Neural Correlates of Predictive Saccades.

Every day we generate motor responses that are timed with external cues. This phenomenon of sensorimotor synchronization has been simplified and studied extensively using finger tapping sequences that are executed in synchrony with auditory stimuli. The predictive saccade paradigm closely resembles the finger tapping task. In this paradigm, participants follow a visual target that "steps" between two fixed locations on a visual screen at predictable ISIs. Eventually, the time from target appearance to saccade initiation (i.e., saccadic RT) becomes predictive with values nearing 0 msec. Unlike the finger tapping literature, neural control of predictive behavior described within the eye movement literature has not been well established and is inconsistent, especially between neuroimaging and patient lesion studies. To resolve these discrepancies, we used fMRI to investigate the neural correlates of predictive saccades by contrasting brain areas involved with behavior generated from the predictive saccade task with behavior generated from a reactive saccade task (saccades are generated toward targets that are unpredictably timed). We observed striking differences in neural recruitment between reactive and predictive conditions: Reactive saccades recruited oculomotor structures, as predicted, whereas predictive saccades recruited brain structures that support timing in motor responses, such as the crus I of the cerebellum, and structures commonly associated with the default mode network. Therefore, our results were more consistent with those found in the finger tapping literature.

Clinical features and psychiatric comorbidities in military veterans with schizophrenia with or without suicidality.

Suicide is currently among the leading causes of death among individuals with schizophrenia. Reducing mortality from suicide remains a major clinical challenge in the care of veterans with schizophrenia. There is a need to increase our understanding of what elevates suicide risk in veterans with schizophrenia as a first step towards the future development of suicide prevention interventions. This study compared demographic and clinical features of military veterans with schizophrenia with vs. without suicidality to determine specific risk factors for suicidality. The sample consisted of two groups of veterans with schizophrenia: suicide ideators and/or attempters (SIA) and individuals without a history of suicidal ideation or attempts (no-SIA). Participants were interviewed using the Structured Clinical Interview for DSM-5 Axis I disorders (SCID-I), Positive and Negative Syndrome Scale for Schizophrenia (PANSS), Hamilton Depression Rating Scale (HDRS), and Schizotypal Personality Questionnaire (SPQ). In bivariate analyses, the PANSS-Positive Symptom scores, PANSS-General Psychopathology scores, HDRS total score, HDRS-Paranoid symptoms item score, and SPQ total scores were higher among SIA compared with no-SIA patients. In this unique clinical sample of veterans with schizophrenia, SIA patients were more likely to have mood disorders, post-traumatic stress disorder (PTSD), and/or alcohol use disorder in comparison to the no-SIA group. Logistic regression analysis indicated that the HDRS total score and presence/absence of comorbid mood disorder drive the difference between the groups. These results indicate that suicide risk assessment in veterans with schizophrenia should include identifying individuals with comorbid mood disorders/symptoms, PTSD, alcohol use disorder, marked positive symptoms, and schizotypal features.