Visual perceptual load and processing of somatosensory stimuli in primary and secondary somatosensory cortices

Abstract

Load theory assumes that neural activation to distractors in early sensory cortices is modulated by the perceptual load of a main task, regardless of whether task and distractor share the same sensory modality or not. While several studies have investigated the question of load effects on distractor processing in early sensory areas, there is no functional magnetic resonance imaging (fMRI) study regarding load effects on somatosensory stimuli. Here, we used fMRI to investigate effects of visual perceptual load on neural responses to somatosensory stimuli applied to the wrist in a study with 44 participants. Perceptual load was manipulated by an established sustained visual detection task, which avoided simultaneous target and distractor presentations. Load was operationalized by detection difficulty of subtle or clear color changes of one of 12 rotating dots. While all somatosensory stimuli led to activation in somatosensory areas SI and SII, we found no statistically significant difference in brain activation to these stimuli under high compared to low sustained visual load. Moreover, exploratory Bayesian analyses supported the absence of differences. Thus, our findings suggest a resistance of somatosensory processing to at least some forms of visual perceptual load, possibly due to behavioural relevance of discrete somatosensory stimuli and separable attentional resources for the somatosensory and visual modality.

Stimulus awareness is associated with secondary somatosensory cortex activation in an inattentional numbness paradigm

“…The sample, which was also part of a previous study on somatosensory processing and therefore described already elsewhere 34 , consisted of 47 participants recruited from the local student community of the University of Münster via public advertisements. All had normal or corrected-to-normal visual acuity and no psychiatric or neurologic illness history.…”

“…We used the same or similar procedures of somatosensory stimulation, visual stimulation and experimental parameters as already described in detail in a previous study on visual load and somatosensory processing 34 .…”

“…The image acquisition and analysis procedure is comparable to our previous study on somatosensory processing and procedures have been already described there in detail 34 .…”