Delta-mediated cross-frequency coupling organizes oscillatory activity across the rat cortico-basal ganglia network

The brain's ability to integrate different behavioral and cognitive processes relies on its capacity to generate neural oscillations in a cooperative and coordinated manner. Cross-frequency coupling (CFC) has recently been proposed as one of the mechanisms involved in organizing brain activity. Here we investigated the phase-to-amplitude CFC (PA-CFC) patterns of the oscillatory activity in the cortico-basal ganglia network of healthy, freely moving rats. Within-structure analysis detected consistent PA-CFC patterns in the four regions analyzed, with the phase of delta waves modulating the amplitude of activity in the gamma (low-gamma ~50 Hz; high-gamma ~80 Hz) and high frequency ranges (high frequency oscillations HFO, ~150 Hz). Between-structure analysis revealed that the phase of delta waves parses the occurrence of transient episodes of coherence in the gamma and high frequency bands across the entire network, providing temporal windows of coherence between different structures. Significantly, this specific spatio-temporal organization was affected by the action of dopaminergic drugs. Taken together, our findings suggest that delta-mediated PA-CFC plays a key role in the organization of local and distant activities in the rat cortico-basal ganglia network by fine-tuning the timing of synchronization events across different structures

Ketamine-Induced Oscillations in the Motor Circuit of the Rat Basal Ganglia

Oscillatory activity can be widely recorded in the cortex and basal ganglia. This activity may play a role not only in the physiology of movement, perception and cognition, but also in the pathophysiology of psychiatric and neurological diseases like schizophrenia or Parkinson's disease. Ketamine administration has been shown to cause an increase in gamma activity in cortical and subcortical structures, and an increase in 150 Hz oscillations in the nucleus accumbens in healthy rats, together with hyperlocomotion

Linear correlations between movement and iCoh values for the 10 mg/Kg ketamine dose.

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Repeated measures two-way ANOVA analysis for the imaginary coherence.

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Ketamine-induced dose-dependent increase in locomotor activity.

<p>Saline/ketamine was administered at time 0 after a 15 minutes habituation period. Ketamine injection produced dose-dependently increases in the locomotor activity.</p

Repeated measures two-way ANOVA analysis for the power.

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Linear correlation between ketamine-induced changes in power/iCoh and locomotor activity.

<p>(A) Pearson's correlation between the power of the high frequency (150 Hz) band and the locomotor activity under the 10 mg/kg ketamine dose showed a very significant correlation (0.8) in the four structures. (B) Linear correlation between the imaginary coherence of the high frequency (150 Hz) band and the locomotor activity under the effect of 10 mg/kg ketamine. The six links showed a highly significant positive correlation.</p

Ketamine-induced changes in inter-nuclear interactions.

<p>Grand-average of the time frequency evolution of the imaginary coherence under the effect of saline injection and three different doses of ketamine (columns) in the six possible links: Cx-CPU, Cx-STN, Cx-SNr, CPU-STN, CPU-SNr and STN-SNr (rows). Saline/ketamine was injected at time 0. No changes in imaginary coherence were observed after saline injection. However, ketamine administration induced marked changes in the imaginary coherence in the low gamma (50 Hz), high gamma (80 Hz) and high frequency (150 Hz) bands. Links between the cortex and the basal ganglia showed a very marked increase in coherence in the HFO band. In contrast, links between basal ganglia nuclei were more coherent in the gamma range.</p