Neurophysiological mechanisms of cognitive impairment in Severe Myoclonic Epileps

婴儿期严重肌阵挛性癫痫（SMEI），也被称为Dravet综合征，是一种与Scn1a基因功能丧失突变相关的儿童疾病，其特征是频繁发作和严重认知障碍。患者通常对抗癫痫药物难以治疗，并且在以后的生活中不能恢复正常的认知功能。为了确定适当的治疗策略以改善认知结果，首先有必要了解认知功能障碍的潜在生物学贡献。虽然癫痫的认知缺陷通常归因于癫痫发作的影响，但我们认为与SMEI相关的遗传缺陷会导致脑网络活动的神经生理改变，并导致独立于癫痫发作的认知障碍。这种可能性可能对研究未来旨在改善认知的治疗方法具有重要意义。这表明，仅仅通过治疗癫痫发作，认知功能可能无法完全恢复。因此，这项研究对于确定是否应该在传统抗癫痫药物的基础上采取额外的治疗策略来开发改善认知结果的疗法是很重要的。

Severe Myoclonic Epilepsy in Infancy (SMEI), also referred to as Dravet syndrome, is a childhood disorder associated with loss-of-function mutations in Scn1a that is characterized by frequent seizures and severe cognitive impairment. Patients are often intractable to anti-epileptic drugs and do not recover normal cognitive function later in life. In order to determine appropriate treatment strategies for improving cognitive outcomes, it is first necessary to understand the underlying biological contributions to cognitive dysfunction. Although the cognitive deficits in epilepsy are often attributed to the impact of seizures, we propose that the genetic deficit associated with SMEI leads to neurophysiological alterations in brain network activity and contributes to cognitive impairment independently of seizures. This possibility may hold important implications for investigating future treatments aimed to improve cognition. It would suggest that cognitive function may not fully recover by treating seizures alone. This investigation will therefore be important to determine if additional treatment strategies to the traditional anti-epileptic drugs should be pursued in the effort to develop therapies for improving cognitive outcome. The Scn1a gene encodes for the type I voltage-gated sodium channel. In the forebrain, Scn1a deficits cause impaired action potential firing of parvalbumin-positive (PV+) interneurons but not excitatory pyramidal cells. In addition to the contribution of this cell type to balancing excitation and inhibition in the brain, PV+ interneurons play critical roles in the spatiotemporal patterning of neural networks, especially during cognitive processes. In the septo-hippocampal system, these cells are required for brain network oscillations and temporal coding, and selective impairments in this interneuron population result in impaired cognitive performance on learning and memory tasks. Therefore, the septo-hippocampal system may be one network affected by Scn1a deficits. The goal of this proposal is to address the question of whether Scn1a deficits contribute to cognitive impairment. We hypothesize that Scn1a deficits in the septo-hippocampal system are sufficient to impair cognition independently of the seizure disorder. We will use in vivo electrophysiological and behavioral techniques combined with RNAi silencing of Scn1a expression in rats to test this hypothesis. Our specific aims are to (1) determine the effects of Scn1a deficits in the septo-hippocampal system on cognition, and (2) to investigate the effects of Scn1a deficits on neural network oscillations and coding. These experiments will be important for elucidating a neural network mechanism that may contribute to impaired cognition caused by Scn1a gene mutations.