Other Areas, Other Emotions

The Insular Cortex

The insular cortex (or insula) is tucked between the frontal and temporal lobes in the Sylvian fissure.

An anatomical illustration from the 1908 edition of Sobotta’s Anatomy Atlas

The insula has extensive reciprocal connections with limbic forebrain areas, such as the amygdala, medial prefrontal cortex, and anterior cingulate gyrus (Augustine, 1996; Craig, 2009). It also has reciprocal connections with frontal, parietal, and temporal cortical areas involved with attention, memory, and cognition (Augustine, 1996).

There is a significant correlation between insular activity and the perception of internal bodily states (Critchley, 2009; Pollatos, et al,. 2007); this function is known as interoception. Various interoceptive stimuli that activate the anterior insula include thirst, sensual touch, itch, distention of the bladder and intestinal tract, exercise, and heartbeat. The connections and activation profile of the insula suggest that it integrates all of the visceral and somatic input and forms a representation of the state of the body (Craig, 2009; Saper, 2002). Interestingly, people with a bigger right insula are better at detecting their heartbeats than are people with a smaller right insula (Critchley et al., 2004), and those same types of people are also more aware of their emotions (L.Barrett et al., 2004).

Several models of emotion speculate that direct access to bodily states is necessary to experience emotion. It may be that the insula plays a key role in this process. Suggestively, fMRI studies show that the anterior insula and anterior cingulate cortex are jointly active in participants experiencing emotional feelings including maternal and romantic love, andger, fear, sadness, happiness, disgust, and trust. It appears, then, that the insula is active with all feelings, both physical (body states) and emotional, suggesting that it may be the junction where cognitive and emotional information are integrated. The role of the insula as “body information central” is also indicated by its connections to networks across the cortex and to the amygdala with its role in evaluating emotional stimuli (Craig, 2009; Critchley, 2009).

Insular activity also has been reported to be associated with evaluative processing, for instance, when people make risk-adverse decisions. The riskier the decision, the more active is the insula (Xue et al., 2010). Its activity is also associated with the perception of positive emotions in other people (Jabbi et al., 2007). Gary Berntson and his colleagues (2011) investigated the role of the insula in evaluative processing by examining valence and arousal ratings in response to picture stimuli. They compared the behavioral performance of three groups of participants: a group of patients with lesions of the insula, a control-lesion group, and an amygdala-lesion group. All patients were asked to rate the positivity and negativity (valence) of each presented picture (from very unpleasant to very pleasant) and how emotionally arousing they found the pictures to be.

The study results showed that patients with insular lesions (compared with patients in the control-lesion group) reported both reduced arousal (to both unpleasant and pleasant stimuli) and reduced valence ratings. In contrast, the arousal ratings of patients with amygdala lesions were selectively attenuated for unpleasant stimuli, but they had the smae positive and negative valence ratings as the control-lesion group. These findings are in line with an earlier study (Berntson et al., 2007), which found that patients with amygdala damage showed a complete lack of an arousal gradient across negative stimuli, although they displayed a typical arousal gradient to positive stimuli. These results were not attributable to the inability of amygdala patients to process the hostile nature of the stimuli, because the patients with amygdala damage accurately recognized and categorized both positive and negative features of the stimuli. Taken together, these results support the view that the insula may play a broad role in integrating affective and cognitive processes, whereas the amydala may have a more selective role in affective arousal, especially for negative stimuli (Bernston et al., 2011).

Casting the amydala as a vigilant watchdog looking out for motivationally relevant stimuli (A. K. Anderson & Phelps, 2001; Whalen, 1998) may prove true, but just what is it watching out for? The answer to that question still eludes investigators. Another fMRI study found that the amydala is more sensitive to valence than to arousal (Anders et al., 2008). A study mentioned previously reported that novel stimuli generated higher peak responses in the amygdala and activated it for longer than did familiar stimuli (Weierich et al., 2010). Obviously, the amygdala remains enigmatic.

Disgust

Disgust is one emotion that has been linked directly to the insula. This finding should be no surprise, given the insula’s role as the great perceiver of bodily states. Based on imaging studies, many cognitive neuroscentists agree that the anterior insula is assential for detecting and experiencing disgust (Phillips et al., 1997, 1998). This conclusion is consistent with a report of a patient who had insula damage and was unable to detect disgust conveyed in various modalities (Calder et al., 2000).

