Topographic representations of object size and relationships with numerosity reveal generalized quantity processing...

Area of Science:

• Neuroscience
• Cognitive Science
• Neuroimaging

Background:

• The brain processes quantities like object number (numerosity) and size to guide behavior.
• Previous research identified topographic maps for numerosity in the brain.
• The existence and organization of object size maps remained unclear.

Purpose of the Study:

• To investigate whether the brain contains topographic maps for visual object size.
• To characterize the neural tuning properties and organization of object size representations.
• To compare object size maps with previously identified numerosity maps.

Main Methods:

• Utilized ultra-high-field (7T) functional magnetic resonance imaging (fMRI).
• Applied population receptive field (pRF) modeling to analyze neural responses.
• Examined responses in the bilateral human posterior parietal cortex.

Main Results:

• Identified tuned responses to visual object size in the posterior parietal cortex.
• Object size tuning exhibited properties like linear Gaussian functions, surround suppression, and narrowing tuning width.
• Responses were organized in bilateral topographic maps, with distinct properties from numerosity maps but significant overlap.
• Object size preferences correlated with numerosity preferences, but not with visual position preferences.

Conclusions:

• The brain possesses topographic maps for object size, organized by distinct mechanisms from numerosity maps.
• Overlapping maps and correlated preferences suggest associated neural representations of size and numerosity.
• These maps are likely emergent properties of the brain, not direct reflections of sensory organ structure.
• Topographic maps may serve as an organizational principle for optimizing cognitive processing and integrating related features for decision-making.