Time-varying effective connectivity during visual object naming as a function of semantic demands

Area of Science:

• Neuroscience
• Cognitive Science
• Psycholinguistics

Background:

• Visual object recognition involves feedforward and recurrent neural processing.
• The precise role of recurrence and its modulation by semantic demands require further investigation.

Purpose of the Study:

• To investigate the causal interactions and effective connectivity during visual object naming.
• To explore how semantic accessing demands modulate recurrent processing using dynamic causal modeling.

Main Methods:

• Magnetoencephalography (MEG) recorded neural activity from 14 healthy participants.
• Dynamic causal modeling (DCM) analyzed effective connectivity between brain regions.
• Object naming tasks varied semantic accessing demands based on psycholinguistic variables.

Main Results:

• Backward connections became active after 200 ms, indicating recurrent processing.
• Semantic demands induced a suppressive effect on backward connections from the inferior frontal cortex (IFC) to occipitotemporal cortex.
• This inhibitory modulation increased with greater semantic demands.

Conclusions:

• The inferior frontal cortex (IFC) plays a key role in top-down modulation of recurrent interactions during object recognition.
• Greater conceptual demands lead to inhibitory modulation of IFC's top-down influence on posterior regions.
• This highlights the dynamic and context-dependent nature of neural connectivity in visual cognition.