Is the human left middle longitudinal fascicle essential for language? A brain electrostimulation study

Area of Science:

• Neuroscience
• Neurosurgery
• Linguistics

Background:

• Human brain pathways for language are not fully understood.
• The middle longitudinal fascicle (MLF) is a recently identified white matter tract.
• The MLF has been hypothesized to be crucial for language processing.

Purpose of the Study:

• To investigate the necessity of the MLF for language processing.
• To determine the functional role of the MLF in language.

Main Methods:

• Studied 8 patients undergoing glioma resection involving the left superior temporal gyrus.
• Assessed language function pre- and postoperatively (3 months).
• Used intraoperative electrostimulation to map language-critical areas and functional boundaries.

Main Results:

• Resections extensively involved the MLF in all patients.
• Electrostimulation of the MLF did not disrupt picture naming.
• The inferior fronto-occipital fascicle was identified as a critical language boundary via semantic paraphasia.
• No new permanent language deficits were observed postoperatively.

Conclusions:

• The MLF may contribute to language but appears non-essential.
• Language processing relies on other pathways, such as the inferior fronto-occipital fascicle.
• Further research is needed to fully elucidate the MLF's role in language networks.