Abnormal brain activity dynamics, in the sense of a thalamocortical dysrhythmia (TCD), has been proposed as the underlying mechanism for a subset of disorders that bridge the traditional delineations of neurology and neuropsychiatry. In order to test this proposal from a psychiatric perspective, a study using magnetoencephalography (MEG) was implemented in subjects with schizophrenic spectrum disorder (n = 14), obsessive–compulsive disorder (n = 10), or depressive disorder (n = 5) and in control individuals (n = 18). Detailed CNS electrophysiological analysis of these patients, using MEG, revealed the presence of abnormal theta range spectral power with typical TCD characteristics, in all cases. The use of independent component analysis and minimum-norm-based methods localized such TCD to ventromedial prefrontal and temporal cortices. The observed mode of oscillation was spectrally equivalent but spatially distinct from that of TCD observed in other related disorders, including Parkinson's disease, central tinnitus, neuropathic pain, and autism. The present results indicate that the functional basis for much of these pathologies may relate most fundamentally to the category of calcium channelopathies and serve as a model for the cellular substrate for low-frequency oscillations present in these psychiatric disorders, providing a basis for therapeutic strategies.

Abnormal thalamocortical dynamics have been proposed as the underlying mechanism for a subset of neurological and psychiatric disorders that include centrally generated pain. Spectral analysis and independent component-based localization of neuromagnetic signals reveal ongoing theta-range activity localized to physiologically significant cortical regions in a group of subjects with well-characterized central and peripheral lesions. In addition, recordings from subjects who failed to obtain relief from spinal cord stimulation (SCS) and from those in whom SCS was successful further delineate thalamocortical dysrhythmias as a mechanism that underlies chronic pain.

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Neuropsychiatric surgery has had a long and complex history with examples of less than optimal surgical procedures implemented in wrong settings. Such past errors have raised important philosophical and ethical issues that remain with us for good reasons. However, the existence of enormous suffering due to chronic therapy-resistant disabling neuropsychiatric disorders compels a search for alternative surgical approaches based on a sound understanding of the underlying physiopathological mechanisms. We bring evidence, from single cell physiology and magnetoencephalography, for the existence of a set of neuropsychiatric disorders characterized by localized and protracted low frequency spontaneous recurrent activation of the thalamocortical system. This condition, labeled thalamocortical dysrhythmia, underlies certain chronic psychotic, affective, obsessive compulsive, anxiety and impulse control disorders. Considering the central role of recurrent oscillatory thalamocortical properties in the generation of normal hemispheric functions, we propose a surgical approach that provides a reestablishment of normal thalamocortical oscillations without reduction of cortical tissue and its specific thalamic connectivity. It consists of small strategically placed pallidal and medial thalamic lesions that serve to make subcritical the increased low frequency thalamocortical recurrent network activity. This result is attained via reduction of both thalamic overinhibition and low frequency oversynchronization. Thalamic disinhibition is obtained by a lesion in the anterior medial paralimbic pallidum. The medial thalamic lesion is localized in the posterior part of the central lateral nucleus, where a large majority of cells have been shown to be locked in low frequency production and to have lost their normal activation patterns. We present here our experience with 11 patients, including clinical follow ups and pre-and postsurgical magnetoencephalographic studies. The evidence speaks (1) for a benign and efficient surgical approach, and (2) for the relevance of the patient's presurgical cognitive and social settings, making them more or less prone to postoperative psychoreactive manifestations upon rekindling of personal goals and social reentry.

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