Discrete and analogue quantity processing in the parietal lobe: A functional MRI study

Fulvia Castelli; Daniel E. Glaser; Brian Butterworth

doi:10.1073/pnas.0600444103

New Research In

Communicated by Charles R. Gallistel, Rutgers, The State University of New Jersey, Piscataway, NJ, January 20, 2006 (received for review August 5, 2005)

Abstract

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.

Footnotes

^§To whom correspondence should be addressed at:
California Institute of Technology, Division of the Humanities and Social Sciences, MC 228-77, Pasadena, CA 91125.
E-mail: fulvia{at}hss.caltech.edu
Author contributions: F.C. designed research; F.C. and D.E.G. performed research; F.C. and D.E.G. analyzed data; and F.C. and B.B. wrote the paper.
Conflict of interest statement: No conflicts declared.
Abbreviations:
DART,
discrete analogue response task;
fMRI,
functional MRI;
IPS,
intraparietal sulcus.
© 2006 by The National Academy of Sciences of the USA