Left anterior temporal cortex actively engages in speech perception: A direct cortical stimulation study

Area of Science:

• Neuroscience
• Neurolinguistics
• Cognitive Science

Background:

• Neuroimaging studies suggest the anterior auditory pathway is vital for speech comprehension.
• Clinical conditions like semantic dementia highlight the importance of this pathway.
• Precise cortical localization of speech perception has been challenging due to neurodegenerative or cerebrovascular factors.

Observation:

• Direct electrical cortical stimulation was used in two epilepsy patients undergoing presurgical evaluation.
• Stimulation sites were precisely mapped to standard anatomical space (MNI).
• A distinct language area was identified in the anterior superior temporal sulcus and gyrus (aSTS/STG).

Findings:

• Electrical stimulation of the left aSTS/STG transiently impaired auditory sentence comprehension in both patients.
• This impairment specifically affected understanding spoken sentences, not visual comprehension or perception of music/sounds.
• Patients reported hearing but not understanding speech, describing it as meaningless utterances.

Implications:

• This study provides the first direct anatomo-functional evidence for the role of the left aSTS/STG in speech perception.
• The findings precisely localize a critical area for speech perception, distinct from posterior language regions.
• This research advances our understanding of the neural basis of language and has potential implications for neurological disorders affecting speech comprehension.