Ethnic differences in physiological responses to fear conditioned stimuli

Abstract

The idea that emotional expression varies with ethnicity is based largely on questionnaires and behavioral observations rather than physiological measures. We therefore compared the skin conductance responses (SCR) of Hispanic (Puerto Rican) and White non-Hispanic subjects in a fear conditioning and fear extinction task. Subjects were recruited from two sites: San Juan, Puerto Rico (PR), and Boston, Massachusetts (MA), using identical methods. A total of 78 healthy subjects (39 from PR, 39 from MA) were divided by sex and matched for age and educational level. Females from the two sites did not differ in their SCRs during any experimental phase of fear conditioning (habituation, conditioning, or extinction). In contrast, PR males responded significantly to the conditioned stimulus than MA males or PR females. Subtracting ethnic differences observed during the habituation phase (prior to conditioning) eliminated differences from subsequent phases, suggesting that PR males are elevated in their response to novelty rather than fear learning. Our findings suggest that, in addition to sex differences, there are ethnic differences in physiological responses to novel stimuli at least in males, which could be relevant for the assessment and treatment of anxiety disorders.

Conflict of interest statement

Competing Interests: The authors have declared that no competing interests exist.

Figures

Figure 1. Schematic representation of research protocol.

Electrodes measuring skin conductance response (SCR) are placed on the palm of the non-dominant hand while shock electrodes were placed on the dominant hand fingers. Subjects first encounter all the images without any shock (habituation) and then in one of the contexts (office) the blue light will be paired with a shock while the red light receives no shock (conditioning). The other context (library) is then shown with no shocks neither in the blue or red light (extinction). Approximately 24 hours later, subjects return and their SCR is measured while seeing the extinction context with no shock (recall) and the conditioning context with no shock (renewal). SCL =  skin conductance level, SCR  =  skin conductance response.

Figure 2. Baseline skin conductance level (SCL) and skin conductance responses (SCR) to CS+ across all experimental phases in males and females at both sites.

A. SCL and responses to CS+ in females in Massachusetts (MA) and Puerto Rico (PR). B. SCL and responses to CS+ in males in Massachusetts (MA) and Puerto Rico (PR). Habit. = Habituation, Cond. = Conditioning, Ext. = Extinction, μS  =  microsiemens. *p

Figure 3. Sex differences at both sites in skin conductance responses (SCR) to CS+ across all experimental phases.

A. Responses to CS+ in males and females in Massachusetts (MA). B. Responses to CS+ in males and females in Puerto Rico (PR). Habit. = Habituation, Cond. = Conditioning, Ext. = Extinction, μS  =  microsiemens. *p

Figure 4. Summary of SCR differences in PR males.

A. Increased SCR during renewal is seen in PR males when compared to PR females, MA males and females. B. PR males show both increased habituation and renewal when compared to PR females, MA males and females.