Nonlocal spatiotemporal representation in the hippocampus of freely flying bats

Navigation occurs through a continuum of space and time. The hippocampus is known to encode the immediate position of moving animals. However, active navigation, especially at high speeds, may require representing navigational information beyond the present moment. Using wireless electrophysiological recordings in freely flying bats, we demonstrate that neural activity in area CA1 predominantly encodes nonlocal spatial information up to meters away from the bat’s present position. This spatiotemporal representation extends both forward and backward in time, with an emphasis on future locations, and is found during both random exploration and goal-directed navigation. The representation of position thus extends along a continuum, with each moment containing information about past, present, and future, and may provide a key mechanism for navigating along self-selected and remembered paths.

Efek Ekstrak Etanol Daun Kelor (Moringa oleifera, Lamk.) Pada Mencit Model Demensia: Kajian Memori Spasial, Kadar Malondialdehid Dan Jumlah Sel Piramidal Hipokampus Area CA1 Dan CA2-CA3

ABSTRAK penyakit sel-sel saraf di otak, akibat hipokampus yang rusak oleh radikal bebas. EEDK (Ekstrak etanol daun kelor) (Moringa oleifera, Lamk.) mengandung phytochemicals, karoten, vitamin, mineral, asam amino, flavonoid dan phenolic, terbukti mengurangi kerusakan oksidatif dan defisit memori. Penelitian ini bertujuan mengetahui efek EEDK terhadap memori spasial, kadar MDA, jumlah sel piramidal hipokampus yang rusak area CA1,CA2-CA3 dan gambaran histopatologi mencit. Rancangan penelitian ini pre test and post test control group design untuk uji memori spasial dan post test control group design untuk uji kadar MDA, jumlah sel piramidal hipokampus dan gambaran histopatologi. Menggunakan 30 ekor mencit terdiri dari 6 kelompok, per kelompok ada 5 ekor mencit, yaitu kelompok kontrol normal, kontrol positif, kontrol negatif, kelompok EEDK 100, 200, dan 400 mg/kgBB, semua diinduksi Pb asetat 50 mg/KgBB kecuali pada kelompok normal. Kontrol positif diobati kuersetin 50 mg/kgBB, sedangkan kontrol negatif tidak diobati. Data uji memori diperoleh dari uji Morris water maze pra dan paska perlakuan, data status antioksidan diperoleh dari uji kadar MDA dan data gambaran histopatologi diperoleh dari perhitungan jumlah sel pyramidal. Analisis data menggunakan repeated measures ANOVA dan ANOVA dengan Post Hoc LSD. Hasil penelitian menunjukkan waktu latensi, uji kadar MDA dan pemeriksaan histopatologi otak terdapat perbedaan bermakna antara kelompok kontrol negatif dengan kelompok EEDK. Pemberian EEDK 400 mg/kgBB paling efektif memperbaiki memori spasial, menurunkan kadar MDA, dan mencegah kerusakan sel piramidal hipokampus area CA1, CA2-CA3.

Differential propagation of ripples along the proximo-distal and septo-temporal axes of dorsal CA1 of rats

The functional connectivity of the hippocampus with its primary cortical input, the entorhinal cortex, is organized topographically. In area CA1 of the hippocampus, this leads to different functional gradients along the proximo-distal and septo-temporal axes of spatial/sensory responsivity and spatial resolution respectively. CA1 ripples, a network phenomenon, allows us to test whether the hippocampal neural network shows corresponding gradients in functional connectivity along the two axes. We studied the occurrence and propagation of ripples across the entire proximo-distal axis along with a comparable spatial range of the septo-temporal axis of dorsal CA1. We observed that ripples could occur at any location, but their probability of co-occurrence and amplitude decreased with increasing distance from the reference tetrode. This reduction was greater along the proximo-distal axis than the septo-temporal axis. Furthermore, we found that ripples propagate primarily along the proximo-distal axis. Thus, over a spatial scale of ~1.5 mm, the network is anisotropic along the two axes, complementing the topographically organized cortico-hippocampal connections.