3-Hz subthreshold oscillations of CA2 neurons In vivo.

The CA2 region is unique in the hippocampus; it receives direct synaptic innervations from several hypothalamic nuclei and expresses various receptors of neuromodulators, including adenosine, vasopressin, and oxytocin. Furthermore, the CA2 region may have distinct brain functions, such as the control of instinctive and social behaviors; however, little is known about the dynamics of the subthreshold membrane potentials of CA2 neurons in vivo. We conducted whole-cell current-clamp recordings from CA2 pyramidal cells in urethane-anesthetized mice and monitored the intrinsic fluctuations in their membrane potentials. The CA2 pyramidal cells emitted spontaneous action potentials at mean firing rates of ∼0.8 Hz. In approximately half of the neurons, the subthreshold membrane potential oscillated at ∼3 Hz. In two neurons, we obtained simultaneous recordings of local field potentials from the CA1 stratum radiatum and demonstrated that the 3-Hz oscillations of CA2 neurons were not correlated with CA1 field potentials. In tetrodotoxin-perfused acute hippocampal slices, the membrane potentials of CA2 pyramidal cells were not preferentially entrained to 3-Hz sinusoidal current inputs, which suggest that intracellular 3-Hz oscillations reflect the neuronal dynamics of the surrounding networks. © 2016 Wiley Periodicals, Inc.

Epilepsy with myoclonic absences in siblings.

BACKGROUND: Epilepsy with myoclonic absences (EMAs) is a distinct form of childhood epilepsy characterized by a peculiar seizure type that identifies this condition. PURPOSE: To describe the clinical, electroencephalographic features, treatment strategies and outcome in this first case series of two siblings with normal intelligence presenting with EMAs. MATERIALS AND METHODS: Both siblings underwent video-polygraphic investigations (simultaneous recording of electroencephalogram [EEG] and electromyogram [EMG] from deltoids), high-resolution magnetic resonance imaging (MRI), karyotyping, neuropsychological evaluation and language assessment. RESULTS: Both the children had a mean age of onset of prototype seizures by 3.5 years. Myoclonic absences (MAs) were characterized by rhythmic, bilateral, synchronous, symmetric 3-Hz spike-wave discharges, associated with EMG myoclonic bursts at 3 Hz, superimposed on a progressively increasing tonic muscle contraction. The interictal EEG showed a normal background activity with bursts of generalized spike and waves (SWs) as well as rare focal SWs independently over bilateral temporal and frontal regions. Increase in the seizure frequency from 5 to 100/day was observed due to use of carbamazepine and phenobarbitone which decreased with its withdrawal and introduction of valproate. Though lamotrigine was given as an add on to valproate, it did not benefit them and was therefore replaced by topiramate at 3.5 mg/kg/day which has maintained them on remission at one year follow up. CONCLUSIONS: Recognition of this ictal pattern allows identification and differentiation of EMAs from other seizure types. Idiopathic and symptomatic EMAs need to be differentiated from childhood absence epilepsy with myoclonia. MAs are worsened by drugs like carbamazepine while valproate either alone or in combination with topiramate (preferred to lamotrigine) gives excellent outcome.