Shifts in gamma phase–amplitude coupling frequency from theta to alpha over posterior cortex during visual tasks

Bradley Voytek

doi:10.3389/fnhum.2010.00191

Abstract

The phase of ongoing theta (4–8 Hz) and alpha (8–12 Hz) electrophysiological oscillations is coupled to high gamma (80–150 Hz) amplitude, which suggests that low-frequency oscillations modulate local cortical activity. While this phase–amplitude coupling (PAC) has been demonstrated in a variety of tasks and cortical regions, it has not been shown whether task demands differentially affect the regional distribution of the preferred low-frequency coupling to high gamma. To address this issue we investigated multiple-rhythm theta/alpha to high gamma PAC in two subjects with implanted subdural electrocorticographic grids. We show that high gamma amplitude couples to the theta and alpha troughs and demonstrate that, during visual tasks, alpha/high gamma coupling preferentially increases in visual cortical regions. These results suggest that low-frequency phase to high-frequency amplitude coupling is modulated by behavioral task and may reflect a mechanism for selection between communicating neuronal networks.

Highlights

Ongoing neuronal oscillations play an important role in perception (Schürmann and Basar, 1994), attention (Fries et al, 2001; Lakatos et al, 2008), and memory (Jensen and Tesche, 2002; Jensen et al, 2002; Pesaran et al, 2002; Buzsáki and Draguhn, 2004; Colgin et al, 2009; Siegel et al, 2009)
Phase–amplitude coupling (PAC) may reflect the means through which multiple overlapping long-range networks can communicate by statistically biasing the extracellular membrane potential in local cortical regions such that neurons will be more likely to fire during particular phases or phase network ensembles of low-frequency oscillations (Klausberger et al, 2003; Haider and McCormick, 2009; Canolty and Knight, in press; Canolty et al, 2010)
Theta power is overall stronger than alpha, alpha power is greater over posterior sites relative to anterior sites (t117 = 2.44, p = 0.016) while theta power is equal across both sites (t117 = 1.05, p = 0.39)

Summary

Introduction

Ongoing neuronal oscillations play an important role in perception (Schürmann and Basar, 1994), attention (Fries et al, 2001; Lakatos et al, 2008), and memory (Jensen and Tesche, 2002; Jensen et al, 2002; Pesaran et al, 2002; Buzsáki and Draguhn, 2004; Colgin et al, 2009; Siegel et al, 2009). Phase–amplitude coupling (PAC) may reflect the means through which multiple overlapping long-range networks can communicate by statistically biasing the extracellular membrane potential in local cortical regions such that neurons will be more likely to fire during particular phases or phase network ensembles of low-frequency oscillations (Klausberger et al, 2003; Haider and McCormick, 2009; Canolty and Knight, in press; Canolty et al, 2010). Such a selection mechanism would support complex behaviors such as top-down attentional modulation in a physiologically plausible manner

Methods

Results

Conclusion