Abstract
Enumeration includes two cognitive processes. One is subitizing (enumeration of small number of objects at once) and the other is counting (a serial process for enumeration of items or events). However the neural mechanism underlying these processes remains unclear. To investigate a cortical mechanism of enumeration, we measured brain activity using functional MRI during performing enumeration tasks. Twenty-six right-handed healthy volunteers participated in this study. In an enumeration task, random dots from one to four were repeatedly displayed on a screen. Subjects were required to count events of stimulus presentation (counting condition) or enumerate the number of dots on the screen (subitizing condition) depending on instructions. We found that the prefrontal cortex (PFC), the dorsal premotor cortex (PMd) and the superior and inferior parietal lobe (PL) were mainly active during both subitizing and counting. Most of these regions overlapped between the two processes. However, different parts of the PFC were active during each process. These results suggest that a common parietofrontal network is involved in both subitizing and counting, and that the PFC plays a role for control of the two enumerative processes. [Jpn J Physiol 55 Suppl:S184 (2005)]
