ID 314 – Dissociating arithmetic processes in the parietal cortex using repetitive transcranial magnetic stimulation

Abstract

Numerical cognition involves arithmetic operations which can either be performed by accessing memory of overlearn facts as in the case of multiplications or by performing actual calculations such as in subtraction. Neuropsychological, neuroimaging and brain stimulation methods in both healthy and patient’s studies suggests the involvement of distinct parietal areas in calculations: the horizontal part of the left intraparietal sulcus (hIPS) for multiplication and the left angular gyrus (ANG) for subtraction. However, the anatomical and functional segregation of both processes is not yet fully established. The present study will use a neuronavigation-guided repetitive Transcranial Magnetic Stimulation (rTMS) to induced temporary focal lesion at the left hIPS during a multiplication and subtraction task and at the left ANG while performing the same task. 1 Hz rTMS with 900 continuous pulses and an intensity of 110% active motor threshold will be used in the study. Our hypothesis is that, if the hIPS is specifically critical for retrieval of arithmetic facts then multiplication task performance during and after rTMS will be impaired but not subtraction. Whereas, rTMS to the left ANG will only disrupt subtraction ability but not multiplication.