The posterior semantic asymmetry (PSA): specific to written not auditory semantic word processing

Area of Science:

• Neuroscience
• Cognitive Psychology
• Psycholinguistics

Background:

• The posterior semantic asymmetry (PSA) is a lateralized event-related potential (ERP) previously identified, thought to reflect semantic processing of visually presented words.
• Understanding the neural basis of semantic activation for different sensory modalities is crucial for cognitive neuroscience.

Purpose of the Study:

• To replicate the finding of the posterior semantic asymmetry (PSA) for visually presented words.
• To investigate whether a comparable ERP reflects semantic processing of auditorily presented words.
• To compare the spatiotemporal patterns of brain electrical activity for visual versus auditory semantic processing.

Main Methods:

• Replication of the posterior semantic asymmetry (PSA) paradigm using visually presented single words.
• Comparison of ERPs during semantic, silent naming, and passive viewing tasks.
• Investigation of ERPs for auditorily presented words using analogous tasks.
• Analysis of event-related potential (ERP) differences in latency, topography, and polarity.

Main Results:

• The posterior semantic asymmetry (PSA), an ERP negativity peaking around 300 ms at temporoparietal electrodes, was replicated for visual words.
• The PSA was more pronounced in a semantic task compared to naming or passive viewing tasks.
• No comparable negativity was observed for auditory words; however, a later left-lateralized positive potential (500-800 ms) varied with semantic task demands, sharing a similar topography with the PSA.

Conclusions:

• The posterior semantic asymmetry (PSA) specifically reflects visual-verbal semantic activation.
• Semantic processing of both visual and auditory words converges on left temporoparietal brain regions.
• Distinct temporal and polarity patterns characterize the brain's electrical responses to visual versus auditory semantic activation.