Thalamic interactions of cerebellum and basal ganglia

Abstract

Cerebellum and basal ganglia are reciprocally interconnected with the neocortex via oligosynaptic loops. The signal pathways of these loops predominantly converge in motor areas of the frontal cortex and are mainly segregated on subcortical level. Recent evidence, however, indicates subcortical interaction of these systems. We have reviewed literature that addresses the question whether, and to what extent, projections of main output nuclei of basal ganglia (reticular part of the substantia nigra, internal segment of the globus pallidus) and cerebellum (deep cerebellar nuclei) interact with each other in the thalamus. To this end, we compiled data from electrophysiological and anatomical studies in rats, cats, dogs, and non-human primates. Evidence suggests the existence of convergence of thalamic projections originating in basal ganglia and cerebellum, albeit sparse and restricted to certain regions. Four regions come into question to contain converging inputs: (1) lateral parts of medial dorsal nucleus (MD); (2) parts of anterior intralaminar nuclei and centromedian and parafascicular nuclei (CM/Pf); (3) ventromedial nucleus (VM); and (4) border regions of cerebellar and ganglia terminal territories in ventral anterior and ventral lateral nuclei (VA-VL). The amount of convergences was found to exhibit marked interspecies differences. To explain the rather sparse convergences of projection territories and to estimate their physiological relevance, we present two conceivable principles of anatomical organization: (1) a "core-and-shell" organization, in which a central core is exclusive to one projection system, while peripheral shell regions intermingle and occasionally converge with other projection systems and (2) convergences that are characteristic to distinct functional networks. The physiological relevance of these convergences is not yet clear. An oculomotor network proposed in this work is an interesting candidate to examine potential ganglia and cerebellar subcortical interactions.

Abnormal sensory gating in patients with different types of focal dystonias

“…Our findings may fit into the proposed “network model” for dystonia if we speculate that neck muscle‐proprioceptive information in CD and forearm muscle‐proprioceptive information in FHD are first processed in the cerebellum and reach the thalamus, where they are integrated with tactile information. By integrating sensory inputs of different types, the thalamus modulates ascending and descending streams of sensory input . It is therefore possible that proprioceptive afferent information flowing from the cerebellum in CD and FHD competes, once it reaches the thalamus, with tactile information during index finger movements, thereby altering the timing of tactile sensory processing gating.…”

“…By integrating sensory inputs of different types, the thalamus modulates ascending and descending streams of sensory input. 40,41 It is therefore possible that proprioceptive afferent information flowing from the cerebellum in CD and FHD competes, once it reaches the thalamus, with tactile information during index finger movements, thereby altering the timing of tactile sensory processing gating.…”

Thalamic afferents to prefrontal cortices from ventral motor nuclei in decision‐making

“…See Hintzen et al . () for a discussion on the functional implications of the overlaps between cerebellar and basal ganglia outputs.…”

“…Comparison of spontaneous rat neuronal activity recorded in VM-VA and VL indicates that the innervation of layer 1 from VM-VA is probably responsible for the large coincident excitation of cortical neurons and the temporal coupling to motor cortex oscillatory frequency (Nakamura et al, 2014). See Hintzen et al (2018) for a discussion on the functional implications of the overlaps between cerebellar and basal ganglia outputs.…”

Acute cerebellar knockdown ofSgcereproduces salient features of Myoclonus-dystonia (DYT11) in mice

“…It is possible 409that DBS of the GPi or VIM may influence cerebellar-recipient regions of the thalamus, disrupting the 410 irregular output from the cerebellum and, in this way, improving motor symptoms. Indeed, there is 411 considerable overlap of cerebellar and pallidal projections in the thalamus(Hintzen et al, 2018). It is 412 also possible, for example, that abnormal cerebellar output alters basal ganglia output and contributes 413 to motor symptoms in dystonia.…”