The relation between acuity of the Approximate Number System and dorsal and ventral stream functions

Children and adults can approximate numbers of items, compare these approximations, and perform approximate arithmetic operations via a non-symbolic, pre-linguistic system called the Approximate Number System (ANS). Studies using neuroimaging techniques demonstrated the role of the parietal cortex in decoding both non-symbolic and symbolic quantity. Although it has been proven that the parietal regions are involved also in visual processing such as coherence motion perception, little is known about the relationship between these visual processes and the ANS. The aim of this study is to investigate whether the acuity in the ANS is related to dorsal and/or ventral visual functions. A sample of sixty-five typical development children (age 6-10 years; 42 males and 23 females) took part in the experiment. ANS acuity was measured using a numerical discrimination task (Halberda et al., 2008) in which participants were briefly shown arrays of yellow and blue dots and had to identify the more numerous array; a motion coherence test and a form coherence test were applied to evaluate dorsal and ventral stream functions respectively. In the motion test participants were asked to detect the direction of moving dots, in the form test participants had to recognize a form created by spatially aligned dots. We found significant correlations between ANS acuity and motion perception ability (p=0.014) as well as form discrimination ability (p=0.047). More specifically, higher performance in the motion and form tests are related to higher ANS acuity. The effect size values show that the magnitude of the relationship with the ANS was higher for the motion (partial η2=0.09) than for the form coherence test (partial η2=0.06). These results demonstrate that both dorsal and ventral visual processing influence ANS acuity but that the association between ANS and dorsal stream processing is slightly stronger.