Synchronization of fronto-parietal beta and theta networks as a signature of visual awareness in neglect

Abstract

The version presented here may differ from the published version or from the version of record. If you wish to cite this item you are advised to consult the publisher's version. Please see the repository url above for details on accessing the published version and note that access may require a subscription. In the neglect syndrome, the perceptual deficit for contra-lesional hemi-space is increasingly viewed as a dysfunction of fronto-parietal cortical networks, the disruption of which has been described in neuroanatomical and hemodynamic studies. Here we exploit the superior temporal resolution of electroencephalography (EEG) to study dynamic transient connectivity of fronto-parietal circuits at early stages of visual perception in neglect. As reflected by interregional phase synchronization in a full-field attention task, two functionally distinct frontoparietal networks, in beta (15-25 Hz) and theta (4-8 Hz) frequency bands, were related to stimulus discrimination within the first 200 ms of visual processing. Neglect pathology was specifically associated with significant suppressions of both beta and theta networks engaging right parietal regions. These connectivity abnormalities occurred in a pattern that was distinctly different from what was observed in right-hemisphere lesion patients without neglect. Also, both beta and theta abnormalities contributed additively to visual awareness decrease, quantified in the Behavioural Inattention Test. These results provide evidence for the impairment of fast dynamic fronto-parietal interactions during early stages of visual processing in neglect pathology. Also, they reveal that different modes of fronto-parietal dysfunction contribute independently to deficits in visual awareness at the behavioural level.

Disruption of large-scale electrophysiological networks in stroke patients with visuospatial neglect

“…Overall, our EEG results converge with previous M/EEG studies reporting electrocortical abnormalities in stroke patients with hemineglect (Colson et al 2001;Demeurisse, Hublet, and Paternot 1998;Yordanova et al 2016) and add novel neurophysiological evidence to support recent findings of neurometabolic (i.e. fMRI) alterations in functional brain networks after stroke .…”

“…These changes are consistent with non-specific effects of brain lesions on focal delta activity (van Dellen et al 2013), and they did not correlate with neglect symptoms. On the other hand, theta connectivity mainly exhibited a bilateral reduction of long-range intra-hemispheric connections, partially consistent with recent work reporting reductions in fronto-parietal theta and beta coherence in other EEG studies of stroke patients with hemineglect (Fellrath et al 2016;Yordanova et al 2017). However, we found that the theta changes did not correlate with neglect severity either, suggesting that the previously reported changes may constitute non-specific sequels of stroke lesions.…”

“…Utilizing this approach, emerging work has suggested that hemineglect might be associated with significant disruptions of brain functional connectivity. Specifically, several functional neuroimaging studies reported that the visuospatial deficits in hemineglect are accompanied with abnormal interhemispheric and/or intrahemispheric connectivity (Baldassarre et al 2014;Fellrath et al 2016;Guggisberg et al 2014;Sasaki et al 2013;Yordanova et al 2016). Most recently, using functional MRI (fMRI), Ramsey and colleagues showed that recovery from hemineglect is linked to the return of previously depressed interhemispheric connectivity between nodes of sensorimotor and attention networks ).…”

Neural Correlates of Single- and Dual-Task Walking in the Real World

“…Intracranial studies on monkeys performing a visual search attention task showed an active involvement of β oscillatory activity in frontal and parietal regions during top-down attention (Buschman and Miller, 2007 ). Neurological impairments, such as neglect, could cause a reduction of frontal-parietal network strength within the θ and β frequency bands during conscious visual tasks (Yordanova et al, 2017 ), validating the hypothesis of their involvement in both spatial attention and visual processing. On the other hand, increased θ activations in both prefrontal and medial-temporal lobe has been previously shown to positively correlate with successful recall of encoded words (Sederberg et al, 2003 ), with successful decision making regardless of spatial learning (Guitart-Masip et al, 2013 ), and with orchestrating item distinction, verbal working memory and long-term memory (Meyer et al, 2015 ).…”

Neural predictors of gait stability when walking freely in the real-world

“…In humans, PPC is believed to be involved in the integration of sensory information with motor plans, which is severely impaired in PD patients with FoG [ 48 ]. Indeed, the spatial navigation deficits seen after damage of bilateral PPC as in Balint’s syndrome [ 49 ] or neglect [ 50 ] arise because of the inability to integrate spatial orientation with current/future planning of the voluntary movement needed to accomplish the end goal. If the PPC is in general believed to play such a complicated role, then each hemispheric area has been characterized with specific roles.…”