Early neurophysiological signatures of multi-digit number length encoding

Area of Science:

• Cognitive Neuroscience
• Psychology
• Neuroimaging

Background:

• The Arabic number system associates number length with magnitude, where longer numbers signify larger values.
• Numerical comparison is affected by misaligned physical and numerical dimensions, with processing improving with greater numerical distance.
• Previous event-related potential (ERP) studies have limited evidence for early numerical information encoding due to visual property confounds.

Purpose of the Study:

• To investigate if number length impacts early multi-digit number processing independently of visual size.
• To differentiate the neural processing stages involved in number magnitude evaluation.
• To explore the influence of numerical syntax on magnitude processing.

Main Methods:

• Two ERP experiments were conducted with 27 participants each.
• Scribbled line patterns controlled for physical length, dissociating it from visual size.
• Participants performed tasks involving digit value comparison and number length judgment under congruent and incongruent conditions.

Main Results:

• Enhanced parieto-occipital N1 negativity (120-150 ms) indicated early number length encoding, independent of visual size.
• Central P2p (150-190 ms) reflected refined numerical distance processing.
• Centro-parietal P3 (300-360 ms) showed congruity effects when numerical magnitude was task-relevant.

Conclusions:

• Three distinct processing stages were identified: early encoding (N1), refined magnitude comparison (P2p), and conflict resolution (P3).
• Number length significantly influences early multi-digit number processing, separate from visual characteristics.
• This study provides novel neurophysiological evidence for the role of number length and numerical syntax in magnitude evaluation.