Thalamus

The thalamus (plural: thalami) sits at the centre of the brain — one in each hemisphere — and serves as the brain's main switchboard. Almost every signal travelling between the body and the cortex, and between cortical regions, passes through the thalamus.

It is sometimes called "the gateway to the cortex" because of this central role.

What it does

The thalamus has dozens of distinct nuclei, each specialising in a different stream of information:

• Sensory relay — the lateral geniculate nucleus relays vision; the medial geniculate handles hearing; the ventral posterior nucleus carries touch and proprioception
• Motor coordination — the ventral lateral nucleus integrates input from the cerebellum and basal ganglia before passing motor commands to the cortex
• Attention and arousal — the reticular and intralaminar nuclei modulate consciousness and selective attention
• Memory — the anterior thalamic nuclei are part of the Papez circuit, linking the hippocampus to the cortex

Why it matters in stroke

The thalamus is densely vascularised and frequently affected by stroke. Even small thalamic infarcts can produce striking deficits: dense sensory loss, attention disorders, severe pain, or cognitive impairment, depending on which nuclei are affected.

Our post-stroke brain ageing research found that thalamic atrophy was one of the regions most strongly linked to accelerated brain age after stroke, alongside the internal capsule and corona radiata.

In neuroimaging

Total thalamic volume is a standard output of subcortical segmentation. More granular pipelines (FreeSurfer's segmentation of thalamic nuclei) can separate the individual nuclei — useful in research on memory, attention, or specific motor disorders.