This is an historical archive of the activities of the MRC Anatomical Neuropharmacology Unit (MRC ANU) that operated at the University of Oxford from 1985 until March 2015. The MRC ANU established a reputation for world-leading research on the brain, for training new generations of scientists, and for engaging the general public in neuroscience. The successes of the MRC ANU are now built upon at the MRC Brain Network Dynamics Unit at the University of Oxford.

Phase locking of motor thalamic neurons to cortical slow oscillations

Kouichi C. Nakamura, Andrew Sharott and Peter Magill at Oxford addressed how the firing rates and patterns are different between neurons in the basal ganglia-recipient zone (BZ) and cerebellar-recipient zone (CZ) of rat motor thalamus across brain states in vivo. Neurons of the motor thalamus mediate basal ganglia and cerebellar influences on cortical activity. To elucidate the net result of γ-aminobutyric acid-releasing or glutamatergic bombardment of the motor thalamus by basal ganglia or cerebellar afferents, respectively, they recorded the spontaneous activities of thalamocortical neurons in distinct identified "input zones" in anesthetized rats during defined cortical activity states. Unexpectedly, the mean rates and brain state dependencies of the firing of BZ neurons CZ neurons were matched during slow-wave activity (SWA) and cortical activation. However, neurons were distinguished during SWA by their firing regularities, low-threshold spike bursts and, more strikingly, by the temporal coupling of their activities to ongoing cortical oscillations. The firing of neurons across the BZ was stronger and more precisely phase-locked to cortical slow (∼1 Hz) oscillations, although both neuron groups preferentially fired at the same phase. In contrast, neurons in BZ and CZ fired at different phases of cortical spindles (7-12 Hz), but with similar strengths of coupled firing. Thus, firing rates do not reflect the predicted inhibitory-excitatory imbalance across the motor thalamus, and input zone-specific temporal coding through oscillatory synchronization with the cortex could partly mediate the different roles of basal ganglia and cerebellum in behavior.