic liability for schizophrenia (i.e., an endophenotype), or whether the motor abnormality is a biomarker specific to the disease state spectrum. There is also limited information about links between dyskinesia and clinically relevant phenomena such as symptoms and cognition. Because dyskinesia marking genetic liability is likely to be subtle, we used sensitive instrument-based measurement of handwriting fluency to quantify dyskinesia in medicated individuals with schizophrenia, unaffected first-degree biological relatives of individuals with schizophrenia, and control participants. Results indicated that medicated individuals with schizophrenia exhibited more dyskinesia than both relatives and controls, with no difference between relatives and controls. Dyskinesia in individuals with *

Background Accurate perception of visual contours is essential for seeing and differentiating objects in the environment. Both the ability to detect visual contours and the influence of perceptual context created by surrounding stimuli are diminished in people with schizophrenia (SCZ). The central aim of the present study was to better understand the biological underpinnings of impaired contour integration and weakened effects of perceptual context. Additionally, we sought to determine whether visual perceptual abnormalities reflect genetic factors in SCZ and are present in other severe mental disorders. Methods We examined behavioral data and event-related potentials (ERPs) collected during the perception of simple linear contours embedded in similar background stimuli in 27 patients with SCZ, 23 patients with bipolar disorder (BP), 23 first-degree relatives of SCZ, and 37 controls. Results SCZ exhibited impaired visual contour detection while BP exhibited intermediate performance. The orientation of neighboring stimuli (i.e. flankers) relative to the contour modulated perception across all groups, but SCZ exhibited weakened suppression by the perceptual context created by flankers. Late visual (occipital P2) and cognitive (centroparietal P3) neural responses showed group differences and flanker orientation effects, unlike earlier ERPs (occipital P1 and N1). Moreover, behavioral effects of flanker context on contour perception were correlated with modulation in P2 & P3 amplitudes. Conclusion In addition to replicating and extending findings of abnormal contour integration and visual context modulation in SCZ, we provide novel evidence that the abnormal use of perceptual context is associated with higher-order sensory and cognitive processes.