Evoked potential augmenting-reducing: A weak link in the biology-personality chain

Defensiveness, anxiety and the amplitude/intensity function of auditory-evoked potentials

This study measured relationships between defensiveness, anxiety, and auditory-evoked potentials to tones of varied intensity. Subjects were designated as defensive if they scored > or = 7 on the L-scale of the Eysenck Personality Questionnaire, and high-anxious if they scored > or = 11 on the N-scale. Four groups resulted: 'high anxious', 'defensive high anxious', 'repressors' (i.e., defensive low anxious) and 'low anxious'. Evoked potentials were recorded from FZ, CZ, PZ, C3, C4, T3 and T4, referenced to linked ears in response to 74, 84, 94 and 104 dB SPL tones. High-defensive subjects showed lower P2 amplitudes to the 94 and 104 dB tones and lower amplitude/intensity slopes at FZ, CZ, C3 and C4. High-anxious subjects showed lower P2 amplitudes to all four stimulus intensities at FZ, CZ and PZ. The results are consistent with the hypothesis that defensiveness is associated with desensitization to intense or painful stimulation.

ERP augmenting/reducing and sensation seeking: a critical review

Event-related potentials (ERPs) are generally considered capable of throwing light on the biological basis of personality traits. In particular, the ERP augmenting/reducing (A/R) phenomenon has been consistently associated with personality dimensions such as sensation seeking or impulsivity. However, doubts have been expressed regarding the validity of published evidence that individuals scoring high as sensation seekers are ERP augmenters. Reports of A/R-sensation seeking correlation in the opposite direction (in keeping with Petrie's hypotheses) threaten the construct validity of A/R, and lack of intermodal consistency throws serious doubts upon the existence of the central input-regulating mechanism once thought to be associated with sensation seeking. With the aim of clarification this article reviews the literature on the relationship between ERP A/R and sensation seeking, discusses the chief problems confronted by research in this area, and makes suggestions for future studies. It is concluded that experimental conditions of stimulus intensity and inter-stimulus interval may have played a part in the inconsistencies. The need to use a variety of measures of sensation seeking is stressed, and a number of other recommendations for research in this field are made.

The psychophysiology of sensation seeking

This article summarizes studies relating the trait of sensation seeking to electrodermal and heart-rate responses and cortical evoked potential arousal. Stimulus factors of novelty, intensity, and stimulus significance are important. High sensation seekers tend to give stronger physiological orienting responses than lows to novel stimuli of moderate intensity, particularly when such stimuli are of specific interest. Lows tend to show defensive responses as defined by heart-rate acceleration. The cortical reaction of the highs tends to be augmented by intense visual or auditory stimuli, while that of the lows tends to be reduced or unresponsive to variations in stimulus intensity. Differences between psychophysiological responses of high and low sensation seekers are interpreted as reflective of different evolved biological strategies for processing novel or intense stimulation.

Psychophysiological correlates of posttraumatic stress disorder in Vietnam veterans

We measured event-related brain potential (ERP) component amplitudes and heart rate (HR) to four intensities of randomly presented tones in two matched groups of drug-free male Vietnam veterans: 12 patients diagnosed with posttraumatic stress disorder (PTSD) and 6 normal combat veterans. Subjects were evaluated with structured diagnostic interviews and anxiety and depression rating scales. We found a significant group X intensity interaction for P2 peak amplitude at CZ. Subjects were classified as augmenters or reducers: positive P2 slopes as a function of stimulus intensity implying augmentation and negative slopes implying reduction. Nine of 12 PTSD subjects were reducers (sensitivity of 75%) and 5 of 6 normals were augmenters (specificity of 83.3%). By the third and fourth second following tone onset, the mean HR of PTSD subjects increased more than twice that of the normals. HR change scores were significantly responsive to the manipulation of stimulus intensity and to the difference between our two groups. P2 reduction differentiates Vietnam veterans with combat-related PTSD from combat veteran controls, and PTSD subjects are more autonomically arousable than their combat veteran peers.