Noritake, A. | Search bioRxiv

bioRxiv2024

Low-invasive, wide-field, and cellular resolution two-photon imaging of neural population activity in brainstem and nucleus tractus solitarii

Brain-viscera communication plays a crucial role in regulating mental health, with the vagus nerve being a key structure mediating this interaction. Clinically, artificial vagus nerve stimulation (VNS) is used to treat various neuropsychiatric disorders, highlighting the importance of vagal afferent fibers in regulating emotion. The nucleus tractus solitarii (NTS) is a brainstem structure proposed to receive signals from vagal afferents and relay them to brain networks for emotion regulation. However, due to the anatomical complexity and difficulty in accessing the deep-brain NTS region in living animals, the mechanisms remain unclear. Here, we developed a wide-field and deep-brain two-photon imaging method using a double-prism based optical interface. This approach enables the identification of cellular-resolution neural activities in the NTS while preserving the cerebellum, which covers the NTS and is important for emotion regulation, intact. We systematically evaluated how NTS neurons respond to VNS and a gastrointestinal hormone, suggesting the usefulness of this method for investigating the role of the vagus-NTS pathway in vivo.

neuroscience↗

bioRxiv2023

Neurofeedback of prefrontal unit activity during working memory in the macaque

Techniques utilizing neurofeedback, a form of biofeedback using neural signals from the brain, have been applied lately to higher association areas such as the lateral prefrontal cortex (LPFC); however, it remains unexplored how well neurofeedback using unit activity in the LPFC modulates its working memory-related activity and performance. To address this issue, we provided neurofeedback of LPFC unit activity during a delay period to two monkeys while they performed a delayed matching-to-paired-sample task. In the task, neurofeedback allowed the animals to shorten the delay length by increasing delay activity and make an earlier choice. Neurofeedback significantly increased delay activity in two-thirds of task-related neurons. Notably, in 16% of these neurons, a preference for delay activity and performance dependent on the stimulus emerged. Although neurofeedback decreased performance primarily due to choice errors, the disassociation of neurofeedback linkage rescued performance. Further, the neuronal activity of simultaneously recorded neurons without neurofeedback linkage suggests that neurofeedback reconfigured the net activity of the LPFC to adapt to new situations. These findings indicate that LPFC neurons can dynamically multiplex different types of information to adapt to environmental changes. Thus, we demonstrated the significant potential of neurofeedback using unit activity to investigate information processing in the brain.

neuroscience↗