40 Hz studies/ Thalamus Theory

Thalamocortical dysrhythmia: A neurological and neuropsychiatric syndrome characterized by magnetoencephalography

Rodolfo R. Llinás*,†, Urs Ribary*, Daniel Jeanmonod‡, Eugene Kronberg*, and Partha P. Mitra§

Author Affiliations: *Department of Physiology and Neuroscience, New York University School of Medicine, 550 First Avenue, New York, NY 10016; ‡Universitätsspital Zurich, Neurochirurgische Klinik, Sternwartstrasse 6, CH-8091 Zurich, Switzerland; and §Bell Laboratories, Lucent Technologies, 600 Mountain Avenue, Murray Hill, NJ 07974

Abstract

Spontaneous magnetoencephalographic activity was recorded in awake, healthy human controls and in patients suffering from neurogenic pain, tinnitus, Parkinson’s disease, or depression. Compared with controls, patients showed increased low-frequency θ rhythmicity, in conjunction with a widespread and marked increase of coherence among high- and low-frequency oscillations. These data indicate the presence of a thalamocortical dysrhythmia, which we propose is responsible for all the above mentioned conditions. This coherent θ activity, the result of a resonant interaction between thalamus and cortex, is due to the generation of low-threshold calcium spike bursts by thalamic cells. The presence of these bursts is directly related to thalamic cell hyperpolarization, brought about by either excess inhibition or disfacilitation. The emergence of positive clinical symptoms is viewed as resulting from ectopic γ-band activation, which we refer to as the “edge effect.” This effect is observable as increased coherence between low- and high-frequency oscillations, probably resulting from inhibitory asymmetry between high- and low-frequency thalamocortical modules at the cortical level.

http://www.pnas.org/content/96/26/15222.full