Year: 2018
Type: article
Abstract: Dopamine neurons in the ventral tegmental area (VTA) are dysregulated in numerous psychiatric disorders, including schizophrenia, addiction, and ADHD. VTA dopamine neurons send strong projections to forebrain areas such as the striatum and the prefrontal cortex (PFC) where they mediate various cognitive and affective processes; these processes range from working memory, attention, decision making, action selection to motivation. Despite the importance of VTA dopamine neurons, we have a limited understanding of how dopamine neuron activity modulates downstream neural activity. The current studies, thus, utilized optogenetics in Th::Cre rats to selectively activate VTA dopamine neurons and investigated how phasic VTA dopamine activity modulates global neural activity. Specifically, these studies examined global forebrain functional magnetic resonance imaging (fMRI) activity and local neural activity within PFC during optogenetic activation of VTA dopamine neurons. The first study demonstrated that phasic VTA dopamine activity increased fMRI responses in several areas, including VTA-innervated limbic regions such as the ventral striatum. Surprisingly, the most prominent fMRI signal increase was observed in the dorsal striatum, which is not traditionally associated with VTA dopamine neurotransmission. These data suggest that there are more robust functional interactions between mesolimbic and non-limbic basal ganglia dopamine circuits than conventionally described. These findings also provide a potential novel framework for understanding dopamine-dependent functions and interpreting data from human studies that primarily rely on fMRI as a non-invasive measure of neural activity. The second study revealed that phasic activation of VTA dopamine neurons in freely moving animals elicited heterogeneous patterns of modulation in PFC neuron spiking activity on both transient and sustained timescales. In addition to the modulation of individual unit activity, dopamine stimulation also generated responses at the population level. Furthermore, dopamine neuron activation enhanced the power of PFC high gamma oscillations and phase amplitude coupling between theta and high gamma frequencies in the local field potentials (LFPs). The effects of VTA dopamine activity were also state-dependent as it generated a robust increase in LFP beta but not high gamma oscillations under isoflurane anesthesia. Thus, activation of dopamine neurons elicits diverse effects on PFC network activity that may be relevant for PFC-dependent cognitive processes.
Author: Sweyta Lohani
Language: English
Subfield: Cellular and Molecular Neuroscience
Field: Neuroscience
Domain: Life Sciences
Open Access status: green
OpenAlex ID: W2794928967