Spatiotemporal dynamics of processing nonsymbolic number: an event-related potential source localization study

Area of Science:

• Cognitive Neuroscience
• Neuroscience
• Psychology

Background:

• Evidence suggests two distinct nonverbal number systems: parallel individuation (PI) for small quantities (1-3) and numerical magnitude for approximate larger quantities.
• Event-related potential (ERP) studies show distinct brain responses for these systems, but their neural generators are not well understood.

Purpose of the Study:

• To identify the cortical origins of ERP signatures associated with the parallel individuation (PI) and numerical magnitude systems.
• To spatially map the neural generators of distinct brain responses to small versus large nonsymbolic numbers.

Main Methods:

• Used source localization (LORETA) to identify cortical origins of ERP signatures.
• Contrasted processing of small versus large nonsymbolic numbers to target known ERP signatures.
• Analyzed event-related potential (ERP) data from adults, infants, and nonhuman animals.

Main Results:

• Early processing of small numbers (PI signature on N1) localized to extrastriate visual regions.
• Processing of large numbers (numerical magnitude signature on P2p) localized to right intraparietal regions.
• Mid-latency small number processing localized to the right temporal-parietal junction and left intraparietal regions.

Conclusions:

• These findings provide spatial information on the neural basis of number representation using ERPs.
• Results support the idea that early attentional processes influence number representation by directing processing to distinct cortical regions.