Summary: Scientists have introduced D-PSCAN, a new minimally invasive imaging approach that provides high-resolution, in vivo visualization of the nucleus tractus solitarii (NTS) in the brainstem. The NTS, a central relay for signals carried by the vagus nerve from internal organs, plays a crucial role in integrating bodily signals that influence emotion, appetite, metabolism, and overall mental health.
Using D-PSCAN, researchers captured how the NTS responds both to electrical vagus nerve stimulation (VNS) and to natural physiological signals, such as the gut hormone cholecystokinin released after feeding. This advance offers a practical way to study brain–body communication at cellular resolution and may guide improvements in clinical interventions like VNS for depression and other neuropsychiatric disorders.
Key Facts:
- High-resolution deep-brain imaging: D-PSCAN enables minimally invasive, wide-field observation of NTS activity in living animals.
- Brain–body integration: The NTS integrates signals from organs via the vagus nerve and influences emotion regulation, appetite, and metabolic processes.
- Clinical relevance: Insights from D-PSCAN can help refine vagus nerve stimulation parameters and inform therapies for neurological and psychiatric conditions.
Source: NINS
Brain–body communication underlies emotional regulation and many aspects of health.
The nucleus tractus solitarii (NTS), located deep in the brainstem beneath the cerebellum, is a gateway for visceral signals transmitted by the vagus nerve. Despite its importance, the NTS’s depth and proximity to critical brainstem structures have made live imaging technically difficult, limiting direct study in behaving animals.
In a study published in Cell Reports Methods (April 4, 2025), Masakazu Agetsuma and colleagues describe D-PSCAN (Double-Prism-based brainStem imaging under Cerebellar Architecture and Neural circuits), an in vivo, two-photon imaging method designed for minimally invasive, wide-field visualization of the NTS at cellular resolution.
Minimally invasive access while preserving cerebellar function
D-PSCAN employs a double microprism assembly implanted between the cerebellum and brainstem. This optical interface provides an extended, unobstructed view of the NTS without removing or damaging the cerebellum, which plays important roles in motor control and emotion regulation. Preserving surrounding structures allows more physiologically relevant observations of NTS activity in living mice.
“One major challenge in studying the NTS is its deep location beneath the cerebellum, which has made observation in living animals difficult,” explains lead author Masakazu Agetsuma. Previous methods sometimes required cerebellar removal, compromising behaviors and brain functions researchers aimed to study.
Cellular-resolution observations of NTS activity
The team validated D-PSCAN by measuring NTS responses to vagus nerve stimulation. They identified stimulation intensity thresholds required to recruit NTS neurons and found that different stimulation parameters produced distinct activation patterns—ranging from sensitization to inhibitory effects. These detailed, parameter-specific observations could inform how VNS is tuned clinically for conditions such as drug-resistant epilepsy and treatment-resistant depression.
To evaluate NTS responses under a physiological stimulus, the researchers also monitored activity evoked by cholecystokinin, a gut hormone released after a meal. D-PSCAN detected robust, hormone-driven activation in the NTS, demonstrating its suitability for studying natural gut–brain signaling in real time.
Implications and future directions
Understanding how the NTS integrates multimodal visceral input is key to deciphering brain–body mechanisms that shape emotion, appetite, energy balance, and metabolic control. D-PSCAN provides a practical platform for mapping these circuits in vivo, enabling experiments that link organ signals to specific neural ensemble dynamics in the NTS.
According to Agetsuma, “The brain–body interaction plays a critical role in emotion regulation, and gaining a deeper understanding of this function is expected to contribute both to the treatment of neuropsychiatric disorders and to the advancement of mental health and well-being.” D-PSCAN is positioned as a versatile research tool spanning basic neuroscience and translational investigations aimed at optimizing neuromodulation therapies.
Beyond emotion and psychiatric research, the method is expected to support studies into appetite regulation, gut–brain communication, cardiovascular reflexes, and how the microbiota may influence central circuits via visceral signals.
About this neuroscience research news
Author: Hayao KIMURA
Source: NINS
Contact: Hayao KIMURA – NINS
Image: The image is credited to Neuroscience News
Original Research: Open access.
“Minimally invasive, wide-field two-photon imaging of the brainstem at cellular resolution” by Masakazu Agetsuma et al., Cell Reports Methods.
Abstract
Minimally invasive, wide-field two-photon imaging of the brainstem at cellular resolution
The nucleus tractus solitarii (NTS) is a critical brainstem hub for transmitting visceral information that shapes emotional states and mediates therapeutic responses to vagus nerve stimulation (VNS). Detailed understanding of how the NTS processes diverse organ-derived signals has been limited by its deep anatomical position and the functional importance of neighboring brainstem regions. To overcome these challenges, the authors developed an in vivo two-photon imaging approach using a double-prism optical interface that preserves surrounding tissue while enabling cellular-resolution observations across a wide field of the brainstem.