when she made errors during the performance of a food-rewarded task, did not do so following the creation of a large bilateral lesion (an area of damage to both sides of brain) of her prefrontal lobes. after hearing about this isolated observation at a scientific meeting in 1935 , moniz persuaded neurosurgeon lima to operate on a series of psychiatric patients; lima cut out six large cores of prefrontal tissue with a surgical device called a leucotome.