Abstract
Despite numerous studies on the neural basis of numerical processing, few studies have examined the neural substrates of one of the most basic numerical processing—number sequence recitation. The present study used fMRI to investigate neural substrates of number sequence recitation, focusing on the intraparietal sulcus (IPS) and perisylvian areas. This study used a 2 (number versus alphabet) × 2 (forward versus backward recitation) design. 12 Chinese undergraduates were asked to recite overtly but gently numerical and alphabetical sequences forward and backward. Results showed that, for both numerical and alphabetic sequences, the left IPS was activated when performing backward recitation, but not when performing forward recitation. In terms of perisylvian areas, all four tasks elicited activation in bilateral superior temporal gyrus and inferior frontal gyrus, but forward recitation elicited greater activation in the left posterior superior temporal gyrus than did backward recitation, whereas backward recitation elicited greater activation in the left inferior frontal gyrus than did forward recitation. These results suggest that forward recitation of numbers and the alphabet is typically based on verbal processing of numbers implemented in the perisylvian area, whereas backward recitation would likely require additional neural resources in the IPS.
Highlights
The past decade has witnessed the most active research in neurobiology of number processing (Butterworth, 1999; Dehaene et al, 2004)
Based on previous research on number processing, we focused our analyses on the intraparietal sulcus (IPS) and perisylvian areas
The present study aimed to investigate neural substrates of number sequence recitation, focusing on the IPS and perisylvian area
Summary
The past decade has witnessed the most active research in neurobiology of number processing (Butterworth, 1999; Dehaene et al, 2004). Despite the numerous studies on number processing and a few studies on object counting (reviewed below), surprisingly not a single study has examined the neural substrates of straightforward number sequence recitation (i.e., reciting 1, 2, 3, 4, etc., without objects), arguably the most basic. Only a few studies have examined the neural bases of tasks that resemble numerical sequence recitation. The present study investigated the neural bases of straightforward numerical sequence recitation by comparing brain activation patterns of forward and backward numerical sequence recitation with a control task (i.e., fixation) and a comparison task (i.e., alphabetic recitation). Based on previous research on number processing, we focused our analyses on the intraparietal sulcus (IPS) and perisylvian areas. In the few sections, we will briefly review the literature on the importance of IPS and perisylvian areas in number processing in general and in tasks similar to number recitation in particular
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