Abstract
The pedunculopontine nucleus (PPN) is a major component of the reticular activating system (RAS) that regulates waking and REM sleep, states of high-frequency EEG activity. Recently, we described the presence of high threshold, voltage-dependent N- and P/Q-type calcium channels in RAS nuclei that subserve gamma band oscillations in the mesopontine PPN, intralaminar parafascicular nucleus (Pf), and pontine subcoeruleus nucleus dorsalis (SubCD). Cortical gamma band activity participates in sensory perception, problem solving, and memory. Rather than participating in the temporal binding of sensory events as in the cortex, gamma band activity in the RAS may participate in the processes of preconscious awareness, and provide the essential stream of information for the formulation of many of our actions. That is, the RAS may play an early permissive role in volition. Our latest results suggest that (1) the manifestation of gamma band activity during waking may employ a separate intracellular pathway compared to that during REM sleep, (2) neuronal calcium sensor (NCS-1) protein, which is over expressed in schizophrenia and bipolar disorder, modulates gamma band oscillations in the PPN in a concentration-dependent manner, (3) leptin, which undergoes resistance in obesity resulting in sleep dysregulation, decreases sodium currents in PPN neurons, accounting for its normal attenuation of waking, and (4) following our discovery of electrical coupling in the RAS, we hypothesize that there are cell clusters within the PPN that may act in concert. These results provide novel information on the mechanisms controlling high-frequency activity related to waking and REM sleep by elements of the RAS.
Highlights
Why is the brainstem involved in the regulation of so many functions? One line of thought is that we must dissect out the foci or nodes responsible for widely disparate functions
Our latest results suggest that [1] the manifestation of gamma band activity during waking may employ a separate intracellular pathway compared to that during REM sleep, [2] neuronal calcium sensor (NCS-1) protein, which is over expressed in schizophrenia and bipolar disorder, modulates gamma band oscillations in the pedunculopontine nucleus (PPN) in a concentration-dependent manner, [3] leptin, which undergoes resistance in obesity resulting in sleep dysregulation, decreases sodium currents in PPN neurons, accounting for its normal attenuation of waking, and [4] following our discovery of electrical coupling in the reticular activating system (RAS), we hypothesize that there are cell clusters within the PPN that may act in concert
What is the unifying function of gamma band activity in the RAS? We proposed that the maintenance of gamma band activity in the RAS provides information for the process necessary to support a state capable of reliably assessing the world around us on a continuous basis
Summary
Why is the brainstem involved in the regulation of so many functions? One line of thought is that we must dissect out the foci or nodes responsible for widely disparate functions. Two processes involved in large-scale communication are coherence, signals mirrored by neurons across different areas, and frequency, the specific firing patterns required to transmit population dynamics across regions. The former process is modulated by electrical coupling while the latter process is mediated by membrane oscillations and synaptic connectivity [1, 2]. The following review targets one component of the reticular activating system (RAS), the pedunculopontine nucleus (PPN), and its involvement in a large number of functions This involvement is anchored by two recently discovered mechanisms, the presence of electrical coupling and generation of gamma band activity. We discuss the role of gamma band membrane oscillations that were recently described in every cell in this nucleus, the presence of cell clusters in the PPN, and how these impact a number of specific functions
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
