MidlineThalamus

MidlineThalamus is a group of nuclei located along the midline of the thalamus, surrounding the third ventricle. The core midline nuclei include the reuniens (RE), rhomboid (RH), and intermediodorsal (IMD) nuclei; the mediodorsal nucleus (MD) is sometimes included as part of this group. These nuclei form reciprocal thalamo-cortical and subcortical circuits that link limbic structures with prefrontal and cingulate cortices.

Afferent connections arise from the hypothalamus, hippocampus, amygdala, and brainstem arousal systems, while efferent projections primarily target the prefrontal cortex (medial and orbital regions) and cingulate cortices. The reuniens, in particular, provides a conduit between the hippocampus and medial prefrontal cortex, supporting communication between memory and executive networks.

Functionally, the midline thalamus participates in arousal and attention, maintenance of cortical activity during wakefulness, and regulation of cognitive processes such as working memory and decision-making. It contributes to the integration of emotional and mnemonic information within thalamo-cortical circuits.

Clinical relevance is mainly derived from its role in consciousness and memory. Disruption of midline thalamic activity can accompany sleep and anesthesia effects, cognitive deficits after thalamic stroke, and certain neuropsychiatric conditions. Experimental studies and imaging have explored deep brain stimulation of midline thalamic nuclei for epilepsy or mood regulation, but clinical applications remain investigational.