Sleep fragmentation and decreased REM sleep in a primate model of diurnal cortical seizures.

Many people with epilepsy suffer from comorbid sleep disorders and sleep fragmentation. While the disruptive nature of seizures on sleep is well documented, it is unclear how diurnal seizures impact sleep quality and for how long these changes persist during the following nights. To better understand this relationship, the sleep architecture of two rhesus macaques were studied before and several nights after penicillin-induced diurnal seizures. These focal seizures stopped naturally, and none occurred at night. We scored sleep-stage during the nights immediately following the seizures, as well as several nights after seizure induction. We noted a significant increase in movement along with a decrease in sleep efficiency, both limited to the night of seizure induction. For both animals, we observed a significant decrease in the number of REM periods that manifested as a decrease in total REM sleep duration, and this phenomenon persisted up to 2 nights after the seizures. We also found a significant increase in the probability to transition from stage N2 to stage N1 on the night of the seizures. This study shows for the first time that the NHP model of penicillin-induced cortical seizures exhibits significant changes in sleep architecture, including an increase in nocturnal movement, change in sleep architecture and a prolonged decrease in REM activity. The prolonged decrease in REM periods compared to the temporary enhanced movement and reduction of sleep efficiency suggest that these seizures may affect two neural circuits, one controlling REM sleep entry and the other controlling nocturnal wakefulness.

Head mounted telemetry system for seizures monitoring and sleep scoring on non-human primate.

Radio telemetry systems are a useful way to continuously monitor broad electrical neuronal activity in behaving animals. It can also be used to study sleep disturbances or monitor seizure activity. Many different telemeter styles are available, but the more versatile and cost-efficient ones are the head mounted systems. They permit long-term recordings and allow more flexibility in the recordings. However, there are currently no such system available for non-human primate (NHP). In fact, the choices for NHP telemetry solutions are very limited. Here, we present a chronically implantable 3D printed chamber specifically designed to accommodate a rodent head-mounted system (RodentPACK) onto a NHP's head. We recorded EEG signal for more than a year, confirmed quality of the signal, and the ability to use the data to monitor sleep activity. We also used two of our epileptic animals to validate the embedded alarm system for real time seizure monitoring. While initially not designed for NHP, but with a minimum number of adaptions, this telemeter is in fact perfectly suitable for NHP experiments. Since early medical intervention during seizures is critical to avoid status epilepticus and to save the animal's life, real time seizures monitoring is becoming a safety requirement in many NHP studies. This method refines the current seizure monitoring methods for NHP and creates a flexible telemetry solution.

The role of the basal ganglia in the control of seizure.

Epilepsy is a network disorder and each type of seizure involves distinct cortical and subcortical network, differently implicated in the control and propagation of the ictal activity. The role of the basal ganglia has been revealed in several cases of focal and generalized seizures. Here, we review the data that show the implication of the basal ganglia in absence, temporal lobe, and neocortical seizures in animal models (rodent, cat, and non-human primate) and in human. Based on these results and the advancement of deep brain stimulation for Parkinson's disease, basal ganglia neuromodulation has been tested with some success that can be equally seen as promising or disappointing. The effect of deep brain stimulation can be considered promising with a 76% in seizure reduction in temporal lobe epilepsy patients, but also disappointing, since only few patients have become seizure free and the antiepileptic effects have been highly variable among patients. This variability could probably be explained by the heterogeneity among the patients included in these clinical studies. To illustrate the importance of specific network identification, electrophysiological activity of the putamen and caudate nucleus has been recorded during penicillin-induced pre-frontal and motor seizures in one monkey. While an increase of the firing rate was found in putamen and caudate nucleus during pre-frontal seizures, only the activity of the putamen cells was increased during motor seizures. These preliminary results demonstrate the implication of the basal ganglia in two types of neocortical seizures and the necessity of studying the network to identify the important nodes implicated in the propagation and control of each type of seizure.

Analyzing the benefit of optical transmission systems based on Root Raised Cosine PS-QPSK and a flexible channel grid.

We numerically investigate the multi-channel transmission performance of Polarization Switched Quadrature Phase Shift Keying (PS-QPSK) and we compare it to the performance of Polarization-Division-Multiplexed QPSK (PDM-QPSK), using Root Raised Cosine (RRC) spectral shaping, in the context of a flexible channel grid. We point out the impact of the roll-off factor and the potential influence of different dispersion compensation scenarios. Finally, the advantage of PS-QPSK against PDM-QPSK is presented as a function of the system parameters, while we also discuss the benefit of a RRC spectral shaping against a tight filtering at the transmitter side with a 2nd order super-Gaussian-shaped filter.