Neural representations of two-digit numbers: a parametric fMRI study

Area of Science:

• Cognitive Neuroscience
• Neuroimaging
• Psychology

Background:

• Human number magnitude processing involves comparing numerical values.
• The unit-decade compatibility effect shows that units influence decisions even when irrelevant to the decade comparison.
• Understanding the neural basis of multi-digit number processing is crucial for cognitive science.

Purpose of the Study:

• To investigate the neural correlates of two-digit Arabic number magnitude processing.
• To examine the influence of decade digit distance and unit distance compatibility on fMRI signals.
• To explore how the symbolic structure of the Arabic number system affects multi-digit number processing.

Main Methods:

• Functional magnetic resonance imaging (fMRI) was used in a rapid event-related design.
• Parametric regressors were defined to analyze the effects of decade distance and unit compatibility.
• Participants performed a task requiring them to identify the larger of two two-digit numbers.

Main Results:

• Activation in the anterior right intraparietal sulcus (IPS) was modulated by unit distance compatibility.
• Decade distance correlated with increased fMRI signal in regions including the left IPS and right anterior/posterior IPS.
• These findings highlight the role of the intraparietal cortex in representing numerical magnitude.

Conclusions:

• Magnitude representations of unit-decade compatibility and decade distance are subserved by the intraparietal cortex.
• The symbolic structure of the Arabic number system significantly influences multi-digit number magnitude processing.
• The findings have implications for understanding general symbolic information processing in the brain.