Mirror neurons are a group of neurons found in the premotor cortex that respond both to witnessed movements in other animals and to the analogous movement in the self. Similar neurons have also been found in the sensory association cortex in the parietal lobe. Some scientists have suggested that mirror neurons might be the basis of empathy. Mirror neurons were discovered when scientists implanted electrodes in monkeys’ brains to measure the electrical activity of single neurons. The cells fired both when the monkey made a particular hand movement and when the experimenter made the same hand movement. The cells did not fire when the experimenter made a different hand movement.