The µ-opioid system promotes visual attention to faces and eyes

Abstract

Paying attention to others' faces and eyes is a cornerstone of human social behavior. The µ-opioid receptor (MOR) system, central to social reward-processing in rodents and primates, has been proposed to mediate the capacity for affiliative reward in humans. We assessed the role of the human MOR system in visual exploration of faces and eyes of conspecifics. Thirty healthy males received a novel, bidirectional battery of psychopharmacological treatment (an MOR agonist, a non-selective opioid antagonist, or placebo, on three separate days). Eye-movements were recorded while participants viewed facial photographs. We predicted that the MOR system would promote visual exploration of faces, and hypothesized that MOR agonism would increase, whereas antagonism decrease overt attention to the information-rich eye region. The expected linear effect of MOR manipulation on visual attention to the stimuli was observed, such that MOR agonism increased while antagonism decreased visual exploration of faces and overt attention to the eyes. The observed effects suggest that the human MOR system promotes overt visual attention to socially significant cues, in line with theories linking reward value to gaze control and target selection. Enhanced attention to others' faces and eyes represents a putative behavioral mechanism through which the human MOR system promotes social interest.

μ-Opioid Modulation of Reported Wanting of Palatable Food Images: A pharmacological fMRI study in healthy humans

“…However, the doses used by Zacny and Lichtor were three to six times the amount administered in this study. A previous study from our lab reported no significant changes in subjective state in healthy participants using a 10mg per oral dose of morphine (Chelnokova et al, 2016;Eikemo et al, 2016;Hanks et al, 1995).…”

“…Participants then received either 10 mg morphine or placebo (double-blind) and were told to swallow the pills immediately with water, and to not look at the pills while ingesting. As in a previous pharmacological study conducted in our lab (Chelnokova et al, 2014;Chelnokova et al, 2016;Eikemo et al, 2016) participants were told that the pills could be either morphine, placebo or naltrexone. Although naltrexone was not included in the present design, the information was kept to avoid recruitment of participants attracted specifically by the prospect of morphine treatment.…”

“…Importantly, we chose a morphine dose that is not expected to cause changes in subjective state, mood, or drug effects such as 'high' or euphoria based on previous research (Chelnokova et al, 2016;Eikemo et al, 2016;Zacny & Lichtor, 2008). To control for potential drug effects on mood or subjective state, we also developed a subjective state questionnaire that was administered before drug administration, during estimated peak effect, and at end of each session (figure 2).…”

“…In order to control for this potential confound in our results, we administered a short eye-hand coordination task (Giovannoni, Van Schalkwyk, Fritz, & Lees, 1999). Based on previous studies from our lab, we do not expect any reduction in motor coordination with a 10mg per oral dose of morphine (Chelnokova et al, 2016;Eikemo et al, 2016).…”

“…Zacny & Lichtor, 2008). Questions were presented in Norwegian, and the version has been used in several previous studies (Chelnokova et al, 2016;Eikemo et al, 2016). Items were rated on an 11-point electronic visual analogue scales (VAS) of 100mm, anchored at 'Not at all' and 'Very much'.…”