Event-related fMRI analysis of the cerebral circuit for number comparison

Abstract

Cerebral activity during number comparison was studied with functional magnetic resonance imaging using an event-related design. We identified an extended network of task-related areas that showed a phasic activation following each trial, including anterior cingulate, bilateral sensorimotor areas, inferior occipito-temporal cortices, posterior parietal cortices, inferior and dorsolateral prefrontal cortices, and thalami. We then tested which of these areas were affected by number notation, numerical distance and response side, three variables that specifically target processes of visual identification, quantity manipulation and motor response in a serial-stage model of the number comparison task. Our results confirm the role of the right fusiform gyrus in digit identification processes, and of the inferior parietal lobule in the internal manipulation of numerical quantities.

Effects of symbol type and numerical distance on the human event-related potential

“…This assumption was confirmed by the fact that occipital clusters showed greater activation to verbal than to Arabic stimuli in fMRI studies (Pinel et al, 1999(Pinel et al, , 2001.…”

“…Unfortunately, these previous studies (Dehaene, 1996;Pinel et al, 1999Pinel et al, , 2001) suffered from two main shortcomings: First, the low-level visual characteristics between Arabic digits and English verbal numerals (e.g., 8 vs. Eight) might have had a crucial effect on the way the numerals were recognized and their magnitudes were processed.…”

Bilateral field interactions and hemispheric asymmetry in number comparison

“…[26,81]) in whom both hemispheres are able to compare numbers. The involvement of the intraparietal sulcus in the manipulation of numerical quantities has further been confirmed in several brain-imaging studies [30,37,78]. Second, the visual Arabic code is localized in the left and right occipitotemporal areas belonging to the ventral visual pathway dedicated to visual recognition.…”

A neural model of how the brain represents and compares multi-digit numbers: spatial and categorical processes

“…The brain area within the Where processing stream that seems to be used for numerical representation is the IPC (namely, the areas around the inferior-parietal -occipital junction (Dehaene et al, 1996;Pesenti et al, 2000;Pinel et al, 1999;Rickard et al, 2000). The SpaN model predicts that this area has a topographic organization that has an ordering related to numerical properties of the stimuli that it processes.…”

“…Recent brain imaging data (Dehaene et al, 1996;Pesenti, Thioux, Seron, & De Volder, 2000;Pinel et al, 1999;Rickard et al, 2000) have identified the inferior parietal cortex (IPC) as a convergence zone during various numerical tasks with inputs and outputs representing different modalities. IPC and adjacent regions are known to play an important role in various spatial tasks, including visuomotor integration (Nishitani, Uutela, Shibasaki, & Hari, 1999), navigation (Maguire et al, 1998), location working memory (Courtney, Ungerleider, Keil, & Haxby, 1996), and tactile object recognition (Deibert et al, 1999).…”