A study done by Giacomo Rizzolatti (see mirror neurons in Chapter 8) and colleagues (Wicker et al., 2003) confirmed these findings and went a step further. These investigators analyzed the neural response during observation of others experiencing disgust while having firsthand experience of disgust. They observed that the same portion of the anterior insula was activated both when participants viewed expressions of disgust in others and when they smelled unpleasant odors (a firsthand experience of disgust). These results are significant for two reasons. First, they suggest that understanding the emotions of others may require stimulating, and thus mildly experiencing, these emotions ourselves (Craig, 2009). This line of thought implies a role for emotion in empathy and theory of mind (discussed in Chapter 13). Second, the results provide additional evidence that the insula is a neural correlate of disgust identification in others and of experiencing disgust directly.

Some have taken all of this evidence to mean that the anterior insula if the region of the brain that is essential for disgust. A large meta-analysis of fMRI studies done by Katherine Vytal and Stephan Hamann (2010) found that disgust consistently activated the inferior frontal gyrus and the anterior insula, and these regions reliably differentiated disgust from all other emotion states. In fact, these researcher’s analysis found locationist evidence for anger, fear, sadness, and happiness. In contrast, Kristen Lindquist and her colleagues (2012), in another large meta-analysis of multiple fMRI studies analyzed by a different method, did not find the insula to be consistently and specifically activated for the motion of disgust. They found that although the anterior insula is more active during instances of disgust perception, anterior insula activation is observed in a number of tasks that involve awareness of body states, such as gastric distention, body movement, and orgasm. They also found that activation of the Left anterior insula was more likely during incidents of anger than of any other emotion. Lindquist and colleagues suggest that the anterior insula plays a key but more general role in representing core affective feelings in awareness. They also found no evidence for a locationist view for the other brain regions. The debate contiues.

Happiness

Over the last several years a small but growing body of research has reported on the neural bases of happiness. It’s not easy to define what makes us happy, so it is a challenging emotion to study. Experimental methods used to study happiness have participants view happy faces, watch films, or try to induce a happy mood by various methods, but they have not been consistently relizble, valid, or comparable across studies. Because of these difficulties, only a few neuroimaging studies have focused on happiness (Habel et al., 2005). One group contrasted participants’ brain activity in response to smiling faces versus sad faces (Lane et al., 1997). In a separate fMRI study, 26 healthy male participants were scanned during sad and happy mood induction as well as while performing a cognitive task that functioned as the experimental control (Habel et al., 2005). Sad and happy moods produced similar activations in the amygdala-hippocampal area extending into the parahippocampal gyrus, prefrontal and temporal cortex, anterior cingulate, and the precuneus. Happiness produced stronger activations in the dorsolateral prefrontal cortex, the cingulate gyrus, the inferior temporal gyrus, and the cerebellum (Figure 10.24). These results reinforce the role of the limbic system and its connections in the processing and expression of positive emotions. Nonetheless, the study of happiness remains extremely challenging. For example, happiness is not necessarily the pposite of sadness. What’s more, happiness is not automatically induced by looking at smiling faces.

Freud equated happiness with pleasure, but others have suggested that is also requires achievement, whether cognitive, aesthetic, or moral. Psychologist Mihaly Csikszentmihalyi suggests that people are really happy when totally immersed in a challenging task that closely matches their abilities (Csikszentmihalyi, 1990). Csikszentmihalyi came to this conclusion following an experiment in which he had participants carry beepers that randomly beeped several times a day. On that signal, they would whisk a notebook from their pockets and jot down what they were doing and how much they were enjoying it. He found that there were two types of pleasure: bodily pleasures such as eating and sex, and , even more enjoyable, the state of being “in the zone,” what Csikszentmihalyi calls flow. Csikszentmihalyi describes flow as the process of having an optimal experience. Flow occurs when you are so into what you are doing that you forget about everything else. It could be riding the top of a wave, working out a theorem, or doing a tango across the dance floor. It involves a challenge that you are equal to, that fully engages your attention, and offers immediate feedback at each step that you are on the right track and pulling it off. When both challenges and skills are high, the person is not only enjoying the moment but also stretching his or her capabilities. This improves the liklihood of learning new skills, and increasing both self-esteem and personal complexity (Csikszentmihalyi & LeFevre, 1989). The concept of flow and what it means suggests that the ciruits involved in pleasure, reward, and motivation are essential in the emotion of happiness.

Love