The role of visual processing on tactile suppression

Abstract

It has been suggested that tactile signals are suppressed on a moving limb to free capacities for processing other relevant sensory signals. In line with this notion, we recently showed that tactile suppression is indeed stronger in the presence of reach-relevant somatosensory signals. Here we examined whether this effect also generalizes to the processing of additional visual signals during reaching. Brief vibrotactile stimuli were presented on the participants’ right index finger either during right-hand reaching to a previously illuminated target LED, or during rest. Participants had to indicate whether they detected the vibrotactile stimulus or not. The target LED remained off (tactile), or was briefly illuminated (tactile & vis) during reaching, providing additional reach-relevant visual information about the target position. If tactile suppression frees capacities for reach-relevant visual information, suppression should be stronger in the tactile & vis compared to the tactile condition. In an additional visual-discrimination condition (tactile & visDis), the target LED flashed once or twice during reaching and participants had to also report the number of flashes. If tactile suppression occurs to free additional capacities for perception-relevant visual signals, tactile suppression should be even stronger in the tactile & visDis compared to the tactile & vis condition. We found that additional visual signals improved reach endpoint accuracy and precision. In all conditions, reaching led to tactile suppression as indicated by higher detection thresholds compared to rest, confirming previous findings. However, tactile suppression was comparable between conditions arguing against the hypothesis that it frees capacities for processing other relevant visual signals.

Anticipatory grasping control modulates somatosensory perception

“…Figure 3a shows the psychometric functions of a representative participant for the predictable and unpredictable blocks. In line with previous studies (Colino & Binsted, 2016;Gertz et al, 2018;Voudouris & Fiehler, 2017a), somatosensory perception was deteriorated in grasping blocks compared to baseline, as this was reflected in elevated detection thresholds in the predictable left (t 19 ¼ 4.6, p , 0.001, Cohen's d ¼ 1.04), predictable center (t 19 ¼ 4.8, p , 0.001, Cohen's d ¼ 1.07), predictable right (t 19 ¼ 4.7, p , 0.001, Cohen's d ¼ 1.05), and unpredictable blocks (t 19 ¼ 6.6, p , 0.001, Cohen's d ¼ 1.48; Figure 3b). Detection precisions did not differ from baseline, all t , 2.3, all p .…”

“…Nevertheless, externally evoked sensations on the moving limb are also suppressed (Buckingham, Carey, Colino, de Grosbois, & Binstead, 2010;Voss, Ingram, Wolpert, & Haggard, 2008;Voudouris & Fiehler, 2017a;Williams & Chapman, 2002), even if these sensations are not related to a predicted sensory outcome of the action. This points to a rather general somatosensory suppression on the moving limb, which may serve the purpose of releasing capacities to process sensory signals that do not arise on the moving limb and may be more relevant (Gertz, Voudouris, & Fiehler, 2017;Haggard & Whitford, 2004;Voudouris & Fiehler, 2017b; but see also Gertz et al, 2018).…”

Age effects on sensorimotor predictions: What drives increased tactile suppression during reaching?

“…Recent evidence indicates stronger suppression in older adults, putatively due to an increased reliance on sensorimotor predictions (Wolpe et al, 2016). We investigated tactile suppression during reaching in an established paradigm that is known to reliably induce an attenuation of tactile signals on the moving limb (Fraser & Fiehler, 2018;Gertz et al, 2018;Gertz et al, 2017;Voudouris & Fiehler, 2017a). Furthermore, we explored how the magnitude of suppression was modulated by cognitive task demands and individual executive resources, respectively.…”

“…We aimed to investigate whether cognitive processes contribute to increased tactile suppression during aging. We assessed the attenuation of tactile perception during reaching movements compared to rest, using a paradigm that has yielded reliable suppression effects in younger adults (Buckingham et al, 2010;Fraser & Fiehler, 2018;Gertz, Fiehler, & Voudouris, 2018;Gertz et al, 2017). It has been consistently shown that externally generated, unpredictable tactile signals are attenuated when applied to the reaching limb.…”

“…In addition, these suppression effects are specifically bound to the reaching limb and are not explained by secondary demands involved in the reaching movement (cf. Gertz et al, 2018). We manipulated cognitive task demands during reaching by introducing an additional memory task.…”