Cellular Dynamics of Cholinergically Induced α (8–13 Hz) Rhythms in Sensory Thalamic NucleiIn Vitro

Abstract

Although EEG ␣ (8 -13 Hz) rhythms are traditionally thought to reflect an "idling" brain state, they are also linked to several important aspects of cognition, perception, and memory. Here we show that reactivating cholinergic input, a key component in normal cognition and memory operations, in slices of the cat primary visual and somatosensory thalamus, produces robust ␣ rhythms. These rhythms rely on activation of muscarinic receptors and are primarily coordinated by activity in the recently discovered, gap junction-coupled subnetwork of high-threshold (HT) bursting thalamocortical neurons. By performing extracellular field recordings in combination with intracellular recordings of these cells, we show that (1) the coupling of HT bursting cells is sparse, with individual neurons typically receiving discernable network input from one or very few additional cells, (2) the phase of oscillatory activity at which these cells prefer to fire is readily modifiable and determined by a combination of network input, intrinsic properties and membrane polarization, and (3) single HT bursting neurons can potently influence the local network state. These results substantially extend the known effects of cholinergic activation on the thalamus and, in combination with previous studies, show that sensory thalamic nuclei possess powerful and dynamically reconfigurable mechanisms for generating synchronized ␣ activity that can be engaged by both descending and ascending arousal systems.

Abnormalities of Cortical Neural Synchronization Mechanisms in Subjects with Mild Cognitive Impairment due to Alzheimer’s and Parkinson’s Diseases: An EEG Study

“…Concerning the present patients' abnormalities in the posterior alpha sources, we can speculate that they reflect an alteration of a complex neurophysiological network regulating the cortical arousal, the generation of alpha rhythms, and the vigilance in the quiet wakefulness [89][90][91]. In physiological conditions, this network controls the interplay of thalamocortical high-threshold and relay-mode neurons, GABAergic interneurons, and cortical pyramidal cells [89][90][91].…”

“…In physiological conditions, this network controls the interplay of thalamocortical high-threshold and relay-mode neurons, GABAergic interneurons, and cortical pyramidal cells [89][90][91]. The main role of that network may be the production of cycles of excitation and inhibition around 70-100 ms in thalamic and cortical neurons [89][90][91].…”

“…In physiological conditions, this network controls the interplay of thalamocortical high-threshold and relay-mode neurons, GABAergic interneurons, and cortical pyramidal cells [89][90][91]. The main role of that network may be the production of cycles of excitation and inhibition around 70-100 ms in thalamic and cortical neurons [89][90][91]. During the active processing of sensorimotor information, these cycles might frame perceptual events in discrete snapshots and would ensure the selectivity of that processing [89][90][91].…”

“…The main role of that network may be the production of cycles of excitation and inhibition around 70-100 ms in thalamic and cortical neurons [89][90][91]. During the active processing of sensorimotor information, these cycles might frame perceptual events in discrete snapshots and would ensure the selectivity of that processing [89][90][91]. According to that neurophysiological model, the prominent occipital and parietal localization of the alpha abnormalities in the present ADMCI and PDMCI subjects would predict an alteration of visuospatial attentional processes, may be related to altered inputs from cholinergic basal forebrain to the visual cortex.…”

Modulation of Visually Evoked Cortical fMRI Responses by Phase of Ongoing Occipital Alpha Oscillations

“…GABAergic feedback from interneurons has been strongly implicated in the physiological mechanism generating the alpha rhythm (Lopes da Silva et al, 1976;Crunelli and Leresche, 1991;Jones et al, 2000;Liley et al, 2002). Thus, it is possible that rhythmic neuronal activity generating the alpha oscillations is a consequence of a GABAergic inhibitory feedback paced by neocortical or thalamic rhythm generators (Hughes and Crunelli, 2005;Lörincz et al, 2008Lörincz et al, , 2009Liley et al, 2010). We suggest that this GABAergic feedback could function to directly dampen processing by providing shunting inhibition to pyramidal neurons or reduce the efficacy of incoming excitatory input.…”