The Preconscious Mind and Gamma Band Activity in the Reticular Activating System

Subimal Datta

doi:10.3389/fneur.2012.00016

Abstract

Gamma waves are high frequency neural oscillations in the range of 30–100 Hz, on average ∼40 Hz. These waves have been implicated in creating the unity of conscious perception, or binding, and are related to awareness, problem solving, and rapid eye movement (REM) sleep. Based on our level of awareness, Sigmund Freud and his followers have divided the mind into three different parts, the preconscious mind, the subconscious mind, and the conscious mind. The preconscious mind includes those things of which we are aware, but to which we are not paying attention. If we choose to pay attention, we bring them to the conscious mind (Civin and Lombardi, 1990). In this issue of Frontiers in Sleep and Chronobiology, Urbano et al. (2012) suggest that gamma band activity in the reticular activating system (RAS) mediates preconscious awareness, and that it is the maintained high frequency activity across various nuclei that keeps the “stream of consciousness,” as William James called it, flowing across our preconscious mind (James, 2007). This mechanism allows us to survive in a complex world, being aware of the traffic and pedestrians around us as we commute to work. When a stimulus introduces potential danger, for example, an oncoming bus, we instantly bring it into conscious control in order to respond.

Highlights

This review article is a collaboration between Dr Edgar Garcia-Rill’s lab at the Center for Translational Neuroscience at the University of Arkansas for Medical Sciences and the lab of Dr Francisco Urbano at the University of Buenos Aires, Argentina. They refer to a series of recent articles published in excellent journals that convincingly demonstrate the presence of gamma band activity in cells of the pedunculopontine tegmental nucleus (PPT), the intralaminar thalamic parafascicular nucleus (Pf), and the pontine subcoeruleus nucleus dorsalis (SubCD; Simon et al, 2010, 2011; Kezunovic et al, 2011, 2012)
The PPT is involved in the modulation of waking and rapid eye movement (REM) sleep, while the Pf can affect cortical arousal, and the SubCD controls phasic pontine-wave (P-wave) activity of REM sleep – all states marked by high frequency activity (Datta, 2010)
Using an in vitro technique, Garcia-Rill’s group found high threshold calcium channels in every PPT and Pf cell, and activation of these channels drives the cells to fire faster and faster, until they plateau at gamma band frequencies

Summary

Introduction

This review article is a collaboration between Dr Edgar Garcia-Rill’s lab at the Center for Translational Neuroscience at the University of Arkansas for Medical Sciences and the lab of Dr Francisco Urbano at the University of Buenos Aires, Argentina. They refer to a series of recent articles published in excellent journals that convincingly demonstrate the presence of gamma band activity in cells of the pedunculopontine tegmental nucleus (PPT), the intralaminar thalamic parafascicular nucleus (Pf), and the pontine subcoeruleus nucleus dorsalis (SubCD; Simon et al, 2010, 2011; Kezunovic et al, 2011, 2012).

Results

Conclusion