Habituation of the electrodermal response - A biological correlate of resilience?

Current approaches to quantifying resilience make extensive use of self-reported data. Problematically, this type of scales is plagued by response distortions-both deliberate and unintentional, particularly in occupational populations. The aim of the current study was to develop an objective index of resilience. The study was conducted in 30 young healthy adults. Following completion of the Connor-Davidson Resilience Scale (CD-RISC) and Depression/Anxiety/Stress Scale (DASS), they were subjected to a series of 15 acoustic startle stimuli (95 dB, 50 ms) presented at random intervals, with respiration, skin conductance and ECG recorded. As expected, resilience (CD-RISC) significantly and negatively correlated with all three DASS subscales-Depression (r = -0.66, p<0.0001), Anxiety (r = -0.50, p<0.005) and Stress (r = -0.48, p<0.005). Acoustic stimuli consistently provoked transient skin conductance (SC) responses, with SC slopes indexing response habituation. This slope significantly and positively correlated with DASS-Depression (r = 0.59, p<0.005), DASS-Anxiety (r = 0.35, p<0.05) and DASS-Total (r = 0.50, p<0.005) scores, and negatively with resilience score (r = -0.47; p = 0.006), indicating that high-resilience individuals are characterized by steeper habituation slopes compared to low-resilience individuals. Our key finding of the connection between habituation of the skin conductance responses to repeated acoustic startle stimulus and resilience-related psychometric constructs suggests that response habituation paradigm has the potential to characterize important attributes of cognitive fitness and well-being-such as depression, anxiety and resilience. With steep negative slopes reflecting faster habituation, lower depression/anxiety and higher resilience, and slower or no habituation characterizing less resilient individuals, this protocol may offer a distortion-free method for objective assessment and monitoring of psychological resilience.

The fusion of unattended duration representations as indexed by the mismatch negativity (MMN).

Within a single train of same-duration (standard) stimuli, an occasional longer-duration (deviant) sound elicits mismatch negativity (MMN) with a peak latency (measured relative to sound onset) reflecting the standard duration representation. When two such trains are presented in a dichotic paradigm, a separate duration representation arises for each train. We examined the role of attention in this segregation. Four sound trains of differing frequencies (1000 and 1200 Hz to one ear, 2000 and 2400 Hz to the other ear) were presented simultaneously. Participants attended the lower frequency (Low) sounds (always 100 ms) in one ear. Duration of the other (High) sounds varied: 100 ms in the Equal condition; 40 ms in the Short condition. If attention was necessary for separation of sound representations, the two attended ear representations were hypothesised to segregate whilst the two unattended ear's representations would remain fused. Duration MMN was recorded to occasional (1 in 18) 150 ms deviants in all trains. In the Short condition, if unattended ear representations fused, earlier peaking unattended Low sound MMN was expected, relative to when this ear was attended. In the same condition, the MMN for unattended High sounds was expected to peak later, relative to when attended. Low sound unattended MMN latency was indeed earlier by ~30 ms relative to when attended. High sound unattended MMN latency, however, only increased ~9 ms in the same transition. This smaller magnitude change is explained by a minimum MMN onset latency. Attention alone appears to offer a basis for segregating MMN representations.