Stimulus- and Response-locked Posterior Contralateral Negativity Bisect Cognitive Operations in Visual Search

Area of Science:

• Cognitive Neuroscience
• Visual Perception
• Human Information Processing

Background:

• Understanding the temporal dynamics of visual search is crucial for cognitive neuroscience.
• Event-related potentials (ERPs) like the N2pc and SPCN offer insights into attention and visual short-term memory.

Purpose of the Study:

• To investigate the flow of information during visual search by analyzing event-related activity.
• To differentiate the neural processes underlying attention deployment and subsequent visual memory encoding.
• To explore how these processes contribute to reaction time (RT) variability.

Main Methods:

• Measured electroencephalography (EEG) event-related activity at posterior sites (PO7/PO8) in 96 participants during a visual search task.
• Analyzed both stimulus-locked (N2pc, SPCN) and response-locked (RLpcN) posterior contralateral negativity.
• Compared ERP components across experimental manipulations and response speed tertiles.

Main Results:

• A response-locked posterior contralateral negativity (RLpcN) with a similar scalp distribution to N2pc and SPCN was observed.
• The early RLpcN reflected initial attention deployment (N2pc), while the later portion reflected visual information processing (SPCN).
• Earlier RLpcN onsets for longer RTs indicated that reaction time variance is largely determined by post-attention processing.

Conclusions:

• The study successfully bisects visual search processing into attention deployment and subsequent information processing stages.
• Response-locked analysis provides a valuable tool for dissecting cognitive processes and their contribution to behavioral variability.
• Findings clarify the temporal relationship between attention, visual short-term memory, and reaction time in visual search.