The goal of the proposed research is to understand how astrocytes, a type of glial cell in the brain, work together with motor cortex neurons to mediate motor learning. Previous studies have shown that a stable ensemble of neurons emerges as an animal becomes expert at a stereotyped movement. It has also been shown that astrocyte calcium signaling, particularly in microdomains of the fine processes surrounding synapses, responds to and correlates with neuronal activity. Astrocyte microdomains are considered to reflect synaptic activity and in turn, influence synaptic function. We hypothesize that a stable pattern of motor cortex astrocyte Ca2+ activity in microdomains develops during acquisition of a stereotyped motor movement in mice, is correlated with neuronal activation and learning, and together with intracellular Ca2+, is potentially causal for learning. We will utilize a range of cutting edge techniques to test this hypothesis, as well as a lever push task, which is a motor learning paradigm that features both associative learning and acquisition of a stereotyped motor movement. We will utilize transgenic mice expressing membrane-bound genetically encoded calcium indicators in astrocytes, combined with high-resolution two-photon imaging, to chronically image calcium microdomain activity as the animal learns to perform the task. These experiments will determine whether unique microdomain activation patterns emerge with motor learning. We then propose to optogenetically disrupt neuronal signaling in the motor cortex using expression of light-activated halorhodopsin or channelrhodopsin in excitatory neurons to inactivate or activate neuronal activity, respectively, in order to determine if patterns of astrocyte calcium activity in microdomains are disrupted along with motor learning. Finally, we will disrupt intracellular calcium signaling in astrocytes using designer receptors exclusively activated by designer drugs (DREADDs) to determine whether there is an effect on motor learning when astrocyte calcium signals, including microdomains, are disrupted. Together, these studies will not only identify an astrocyte ?signature? encoded by microdomains which is associated with motor learning, but also provide mechanistic insight into how this activity structure is regulated by neuronal activation, and how, alongside intracellular Ca2+ signaling, it influences motor learning. Given that astrocyte dysfunction has been implicated in a number of neurological conditions that involve aberrant neuronal circuit function, including schizophrenia, depression, and epilepsy, advancing our understanding of astrocyte-neuron interactions will fill critical gaps in knowledge and potentially contribute to novel therapeutics.
Astrocytes are a type of glial cell in the brain, which have been shown to respond to and modulate neuronal activity during animal behavior with increases in intracellular calcium signaling. They have been implicated in a number of neurological conditions, such as depression, epilepsy, and neuropsychiatric disorders. Further understanding of astrocyte-neuron interactions will guide our understanding of neurological disease mechanisms and allow for the development of novel therapeutic strategies.
