Elements of exogenous attentional cueing preserved during optokinetic motion of the visual scene.

Navigating through our environment raises challenges for perception by generating salient background visual motion and eliciting prominent eye movements to stabilise the retinal image. It remains unclear if exogenous spatial attentional orienting is possible during background motion and the eye movements it causes and whether this compromises the underlying neural processing. To test this, we combined exogenous orienting, visual scene motion, and electroencephalography (EEG). A total of 26 participants viewed a background of moving black and grey bars (optokinetic stimulation). We tested for effects of non-spatially predictive peripheral cueing on visual motion discrimination of a target dot, presented either at the same (valid) or opposite (invalid) location as the preceding cue. Valid cueing decreased reaction times not only when participants kept their gaze fixed on a central point (fixation blocks) but also even when there was no fixation point, so that participants performed intensive, repetitive tracking eye movements (eye movement blocks). Overall, manual response reaction times were slower during eye movements. Cueing also produced reliable effects on neural activity on either block, including within the first 120 ms of neural processing of the target. The key pattern with larger event-related potential (ERP) amplitudes on invalid versus valid trials showed that the neural substrate of exogenous cueing was highly similar during eye movements or fixation. Exogenous peripheral cueing and its neural correlates are robust against distraction from the moving visual scene, important for perceptual cognition during navigation.

Right frontal eye field has perceptual and oculomotor functions during optokinetic stimulation and nystagmus.

The right frontal eye field (rFEF) is associated with visual perception and eye movements. rFEF is activated during optokinetic nystagmus (OKN), a reflex that moves the eye in response to visual motion (optokinetic stimulation, OKS). It remains unclear whether rFEF plays causal perceptual and/or oculomotor roles during OKS and OKN. To test this, participants viewed a leftward-moving visual scene of vertical bars and judged whether a flashed dot was moving. Single pulses of transcranial magnetic stimulation (TMS) were applied to rFEF on half of trials. In half of blocks, to explore oculomotor control, participants performed an OKN in response to the OKS. rFEF TMS, during OKN, made participants more accurate on trials when the dot was still, and it slowed eye movements. In separate blocks, participants fixated during OKS. This not only controlled for eye movements but also allowed the use of EEG to explore the FEF's role in visual motion discrimination. In these blocks, by contrast, leftward dot motion discrimination was impaired, associated with a disruption of the frontal-posterior balance in alpha-band oscillations. None of these effects occurred in a control site (M1) experiment. These results demonstrate multiple related yet dissociable causal roles of the right FEF during optokinetic stimulation.NEW & NOTEWORTHY This study demonstrates causal roles of the right frontal eye field (FEF) in motion discrimination and eye movement control during visual scene motion: previous work had only examined other stimuli and eye movements such as saccades. Using combined transcranial magnetic stimulation and EEG and a novel optokinetic stimulation motion-discrimination task, we find evidence for multiple related yet dissociable causal roles within the FEF: perceptual processing during optokinetic stimulation, generation of the optokinetic nystagmus, and the maintenance of alpha oscillations.

To Move or Not to Move? Functional Role of Ventral Premotor Cortex in Motor Monitoring During Limb Immobilization.

Anatomo-clinical evidence from motor-awareness disorders after brain-damages suggests that the premotor cortex (PMC) is involved in motor-monitoring of voluntary actions. Indeed, PMC lesions prevent patients from detecting the mismatch between intended, but not executed, movements with the paralyzed limb. This functional magnetic resonance imaging study compared, in healthy subjects, free movements against blocked movements, precluded by a cast. Cast-related corticospinal excitability changes were investigated by using transcranial magnetic stimulation. Immediately after the immobilization, when the cast prevented the execution of left-hand movements, the contralateral right (ventral) vPMC showed both increased hemodynamic activity and increased functional connectivity with the hand area in the right somatosensory cortex, suggesting a vPMC involvement in detecting the mismatch between planned and executed movements. Crucially, after 1 week of immobilization, when the motor system had likely learned that no movement could be executed and, therefore, predictions about motor consequences were changed, vPMC did not show the enhanced activity as if no incongruence has to be detected. This can be interpreted as a consequence of the plastic changes induced by long-lasting immobilization, as also proved by the cast-related corticospinal excitability modulation in our subjects. The present findings highlight the crucial role of vPMC in the anatomo-functional network generating the human motor-awareness.

Abnormal Sense of Agency in Patients with Schizophrenia: Evidence from Bimanual Coupling Paradigm.

A fruitful approach to the understanding the human awareness of action is the study of those pathologies in which some aspects of it are altered. Previous evidences showed that patients with schizophrenia tend to attribute someone else' actions to their own, as internally, rather than externally, generated. Here, we asked whether schizophrenics have an "excessive" sense of agency, while observing others' movements. We took advantage from the circles-lines task, known to show bimanual interferences. Twenty schizophrenics and 20 age-matched healthy controls were administered: (a) the bimanual version of the task: drawing lines with one hand and circles with the other; and (b) a modified version: drawing lines while observing the examiner drawing circles. In the bimanual version, patients and controls showed a comparable interference effect. In the observation version, schizophrenics, compared to controls, showed a significantly greater interference effect of the examiners' hand drawing circles on the own hand drawing lines. This effect was significantly correlated to the strength of the positive symptoms (hallucinations and delusions) and to the alteration of the sense of agency, reported during the task. These findings suggest that an altered sense of agency, as shown by schizophrenics, can induce objective consequences on the motor system.