Topographic numerosity maps cover subitizing and estimation ranges.

Area of Science:

• Cognitive Neuroscience
• Neuroimaging
• Computational Neuroscience

Background:

• Numerosity, the perception of item quantity, guides behavior and decision-making.
• The approximate number system (ANS) represents non-symbolic numerosities.
• Distinct behavioral performance suggests different neural implementations for small (subitizing range) versus large numerosities.

Purpose of the Study:

• To investigate how neural populations respond to large numerosities within the approximate number system.
• To determine if neural representations of large numerosities are organized similarly to those of small numerosities.

Main Methods:

• Utilized 7 Tesla functional magnetic resonance imaging (7T fMRI) for high-resolution brain activity measurement.
• Employed biologically-inspired analyses to examine neural population responses to numerosities.
• Mapped hemodynamic responses to a range of numerosities, including those beyond the subitizing range.

Main Results:

• Identified a network of neural populations tuned to both small and large numerosities.
• Demonstrated that these numerosity-tuned populations are organized within the same topographical maps.
• Revealed a continuum of numerosity preferences across these maps, covering the subitizing range and larger quantities.

Conclusions:

• Neural representations of numerosity exhibit a continuum, suggesting a unified neural mechanism for number processing.
• The same topographical maps accommodate preferences for both small and large numerosities.
• Hypothesized that variations in map properties (e.g., cortical magnification, tuning width) explain behavioral differences in numerosity perception.