Topographic representation of numerosity in human parietal lobe B Harvey1, B Klein1, N Petridou2, S Dumoulin1 |
|---|
1Experimental Psychology/Helmholz Institute, Utrecht University, Netherlands |
| Numerosity, the set size of a group of items, is processed by association cortex, but certain aspects mirror properties of primary senses (Dehaene, 1997; Burr and Ross, 2008). Sensory cortices contain topographic maps reflecting the structure of sensory organs such as the retina, cochlea or skin. Is the cortical representation and processing of numerosity organized topographically, even though no sensory organ has a numerical structure? Using high-field fMRI (7T) and custom-built model-based analysis that captures numerosity tuning using population receptive field methods (Dumoulin and Wandell, 2008), we describe neural populations tuned to small numerosities (within the subitizing range) in human parietal cortex. These neural populations are organized topographically, forming a numerosity map where preferred numerosity increases from medial to lateral cortex. This numerosity map is robust to changes in low-level stimulus features. Furthermore, the cortical surface area devoted to specific numerosities (cortical magnification factor) decreases with increasing numerosity, and the tuning width is proportional to preferred numerosity. These organizational properties mirror key features of sensory and motor topographic maps, extending topographic principles to representation of higher-order abstract features in association cortex and supporting the analogy between numerosity and other senses. |
| Up Home |
|---|