x provides executive control over motivational drives; it is responsible for identifying and carrying out the individual’s goals. All mammals have an executive cortical area sending “top-down” instructions to more primitive deep-brain centers. For example, during breeding it directs the devoted behavior required for successful reproduction, including ignoring hunger and fatigue when necessary. People with AN behave as though it is necessary to ignore hunger and fatigue although starving. Brooks and colleagues found that enhanced working memory (WM) interacted with limbic processes to foster impulse control in AN (44).Normally when hungry people imagine drinking chocolate milk neural activity increases in reward and taste centers. The insula connects and interprets sensory information from the body into self-awareness of the condition of the body, including hunger and pain, thus is important in homeostasis. When hungry people with AN imagine food, activity is inhibited in parts of the insula that evaluate the meaning of hunger signals and anticipate taste (45-47). They pay little attention to food when hungry(48). Reduced activation of somatosensory appetite-related regions is combined with greater activity in the amygdala and the cingulate cortex, emotional centers that evaluate and respond to dangers (45, 49). In other words, thinking about eating silences neural regions that complain of hunger and activates of anxiety and fear centers. One of the most startling symptoms of AN is that victims see fat on their emaciated bodies (1); this body image distortion increases as more weight is lost. Now, brain-imaging researchers have discovered part of the reason. When underweight women with AN look at their own bodies, fMRI images show inhibition of the primary visual and visual association cortex (50). Meanwhile the part of the parietal cortex responsible for body image is hyperactive, filling in a fattened likeness (51). We think that the visual illusion of extra fat stores would have given starving migrators the confidence to make a difficult journey.
Thus, for underweight people with AN, self-control is strengthened while awareness (imagination) of food and its taste is dampened and fear centers are excessively active. Behaviors that everyone–including the victims– attributed to conscious choices could be seen to activate furious activity in deep brain structures involved in decision making, controlling behavior, evaluating primal danger, and evaluating food. These findings help explain what people with AN must overcome in order to recover.
Gene x environment interactions
The specific environmental triggers that activate AN genes point to its function for hunter gather bands (52). High levels of estrogen are often required in addition to weight loss for the genetic program to manifest (52, 53). AN genes are more rarely activated in males or in prepubertal girls. This indicates that it was a better bet for teen-aged girls than for small children and males to travel in times of famine. Why would that be? According to ethnographic records, when travelers encountered an enemy band, a reproductive female was more likely to survive and be adopted into the new group; molecular genetic evidence also supports the idea that females migrated farther in the Paleolithic (54). The preponderance of females developing anorexia nervosa has often been explained by female weaknesses. These gene and environment interactions suggest a very different conclusion; during Paleolithic famine, brave, self-controlled young women searched for better lands for their bands.
Over-controlled or self-controlled?
Before AN derailed them, patients were typically high-achievers on track to a successful life. Their premorbid personalities were typically ascetic; in one study 23% had autism spectrum traits (55). However, in their brothers the same scholarly and anxious childhood temperament often leads to success in technically demanding fields, while the same traits in their anorectic sisters is retroactively deemed pathological.
In general self-control is a p