On the role of visual experience in mathematical development: Evidence from blind mathematicians

Abstract

Advanced mathematical reasoning, regardless of domain or difficulty, activates a reproducible set of bilateral brain areas including intraparietal, inferior temporal and dorsal prefrontal cortex. The respective roles of genetics, experience and education in the development of this math-responsive network, however, remain unresolved. Here, we investigate the role of visual experience by studying the exceptional case of three professional mathematicians who were blind from birth (n = 1) or became blind during childhood (n = 2). Subjects were scanned with fMRI while they judged the truth value of spoken mathematical and nonmathematical statements. Blind mathematicians activated the classical network of math-related areas during mathematical reflection, similar to that found in a group of sighted professional mathematicians. Thus, brain networks for advanced mathematical reasoning can develop in the absence of visual experience. Additional activations were found in occipital cortex, even in individuals who became blind during childhood, suggesting that either mental imagery or a more radical repurposing of visual cortex may occur in blind mathematicians.

Neural basis of approximate number system develops independent of visual experience

“…The present findings are consistent with prior evidence that the rMOG acquires responses to symbolic number in blindness (Amalric et al, 2017;Crollen et al, 2019;Kanjlia et al, 2016). Like the IPS, the rMOG of blind individuals responds preferentially during math calculation than sentence comprehension and activity increases with the difficulty of math equations (Kanjlia et al, 2016).…”

“…Congenitally blind individuals show similar or slightly better performance than sighted individuals when estimating numbers of tones, footsteps or finger taps, and performance is ratio-dependent in both groups . Prior studies also find that, like people who are sighted, individuals who are congenitally blind recruit the IPS during symbolic number reasoning and show similar behavioral correlations between numerical approximation and symbolic math performance across individuals (Amalric et al, 2017;Crollen et al, 2019;Kanjlia, Feigenson, et al, 2018;Kanjlia et al, 2016). Together, these findings suggest that numerical representations are established in the IPS independent of gross differences in sensory experience.…”

“…It is now known that vision is not required for the development of symbolic number responses in the IPS. In both congenitally blind and sighted individuals, the IPS is more active during math calculation than sentence comprehension and demonstrates sensitivity to the number of digits and algebraic complexity of math equations (Amalric, Denghien, & Dehaene, 2017;Crollen et al, 2019;Kanjlia, Lane, Feigenson, & Bedny, 2016). However, these findings leave open the question of whether the neural basis of our basic approximate number system is preserved in the absence of vision.…”

“…A second goal of the current study was to investigate potential cross-modal recruitment of the visual cortex for approximate number processing. In addition to the IPS, congenitally blind but not sighted individuals recruit parts of dorsal occipital cortex, specifically the right middle occipital gyrus (rMOG), during math calculation (Amalric et al, 2017;Crollen et al, 2019;Kanjlia et al, 2016). Furthermore, like the IPS, the math-responsive area of the "visual" cortex in blind participants was sensitive to the number of digits and algebraic complexity of math equations (Kanjlia et al, 2016).…”

Sensitive period for cognitive repurposing of human visual cortex

“…Parts of the visual cortex, such as lateral occipital and ventral occipito-temporal regions, are active during sentence comprehension and increase activity with the grammatical complexity of spoken sentences (Bedny et al, 2011;Lane et al, 2015). A separate dorsal visual region (right middle occipital gyrus, rMOG) is active during math calculation and increases activity with the difficulty of math equations (Kanjlia et al 2016;Amalric et al 2017). There is evidence that visual cortex activity during higher-cognitive tasks in blindness is behaviorally relevant.…”