Motor thalamus integration of cortical, cerebellar and basal ganglia information: implications for normal and parkinsonian conditions
Front. Comput. Neurosci.. 2013-01-01; 7:
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1. Front Comput Neurosci. 2013 Nov 11;7:163. doi: 10.3389/fncom.2013.00163.
Motor thalamus integration of cortical, cerebellar and basal ganglia information:
implications for normal and parkinsonian conditions.
Bosch-Bouju C(1), Hyland BI, Parr-Brownlie LC.
(1)1Department of Anatomy, Otago School of Medical Science, University of Otago
Dunedin, New Zealand ; 2Brain Health Research Centre, Otago School of Medical
Science, University of Otago Dunedin, New Zealand.
Motor thalamus (Mthal) is implicated in the control of movement because it is
strategically located between motor areas of the cerebral cortex and
motor-related subcortical structures, such as the cerebellum and basal ganglia
(BG). The role of BG and cerebellum in motor control has been extensively studied
but how Mthal processes inputs from these two networks is unclear. Specifically,
there is considerable debate about the role of BG inputs on Mthal activity. This
review summarizes anatomical and physiological knowledge of the Mthal and its
afferents and reviews current theories of Mthal function by discussing the impact
of cortical, BG and cerebellar inputs on Mthal activity. One view is that Mthal
activity in BG and cerebellar-receiving territories is primarily “driven” by
glutamatergic inputs from the cortex or cerebellum, respectively, whereas BG
inputs are modulatory and do not strongly determine Mthal activity. This theory
is steeped in the assumption that the Mthal processes information in the same way
as sensory thalamus, through interactions of modulatory inputs with a single
driver input. Another view, from BG models, is that BG exert primary control on
the BG-receiving Mthal so it effectively relays information from BG to cortex. We
propose a new “super-integrator” theory where each Mthal territory processes
multiple driver or driver-like inputs (cortex and BG, cortex and cerebellum),
which are the result of considerable integrative processing. Thus, BG and
cerebellar Mthal territories assimilate motivational and proprioceptive motor
information previously integrated in cortico-BG and cortico-cerebellar networks,
respectively, to develop sophisticated motor signals that are transmitted in
parallel pathways to cortical areas for optimal generation of motor programmes.
Finally, we briefly review the pathophysiological changes that occur in the BG in
parkinsonism and generate testable hypotheses about how these may affect
processing of inputs in the Mthal.