Numeracy has significant implications throughout the life course. Its agei nduced decline represents a vulnerability factor in elderly populations when it comes to solving everyday tasks. However, the reasons behind age-induced decline in numeracy are still unclear. In this study, we used a parity judgment task to study variations in number cognition between old and young participants. Since numeracy is associated with both symbolic and nonsymbolic representations, three numerical formats were used: arabic digits (N), finger representations (F), and dots (D). Fifty-three healthy subjects joined the study: 31 young (24.1±4.73 y.o.) and 22 old (68.8±4.38 y.o.). EEG (64 channels) was recorded during the task. Mixed Effects Models analysis showed that performance accuracy for D was significantly lower than for N and F (p = .02). There were significant main effects for reaction time for Group (old, young), Condition (N, F, D) and Gender. Notably, old adults responded slower than young adults (p < .001) and both groups performed significantly faster in the task for N compared to F and D (p < .001). Significant interaction effects showed that performance between males and females were comparable for arabic digits (p = .14), with females showing significantly slower response for non-symbolic stimuli than males (F, p = 0.04; D, p = .007). In sensor space, multivariate pattern analysis shows that the neural correlates supporting the different number representations can be classified as categorically separate, with an early dissociation (~200 ms) between N, F, and D stimuli when compared to each other. This provides provisional evidence that symbolic and non-symbolic representations recruit functionally distinct neuronal processes. Subjects in the old group showed a slight reduction in decoding and an increase in its latency. Numerical cognition involves a highly-integrated network, with a key role of the intraparietal sulcus and fusiform gyrus. In source space, we found reduced activation levels and increased latency of response in the primary cortical areas involved in numerical cognition in the old group. In the same group, all stimuli also induced a wider cortical response with respect to young subjects. We hypothesize that the reduced activity of the main cortical areas may contribute to the age-induced decay in numeracy and that the recruitment of other cortical areas may serve as a compensatory mechanism. The results of this exploratory study provide further evidence for the multifaceted processes involved in numerical reasoning and its age-related decline, with a potentially distinct neural network for symbolic and nonsymbolic numerical representations.
Symbolic and non-symbolic numerical representations in old and young subjects: an exploratory EEG study
MELONI CARLAMembro del Collaboration Group
;FANARI RACHELEMembro del Collaboration Group
;
2024-01-01
Abstract
Numeracy has significant implications throughout the life course. Its agei nduced decline represents a vulnerability factor in elderly populations when it comes to solving everyday tasks. However, the reasons behind age-induced decline in numeracy are still unclear. In this study, we used a parity judgment task to study variations in number cognition between old and young participants. Since numeracy is associated with both symbolic and nonsymbolic representations, three numerical formats were used: arabic digits (N), finger representations (F), and dots (D). Fifty-three healthy subjects joined the study: 31 young (24.1±4.73 y.o.) and 22 old (68.8±4.38 y.o.). EEG (64 channels) was recorded during the task. Mixed Effects Models analysis showed that performance accuracy for D was significantly lower than for N and F (p = .02). There were significant main effects for reaction time for Group (old, young), Condition (N, F, D) and Gender. Notably, old adults responded slower than young adults (p < .001) and both groups performed significantly faster in the task for N compared to F and D (p < .001). Significant interaction effects showed that performance between males and females were comparable for arabic digits (p = .14), with females showing significantly slower response for non-symbolic stimuli than males (F, p = 0.04; D, p = .007). In sensor space, multivariate pattern analysis shows that the neural correlates supporting the different number representations can be classified as categorically separate, with an early dissociation (~200 ms) between N, F, and D stimuli when compared to each other. This provides provisional evidence that symbolic and non-symbolic representations recruit functionally distinct neuronal processes. Subjects in the old group showed a slight reduction in decoding and an increase in its latency. Numerical cognition involves a highly-integrated network, with a key role of the intraparietal sulcus and fusiform gyrus. In source space, we found reduced activation levels and increased latency of response in the primary cortical areas involved in numerical cognition in the old group. In the same group, all stimuli also induced a wider cortical response with respect to young subjects. We hypothesize that the reduced activity of the main cortical areas may contribute to the age-induced decay in numeracy and that the recruitment of other cortical areas may serve as a compensatory mechanism. The results of this exploratory study provide further evidence for the multifaceted processes involved in numerical reasoning and its age-related decline, with a potentially distinct neural network for symbolic and nonsymbolic numerical representations.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.