Nature and electrophysiologic properties of thalamic ventrolateral nucleus neurons reactive to the paleocerebellar stimulation: an extracellular and intracellular study

Cerebellar deep brain stimulation for chronic post-stroke motor rehabilitation: a phase I trial

Upper-extremity impairment after stroke remains a major therapeutic challenge and a target of neuromodulation treatment efforts. In this open-label, non-randomized phase I trial, we applied deep brain stimulation to the cerebellar dentate nucleus combined with renewed physical rehabilitation to promote functional reorganization of ipsilesional cortex in 12 individuals with persistent (1-3 years), moderate-to-severe upper-extremity impairment. No serious perioperative or stimulation-related adverse events were encountered, with participants demonstrating a seven-point median improvement on the Upper-Extremity Fugl-Meyer Assessment. All individuals who enrolled with partial preservation of distal motor function exceeded minimal clinically important difference regardless of time since stroke, with a median improvement of 15 Upper-Extremity Fugl-Meyer Assessment points. These robust functional gains were directly correlated with cortical reorganization evidenced by increased ipsilesional metabolism. Our findings support the safety and feasibility of deep brain stimulation to the cerebellar dentate nucleus as a promising tool for modulation of late-stage neuroplasticity for functional recovery and the need for larger clinical trials. ClinicalTrials.gov registration: NCT02835443 .

Physiological and morphological analyses of ventral anterior and ventral lateral thalamic neurons in the cat

Intracellular recordings were made from ventral anterior and ventral lateral (VA-VL) thalamic neurons in the cat. VA-VL neurons were tested for responsiveness to activation of cortical, pallidal and cerebellar afferents, and were identified morphologically by intracellular injection of HRP. Orthodromic activation of cortical and pallidal afferents produced primarily an initial inhibition (due in part to oligosynaptic circuitry) while activation of cerebellar afferents produced an initial excitation in the majority of neurons tested. Antidromic activation of thalamocortical relay neurons was observed in 32% of the neurons tested. Neurons showing short latency responses to activation of globus pallidus-entopeduncular nucleus and cerebellar peduncle were concentrated in the medical and ventral portions of the VA-VL complex, respectively. Neurons showing short latency responses to activation of the neocortex were located throughout the entire extent of the VA-VL complex. Only 3% of the neurons tested showed short-latency convergence of cortical, pallidal and cerebellar afferents. In contrast, 53% of neurons tested showed long latency triple convergence. Eight VA-VL neurons were stained intracellularly with HRP. Based on dendritic morphology, the labeled neurons were separated into two types: a stellate type with dendrites that spread radially from the soma, and a fusiform type with dendrites that were oriented mainly parallel to the long axis of the soma. Both types of neuron were aspiny although the dendrites of the stellate cells exhibited short appendages.

Electrophysiologic properties and nature of ventrolateral thalamic nucleus neurons reactive to converging inputs of paleo- and neocerebellar origin

Acute experiments were carried out in chloralose-anesthetized, curarized, and artificially ventilated cats to investigate the consistency and functional characteristics of converging cerebellar nuclear (fastigial, interpositus, dentate nuclei) inputs to single neurons of the ventrolateral thalamic nucleus, and the nature (thalamocortical relay or interneuronal) of its convergent neuronal population responsive to stimulation of the cerebellar nuclei. From unitary analysis of both extra- and juxtacellular recordings, we conclude that convergence of paleo- and neocerebellar impulses on thalamic ventrolateral neurons occurs widely, and that both excitatory (mono- and polysynaptic) and inhibitory (di- and polysynaptic) effects are induced on the same neurons by cerebellar nuclei stimulation; these effects concern about 40% of the thalamic ventrolateral neuronal population tested using the extracellular recording technique and about 75% of the ventrolateral nucleus neurons tested using the juxtacellular recording; activation of neocerebellar nuclear outputs generates mainly excitatory and excitatory-inhibitory response patterns, whereas activation of the paleocerebellar nuclear outputs evokes predominantly inhibitory and excitatory-inhibitory response patterns; the convergent paleo- neocerebellar neurons are found commonly in the more anterior ventrolateral nucleus stereotaxic planes; and from the results obtained by stimulation of the somatomotor cortical areas, a large proportion of the ventrolateral nucleus convergent units consists of thalamocortical relay cells. The results have implications for a possible integration between posture and voluntary movements at the level of the thalamic relay nucleus of the cerebellar-cortical pathway, and an interaction between central feedback and peripheral feedback in the programming, execution, and correction of voluntary movements.

Fastigial unit activity during voluntary movement in primates

To examine the proposition that fastigial n. of cerebellum provides a fast feedback pathway to suprasegmental structures for spinal information regarding movement. Macaca irus were trained to make flexion and/or extension voluntary wrist movements. Fastigial neuron activity was then correlated with force, velocity, handle position and with shoulder or forearm muscle activity. From 200 units (75% participating), our data establish that fastigial neurons are uniformly recruited after movement onset, processing force-velocity information. Units were found specifically correlated with force or velocity alone. Fastigial activity is strategically placed to provide a 'correction' signal path for motor performance.