Romeo, Z. | Search bioRxiv

bioRxiv2023

Susceptibility to multitasking in chronic stroke is associated to damage of the multiple demand system and leads to lateralized visuospatial deficits

Functional impairment after stroke is related to the amount of brain damage but there is no strict correspondence between lesion and magnitude of the deficit or its recovery. Theoretical constructs such as cognitive or brain reserve have been invoked as unspecific protective factors to explain this mismatch. Here, we consider the opposite point of view, that is the instances in which this protection is lost or overturned. Several studies have shown - in domains encompassing sensory, motor, and cognitive deficits - that paradigms in which the inherent processing limits of the brain are stressed (e.g., by introducing multitasking and attentional load), are indeed capable to unveil the presence of deficits that are otherwise missed. We administered a computerized multitasking paradigm to a sample of 46 consecutive patients with first-ever unilateral subacute to chronic stroke and no sign of lateralized spatial-attentional disorders according to established diagnostic tests. We then used cluster analysis to classify patients, in a purely data-driven manner, according to their multivariate pattern of performance across different conditions (e.g., single- vs dual-tasking, ipsi- vs. contra-lesional stimuli). This enabled us to identify, within a group of putatively spared patients, a cluster of individuals presenting with stark contralesional biases of spatial awareness exclusively in conditions of concurrent attentional load, i.e. a phenotype characterised by high susceptibility to multitasking. This construct was also captured by a latent factor obtained from principal component analysis, providing a continuous susceptibility index across the whole sample. In spite of similar lesion volume, patients in the high susceptibility cluster presented worse performance in activities of daily living and neuropsychological tests evaluating domain-general abilities spanning attention, executive functions, and reasoning. Multivariate predictive modeling based on lesions location and structural disconnections revealed distinctive correlates of high sensitivity to multitasking in the Multiple-Demand (MD) System, a network of frontal and fronto-parietal areas subserving domain general processes. Damage in these areas may critically interact with domain-specific ones (e.g., devoted to spatial attention), resulting in subtle, but significant difficulties for patients in everyday life situations. In conclusion, the construct of susceptibility to multitasking has the promising potential to provide us a better understanding of what marks the passage, after brain damage, to clinically visible deficits. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=113 SRC="FIGDIR/small/561866v1_ufig1.gif" ALT="Figure 1"> View larger version (42K): org.highwire.dtl.DTLVardef@a1bc89org.highwire.dtl.DTLVardef@60cfedorg.highwire.dtl.DTLVardef@1f2ed85org.highwire.dtl.DTLVardef@1c7e5ec_HPS_FORMAT_FIGEXP M_FIG C_FIG

neuroscience↗

bioRxiv2020

Distinct Contributions of Nonpredictive and Predictive Peripheral Cues to Visual Conscious Perception: an MEG study

How do attentional networks influence conscious perception? To answer this question, we used magnetoencephalography (MEG) in human participants, and assessed the effects of spatially nonpredictive or predictive supra-threshold peripheral cues on the conscious perception of near-threshold Gabors. Three main results emerged. (1) As compared with invalid cues, both nonpredictive and predictive valid cues increased conscious detection. Yet, only predictive cues shifted the response criterion towards a more liberal decision (i.e., willingness to report the presence of a target under conditions of greater perceptual uncertainty) and affected target contrast leading to 50% detections. (2) Conscious perception following valid predictive cues was associated to enhanced activity in frontoparietal networks. These responses were lateralized to the left hemisphere during attentional orienting, and to the right hemisphere during target processing. The involvement of frontoparietal networks occurred earlier in valid than in invalid trials, a possible neural marker of the cost of re-orienting attention. (3) When detected targets were preceded by invalid predictive cues, and thus reorienting to the target was required, neural responses occurred in left hemisphere temporo-occipital regions during attentional orienting, and in right hemisphere anterior insular and temporo-occipital regions during target processing. These results confirm and specify the role of frontoparietal networks in modulating conscious processing, and detail how invalid orienting of spatial attention disrupts conscious processing. Significance StatementDo we need to pay attention to external objects in order to become aware of them? Characterizing the spatiotemporal dynamics of attentional effects on visual perception is critical to understand how humans process and select relevant information. Participants detected near-threshold visual targets preceded by supra-threshold spatial cues with varying degrees of predictivity, while their brain activity was recorded using magnetoencephalography. Results demonstrated that valid predictive cues biased participants conscious perception through an early recruitment of frontoparietal regions, and that attentional costs associated to invalid predictive cues were related to activation of the right hemisphere ventral network. This work characterizes the neural dynamics associated with the cost of attentional reorienting on conscious processing.

neuroscience↗