Abstract
Recently there has been renewed interest in the habenula; a pair of small, highly evolutionarily conserved epithalamic nuclei adjacent to the medial dorsal (MD) nucleus of the thalamus. The habenula has been implicated in a range of behaviours including sleep, stress and pain, and studies in non-human primates have suggested a potentially important role in reinforcement processing, putatively via its effects on monoaminergic neurotransmission. Over the last decade, an increasing number of neuroimaging studies have reported functional responses in the human habenula using functional magnetic resonance imaging (fMRI). However, standard fMRI analysis approaches face several challenges in isolating signal from this structure because of its relatively small size, around 30 mm3 in volume. In this paper we offer a set of guidelines for locating and manually tracing the habenula in humans using high-resolution T1-weighted structural images. We also offer recommendations for appropriate pre-processing and analysis of high-resolution functional magnetic resonance imaging (fMRI) data such that signal from the habenula can be accurately resolved from that in surrounding structures.
Highlights
The habenula comprises a pair of small nuclei adjacent to the posterior end of the medial dorsal (MD) thalamus and in many vertebrates can be divided into medial (MHb) and lateral (LHb) portions (Andres et al, 1999)
Spatial normalisation parameters were generated for transforming the grey matter component of our DARTEL template image to the segmented grey matter component of the SPM single subject template image in Montreal Neurological Institute (MNI) space
In order to map from each individual structural scan to DARTEL template to MNI space, the MNI-to-template spatial normalisation parameters were combined with the deformations estimated by DARTEL and applied to the anatomical image and the habenula region of interest (ROI) for each subject
Summary
The habenula comprises a pair of small nuclei adjacent to the posterior end of the medial dorsal (MD) thalamus and in many vertebrates can be divided into medial (MHb) and lateral (LHb) portions (Andres et al, 1999). The LHb has substantial reciprocal anatomical connections with serotonergic neurons in the median and dorsal raphe nuclei (Herkenham, 1979) and in rats receives a direct cortical projection from prelimbic frontal cortex (Beckstead, 1979). This unique position, as a hub between corticolimbic and midbrain monoaminergic regions, could allow positively or negatively valenced states or stimuli to modulate motor output, consistent with the hypothesis that the habenula plays a critical role in the motivational aspects of reinforcement learning and decision-making, as extensively
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