Short Conduction Delays Cause Inhibition Rather than Excitation to Favor Synchrony in Hybrid Neuronal Networks of the Entorhinal Cortex

How stable synchrony in neuronal networks is sustained in the presence of conduction delays is an open question. The Dynamic Clamp was used to measure phase resetting curves (PRCs) for entorhinal cortical cells, and then to construct networks of two such neurons. PRCs were in general Type I (all advances or all delays) or weakly type II with a small region at early phases with the opposite type of resetting. We used previously developed theoretical methods based on PRCs under the assumption of pulsatile coupling to predict the delays that synchronize these hybrid circuits. For excitatory coupling, synchrony was predicted and observed only with no delay and for delays greater than half a network period that cause each neuron to receive an input late in its firing cycle and almost immediately fire an action potential. Synchronization for these long delays was surprisingly tight and robust to the noise and heterogeneity inherent in a biological system. In contrast to excitatory coupling, inhibitory coupling led to antiphase for no delay, very short delays and delays close to a network period, but to near-synchrony for a wide range of relatively short delays. PRC-based methods show that conduction delays can stabilize synchrony in several ways, including neutralizing a discontinuity introduced by strong inhibition, favoring synchrony in the case of noisy bistability, and avoiding an initial destabilizing region of a weakly type II PRC. PRCs can identify optimal conduction delays favoring synchronization at a given frequency, and also predict robustness to noise and heterogeneity

Hepatoprotective activity of Indian Phyllanthus

Context: Phyllanthus (Euphorbiaceae) species are traditionally well-known for their medicinal properties including hepatoprotective activity. Objective: The study assessed the hepatoprotective and antioxidant activities of 11 Phyllanthus species, P. amarus Schumach., P. urinaria L., P. debilis Klein ex Willd, P. tenellus Roxb., P. virgatus G. Forst., P. maderaspatensis L., P. reticulatus Poir., P. polyphyllus Willd., P. emblica L., P. indofischerii Bennet. and P. acidus (L.) Skeels. Materials and methods: The dried leaves and stems of each plant species were extracted in methanol and successively in water. The extracts were screened for hepatoprotective activity at a concentration of 50 μg/mL against tert-butyl hydroperoxide (t-BH) induced toxicity in HepG2 cells. Seven extracts from five species that showed hepatoprotective activity were assessed for their 50% effective concentration (EC50) values and their antioxidant activity using a DPPH assay. Phyllanthin and hypophyllanthin contents were also determined in these Phyllanthus species. Results: The methanol extracts of P. polyphyllus, P. emblica and P. indofischeri showed high levels of hepatoprotective activity with EC50 values of 12, 19 and 28 μg/mL and IC50 of 3.77, 3.38 and 5.8 μg/mL for DPPH scavenging activity respectively against an IC50 of 3.69 μg/mL for ascorbic acid. None of these activities could be attributed to phyllanthin and hypophyllanthin. Discussion and conclusion: The hepatoprotective and antioxidant activities of P. indofischeri are demonstrated for the first time in literature. The study also confirms the hepatoprotective and antioxidant activities of leaves of P. emblica and P. polyphyllus. The molecule(s) responsible for the activities is being investigated

Temporal Causal Inference With Stochastic Audiovisual Sequences

Data and stimulus sequences described in the paper.NIH EY082