Differences in startle reflex and prepulse inhibition in European‐Americans and African‐Americans

Abstract

The acoustic startle reflex and its modulation by a prepulse are psychophysiological phenomena that are commonly studied to evaluate various aspects of information processing. Recent reports in human populations suggest that subjects from disparate racial backgrounds may have significant differences in the startle response. To determine if this pattern could be observed in our subject population, and whether it extended to prepulse inhibition (PPI), we evaluated baseline startle parameters and PPI in 53 African-Americans (AA) and 38 European-Americans (EA). In AA compared to EA, mean startle magnitude and probability of blink response were lower, with no difference in habituation. PPI was greater in AA than EA when groups were matched on baseline startle magnitude. These findings support the idea of racial differences in startle response. Implications for study design are highlighted, and possible environmental and genetic influences are considered.

Sensorimotor gating in healthy adults tested over a 15 year period

“…Racial differences in PPI have been reported previously, and while the present sample was relatively limited in diversity, our findings support those reported previously by Hasenkamp et al (2008), that PPI is elevated in African American vs. European American healthy adults. While it is impossible to rule out a contribution of startle magnitude differences to this observation, it is evident that comparably lower startle magnitude in Asian American vs. European American subjects was not accompanied by differences in PPI.…”

“…Relatively reduced startle magnitude among Asian and African American vs. European American participants was clearly evident in this inclusive sample; this Asian vs. White difference had been reported in a small subset of this sample (Swerdlow et al 2005), and the African American vs. White difference had been reported previously by others (Hasenkamp et al 2008). Elevated startle magnitude among our subjects with blue vs. brown eyes seemingly parallels reports by others (Barker et al 2014; Rosenberg & Kagan 1989); however, unlike these previous reports in White children, in our present multi-racial adult sample, this difference was accounted for entirely by the skewed racial distribution of eye colors.…”

“…Racial differences have been reported in startle measures, including PPI, with African American > European American PPI levels detected in healthy subjects for 30-120 ms prepulse intervals (Hasenkamp et al 2008). A similar pattern was detected in the present sample using these prepulse intervals (Figure 3C).…”

“…For analyses of racial differences in startle variables (e.g. Hasenkamp et al 2008; Swerdlow et al 2005), self-reported race was recorded for the following groups: White (not Hispanic) and White (Hispanic) (collectively, “European Americans”), Black / African American, Asian, Native American, Pacific Islander, and “multiple races”; based on sample size, only some subgroups were used in specific analyses as described in the Results. Subjects self-identified as Asian were also asked to identify a country of ancestry, based on reports of differential COMT effects among individuals of Chinese Han vs. European ancestry (Wang et al 2013).…”

“…C. Sex difference in PPI, collapsed across 10-120 ms intervals (F=5.62, df 1,204, p<0.02; data included only from years when both men and women were tested (10/2009 - 2016). D. Racial differences in PPI, collapsed across 30-120 ms intervals, as per Hasenkamp et al (2008) (EA vs. Afa: F=4.65, df 1,296, p<0.035). E. No effect of rs4680 status on PPI collapsed across men and women, when analyzed by genotype as in Roussos et al (2008) (left), but significant sex × genotype interaction (F=5.44, df 1,133, p<0.025) with medium effect size, opposite genotype effects in women vs. men, when analyzed based on presence or absence of any Val allele (right).…”