Thalamo-hippocampal pathway regulates incidental memory capacity in mice.

Incidental memory can be challenged by increasing either the retention delay or the memory load. The dorsal hippocampus (dHP) appears to help with both consolidation from short-term (STM) to long-term memory (LTM), and higher memory loads, but the mechanism is not fully understood. Here we find that female mice, despite having the same STM capacity of 6 objects and higher resistance to distraction in our different object recognition task (DOT), when tested over 1 h or 24 h delays appear to transfer to LTM only 4 objects, whereas male mice have an STM capacity of 6 objects in this task. In male mice the dHP shows greater activation (as measured by c-Fos expression), whereas female mice show greater activation of the ventral midline thalamus (VMT). Optogenetic inhibition of the VMT-dHP pathway during off-line memory consolidation enables 6-object LTM retention in females, while chemogenetic VMT-activation impairs it in males. Thus, removing or enhancing sub-cortical inhibitory control over the hippocampus leads to differences in incidental memory.

Vagal Nerve Stimulation for Drug-Resistant Epilepsy: Adverse Events and Outcome in a Series of Patients with Long-Term Follow-Up.

BACKGROUND: Vagal nerve stimulation (VNS) is a palliative treatment option for drug-resistant epilepsy. The aim of this study was to describe the clinical and demographic features of selected patients scheduled for VNS and to evaluate the long-term efficacy of VNS in seizure control. MATERIALS AND METHODS: Between 2006 and 2013, 32 consecutive epileptic patients (14 male and 18 female) were enrolled at our Institute for VNS implantation. In all cases resective surgery had previously been excluded by the use of a noninvasive presurgical study protocol. Mean age was 32 years (range 18-50), and mean epilepsy duration 23 years (range 11-39). All subjects were followed-up for at least 2 years (mean 6 years, range 2-9) after VNS implantation. Patients were considered responders when a reduction of seizures of more than 50 % was reported. RESULTS: All patients had complex partial seizures, in 81 % of the patients with secondary generalization and in 56 % with drop attacks. Neurological examination revealed focal deficits in 19 % of the patients. Brain magnetic resonance imaging (MRI) was positive in 47 % of the patients. No surgical complications were observed in this series. Three patients were lost to follow-up. Twelve patients were classified as responders. Among the others, 1 patient experienced side effects (snoring and groaning during sleep) and the device was removed. CONCLUSIONS: Our data confirm that VNS is a safe procedure and a valid palliative treatment option for drug-resistant epileptic patients not suitable for resective surgery.