The publisher's final edited version of this article is available at Neuroimage
Abstract
Although
social withdrawal is a prominent symptom of sickness, the mechanisms
associated with this behavioral change remain unclear. In animals, the
amygdala is a key neural region involved in sickness-induced social
withdrawal. Consistent with this, in humans, heightened amygdala
activity to negative social cues is associated with social avoidance
tendencies. Based on these findings, we investigated whether an
experimental inflammatory challenge selectively increased amygdala
activity to socially threatening images as well as whether this activity
related to feelings of social disconnection. Thirty-nine participants
were randomly assigned to receive either placebo or low-dose endotoxin,
which increases inflammatory activity. Pro-inflammatory cytokines were
assessed at 7 hourly time points via blood draws; self-reported feelings
of social disconnection and physical sickness symptoms were assessed
hourly as well. Two hours post-injection, participants underwent an fMRI
procedure to assess amygdala reactivity during the presentation of
socially threatening images (fear faces) as well as non-socially
threatening images (guns), socially non-threatening images (happy
faces), and non-social, non-threatening images (household objects).
Endotoxin led to greater amygdala activity in response to socially
threatening vs. all other types of images. No such differences were
found for placebo participants. Additionally, increased amygdala
activity in endotoxin participants during the viewing of socially vs.
non-socially threatening images was associated with increased feelings
of social disconnection. These findings highlight the amygdala as a
neural region that may be important for sickness-induced social
withdrawal. The implications of amygdalar involvement in
sickness-induced social withdrawal are discussed.
Keywords: amygdala, inflammation, social, functional magnetic resonance imaging, cytokines, social withdrawal
For full text of article go to:
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3348143/
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