Dissociable Contributions of the Human Amygdala and Orbitofrontal Cortex to Incentive Motivation and Goal Selection

Abstract

Theories of incentive motivation attempt to capture the way in which objects and events in the world can acquire high motivational value and drive behavior, even in the absence of a clear biological need. In addition, for an individual to select the most appropriate goal, the incentive values of competing desirable objects need to be defined and compared. The present study examined the neural substrates by which appetitive incentive value influences prospective goal selection, using positron emission tomographic neuroimaging in humans. Sated subjects were shown a series of restaurant menus that varied in incentive value, specifically tailored for each individual, and in half the trials, were asked to make a selection from the menu. The amygdala was activated by high-incentive menus regardless of whether a choice was required. Indeed, activity in this region varied as a function of individual subjective ratings of incentive value. In contrast, distinct regions of the orbitofrontal cortex were recruited both during incentive judgments and goal selection. Activity in the medial orbital cortex showed a greater response to high-incentive menus and when making a choice, with the latter activity also correlating with subjective ratings of difficulty. Lateral orbitofrontal activity was observed selectively when participants had to suppress responses to alternative desirable items to select their most preferred. Taken together, these data highlight the differential contribution of the amygdala and regions within the orbitofrontal cortex in a neural system underlying the selection of goals based on the prospective incentive value of stimuli, over and above homeostatic influences.

Preliminary fMRI findings concerning the influence of 5‐HTP on food selection

“…(2009) have argued that explicit processing of food is carried out by the amygdala and the medial orbital gyrus as increased activation of these regions are observed when participants are asked to judge the palatability of food. In general, the amygdala seems to have extended roles in the orexigenic network, as in conjunction with the lateral orbital gyrus (BA 47) it has been proposed to modulate states of hunger (Laan et al., 2011), whereas when taken together with the cingulate gyrus, it has been suggested to be involved in food desirability and the motivational salience of food (Arana et al., 2003; Shin et al., 2009). This is probably because of its strategic position in the cortex.…”

“…It would be surprising to expect a protein preference in controls since it would decrease levels of 5‐HT and promote LNAAs competition (Fadda, 2000; Weingarten & Elston, 1991; Young et al., 1988). Support for macronutrient selection can be found in studies that examined cortical activity in response to cravings (Pelchat et al., 2004; Small et al., 2001), overconsumption of chocolate despite satiety (Small et al., 2001) as well as incentive motivation and food selection (Arana et al., 2003). Small et al.…”

“…In addition, comparison between individuals of balance and monotonous diets yielded activation clusters at the left hippocampus and insula as well as the right caudate nucleus. Finally, in another study when individuals were asked to judge from a menu, the appetitive incentive value of food, areas of the amygdala and the medial orbitofrontal cortex were activated (Arana et al., 2003). …”

“…(2004), Small et al. (2001), and Tataranni et al (1999) indicate the initiation of a feeding episode and the motivation to engage with the presented food as it is signified by the activity of the medial OFC (Arana et al., 2003). On the other hand, the vitamin C group showed bilateral activity in response to protein at the anterior cingulate gyrus (BA 24, 31) as well as the left caudolateral OFC (BA 10).…”

“…(1999) have also shown the insular cortex to be associated with conditions of hunger. Also within the limbic system, the amygdala and cingulate cortex not only show a positive correlation with hunger but they also display sensitivity to food desirability (Arana et al., 2003; Shin, Zheng, & Berthoud, 2009). For instance the anterior cingulate shows an inverse relation with the desirability of chocolate, higher functional activity for high versus low caloric food, as well as greater activity in satiation compared to hunger (Killgore & Yurgelun‐Todd, 2005; Santel, Baving, Krauel, Munte, & Rotte, 2006; Small, Zatorre, Dagher, Evans, & Jones‐Gotman, 2001).…”