Cognitive and linguistic dysfunction after thalamic stroke and recovery process: possible mechanism

Area of Science:

• Neuroscience
• Cognitive Neurology
• Speech and Language Pathology

Background:

• Thalamic stroke can lead to cognitive and linguistic deficits, including aphasia, with unclear underlying mechanisms.
• The transient nature of word retrieval difficulty in acute thalamic stroke and its recovery pattern are not well understood.
• Similarities between supplementary motor area (SMA) aphasia and thalamic aphasia suggest shared neural systems.

Purpose of the Study:

• To investigate the neural mechanisms underlying cognitive and linguistic problems, specifically word retrieval difficulty, following thalamic stroke.
• To explore the role of the supplementary motor area (SMA) and inferior frontal cortex (IFG) in thalamic aphasia and its recovery.
• To examine long-term changes in hemodynamic responses in the SMA during verbal tasks using functional near-infrared spectroscopy (f-NIRS).

Main Methods:

• Utilized hybrid neuroimaging techniques: single-photon emission computed tomography (SPECT) and functional near-infrared spectroscopy (f-NIRS).
• SPECT was used to visualize brain perfusion abnormalities associated with word retrieval difficulty and aphasia.
• f-NIRS monitored hemodynamic SMA responses during phonemic verbal tasks to assess changes over time.

Main Results:

• SPECT revealed perfusion abnormalities in the fronto-parieto-cerebellar-thalamic loop and bilateral SMA and IFG regions.
• f-NIRS demonstrated a significant decline in word retrieval linked to posterior SMA responses in acute thalamic stroke.
• Rapid recovery of word retrieval difficulty correlated with increased bilateral SMA responses at follow-up.

Conclusions:

• Cognitive deficits in thalamic stroke involve the fronto-parieto-cerebellar-thalamic loop.
• Linguistic impairments are associated with SMA, IFG, and other language-related areas.
• Bilateral SMA plays a critical role in word retrieval recovery, with right-sided language regions influencing overall aphasia recovery.