Task modulation of spatiotemporal dynamics in semantic brain networks: An EEG/MEG study

Area of Science:

• Cognitive Neuroscience
• Neuroimaging
• Psycholinguistics

Background:

• Understanding how the brain retrieves word meaning is crucial for cognitive neuroscience.
• Semantic brain networks involve complex spatiotemporal dynamics.
• Previous research has not fully elucidated the temporal evolution and interaction of these networks during word meaning retrieval.

Purpose of the Study:

• To investigate the spatiotemporal evolution of brain activity in distributed semantic networks.
• To compare brain dynamics during visual lexical decision (LD) and semantic decision (SD) tasks.
• To explore the functional connectivity between brain regions involved in semantic processing.

Main Methods:

• Analysis of whole-cortex evoked responses and spectral functional connectivity (coherence).
• Utilized source-estimated electroencephalography (EEG) and magnetoencephalography (MEG) recordings.
• Quantified spatial resolution limitations using a leakage index.

Main Results:

• Semantic decision tasks showed larger activation than lexical decision tasks, originating in visual areas and progressing to temporal lobe regions.
• Significant functional connectivity was observed between anterior temporal lobes (ATL) and posterior temporal cortex (PTC), and between left ATL and inferior frontal gyrus (IFG).
• Left ATL showed early, lateralized activation, while both left and right ATL were involved in semantic processing, with right ATL engagement increasing in more demanding tasks.

Conclusions:

• Semantic information retrieval involves a sequential modulation of visual, attentional, multimodal semantic, and control processes.
• Both evoked responses and functional connectivity analyses are complementary and essential for understanding dynamic brain processes.
• The findings highlight the dynamic interplay of brain regions, including the anterior temporal lobes, in processing word meaning.