Stage-Specific Processing in Numerosity Working Memory: ERP Evidence for Load and Mismatch Effects in a Delayed...

Area of Science:

• Cognitive Neuroscience
• Psychology
• Human Perception

Background:

• Numerosity is processed via symbolic and non-symbolic formats.
• Understanding how numerosity load affects working memory (WM) across encoding, maintenance, and comparison is crucial.
• Previous research has not fully elucidated these effects within a unified paradigm, particularly for numerosities 4-6.

Purpose of the Study:

• To investigate the temporal dynamics of numerosity load effects across WM encoding, maintenance, and comparison.
• To examine how different representational formats (dot arrays, digits) influence these processes.
• To differentiate the neural correlates of numerosity processing and match status evaluation.

Main Methods:

• A delayed match-to-sample task was employed with varying numerosity (4-6) and match status.
• Two test blocks were used: dot-digit and dot-dot comparisons.
• Event-related potentials (ERPs) including P1, N1, N2, and P3 were recorded to assess neural activity.

Main Results:

• Higher numerosity decreased accuracy and increased reaction times (RTs), with greater costs in dot-dot comparisons.
• Occipital P1 and N1 amplitudes decreased with increasing numerosity during sample onset.
• Numerosity modulated posterior ERPs during a specific delay window (450-650 ms); mismatch effects emerged at test, particularly N2 amplitude.
• N2 was modulated by numerosity in dot-dot comparisons, independent of RTs.

Conclusions:

• Numerosity load differentially impacts early encoding and a specific maintenance interval within WM.
• Mismatch detection primarily engages test-stage comparison processes.
• Format alignment (dot-dot) enhances mismatch-related neural activity and late evaluative processing.