Emotional modulation of the postauricular reflex
Emotional modulation of the postauricular reflex
Emotional modulation of the postauricular reflex
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Emotion and <strong>the</strong> post-auricular <strong>reflex</strong> 431<br />
2000) and with motor deficits arising from Parkinson’s disease in<br />
humans (Heim et al., 2002).<br />
An alternative possibility is that increased post-auricular<br />
reactivity reflects enhanced orienting to <strong>the</strong> noise probe stimulus.<br />
Indeed, <strong>the</strong>re is evidence that unexpected noises can evoke<br />
observable movement <strong>of</strong> <strong>the</strong> post-auricular (pinna) muscle in<br />
primates in whom this muscle serves more than a vestigial<br />
function. Naturalistic observations <strong>of</strong> Hanuman langurs, a lower<br />
primate species, have revealed that in adult males, loud and<br />
surprising sounds yield brief (i.e., 0.2–0.3 s) movements <strong>of</strong> both<br />
<strong>the</strong> pinna and <strong>the</strong> head in <strong>the</strong> direction <strong>of</strong> <strong>the</strong> noise (Trivedi &<br />
Mohnot, 2002), suggesting that <strong>the</strong> pinna <strong>reflex</strong> serves an<br />
orienting function in this primate species. It may be that states <strong>of</strong><br />
attentional engagement, such as those associated with viewing <strong>of</strong><br />
pleasurable pictures, facilitate this phasic <strong>reflex</strong>ive orienting<br />
reaction. However, because pleasant and unpleasant pictures<br />
engage more attention than neutral (Lang et al., 1990, 1997), <strong>the</strong><br />
predicted attentional pattern would have been one <strong>of</strong> <strong>postauricular</strong><br />
<strong>reflex</strong> inhibition for both affective categories compared<br />
to neutral. Fur<strong>the</strong>rmore, juveniles and females <strong>of</strong> this species<br />
exhibit greater short-duration pinna movements primarily<br />
during play, feeding, and foraging for food (Trivedi & Mohnot,<br />
2002), suggesting heightened responsiveness <strong>of</strong> this <strong>reflex</strong>ive<br />
system specifically during pleasurable activities.<br />
Never<strong>the</strong>less, <strong>the</strong>re is evidence that unpleasant pictures also<br />
engage attention (Lang et al., 1997), so it is possible that some<br />
types <strong>of</strong> aversive pictures might likewise facilitate <strong>the</strong> <strong>postauricular</strong><br />
<strong>reflex</strong>. The current study focused on threat and physical<br />
attack pictures that tend to be perceived as fearful. Modulatory<br />
Ames, K. A., Merritt, N. P., Stout, K., & Hetrick, W. P. (2003).<br />
Differential effects <strong>of</strong> affective <strong>modulation</strong> on orbicularis and <strong>postauricular</strong><br />
indices <strong>of</strong> startle. Psychophysiology, 40, S22.<br />
Anthony, B. J., & Graham, F. K. (1985). Blink <strong>reflex</strong> modification by<br />
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processing. Biological Psychology, 21, 43–59.<br />
Benning, S. D., Patrick, C. J., Hicks, B., Blonigen, D., & Lang, A. R.<br />
(2001). Affective <strong>modulation</strong> <strong>of</strong> blink startle and post-auricular<br />
<strong>reflex</strong>es to noise probes. Psychophysiology, 38, S24.<br />
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Bradley, M. M., Drobes, D., & Lang, P. J. (1996). A probe for all<br />
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Gainesville, FL: The Center for Research in Psychophysiology,<br />
University <strong>of</strong> Florida.<br />
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effects may differ for o<strong>the</strong>r aversive contents, such as sadness,<br />
disgust, or mutilation pictures. It will also be important in future<br />
research to examine effects for o<strong>the</strong>r pleasurable picture contents<br />
(e.g., babies, animals, food). In addition, <strong>the</strong>re are o<strong>the</strong>r<br />
limitations <strong>of</strong> <strong>the</strong> current study that need to be addressed before<br />
firm conclusions can be advanced regarding <strong>the</strong> post-auricular<br />
<strong>reflex</strong> as an index <strong>of</strong> emotion. The current sample included only<br />
men; thus, it will be important to replicate <strong>the</strong>se findings in<br />
women. Fur<strong>the</strong>rmore, it will be important to assess <strong>modulation</strong><br />
<strong>of</strong> <strong>the</strong> post-auricular <strong>reflex</strong> in emotional processing tasks o<strong>the</strong>r<br />
than picture viewing. A key question is whe<strong>the</strong>r potentiation <strong>of</strong><br />
<strong>the</strong> post-auricular <strong>reflex</strong> would be observed in appetitive<br />
conditioning or reward anticipation contexts, as is true for<br />
startle in corresponding aversive paradigms (e.g., Hamm,<br />
Greenwald, Bradley, & Lang, 1993; Patrick & Berthot, 1995).<br />
Affirmative findings would lend support to <strong>the</strong> idea that <strong>the</strong> <strong>postauricular</strong><br />
<strong>reflex</strong> is primed during appetitive states. Finally, in light<br />
<strong>of</strong> recent data indicating that hedonic valence and approach–<br />
withdrawal aspects <strong>of</strong> emotion are dissociable, it would be<br />
informative to assess whe<strong>the</strong>r <strong>the</strong> post-auricular <strong>reflex</strong> is<br />
enhanced or inhibited during a negatively valent approach state<br />
(e.g., anger; Harmon-Jones & Sigelman, 2001).<br />
Notwithstanding <strong>the</strong>se limitations, <strong>the</strong> findings <strong>of</strong> our study<br />
are intriguing. They suggest that <strong>the</strong> post-auricular <strong>reflex</strong>, which<br />
is evoked by <strong>the</strong> same acoustic probe as <strong>the</strong> startle <strong>reflex</strong>, may<br />
provide an index <strong>of</strong> appetitive system activation. If so, this<br />
<strong>reflex</strong>ive measure could provide a valuable tool for studying basic<br />
appetitive processes and investigating deficiencies in positive<br />
affect associated with psychopathology.<br />
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