3 research outputs found
Recommended from our members
Sustained Spatial Attention in Touch: Modality-Specific and Multimodal Mechanisms
Sustained attention to a body location results in enhanced processing of tactile stimuli presented at that location compared to another unattended location. In this paper, we review studies investigating the neural orrelates of sustained spatial attention in touch. These studies consistently show that activity within modality-specific somatosensory areas (SI and SII) is modulated by sustained tactile-spatial attention. Recent evidence suggests that these somatosensory areas may be recruited as part of a larger cortical network, also including higher-level multimodal regions involved in spatial selection across modalities. We discuss, in turn, the following multimodal effects in sustained tactile-spatial attention tasks. First, cross-modal attentional links between touch and vision, reflected in enhanced processing of task-irrelevant visual stimuli at tactually attended locations, are mediated by common (multimodal) representations of external space. Second, vision of the body modulates activity underlying sustained tactile-spatial attention, facilitating attentional modulation of tactile processing in between-hand (when hands are sufficiently far apart) and impairing attentional modulation in within-hand selection tasks. Finally, body posture influences mechanisms of sustained tactile-spatial attention, relying, at least partly, on remapping of tactile stimuli in external, visually defined, spatial coordinates. Taken together, the findings reviewed in this paper indicate that sustained spatial attention in touch is subserved by both modality-specific and multimodal mechanisms. The interplay between these mechanisms allows flexible and efficient spatial selection within and across sensory modalities
Recommended from our members
Crossmodal spatial representations: behavioural and electrophysiological evidence on the effects of vision and posture on somatosensory processing in normal population and in right-brain-damaged patients
Interactions between different sensory modalities can affect processing of unisensory information, at both a perceptual and a neural level. The studies reported in this thesis address the effects of crossmodal interactions between vision and touch on tactile processing. In particular, these studies provide new behavioural and neural (ERP; event related potentials) evidence showing that: i) crossmodal interactions enhance tactile processing when (task-irrelevant) visual stimuli are presented, simultaneously with touch, at the same location as tactile stimuli compared to a different location in near or in far space; ii) crossmodal interactions between spatial congruent visual and tactile stimuli enhance tactile processing compared to incongruent visuo-tactile stimulation, also when (task-irrelevant) visual stimuli presented near the body are observed indirectly in a mirror (i.e., appearing in far space), although in this condition these crossmodal spatial modulations are delayed compared to direct viewing of the visual stimuli; iii) vision of the body (i.e., the hands) facilitates tactile-spatial attentional selection, as compared to no visual input (blindfolded condition), and also compared to visual-spatial information only (i.e., when the hands are hidden from view); iv) in rightbrain- damaged patients with tactile neglect and/or extinction, vision of the stimulated hand may further improve speed processing of contralesional tactile stimuli when the left, contralesional hand is placed in the right, 'intact' hemispace, under crossed posture.
In these studies, visual modulations of touch were present at early time intervals (i.e., early ERP components), suggesting that crossmodal spatial interactions can affect processing in cortical areas that have been considered 'modality-specific', namely, the secondary somatosensory cortex (SII). Taken together, the findings from the studies in this thesis provide new behavioural and ERP evidence in support of crossmodal spatial representations of the body and ofthe space surrounding the body (i.e., peripersonal space) in humans
Recommended from our members
To Blink or Not to Blink: Fine Cognitive Tuning of the Defensive Peripersonal Space
The blink reflex elicited by the electrical stimulation of the median nerve at the wrist (hand blink reflex, HBR) is a subcortical, defensive response that is enhanced when the stimulated hand is inside the peripersonal space of the face. Such enhancement results from a tonic, topdown modulation of the excitability of the brainstem interneurons mediating the HBR. Here we aim to (1) characterize the somatotopical specificity of this top down modulation and (2) investigate the effect of cognitive expectations on such modulation. Experiment 1 showed that the somatotopical specificity of the HBR enhancement is not only heterosegmental, but also partially homosegmental, i.e. the enhancement is greater for the HBR elicited by stimulation of the hand located inside the peripersonal space of the face, as compared to the HBR elicited by the stimulation of the other hand, always kept far from the face. Experiment 2 showed that the top-down modulation of the HBR is triggered only when the participants expect to receive stimuli on the hand placed inside the peripersonal space of the face, and is
thus strongly dependent on cognitive expectations. Taken together, these findings indicate a fine somatotopical and cognitive tuning of the excitability of brainstem circuits subserving the HBR, whose strength is adjusted depending on the context in a purposeful manner