The impact of orbital prefrontal cortex damage on emotional activation to unanticipated and anticipated acoustic startle stimuli

Damage to the orbital prefrontal cortex has been implicated in selectively diminishing electrodermal autonomic nervous system responses to anticipated punishing stimuli (e.g., losing money; Bechara, Damasio, & Damasio, 2000), but not to unanticipated punishing stimuli (e.g., loud noises; Damasio, Tranel, & Damasio, 1990). We extended this research by examining the effects of orbitofrontal damage on emotional responses to unanticipated and anticipated acoustic startles and collecting a more extensive set of physiological measures, emotional facial behavior, and self-reported emotional experience. Consistent with previous research, patients showed intact physiology to an unanticipated startle but failed to show appropriate anticipatory cardiovascular responses (patients’ heart rates decreased, controls’ increased). In addition, patients displayed more surprise facial behavior and reported marginally more fear than did controls in response to the unanticipated startle. Thus, orbitofrontal damage may compromise the ability to anticipate physiologically the onset of aversive stimuli, despite intact or enhanced emotional responses when such stimuli occur unexpectedly.     

Prepared movements are elicited early by startle

A startle stimulus has been shown to elicit a ballistic response in a reaction time (RT) task at very short latencies without involvement of the cerebral cortex (J. Valls-Sole, J. C. Rothwell, F. Gooulard, G. Cossu, & E. Munoz, 1999). The present authors examined the nature of the startle response. A simple RT task was used in which 8 participants performed arm extension movements to 3 target distances (20 degrees, 40 degrees, and 60 degrees ) in a blocked design. An unpredictable startling acoustic stimulus (124 dB) replaced the imperative stimulus in certain trials. The authors verified the presence of a startle response independent from the prepared response by observing electromyographic (EMG) activity in sternocleidomastoid and orbicularis oculi muscles. Findings indicated that when the participant was startled, the intended voluntary response was produced at significantly shorter response latencies. Furthermore, the kinematic variables of the observed response during startle trials for all 3 target distances were mostly unchanged. The EMG characteristics of the responses were not modified, indicating that the response produced was indeed the prepared and intended response.     

Errors are aversive: defensive motivation and the error-related negativity

The error-related negativity (ERN) is a negative deflection in the event-related potential that is maximal approximately 50 ms after the commission of an error. The ERN is generated in the anterior cingulate cortex, a region of the medial prefrontal cortex implicated in both cognitive and emotional processing. Affective and motivational variables influence the magnitude of the ERN, which suggests that the ERN may relate to emotional or motivational aspects of error detection. In the present study, we evaluated the possibility that errors prime defensive motivational responses, and that the ERN may predict the magnitude of defensive reactivity after errors. We found that (a) the defensive startle response was larger following errors than following correct responses, and (b) the magnitude of the ERN predicted the degree of startle potentiation following errors. Thus, response errors prime defensive motivation-and the ERN predicts individual differences in the aversive response to errors.     

惊跳反射的生理心理机制

惊跳反射作为动物及人类在应对意外刺激或遇到险情时的一种避险保护反应,具有重要的生物学意义。以往的研究较多关注听觉惊跳反射,在反应指标上多采用眼部及面部表情肌的反应,如眨眼反射。惊跳反射的生理机制为突发性强刺激直接传向杏仁核的直接通路所致。惊跳反射增强的心理机制可能为致敏作用或恐惧性条件作用,而惊跳反射衰减的心理机制可能是适应、前脉冲抑制或愉快衰减。未来的研究应关注视觉惊跳反射,观察全身躯体姿势维持肌肉群的反应模式,并以先进设备对惊跳反射的信息加工脑机制进行深入的研究     

Social stimuli increase physiological reactivity but not defensive responses

Emotional reactions are crucial in survival because they provide approach and withdrawal behaviors. However, an unsolved question is whether the social content of the affective stimuli has a specific effect on emotional responses. We studied whether the social content of affective pictures influenced the defensive response and response mobilization. For this purpose, we recorded startle blink reflex (a defensive response) and skin conductance responses (a measure of unspecific physiological reactivity or arousal) in 73 participants while they viewed a series of 81 pictures of varying affective valence and social content. Our results revealed that defense response, as indicated by increases in the magnitude of the startle blink reflex, was mainly dependent on threatening or unpleasant cues, but was unrelated to the social content of the pictures. The social content, however, had an influence on pleasant stimuli, provoking an increase in resource mobilization, as reflected by changes in electrodermal activity. Hence, the social content of the affective stimuli may increase the physiological arousal elicited by pleasant stimuli, and it appears to be unrelated to the defense reactivity provoked by unpleasant stimuli.     

Prepulse effects on magnitude estimation of startle-eliciting stimuli and startle responses

The present studies investigated the relationship between prepulse effects on the modification of the brainstem startle reflex and magnitude estimates of startle-eliciting stimuli. In Experiment 1, startle eyeblink responses were elicited in 24 students, half of whom were instructed to estimate the loudness of the startle stimulus (actual intensities of 80, 90, and 100 dB) and half of whom were instructed to estimate the magnitude of their eyeblink. When weak acoustic prepulses preceded the startle-eliciting stimulus, eyeblink amplitude was inhibited, and estimates of response magnitude decreased, but estimates of startle stimulus magnitude decreased only when 100-dB startle stimuli were presented. In Experiment 2, the same startle stimuli were preceded on some trials by a vibrotactile prepulse to the hand. In conditions in which startle amplitude was inhibited, startle stimulus magnitude estimates were not affected. This suggests that the effect of acoustic prepulses on 100-dB startle stimuli in Experiment 1 may have been due to loudness assimilation, an effect independent of the prepulse inhibition of startle responding.     

