Nonlinear interactions of high-frequency oscillations in the human somatosensory system

MEG reveals a fast pathway from somatosensory cortex to occipital areas via posterior parietal cortex in a blind subject

“…However, many recent MEG studies have reported activations generated in deep subcortical structures such as thalamus (Attal et al, 2012; Wang et al, 2012; Tenney et al, 2013), including in response to somatosensory stimulation (Hashimoto et al, 2001; Tecchio et al, 2005; Jaros et al, 2008; Kimura et al, 2008; Milde et al, 2009; Papadelis et al, 2012). These results indicate that neural activity in thalamus and other subcortical structures generate detectable MEG signals and can be identified if appropriate methods are used.…”

Functional Brain Imaging with M/EEG Using Structured Sparsity in Time-Frequency Dictionaries

“…3(a)) represent 1 high and 3 low frequency components. The time course of the oscillatory high frequency component is modeled by a Gabor atom, whereas the time courses of the low frequency components were obtained from a somatosensory evoked potential study [14] by fitting manually ECDs to the P15, N20 and P23 components. To make the comparison of the priors independent of the forward model and the sources spatial configuration, the linear forward operator was a random matrix, whose columns are normalized to 1.…”

Primary somatosensory contextual modulation is encoded by oscillation frequency change

“…The tangentially oriented HFct (high frequency cortical tangential source) showed a stable localization near BA 3b, while the HFcr (high frequency cortical radial source) was located near BA 1 (Allison et al, 1989a(Allison et al, , 1991. Furthermore, the subcortical HFp (high frequency subcortical radial source) was located near the thalamus (Gobbele et al, 1999;Jaros et al, 2008).…”

“…For the source localization a fixed dipole approach was chosen. Specifically, a cortical radial source (HFcr), a cortical tangential source (HFct), and a subcortical radial source (HFp) were fitted (Scherg and Buchner, 1993;Buchner et al, 1994Buchner et al, , 1995Haueisen et al, 2007;Jaros et al, 2008;Milde et al, 2009). The unexplained variance after the dipole fit for combined EEG and MEG dipoles was 39.4% (±4.6) for HF dipoles in a time range of 16-25 ms (average over all volunteers).…”

“…The first cortical response, N20, originates primarily in Brodmann area (BA) 3b at the posterior wall of the postcentral gyrus (Allison et al, 1989a(Allison et al, ,b, 1991 and is followed by the P22, which has been ascribed to BA 1 (Allison et al, 1989b). An even earlier positive peak at approximately 16 ms probably originates from deep thalamo-cortical axons (Gobbele et al, 1999;Jaros et al, 2008). Owing to the predominantly radial orientation of the P16 and P22, both components show a higher signal-to-noise ratio (SNR) in electroencephalogram (EEG) as compared to magnetoencephalogram (MEG) recordings (Wood et al, 1985;Haueisen et al, 1995).…”