Investigating the generators of the scalp recorded visuo-verbal P300 using cortically constrained source localization

Area of Science:

• Neuroscience
• Cognitive Neuroscience
• Electrophysiology

Background:

• The neural generators of the scalp-recorded P300 event-related potential remain unclear.
• Previous source localization studies often used dipole models, primarily implicating medial temporal/hippocampal regions.
• Limited information exists on the contribution of cortical areas to P3 generation.

Purpose of the Study:

• To identify the cortical generators of the P300 using advanced source localization techniques.
• To investigate the role of specific brain regions in processing target stimuli during an Oddball task.

Main Methods:

• Recorded event-related potentials (ERPs) from 5 subjects using a 124-channel sensor array during a visuo-verbal Oddball task.
• Employed cortically constrained, MRI-guided boundary element modeling for individual subject source localization.
• Created a group cortical surface by non-linear warping and averaging for group-level analysis.

Main Results:

• P300 generators were primarily localized to the intraparietal sulcus (IPS) and superior parietal lobes (SPL) bilaterally in all subjects.
• Two subjects also exhibited activity in the lingual/inferior occipital gyrus and mid-fusiform gyrus.
• Group analysis confirmed bilateral IPS/SPL activation and left-dominant lingual/inferior occipital gyrus activity.

Conclusions:

• The IPS and SPL are identified as principal cortical generators of the P300, supporting their role in working memory, attention, and visuo-motor integration.
• Left lingual/inferior occipital gyrus activation suggests involvement in visual word form analysis.
• This study provides a more detailed cortical mapping of P300 generators than previous methods.