Basal ganglia output to the thalamus: still a paradox

Jesse H. Goldberg1*, Michael A. Farries2, and Michale S. Fee1
1 McGovern Institute for Brain Research, Department of Brain and Cognitive Sciences, Massachusetts Institute of Technology,
Cambridge, MA, USA
2 Department of Biology, University of Texas at San Antonio, San Antonio, TX, USA

The basal ganglia (BG)-recipient thalamus controls
motor output but it remains unclear how its activity
is regulated. Several studies report that thalamic activation
occurs via disinhibition during pauses in the
firing of inhibitory pallidal inputs from the BG. Other
studies indicate that thalamic spiking is triggered by
pallidal inputs via post-inhibitory ‘rebound’ calcium
spikes. Finally excitatory cortical inputs can drive thalamic
activity, which becomes entrained, or timelocked,
to pallidal spikes. We present a unifying framework
where these seemingly distinct results arise from
a continuum of thalamic firing ‘modes’ controlled by
excitatory inputs. We provide a mechanistic explanation
for paradoxical pallidothalamic coactivations observed
during behavior that raises new questions about
what information is integrated in the thalamus to control

behavior.

For More Reading: Trends in Neurosciences December 2013, Vol. 36, No. 12