Influence of Astrocytes on Working Memory

Abstract

The central nervous system is the key controller in the human body. All aspects of live - from basic functions such as breathing to higher cognitive processes as memory building or complex decision making - have a network of neural cells at its core. While neuronal cells have been subject to intensive research for more than a century, the role of glial cells - the second major group of cell types in the brain - including astrocytes is still relatively unknown or contradictory. The focus of this thesis lies on memory processes and the astrocytic impact on them.
Working memory is a memory module which describes the short-term storage and processing of input data. A classic example is remembering a phone number before noting it down or typing it. Working memory is the fundamental building block for many cognitive functions such as prediction, goal-directed behavior and decision-making. Its impairment is tragically visible in various forms of dementia which can be caused by Alzheimer’s Disease or Parkinson’s Disease. Understanding the role of an astrocytic pathway as a possible underlying mechanism of working memory, could help strategies to prevent and treat these diseases and improve patients’ quality of life. The goal of this thesis is to provide support for astrocytic gliotransmission as a fundamental pathway in regard to Working memory. To this end, stability analysis of a tripartite model
with novel modifications shows the ability of extended firing in the presence of gliotransmission and hence, the principal ability for memory storage. Building upon this cell model, a complex network consisting of an established neuron-astrocyte structure is investigated. Different simulation scenarios show the possibility of astrocytes to store neuronal information during the absence of input signal and thus, showing a possible method for working memory.
Simultaneously, two competing theories of persistent and sparse delay activity are explained by varying strength of astrocytic gliotransmission while showing working memory functionality for both cases. Classical working memory experiments on primates are used as guiding points for the simulation sequence in order to provide comparability and authenticity.