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The reactions of 93 neurons in the parafascicular complex (CM-Pf) of the human thalamus were studied by microelectrode recording during stereotaxic neurosurgical operations in patients with spastic torticollis. High reactivity was demonstrated for two previously classified types of neurons with identical irregular (type A) and bursting Ca2+ -dependent (type B) activities in response to presentation of relevant verbal stimuli evoking selective attention in humans. Concordant changes in the network activity of A and B neurons were observed, in the form of linked activatory-inhibitory patterns of responses and the appearance, at the moment of presentation of an imperative morpheme of the command stimulus, of rapidly occurring intercellular interactions consisting of local synchronization with simultaneously developing rhythmic oscillatory (3-4 Hz) activity. Data are presented on the existence of a direct connection between these neuronal rearrangements and activation of selective attention, providing evidence for the involvement of the thalamic parafascicular complex (CM-Pf) in the mechanisms of selective attention and processing of relevant verbal information during the preparative period of voluntary actions.

Background Early theories for cervical dystonia, as promoted by Hassler, emphasized the role of midbrain interstitial nucleus of Cajal. Focus then shifted to basal ganglia, and it was further supported with the success of deep brain stimulation. Contemporary theories suggested the role of cerebellum. But even more recent hypotheses renewed interest in midbrain. Although pretectum was visited on several occasions, we still do not know about the physiology of midbrain neurons in cervical dystonia. Methods We analyzed the unique database of pretectal neurons collected in 1970s and 1980s during historic stereotactic surgeries aimed to treat cervical dystonia. This database is valuable because such recordings could otherwise never be obtained from humans. Results We found three types of eye or neck movement sensitivity, eye-only neurons responded to pure vertical eye movements; the neck-only neurons were sensitive to pure neck movements; and the combined eye-neck neurons. There were two neuronal subtypes – burst-tonic and tonic. The eye-neck or eye-only neurons sustained their activity during eccentric gaze holding. In contrast, the response of neck-only and eye-neck neurons exponentially decayed during neck movements. Conclusions Modern quantitative analysis of historic database of midbrain single-units from patients with cervical dystonia might support novel hypotheses for normal and abnormal head movements. This data, collected almost four decades ago, must be carefully viewed, especially because it was acquired using a less sophisticated technology available at that time, the aim was not to address specific hypothesis but to make an accurate lesion providing optimal relief from dystonia.

The quantitative functional analysis of firing patterns has made it possi-ble to classify human VL neurons into two basic types: (1), units with irregular unitary 3-to 20-imp/s activity (A type) and (2) units with short (10–30 ms) rhythmic (3–6 Hz) burst discharges (B type). These two basic types of VL neurons, determined by differences of their discharge patterns and functional properties, are theorized to play a significant role in motor and rhythmic thalamic mechanisms related to parkinsonian tremor. Despite the absence of any direct relationship between rhythmic (3–6 Hz) bursting VL and Rt neurons of the B type and parkinsonian tremor, some indirect relations between them were found.

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