# Distinguishing the activity of adjacent somatosensory nuclei within the brainstem using 3T fMRI

## TL;DR

This study shows how to distinguish brainstem activity related to touch using 3T fMRI, offering new insights into human sensory processing.

## Contribution

The novel contribution is demonstrating that multivariate analysis can decode brainstem somatosensory activity with 3T fMRI.

## Key findings

- Univariate analysis could not clearly differentiate hand and face activation in the brainstem.
- Multivariate classification successfully decoded somatosensory activity patterns in the brainstem, thalamus, and S1.
- The method provides a reliable way to study brainstem signal processing in humans.

## Abstract

Experimental evidence in animal models indicates that the brainstem plays a major role in sensory modulation. However, mapping functional activity within the human brainstem presents many methodological challenges. These constraints have deterred essential research into human sensory brainstem processing. Here, using a 3T functional Magnetic Resonance Imaging (fMRI) sequence optimised for the brainstem, combined with uni- and multivariate analysis approaches, we investigated the extent to which functional activity of neighbouring somatosensory nuclei can be delineated in the brainstem, thalamus, and primary somatosensory cortex (S1). Whilst traditional univariate approaches offered limited differentiation between adjacent hand and face activation in the brainstem, multivariate classification enabled above-chance decoding of these activity patterns across S1, the thalamus, and the brainstem. Our findings establish a robust methodological approach to explore signal processing within the brainstem and across the entire somatosensory stream. This is a fundamental step towards broadening our understanding of somatosensory processing within humans and determining what changes in sensory integration may occur in clinical populations following sensory deprivation.