Astrocytes Help Manipulate Synaptic Activity in Learning and Memory

Better learning and longer memories

RIKEN neuroscientists have identified an intriguing system for how neuronal activity in mice is dynamically tuned (with signaling at some synapses increasing, while other synapses go silent) in order to stimulate the process of learning and memory development. This discovery offers new insights into the function of brain cells called astrocytes play in memory development.

A group led by Yukiko Goda of the RIKEN Center for Brain Science aims to comprehend the neural processes underlying learning and memory development. Goda claims that his team’s primary objectives is to comprehend how the strengths of specific synapses are established and dynamically adjusted.

In a 2016 report, Goda’s group used cell cultures derived from rat brains to examine the habits of basic systems in which several input neurons developed synaptic links with the dendrite of a single recipient neuron. They established that astrocytes (a highly plentiful population of cells that serve several vital supporting functions in the brain) assisted in strengthening active synapses while weakening less-active synaptic links.

Currently, the group has probed this regulatory system more deeply.Specifically, they concentrated on the role of receptors for the neurotransmitter N-methyl-D-aspartate (NMDA) in the mouse hippocampus, the brain area responsible for memory creation.

Goda detailed that NMDA is a reputable element of neuronal signaling in the hippocampus. However, the concept of astrocyte NMDA receptors has met with some skepticism. However, her group’s previous work provided engaging proof that such receptors are directly associated with tuning nearby neurons’ links.

Understanding Astrocytes

In this study, Goda and coworkers utilized different interventions to interfere with NMDA receptor activity in mouse astrocytes. These treatments impacted activity on the presynaptic side of synapses, regulating input neurons’ terminals instead of the dendrites of the neurons that received those signals. As a result, synaptic activity between input and receiver neurons became more stable overall, instead of changing dynamically to favor activity at some synapses relative to others.

Mathematical modeling, carried out in cooperation with Tomoki Fukai’s group at the Okinawa Institute of Science and Technology Graduate University (OIST), shared that these modifications in synaptic activity significantly decreased neural plasticity in the hippocampus, specifically the selective reinforcement of memories via the strengthening and weakening of synapses between neurons.

Goda claims that his team’s work proves that astrocyte signaling helps ensure the wide circulation of presynaptic strengths.

The group is attempting to better comprehend the organization, activity, and circulation of NMDA receptors in hippocampal astrocytes and the wider impact of these non-neuronal receptors on animal behavior. Goda stated that he and his team wish to discover whether mice with damaged astrocyte NMDA receptors show modified hippocampal network activity and, if so, whether those modifications connect to spatial and contextual learning.

Originally published by: medicalxpress.com