Motor afferents from the cerebellum, zona incerta and substantia nigra to the mediodorsal thalamic nucleus in the rat

Abstract

The mediodorsal (MD) thalamic nucleus provides information from subcortical structures to the prefrontal cortex. The human MD thalamic nucleus has been implicated in a great variety of different clinical conditions and normal functions ranging from schizophrenia, Parkinsonism and epilepsy to many cognitive functions. In the rat the MD thalamic nucleus is divided into three cytoarchitectonic sectors whereas in the primates it is divided into two; medial one-third (magnocellular) and lateral two-thirds further the lateral sector is divided into pars parvocellularis pars multiformis, pars fasciculosa and pars caudalis. In this study we used a retrograde tracer, fluoro-gold (FG) to evaluate some of the afferents reaching the lateral sector of the MD (MDl) thalamic nucleus. The results of the present study have shown that MDl receives afferent connections from the lateral cerebellar nucleus (dentate nucleus), substantia nigra pars reticulata (SNR) and zona incerta (ZI). Subsequent to FG injections into the MDl, labeled cells were observed mainly bilaterally but were sparser on the contralateral side than ipsilaterally from each of the three structures listed. All three afferents showed a topographical organization. The labeled neurons were localized at the dorsomedial aspect of the lateral cerebellar nucleus, the dorsoventral aspect of the SNR and in the dorsal sector of the ZI. The lateral cerebellar nucleus reached the MDl via the superior cerebellar peduncle. No other deep cerebellar nuclei showed labeled cells. There were no labeled cells in the substantia nigra pars compacta (SNC). Although the three regions identified here are recognized as having motor functions, the connections to MD suggest that their outputs also play a role in cognitive or other higher cortical functions.

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

“…This output contacts ventral motor thalamic nuclei -particularly the ventromedial nucleus (Beckstead et al, 1979;Di Chiara et al, 1979;Herkenham, 1979;Gerfen et al, 1982;Williams & Faull, 1988;Kha et al, 2000Kha et al, , 2001Gulcebi et al, 2012). SNr further sends contacts to the lateral part of MD thalamus, that also receives inputs from the dentate deep cerebellar nucleus (Cavdar et al, 2014). Other thalamic nuclei targeted by basal ganglia outputs are the external-parallamenar MD, parafascicular, centromedial, paracentral, and reticular nuclei (Gerfen et al, 1982;Tsumori et al, 2000Tsumori et al, , 2002Gulcebi et al, 2012).…”

Possible mechanisms of interdependent roles of the basal ganglia and cerebellum in the functioning of motor and sensory systems

“…3). Топографическая организация проявляется в том, что в проекционные сенсорные талами-Возможные механизмы взаимозависимого участия базальных ганглиев... ческие ядра (наружное и внутреннее коленчатые тела), в связанное с моторной корой вентролатеральное ядро и в связанное с ПфК медиодорзальное ядро возбуждение поступает из разных ядер ГЯМ (Bohne et al 2019;Çavdar et al 2014;Halverson et al 2010;Nakamura 2018). Афференты из вентролатерального таламического ядра конвергируют на нейронах дорзальной (моторной) части стриатума с афферентами из моторной коры (McFarland, Haber 2000).…”