Ordek G, Groth JD, Sahin M. Differential effects of ketamine/ xylazine anesthesia on the cerebral and cerebellar cortical activities in the rat.
The cerebellum is involved in sensory-motor integration and cognitive functions. The origin and function of the field potential oscillations in the cerebellum, especially in the high frequencies, have not been explored sufficiently. The primary objective of this study was to investigate the spatio-temporal characteristics of high frequency field potentials (150–350 Hz) in the cerebellar cortex in a behavioral context. To this end, we recorded from the paramedian lobule in rats using micro electro-corticogram (μ-ECoG) electrode arrays while the animal performed a lever press task using the forelimb. The phase synchrony analysis shows that the high frequency oscillations recorded at multiple points across the paramedian cortex episodically synchronize immediately before and desynchronize during the lever press. The electrode contacts were grouped according to their temporal course of phase synchrony around the time of lever press. Contact groups presented patches with slightly stronger synchrony values in the medio-lateral direction, and did not appear to form parasagittal zones. The size and location of these patches on the cortical surface are in agreement with the sensory evoked granular layer patches originally reported by Welker's lab (Shambes et al., 1978). Spatiotemporal synchrony of high frequency field potentials has not been reported at such large-scales previously in the cerebellar cortex.
Cerebellum is a highly organized structure with a crystalline morphology that has always intrigued neuroscientists. Much of the cerebellar research has been conducted in anesthetized animals, particularly using ketamine and xylazine combination. It is not clear how the cerebellar cortical circuitry is affected by anesthesia. In this study, we have recorded spontaneous and evoked potentials from the cerebellar surface with chronically implanted, flexible-substrate, multi-electrode arrays. The frequency contents of the spontaneous activity suggest that ketamine/xylazine anesthesia suppresses most of the components except those below 30 Hz. This preliminary study also showed that multi channels of cerebellar cortical activity can be recorded using flexible multi-electrode arrays in behaving animals, which is very challenging task with single microelectrodes.
Recordings were performed on the rat paramedian lobule of the cerebellum with a surface micro-electrode array during hand licking and quiet states. The Fast Fourier Transform (FFT) and average coherence both showed a change in the frequency distributions between active and quiet conditions. The signals were segregated into different frequency bands and the signal compositions were analyzed. In each of the bands an increase in neural activity was seen at the onset of activity. Frequency coherence analysis was performed between electrodes at two different separations for active and quiet conditions. The coherence analysis showed that there was an increase in coherence for shorter distances and during activity.
Cerebellum is highly susceptible to traumatic injuries, and yet it has rarely been studied in the context of traumatic brain injury (TBI). Much of the TBI research in the cerebellum has been conducted through histochemical techniques, particularly using selective protein staining. In this study, we investigated if fluid percussion injury (FPI) was detectable using electrophysiological recordings of the cerebellar activity with multi-contact array electrodes. Rats were chronically implanted with micro ECoG electrodes on the paramedian lobule (PML). The FPI was induced via a skull opening near the electrode implant on the cerebellum. Spontaneous and evoked potentials (EPs) featured almost immediate alterations in their waveform patterns after the delivery of pressure pulse. Recorded evoked potential amplitudes declined drastically by the next day. We also studied the linear correlation changes between all the electrode contact pairs and observed a significant decrease (R from > 0.7 to < !0.4, p <.001) as a result of injury. The results suggest that electrophysiological recording with chronic electrode implants can be used as a method of detection and longitudinal monitoring of subtle effects of TBI in the cerebellar circuits.
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