Motion on Numbers: Transcranial Magnetic Stimulation on the Ventral Intraparietal Sulcus Alters Both Numerical and Motion Processes

Abstract

It has often been proposed that there is a close link between representation of number and space. In the present work, single-pulse transcranial magnetic stimulation (TMS) was applied to the ventral intraparietal sulcus (VIPS) to determine effects on performance in motion detection and number comparison tasks. Participants' reaction times and thresholds for perception of laterally presented coherent motion in random dot kinematograms increased significantly when the contralateral VIPS was stimulated in contrast to the interhemispheric sulcus (Experiment 1) and to the ipsilateral VIPS (Experiment 2). In number comparison tasks, participants compared the magnitude of the laterally presented numbers 1-9 with the number 5. Again, reaction times significantly increased when TMS was applied to the contralateral VIPS in contrast to control sites. The finding that VIPS-directed TMS results in impaired efficiency in both motion perception and number comparison suggests that these processes share a common neural substrate.

Causal role of the posterior parietal cortex for two-digit mental subtraction and addition: A repetitive TMS study

“…VIPS is a sensory motion-sensitive area (Nieder, 2004), which acts in conjunction with the HIPS to operate over the MNL (Salillas et al, 2009;Salillas et al, 2012). In particular, as pointed out by Salillas and colleagues, VIPS would support attention shifts along the MNL in number comparison (Salillas et al, 2009) and also in simple calculation tasks (Salillas et al, 2012). Our results are in line with this view, extending the role of VIPS in number processing to complex mental calculation.…”

“…Conversely, our results suggest a more bilateral involvement for VIPS, which corresponds to human vIPS (Shulman et al, 1999) and to the junction of intraparietal and transverse occipital sulci (Wojciulik and Kanwisher, 1999). VIPS is a sensory motion-sensitive area (Nieder, 2004), which acts in conjunction with the HIPS to operate over the MNL (Salillas et al, 2009;Salillas et al, 2012). In particular, as pointed out by Salillas and colleagues, VIPS would support attention shifts along the MNL in number comparison (Salillas et al, 2009) and also in simple calculation tasks (Salillas et al, 2012).…”

“…In contrast, the VIPS site (see Fig. 2) was found in TMS formance in motion perception (Salillas et al, 2009), number comparison (Salillas et al, 2009), and simple calculation (Salillas et al, 2012) tasks, suggesting its role in sustaining use of the MNL.…”

“…Consistently with the idea that two-digit additions determine attentional shift along the MNL compared to two-digit subtraction (Masson and Pesenti, 2014;Lindemann and Tira, 2015), we expect to find a greater rightward asymmetry for the involvement of HIPS, especially during complex additions, due to the fact that the right HIPS is involved not only in the quantity system (e.g., Feher et al, 2007;Menon et al, 2000), but also in processing the order information along the MNL (Knops and Willems, 2014). We also expect to find the involvement of VIPS, especially during complex additions, as this area underpins the use of the MNL (Salillas et al, 2009(Salillas et al, , 2012. On the contrary, finding particular functional asymmetries for the involvement of ANG and SMG in both operations would not be expected, given the contribution of these two areas to more general cognitive processes involved in the calculation Zago and TzourioMazoyer, 2002).…”

“…TMS studies have shown that specific RH areas are involved in specific simple mental arithmetic operations (for a review see Salillas and Semenza, 2015). For example, it has been shown that the efficiency in performance for simple multiplications not only involves HIPS but also depends on a motion-sensitive area, i.e., the ventral region of the intraparietal sulcus (VIPS) of the RH (Salillas et al, 2009;Salillas et al, 2012). Using navigated repetitive TMS (rTMS) for preoperative mapping of calculation function, a more recent study found that one-digit addition-related areas were predominantly localized in the LH, while one-digit subtraction-related ones were localized in the RH (Maurer et al, 2015).…”