Regions in the human inferior temporal gyrus are engaged in numerosity processing across visual stimulus categories

The visual number form areas (here referred to as ITG-math) have gained recent attention as a neural substrate of mathematical cognition. Yet, the function of these regions remains debated with some research suggesting selectivity for digits and others suggesting a visual stimulus-independent role in mathematical processing. Here we addressed this debate by exploring the impact of different tasks and stimuli on neural responses in ITG-math. Participants were presented with digits and UFOs, while performing a 1-back task either on stimulus numerosity or on stimulus color. We collected two sessions of this experiment from 17 healthy adults and could identify voxels with higher responses in the numerosity than the color task in 92% of the participants, whereas contrasting digits with UFOs lead to selective responses in only 35% of the participants. Accordingly, in independent data, ITG-math showed a task preference, but no stimulus preference. Multivariate analyses further revealed task encoding, and a combination of task and stimulus encoding, in the left and right ITG-math, respectively. Our work hence supports the notion that the role of ITG-math in mathematical cognition goes beyond the encoding of digits.