See no evil: Attentional bias towards threat is diminished in aged monkeys

Abstract

Prior evidence demonstrates that relative to younger adults, older human adults exhibit attentional biases towards positive and/or away from negative socioaffective stimuli (i.e., the age-related positivity effect). Whether or not the effect is phylogenetically conserved is currently unknown and its biopsychosocial origins are debated. To address this gap, we evaluated how visual processing of socioaffective stimuli differs in aged, compared to middle-aged, rhesus monkeys (Macaca mulatta) using eye-tracking in two experimental designs that are directly comparable to those historically used for evaluating attentional biases in humans. Results of our study demonstrate that while younger rhesus possess robust attentional biases towards threatening pictures of conspecifics faces, aged animals evidence no such bias. Critically, these biases emerged only when threatening faces were paired with neutral and not ostensibly ‘positive’ faces, suggesting social context modifies the effect. Results of our study suggest evolutionarily shared mechanisms drive age-related decline in visual biases towards negative stimuli in aging across primate species.

Cardiac psychophysiological tuning to socioaffective content is disrupted in aged rhesus monkeys (Macaca mulatta)

“…Although RSA correlated with the socioaffective content of videos in the middle‐aged monkeys of our study, this was not the case for our aged animals—even though older monkeys were just as engaged with the video stimuli compared to their middle‐aged counterparts, as indexed by the number of fixations made to the stimuli. Age‐related diminishment in RSA activation may be one mechanism through which aging leads to several changes in socioaffective behavior in humans and nonhuman primates, such as decline in overall sociality (humans: Cornwell et al, 2008; McPherson et al, 2006, for a review of the nonhuman primate literature, see Rosati et al, 2020) and preferential psychological processing of positive over negative affective information (Carstensen & DeLiema, 2018; Machanda & Rosati, 2020; Santistevan et al, 2022). That is, if it is the case that the vagal activity is involved in mediating social approach, the fact that the vagal system is disrupted in aging lends credence to the hypothesis that age‐related changes to vagal function and social behavior are causally linked.…”

“…Testing occurred Monday through Friday between 0800 and 1800 h over 2 weeks (10 days) of testing, with a two‐day break on the weekend. Animals had been previously acclimated to this testing environment and trained to interact with the eye‐tracker for a juice reward for the purposes of another eye‐tracking experiment that preceded this study (Santistevan et al, 2022). Animals were box transported individually from their home enclosure to the testing room, where they were transferred to a custom nonhuman primate chair, had their arms and legs lightly restrained with soft leather straps, and had disposable spot Ag/AgCl+ electrodes (Covidien, Dublin, Ireland) placed on their chest and back to record electrocardiogram ( ECG , modified Lead 2 configuration) and impedance cardiogram (ICG).…”