![]() ![]() ![]() The hippocampus is an appealing target for stereotactic neuromodulation techniques, being a frequent target for stereotactic implantation of recording depth electrodes by epilepsy surgeons. 79 Thus, availability of a treatment that can decrease seizure frequency in MTLE to a similar degree as ablative or resective procedures but that preserves interictal function would represent a major advance in the surgical treatment of epilepsy. In fact, open resection is associated with a high rate of lateral temporal lobe dysfunction regardless of approach, such as naming or object recognition deficits. However, hippocampal resection or ablation may be contraindicated in patients with dominant-onset MTLE with preserved verbal memory and/or dominant temporal lobe function, patients with bilateral mesial temporal onset, or those with recurrent MTLE contralateral to a prior resection. Patients with mesial temporal lobe epilepsy (MTLE), the most common form of drug-resistant epilepsy, have a high rate of seizure freedom 75 after amygdalohippocampal resection, 3,5,8,76 whether by anterior temporal lobectomy (approximately 75%) or selective amygdalohippocampectomy (approximately 72%), or by stereotactic ablation (radiofrequency or laser 77,78). Richard Winn MD, in Youmans and Winn Neurological Surgery, 2017 Hippocampus Information obtained will be contribute to a greater understanding of the hippocampus, and may illuminate some of the cellular and molecular events involved in the development, maintenance and decline of normal cognitive function.H. The cellular mechanisms by which estrogen can influence the developing hippocampus have not been examined and is the focus of this outline. Furthermore, hormonally mediated changes in neurotrophin expression during development may be causally related to plasticity in the adult hippocampus. It follows, then, that estrogen induced changes in neurotrophin synthesis is an important mediator of differentiation of the brain, and specifically the hippocampus. In the adult rat, estrogen regulates mRNA levels of BDNF and its high affinity receptor, trkB, in several regions of the rat brain. In addition to the modulation of synaptic transmission and plasticity, BDNF may also be involved in hippocampal synaptogenesis. Moreover, the expression of neurotrophic factors has the ability to acutely modulate synaptic transmission by presynaptic as well as postsynaptic mechanisms. Neurotrophins are widely expressed in the CNS and are involved in complex and activity-dependent modulation of dendritic and axonal growth. During this time period estrogen has been shown to have a number of transcriptional effects, mediated by steroid receptor coregulatory proteins, on morphological and biochemical properties of hippocampal neurons that would predict an excitatory action of this steroid on synaptic physiology in the hippocampus.Īdditionally, the neurotrophins, including brain-derived neurotrophic factor (BDNF), also affect the long-term survival and differentiation of hippocampal cells during development, and their viability in adulthood. Furthermore, there is a transient increase in the expression of estrogen receptors during the first postnatal week of life a period that is active in neuronal differentiation and synaptogenesis. Estrogen receptors have been found in cells of the hippocampus using a variety of techniques. ![]() The mechanism and sites of action for the effects of estradiol on cognitive performance and epileptic seizure activity have not been established, but one probable site is the hippocampus, a steroid-responsive region of the brain. These early influences of steroids on the brain are essentially permanent and in part determine the steroid responsiveness of the adult brain. Furthermore, ovarian steroids act during development to alter the neuronal cytoarchitecture and synaptic connectivity. Estrogens act to alter certain aspects of cognitive performance and pathology such as epileptic seizure activity and Alzheimer’s disease. In addition to their primary role in the maintenance and regulation of reproductive capacity, ovarian steroid hormones acting through specific nuclear receptors influence more general neurobiological functions, such as perceptual-spatial skills and learning and memory. ![]()
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