Abstract
The medial forebrain bundle (MFB) is a white matter pathway that traverses through mesolimbic structures and includes dopaminergic neural fibers ascending from the ventral tegmental area. Since dopaminergic signals represent hedonic responses, electrical stimulation of the MFB in animals has been used as a neural reward for operant and spatial tasks. MFB stimulation strongly motivates animals to rapidly learn to perform a variety of behavioral tasks to obtain a reward. Although the MFB is known to connect various brain regions and MFB stimulation dynamically modulates animal behavior, how central and peripheral functions are affected by MFB stimulation per se is poorly understood. To address this question, we simultaneously recorded electrocorticograms (ECoGs) in the primary motor cortex (M1), primary somatosensory cortex, and olfactory bulb of behaving rats while electrically stimulating the MFB. We found that MFB stimulation increased the locomotor activity of rats. Spectral analysis confirmed that immediately after MFB stimulation, sniffing activity was facilitated and the power of gamma oscillations in the M1 was increased. After sniffing activity and motor cortical gamma oscillations were facilitated, animals started to move. These results provide insight into the importance of sniffing activity and cortical gamma oscillations for motor execution and learning facilitated by MFB stimulation.
Significance statement
Electrical stimulation of the medial forebrain bundle (MFB) in the brain reward system motivates animals to perform a variety of behavioral tasks. However, how MFB stimulation per se influences neural activity and relevant behavior remains incompletely understood. We recorded neural activity from the olfactory bulb, the primary motor cortex, and the primary somatosensory cortex of freely moving rats and monitored their behavior while regularly stimulating the MFB of the rats. We found that stimulation of the rat MFB facilitated sniffing activity and enhanced gamma oscillations only in the primary motor cortex, and subsequently induced locomotion. Our findings suggest the possible contribution of gamma oscillations to motor execution and learning facilitated by MFB stimulation.
Footnotes
The authors have no conflicts of interest to disclose with respect to this research.
This work was supported by JST ERATO (JPMJER1801), Institute for AI and Beyond of the University of Tokyo, and JSPS Grants-in-Aid for Scientific Research (18H05525 and 20K15926).
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