The attentive homunculus: ERP evidence for somatotopic allocation of attention in tactile search

Bettina Forster,Maria Tziraki,Alexander Jones

doi:10.1016/j.neuropsychologia.2016.02.009

Bettina Forster, Maria Tziraki + Show 1 more

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https://doi.org/10.1016/j.neuropsychologia.2016.02.009

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Abstract

Our brain constantly receives tactile information from the body’s surface. We often only become aware of this information when directing our attention towards the body. Here, we report a study investigating the behavioural and neural response when selecting a target amongst distractor vibrations presented simultaneously to several locations either across the hands or body. Comparable visual search studies have revealed the N2pc as the neural correlate of visual selective attention. Analogously, we describe an enhanced negativity contralateral to the tactile target side. This effect is strongest over somatosensory areas and lasts approximately 200ms from the onset of the somatosensory N140 ERP component. Based on these characteristics we named this electrophysiological signature of attentional tactile target selection during tactile search the N140-central-contralateral (N140cc). Furthermore, we present supporting evince that the N140cc reflects attentional enhancement of target rather than suppression of distractor locations; the component was not reliably altered by distractor but rather by target location changes. Taken together, our findings present a novel electrophysiological marker of tactile search and show how attentional selection of touch operates by mainly enhancing task relevant locations within the somatosensory homunculus.

Highlights

Attention mechanisms allow our brain to prioritise information from the incoming stream(s) of sensory information (e.g. Carrasco, 2011 for review)
Behavioural analyses Response speed for correct responses and accuracy on target-present trials were analysed separately with repeated measures ANOVAs for the between subject factor Target type and within-subject factors Task, Target location (Finger/Shoulder/Toe vs. Index/Middle/Ring Finger) and Target side. These analyses showed no reliable difference in response speed between Target type (tap target = 695 ms vs. buzz target = 612 ms; F(1,14) = 1.67, n.s., η2p=.10) or Tasks (body task = 682 ms vs. hand task = 624 ms; F(1,14) = 2.87, n.s., η2p=.17)1 and no interaction between Task and Target location (F(2,28) = .89, n.s., η2p=.06)
Participants performed better in the hand (96% correct) than in the body task (91% correct; F(1,14)=5.52, p=.034, η2p=.28) but there was no interaction between Task and Target location (F(2, 28)=.02, n.s., η2p=.12)

Summary

Introduction

Attention mechanisms allow our brain to prioritise information from the incoming stream(s) of sensory information (e.g. Carrasco, 2011 for review). Visual search tasks are a popular tool to study the selection of information from multiple simultaneous inputs on a behavioural as well as a neural level (see Eimer, 2014 for review). Event-related potentials (ERPs) allow studying neural processes over time and have been successfully employing in visual search tasks revealing the functional and temporal organisation of visual spatial attention mechanisms. The N2pc reflects the focusing of attention on a visual target amongst distractors (Luck and Hillyard, 1994) and neuroimaging studies have identified the locus of this modulation in visual extrastriate areas (e.g., Hopf et al, 2000). Studies investigating the N2pc revealed diverse aspects of visual spatial attention including attentional capture, top-down and bottom-up influences on attentional selection and the timing of attentional allocation (see Luck, 2011 and Eimer, 2014 for reviews)

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