Abstract
The ability to perform basic math is crucial for our daily life, yet how our brain supports this skill is not fully understood. Recent research has identified an area in the human inferior temporal gyrus (ITG), which responds more strongly to Arabic numbers relative to other visual stimuli and is hence suggested to be responsible for the visual encoding of numbers. However, other recent studies have reported activations in the ITG during mathematical tasks, even in the absence of visually presented numbers. To address this debate, we conducted three fMRI experiments in 15 participants that systematically varied tasks and visual stimuli. While we replicated findings of higher ITG responses to Arabic numbers than character-like stimuli during a 1-back task, this preference to Arabic numbers was abolished when participants were engaged in mathematical processing. Instead responses in the ITG were higher when subjects were engaged in adding vs. reading or color tasks, irrespective of the stimuli the tasks were performed on (number/letter morphs, hands, or dice). Likewise, multivariate pattern analyses reveal that mathematical task can be successfully and consistently decoded from distributed ITG responses (mean decoding accuracy across experiments (±SEM): 89(3)%). Decoding of task was also substantially higher than decoding of number stimulus, which was not robust (mean decoding accuracy across experiments (±SEM): 53(4)%). These data suggest that the ITG is involved in mathematical processing rather than the visual processing of Arabic number form. We propose that this region ascribes numerical content to visual inputs, irrespective of the nature of the stimulus.
Meeting abstract presented at VSS 2018