A Brief History of Intelligence: Evolution, AI, and the Five Breakthroughs That Made Our Brains

by Max Solomon Bennett

While damage to the aPFC deprives animals of their intentions, as we saw with patient L, damage to parts of the premotor cortex seems to disconnect the proper flow of these intentions from high-level goals to specific movements. This can cause “alien limb syndrome”: patients will claim that certain parts of their bodies are moving on their own without their control. Signs of such alien movements are also seen in rodents with damage to the premotor cortex. Such damage also causes what is called “utilization behavior” or “field-dependent behavior,” where patients will execute motor sequences devoid of any clear goal: They will drink from empty cups, put on other people’s jackets even though they aren’t going anywhere, scribble with pencils, or do any other behavior that nearby stimuli suggest. All this is the result of a broken hierarchy—parts of the motor cortex are now unconstrained by top-down intentions from the aPFC flowing through the premotor cortex, and hence the motor cortex independently sets low-level goals for motor sequences.