Microstimulation in the Region of the Human Thalamic Principal Somatic Sensory Nucleus Evokes Sensations Like Those of Mechanical Stimulation and Movement

Abstract

We explored the region of human thalamic somatic sensory nucleus (ventral caudal, Vc), corresponding to monkey ventral posterior (VP), with threshold microstimulation (TMIS) during stereotactic procedures for the treatment of tremor. Of 122 sites in 116 patients (124 thalami) where mechanical (touch, pressure, and sharp) or movement [movement through the body (movement) and vibration] sensations were evoked, 72 sites were found in the core or in adjacent regions, posterior-inferior (33), inferior (4), and posterior to the core (13). Sites where TMIS evoked touch were less frequently found in the core than those where movement or pressure sensations were evoked. Pressure was more commonly (P < 0.05) evoked than vibration at sites where cells had intraoral receptive fields (RFs). Touch and vibration were more commonly (P < 0.05) evoked than pressure at sites where cells had facial RFs, consistent with the relative density of rapidly adapting (RA) receptors in the mouth and face. Sites described as deep and movement were found superior and anterior in the core, consistent with the location of cells responding to stimulation of muscle afferents. At 72 of 122 sites, TMIS evoked the same sensation at two or more sites in the same plane. Of these sites, 58 are adjacent to each other, in a cluster, consistent with studies of the localization of cells responding to different modalities. These results demonstrate that mechanical and movement sensations can be evoked by stimulation in the region of Vc. The characteristics of these sites suggest that the sensations are evoked by stimulation of pathways specific to cutaneous and deep mechanoreceptors.

Lesions Limited to the Human Thalamic Principal Somatosensory Nucleus (Ventral Caudal) Are Associated with Loss of Cold Sensations and Central Pain

“…Previous electrophysiological studies have provided strong evidence that neurons in Vc, the terminus of the dorsal columnmedial lemniscus pathway, mediate the sensations evoked by tactile stimuli (Mountcastle, 1984;Lenz et al, 1988b;Ohara et al, 2004). Finally, all of these results are consistent with studies of spinal cord lesions, which demonstrate that the dorsal columns are essential for normal tactile sensation (Noordenbos and Wall, 1976;Nathan et al, 1986).…”

“…The lesion in this patient included dorsal ventral intermediate and anterodorsal Vc, which may receive muscle afferent input via the medial lemniscus (Jones et al, 1982) although the Schaltenbrand atlas does not show anterodorsal Vc (Hirai and Jones, 1989). In these regions, neurons respond to joint movement, and stimulation evokes deep and movement sensations (Lenz et al, 1988a;Ohara et al, 2004). These observations suggest that input arising from deep afferents may be interrupted by the Vc-plus lesion in patient 13, so that hypersensitivity to movement is mediated through the STT, which is another source of deep afferent information to Vc thalamus (Foreman et al, 1979;Leijon et al, 1989;Dougherty et al, 1992;Bowsher, 1996).…”

Primate Reaching Cued by Multichannel Spatiotemporal Cortical Microstimulation

“…Numerous publications have raised the question of whether electrical microstimulation of sensory areas evokes perceptions (Romo et al, 1998(Romo et al, , 2000(Romo et al, , 2002Liu and Newsome, 2000;Ohara et al, 2004;Otto et al, 2005;Tehovnik and Slocum, 2005). Romo et al (1998), who studied single-channel acute microstimulation of S1 in rhesus monkeys, made a strong argument in favor of perceptions evoked by microstimulation being similar to those evoked by skin vibrotactile stimulation.…”

“…Impressively, Talwar et al (2002) used microstimulation of the rat barrel cortex to guide rats through a complex terrain. Although it is often difficult to prove that animals experience perceptions during microstimulation, microstimulation-induced perceptions have been demonstrated in humans (Penfield and Perot, 1963;Brindley and Lewin, 1968;Dobelle et al, 1976;Davis et al, 1998;Kiss et al, 2003;Ohara et al, 2004).…”

Neuronal responses to tactile stimuli and tactile sensations evoked by microstimulation in the human thalamic principal somatic sensory nucleus (ventral caudal)

“…Based on PFs, the increased representation of the stump versus that of the same part of the body in controls (Fig. 4B, trajectory S2; Lenz et al 1998b;Ohara et al 2004) is evidence for reorganization of the image of the limb, which is embedded in thalamocortical circuits (Jensen and Rasmussen 1994;Jensen et al 1984).…”