Abstract
Using magnetoencephalography (MEG), this study investigates the spatio-temporal dynamics of the multilevel cortical processing of somatosensory change detection. Neuromagnetic signals of 16 healthy adult subjects (7 females and 9 males, mean age 29 ± 3 years) were recorded using whole-scalp-covering MEG while they underwent an oddball paradigm based on simple standard (right index fingertip tactile stimulation) and deviant (simultaneous right index fingertip and middle phalanx tactile stimulation) stimuli gathered into sequences to create and then deviate from stimulus patterns at multiple (local vs. global) levels of complexity. Five healthy adult subjects (3 females and 2 males, mean age 31, 6 ± 2 years) also underwent a similar oddball paradigm in which standard and deviant stimuli were flipped. Local deviations led to a somatosensory mismatch response peaking at 55–130 ms post-stimulus onset with a cortical generator located at the contralateral secondary somatosensory (cSII) cortex. The mismatch response was independent of the deviant stimuli physical characteristics. Global deviants led to a P300 response with cortical sources located bilaterally at temporo-parietal junction (TPJ) and supplementary motor area (SMA). The posterior parietal cortex (PPC) and the SMA were found to generate a contingent magnetic variation (CMV) attributed to top-down expectations. Amplitude of mismatch responses were modulated by top-down expectations and correlated with both the magnitude of the CMV and the P300 amplitude at the right TPJ. These results provide novel empirical evidence for a unified sensory novelty detection system in the human brain by linking detection of salient sensory stimuli in personal and extra-personal spaces to a common framework of multilevel cortical processing.
Highlights
The ability to evolve safely in an environment highly depends on the ability to detect novel and unexpected events
Using a mechanical unilateral tactile oddball paradigm, this study provides novel empirical evidence favoring a multilevel cortical processing for somatosensory novelty detection that involves multiple segregated cortical regions
In session 1, a significant msMMN was found in 75% of the included subjects, which is in agreement with the occurrence of auditory mismatch negativity (MMN) in healthy adult subjects
Summary
The ability to evolve safely in an environment highly depends on the ability to detect novel and unexpected events. The integration of those different electrophysiological responses within the context of predictive coding has been achieved for the auditory modality This was accomplished by using an oddball design based on simple tones gathered into sequences to create stimulus patterns at multiple levels of predictive complexity and deviate from them (Bekinschtein et al, 2009; Wacongne et al, 2011; Chennu et al, 2013). We adapted the integrative oddball paradigm developed for the auditory modality (Bekinschtein et al, 2009; Wacongne et al, 2011; Chennu et al, 2013) to the somatosensory (tactile) modality This oddball paradigm was initially designed to simultaneously investigate the multiple levels of cortical processing involved in auditory change detection at both the preattentional and the attentional levels. If somatosensory change detection involves multilevel cortical processing patterns similar to those in auditory and visual change detection, this study would provide novel empirical data supporting a unified account for the cortical processing of novel sensory stimuli in the human brain
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