ABSTRACT
Stroke frequently produces attentional dysfunctions including symptoms of hemispatial neglect, which is characterized by a breakdown of awareness for the contralesional hemispace. Recent studies with functional MRI (fMRI) suggest that hemineglect patients display abnormal intra- and interhemispheric functional connectivity. However, since stroke is a vascular disorder and fMRI signals remain sensitive to nonneuronal (i.e., vascular) coupling, more direct demonstrations of neural network dysfunction in hemispatial neglect are warranted. Here, we utilize electroencephalogram (EEG) source imaging to uncover differences in resting-state network organization between patients with right hemispheric stroke (N = 15) and age-matched, healthy controls (N = 27), and determine the relationship between hemineglect symptoms and brain network organization. We estimated intra- and interregional differences in cortical communication by calculating the spectral power and amplitude envelope correlations of narrow-band EEG oscillations. We first observed focal frequency-slowing within the right posterior cortical regions, reflected in relative delta/theta power increases and alpha/beta/gamma decreases. Secondly, nodes within the right temporal and parietal cortex consistently displayed anomalous intra- and interhemispheric coupling, stronger in delta and gamma bands, and weaker in theta, alpha, and beta bands. Finally, a significant association was observed between the severity of left-hemispace search deficits (e.g., cancellation test omissions) and reduced functional connectivity within the alpha and beta bands. In sum, our novel results validate the hypothesis of large-scale cortical network disruption following stroke and reinforce the proposal that abnormal brain oscillations may be intimately involved in the pathophysiology of visuospatial neglect.
ABSTRACT
Goal-directed behaviour (GDB), the capacity that allows us to control our environment according to our desires and needs, requires different stages from initial intention to goal achievement. Although GDB is frequently disrupted after acquired brain injury, few studies have addressed the remediation of reduced GDB in patients with severe brain injury. The present study aimed to raise this question in RZ, a patient with severe brain injury who presented a serious reduction in GDB related to difficulties in creating an intention from internal determinants and in selecting an action plan, as well as to memory and attentional impairments. Our objective was to investigate the efficacy of an intervention programme to create and trigger a specific intention in RZ. More specifically, this programme consisted in written prompts, first accompanied by an alarm provided by his mobile phone, but gradually reduced until only the alarm remained, which was implemented in order to improve RZ's attendance at workshop sessions. Results showed that RZ's attendance rate at the workshop sessions increased, indicating that the use of an external device allowed us to create and trigger intention in a patient with severe cognitive impairments.
