Comparing Parietal Quantity-Processing Mechanisms between Humans and Macaques.

Area of Science:

• Cognitive Neuroscience
• Comparative Neuroanatomy
• Neuroimaging

Background:

• Previous research often assumes functional homology in quantity processing between human and macaque intraparietal sulcus (IPS) based on similar task responses.
• Direct comparison between macaque single-cell neurophysiology and human functional magnetic resonance imaging (fMRI) is challenging due to methodological differences.

Purpose of the Study:

• To investigate the functional homology of quantity processing regions in the human and macaque brain.
• To clarify the role of the intraparietal sulcus (IPS) in processing numerical and physical quantities across species.

Main Methods:

• Utilized fMRI with neural tuning models to enable closer comparison between human and macaque brain activity.
• Analyzed responses to physical quantities and symbolic numbers in both human and macaque participants.

Main Results:

• Human numerosity-selective responses were identified primarily outside the IPS, challenging the assumed homology.
• The human IPS appears to host a network involved in comparing physical quantities, symbolic numbers, and other features.

Conclusions:

• Functional similarities in processing physical quantities suggest a novel homology, but human IPS shows distinct functions.
• The human IPS network likely integrates physical quantity processing with spatial and linguistic information.