Directional analysis of coherent oscillatory field potentials in the cerebral cortex and basal ganglia of the rat

Abstract

Population activity in cortico-basal ganglia circuits is synchronized at different frequencies according to brain state. However, the structures that are likely to drive the synchronization of activity in these circuits remain unclear. Furthermore, it is not known whether the direction of transmission of activity is fixed or dependent on brain state. We have used the directed transfer function (DTF) to investigate the direction in which coherent activity is effectively driven in cortico-basal ganglia circuits. Local field potentials (LFPs) were simultaneously recorded in the subthalamic nucleus (STN), globus pallidus (GP) and substantia nigra pars reticulata (SNr), together with the ipsilateral frontal electrocorticogram (ECoG) of anaesthetized rats. Directional analysis was performed on recordings made during robust cortical slow-wave activity (SWA) and 'global activation'. During SWA, there was coherence at ∼1 Hz between ECoG and basal ganglia LFPs, with much of the coherent activity directed from cortex to basal ganglia. There were similar coherent activities at ∼1 Hz within the basal ganglia, with more activity directed from SNr to GP and STN, and from STN to GP rather than vice versa. During global activation, peaks in coherent activity were seen at higher frequencies (15-60 Hz), with most coherence also directed from cortex to basal ganglia. Within the basal ganglia, however, coherence was predominantly directed from GP to STN and SNr. Together, these results highlight a lead role for the cortex in activity relationships with the basal ganglia, and further suggest that the effective direction of coupling between basal ganglia nuclei is dynamically organized according to brain state, with activity relationships involving the GP displaying the greatest capacity to change.

Effects of Anesthesia on Effective Connectivity in the Brain

“…They found that effective connectivity became bidirectional in freely behaving animals. In agreement with Sharott A report, effective connectivity was unidirectional, from cortex to striatum, during natural sleep and anesthesia [74].…”

Temporal sequence of ictal discharges propagation in the corticolimbic basal ganglia system during amygdala kindled seizures in freely moving rats

“…It is possible that ictal discharge may pass through the cortex before reaching the STN, the possibility was supported by the fact that the STN lagged behind the Ctx in synchronized firing. A recent study by Sharott et al (2005) revealed similar SNr to STN signal transfer directions during a period with 1 Hz slow wave cortical activity, whereas the direction was reversed during 15 Hz high frequency oscillations. A low frequency oscillation (around 2 Hz) was found during stage 5 amygdala kindled seizures in our study (Woodward et al, 2003), suggesting that there may be a common mechanism underlying SNr-STN signal transfer direction in both studies.…”

Altered neuronal activity relationships between the pedunculopontine nucleus and motor cortex in a rodent model of Parkinson's disease

“…Consistently, cortical spiking activity has been shown to predominantly occur at the troughs of cortical LFP oscillations in awake animals Fetz, 1996a, 1996b;Donoghue et al, 1998), in anesthetized animals Rasch et al, 2008), and at the troughs of slow cortical LFP oscillations (<1 Hz) observed during sleep (Destexhe et al, 1999). Firing in the STN and SNpr is also locked to the troughs of MCx LFP oscillations after dopamine loss suggesting that firing in these structures is in phase with firing in the MCx (Magill et al, 2001;Tseng et al, 2001b;Murer et al, 2002;Belluscio et al, 2003;Sharott et al, 2005;Walters et al, 2007).…”