Neurophysiological mechanisms of cognitive impairment in Severe Myoclonic Epileps

婴儿严重肌阵挛性癫痫（SMEI），也称为Dravet综合征，是一种与Scn1a功能缺失突变相关的儿童疾病，其特征是频繁癫痫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无法恢复正常的认知功能。为了确定改善认知结果的适当治疗策略，首先需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往往归因于癫痫发作的影响，我们提出，与SMEI相关的遗传缺陷导致脑网络活动的神经生理学改变，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，认知功能可能无法通过单独治疗癫痫发作完全恢复。因此，这项调查将是重要的，以确定是否额外的治疗策略，以传统的抗癫痫药物应追求在努力开发治疗，以改善认知结果。 Scn1a基因编码I型电压门控钠通道。在前脑，Scn1a赤字导致受损的动作电位发射的小白蛋白阳性（PV+）的中间神经元，但不是兴奋性锥体细胞。除了这种细胞类型对平衡大脑中的兴奋和抑制的贡献外，PV+中间神经元在神经网络的时空模式中发挥关键作用，特别是在认知过程中。在隔-海马系统中，这些细胞是脑网络振荡和时间编码所需的，并且该中间神经元群体中的选择性损伤导致学习和记忆任务的认知性能受损。因此，隔-海马系统可能是Scn1a缺陷影响的一个网络。该提案的目标是解决Scn1a缺陷是否会导致认知障碍的问题。我们假设，间隔-海马系统中的Scn1a缺陷足以损害独立于癫痫发作障碍的认知。我们将使用体内电生理和行为技术结合RNAi沉默Scn1a表达的大鼠来验证这一假设。我们的具体目标是（1）确定隔海马系统中Scn1a缺陷对认知的影响，以及（2）研究Scn1a缺陷对神经网络振荡和编码的影响。这些实验对于阐明可能导致Scn1a基因突变引起的认知受损的神经网络机制非常重要。

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.