Discrete and Analogue Quantity Processing in the Parietal Lobe: A Functional MRI Study

• Published in: Proceedings of the National Academy of Sciences - PNAS Vol. 103; no. 12; pp. 4693 - 4698
• Main Authors: Castelli, Fulvia, Glaser, Daniel E., Butterworth, Brian
• Format: Journal Article
• Language: English
• Published: United States National Academy of Sciences 21.03.2006; National Acad Sciences
• Subjects: Adolescent; Adult; Biological Sciences; Brain Mapping; City squares; Eyes & eyesight; Female; Humans; Magnetic Resonance Imaging; Male; Mental objects; Mental stimulation; Neuroimaging; Neurons; Neuroscience; Neurosciences; NMR; Nuclear magnetic resonance; Parietal lobe; Parietal Lobe - physiology; Perception - physiology; Rectangles; Spatial analysis; Symbolism; Transition zone; Visual perception
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.0600444103

The human intraparietal sulcus (IPS) is implicated in processing symbolic number information and possibly in nonsymbolic number information. Specific IPS activity for discrete quantities (numerosities) as compared with continuous, analogue quantity has not been demonstrated. Here we use a stimulus-driven paradigm to distinguish automatic estimation of "how many things" from "how much" and "how long." The discrete analogue response task (DART) uses the perception of hues which can change either abruptly (discrete, numerous stimuli) or smoothly (analogue, nonnumerous stimuli) in space or in time. Subjects decide whether they saw more green or more blue. A conjunction analysis of spatial and temporal conditions revealed that bilateral IPS was significantly more active during the processing of discrete stimuli than during analogue stimuli, as was a parietal-occipital transition zone. We suggest that processing numerosity is a distinct process from processing analogue quantity, whether extended in space or time, and that an intraparietal network connects objects' segmentation to the estimation of their numerosity.