A common neural substrate for language production and verbal working memory.

Area of Science:

• Cognitive Neuroscience
• Psycholinguistics
• Neuroscience

Background:

• Influential models propose verbal working memory (VWM) is independent of language production and comprehension systems.
• An alternative hypothesis suggests VWM maintenance involves temporary activation of the language production system.
• This study investigates if VWM for nonwords relies on phonological encoding and articulatory planning stages of speech production.

Purpose of the Study:

• To test the hypothesis that verbal working memory (VWM) maintenance for nonwords is subserved by the language production system.
• To identify specific brain regions involved in VWM maintenance using fMRI and rTMS.
• To provide causal evidence for the role of speech production processes in VWM.

Main Methods:

• fMRI was used to identify brain regions for phonological encoding (pSTG) and lexical-semantic retrieval (MTG).
• Repetitive transcranial magnetic stimulation (rTMS) was applied to pSTG and MTG during language production and VWM tasks.
• Tasks included paced reading, delayed serial recall of nonwords, and picture naming.

Main Results:

• rTMS to the pSTG increased errors in paced reading and delayed serial recall of nonwords.
• rTMS to the MTG did not affect VWM performance but impacted picture naming (lexical-semantic retrieval).
• These findings suggest the pSTG is critical for VWM maintenance of nonwords.

Conclusions:

• The study provides the first causal evidence that verbal working memory (VWM) maintenance directly depends on speech production processes.
• Specifically, the posterior superior temporal gyrus (pSTG), involved in phonological encoding, is crucial for VWM of nonwords.
• This supports the hypothesis that VWM utilizes temporary activation of the language production system.