Oscillatory activity in neocortical networks during tactile discrimination near the limit of spatial acuity

Abstract

Oscillatory interactions within functionally specialized but distributed brain regions are believed to be central to perceptual and cognitive functions. Here, using human scalp electroencephalography (EEG) recordings combined with source reconstruction techniques, we study how oscillatory activity functionally organizes different neocortical regions during a tactile discrimination task near the limit of spatial acuity. While undergoing EEG recordings, blindfolded participants felt a linear three-dot array presented electromechanically, under computer control, and reported whether the central dot was offset to the left or right. The average brain response differed significantly for trials with correct and incorrect perceptual responses in the timeframe between 140 and 175 ms. During trials with correct responses, source-level peak activity appeared in the left primary somatosensory cortex (SI) at around 45 ms, in the right lateral occipital complex (LOC) at 130 ms, in the right posterior intraparietal sulcus (pIPS) at 160 ms, and finally in the left dorsolateral prefrontal cortex (dlPFC) at 175 ms. Spectral interdependency analysis of activity in these nodes showed two distinct distributed networks, a dominantly feedforward network in the beta band (12-30 Hz) that included all four nodes and a recurrent network in the gamma band (30 -100 Hz) that linked SI, pIPS and dlPFC. Measures of network activity in both bands were correlated with the accuracy of task performance. These findings suggest that beta and gamma band oscillatory networks coordinate activity between neocortical regions mediating sensory and cognitive processing to arrive at tactile perceptual decisions.

Crossmodal and multisensory interactions between vision and touch

“…Human electrophysiological studies are consistent with this possibility: activity in somatosensory cortex propagates to the LOC as early as 150ms after stimulus onset (Lucan et al, 2010; Adhikari et al, 2014) in a beta-band oscillatory network (Adhikari et al, 2014). This might reflect cortical pathways between primary somatosensory and visual cortices demonstrated in the macaque (Négyessy et al, 2006).…”

Resting BOLD fluctuations in the primary somatosensory cortex correlate with tactile acuity

“…For example, tactile discrimination abilities, have consistently shown relationships with a number of cortical processing markers. Predictive measures include changes in S1 cortical activity (Hoeffken et al, 2007; Pleger et al, 2006, 2001; Ragert et al, 2003; Tegenthoff et al, 2005), finger map size (Duncan & Boynton, 2007), and EEG oscillations (Adhikari, Sathian, Epstein, Lamichhane, & Dhamala, 2014), confirming that activity in S1 is related to task performance.…”

Interactions Among the Brain Default-Mode, Salience, and Central-Executive Networks During Perceptual Decision-Making of Moving Dots

“…The threshold value of GC, for statistical significance, was computed from surrogate data methods by using data permutation calculating GC values and a gamma-function to a distribution of maximum GC values from each permutation (Adhikari et al, 2014;Blair and Karniski, 1993). This threshold was designed to reject a null hypothesis of no interdependence at a significance level of p < 10 À3 .…”