Logical negation mapped onto the brain
Authors: Grodzinsky, Y., Deschamps, I., Pieperhoff, P. et al.
Published in Brain Struct Funct 225, 19–31 (2020)
High-level cognitive capacities that serve communication, reasoning and calculation are essential for finding our way in the world. What brain parts are entrusted with these, and are they special? These questions touch on issues at the heart of perennial philosophical, cognitive, and neurological debates. We know much about language and math in the brain, but less about logic. We, a group of German (FZ Jülich), Canadian (Laval) and Israeli (ELSC, HUJI) researchers combined linguistic, logical, imaging and anatomical technologies to address this question. We homed in on a previously unknown small brain area, dedicated to an important logical function – negation (usually identified with words like “no” or “not”, the minus symbol “–“, or the logical symbol “¬”). Our study had 4 stages: 1. A behavioral experiment that measured the time it costs humans to process logical negation; 2. A functional imaging study that localized the brain basis for this ability in brain space, and separated it from other cognitive functions like language and math (Fig. 1, click for all figures); 3. An anatomical investigation, which studied the microscopic anatomical basis of the active location, and delineated its borders (Fig. 2); 4. An integrative part, that demonstrated a high degree of overlap between the functional and the anatomical (Fig. 3). We conclude that there is an anatomically uniform, well-delineated brain area dedicated to negation, a central logical operation (click for video). Its location relative to other brain functions suggests that it mediates between language and reasoning areas. This discovery, moreover, teaches us that language, logic and math rely on distinct modules in the human brain.