Reduced Reach-Related Modulation of Motor Thalamus Neural Activity in a Rat Model of Parkinson’s Disease

C. Bosch-Bouju, R. A. Smither, B. I. Hyland, L. C. Parr-Brownlie
Journal of Neuroscience. 2014-11-26; 34(48): 15836-15850
DOI: 10.1523/jneurosci.0893-14.2014

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1. J Neurosci. 2014 Nov 26;34(48):15836-50. doi: 10.1523/JNEUROSCI.0893-14.2014.

Reduced reach-related modulation of motor thalamus neural activity in a rat model
of Parkinson’s disease.

Bosch-Bouju C(1), Smither RA(2), Hyland BI(2), Parr-Brownlie LC(3).

Author information:
(1)Department of Anatomy and.
(2)Department of Physiology, Otago School of Medical Science, Brain Health
Research Centre, University of Otago, Dunedin 9054, New Zealand.
(3)Department of Anatomy and .

Motor thalamus (Mthal) is a key node in the corticobasal ganglia (BG) loop that
controls complex, cognitive aspects of movement. In Parkinson’s disease (PD),
profound alterations in neuronal activity occur in BG nuclei and cortex. Because
Mthal is located between these two structures, altered Mthal activity has been
assumed to underlie the pathogenesis of PD motor deficits. However, to date,
inconsistent changes in neuronal firing rate and pattern have been reported in
parkinsonian animals. Moreover, although a distinct firing pattern of Mthal
neurons, called low-threshold calcium spike bursts (LTS bursts), is observed in
reduced preparations, it remains unknown whether they occur or what their role
might be in behaving animals. We recorded Mthal spiking activity in control and
unilateral 6-hydroxydopamine lesioned rats performing a skilled forelimb-reaching
task. We show for the first time that Mthal firing rate in control rats is
modulated in a temporally precise pattern during reach-to-grasp movements, with a
peak at the time of the reach-end and troughs just before and after it. We
identified LTS-like events on the basis of LTS burst characteristics. These were
rare, but also modulated, decreasing in incidence just after reach-end. The
inhibitory modulations in firing rate and LTS-like events were abolished in
parkinsonian rats. These data confirm that nigrostriatal dopamine depletion is
accompanied by profound and specific deficits in movement-related Mthal activity.
These changes would severely impair Mthal contributions to motor program
development in motor cortex and are likely to be an important factor underlying
the movement deficits of PD.

Copyright © 2014 the authors 0270-6474/14/3415836-15$15.00/0.

DOI: 10.1523/JNEUROSCI.0893-14.2014
PMID: 25429126 [Indexed for MEDLINE]

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