Alcohol effects on affective response during variable and fixed duration threat

ABSTRACT Recent research indicates that fear and anxiety are distinct processes with separable neurobiological substrates. Experimental procedures using predictable vs. unpredictable shock administration have been used to elicit fear vs. anxiety, respectively (Grillon et al, 2004). Using these procedures, our lab has demonstrated that alcohol reduces anxiety to unpredictable shock but not fear to predictable shock (Moberg & Curtin, 2009). However, this manipulation of predictability varied both the probability and temporal precision of shock threat, raising critical questions as to which stimulus characteristics are central to both the elicitation of anxiety and the anxiolytic effects of alcohol.To disentangle these two characteristics, we developed a novel paradigm to systematically vary temporal occurrence of threat while holding the probability of threat occurrence constant. Intoxicated (0.08% BAC), non-intoxicated, and placebo participants viewed a series of visual cues. Fixed 5s cue presentations were equivalent to predictable shock cues that elicited fear in earlier research. Variable duration cues (5s, 20s, 50s, or 80s) were designed to elicit anxiety due to the temporal uncertainly of the threat occurrence. Startle potentiation (SP) relative to matched cue periods in no-shock blocks provided the primary measure of affective response.All shock cues produced robust SP. Additionally, two key findings were observed. We first examined affective response during the first 4 seconds of the cue presentation, such that startle probe occurrence was matched between variable and fixed duration blocks. We found that alcohol significantly reduced SP during variable duration threat cues, whereas there was no detectable alcohol effect during fixed duration threat cues. We then examined affective response later during each variable duration cue. We found that alcohol reduced SP during later time points in the longer cues, suggesting that the alcohol effects persist over time.These results build on evidence suggesting that fear and anxiety are distinct, separable affective responses, and suggest that anxiety can be elicited by altering either threat probability or temporal precision. Underscoring previous findings that alcohol selectively reduces anxiety but not fear, this work has important implications for high rates of comorbidity between anxiety disorders and alcoholism.