Emotional-processing in posttraumatic stress disorder II: startle reflex modulation during picture processing

This study examined the impact of a trauma-related stressor on subsequent emotional behavior in veterans with (n = 35) and without (n = 24) posttraumatic stress disorder (PTSD). Self-report and physiological responses, including acoustic startle, were recorded during viewing of emotionally evocative photographs at baseline and following exposure to trauma-related and non-trauma-related stressors. The 2 groups exhibited equivalent patterns of emotional response across self-report and physiological measures at baseline. In contrast, following the trauma challenge, participants with PTSD showed a pattern of startle modulation suggestive of greater defensive reactivity and reduced visual perceptual engagement. These findings, along with augmented corrugator EMG reactivity during the same interval, suggest that trauma-related reexperiencing primes subsequent negative emotional responding in individuals with PTSD.     

Impact of Relevance and Distraction on Driving Performance and Visual Attention in a Simulated Driving Environment

Previous demonstrations of the impact of cellular phone conversations on visual attention when driving have primarily focused on attention to stimuli that are not relevant to driving. In contrast, we used a driving simulator and eye tracking to examine attention allocation across driving‐relevant and driving‐irrelevant items in the environment depending on whether drivers were distracted. Performance measures indicated that distraction negatively impacted vehicle control. However, driving relevance and the presence of distraction did not interact, suggesting that participants responded to potential hazards similarly in driving‐only and distraction conditions. In contrast, eye movement results indicated an interaction between distraction and relevance. Drivers attended more to driving‐relevant objects, and these objects showed smaller decrements in number of gazes in the distraction condition, compared with less relevant items. Even under distraction conditions, experienced drivers continued to attend to potential hazards, allocating less attention to billboards and roadway signage. Copyright © 2013 John Wiley & Sons, Ltd.     

Flexible emotional responsiveness in trait resilience

Field studies and laboratory experiments have documented that a key component of resilience is emotional flexibility--the ability to respond flexibly to changing emotional circumstances. In the present study we tested the hypotheses that resilient people exhibit emotional flexibility: (a) in response to frequently changing emotional stimuli and (b) across multiple modalities of emotional responding. As participants viewed a series of emotional pictures, we assessed their self-reported affect, facial muscle activity, and startle reflexes. Higher trait resilience predicted more divergent affective and facial responses (corrugator and zygomatic) to positive versus negative pictures. Thus, compared with their low-resilient counterparts, resilient people appear to be able to more flexibly match their emotional responses to the frequently changing emotional stimuli. Moreover, whereas high-trait-resilient participants exhibited divergent startle responses to positive versus negative pictures regardless of the valence of the preceding trial, low-trait-resilient participants did not exhibit divergent startle responses when the preceding picture was negative. High-trait-resilient individuals, therefore, appear to be better able than are their low-resilient counterparts to either switch or maintain their emotional responses depending on whether the emotional context changes. The present findings broaden our understanding of the mechanisms underlying resilience by demonstrating that resilient people are able to flexibly change their affective and physiological responses to match the demands of frequently changing environmental circumstances.     

Differences in startle reactivity during the perception of angry and fearful faces

Emotion researchers often categorize angry and fearful face stimuli as "negative" or "threatening". Perception of fear and anger, however, appears to be mediated by dissociable neural circuitries and often elicit distinguishable behavioral responses. The authors sought to elucidate whether viewing anger and fear expressions produce dissociable psychophysiological responses (i.e., the startle reflex). The results of two experiments using different facial stimulus sets (representing anger, fear, neutral, and happy) indicated that viewing anger was associated with a significantly heightened startle response (p < .05) relative to viewing fear, happy, and neutral. This finding suggests that while anger and fear faces convey messages of "threat", their priming effect on startle circuitry differs. Thus, angry expressions, representing viewer-directed threat with an unambiguous source (i.e., the expresser), may more effectively induce a motivational propensity to withdraw or escape. The source of threat is comparatively less clear for fearful faces. The differential effects of these two facial threat signals on the defensive motivational system adds to growing literature highlighting the importance of distinguishing between emotional stimuli of similar valence, along lines of meaning and functional impact.     

Modulation of unconditioned defense reflexes by a putative emotive Pavlovian conditioned stimulus

Four experiments showed differential modulation of defensive unconditioned responses (URs) in rabbits by contextual stimuli that Brandon and Wagner (1991) have shown similarly to modulate conditioned eyeblink responses. Two 30-s auditory cues, A and B, were differentially paired with shock. Tests were presentations of a response-eliciting probe stimulus within A, B, or a comparable blank interval, Experiments 1 and 2 demonstrated that A and B differentially facilitated eyeblink URs, and Experiments 3 and 4 showed that A and B similarly differentially facilitated startle responses elicited by airpuffs to the ear. These data are consistent with a characterization of Pavlovian conditioning that distinguishes between emotive and sensory conditioning and assumes that conditioned emotional responses similarly modulate specific conditioned and unconditioned defensive reflexes (Konorski, 1967; Wagner & Brandon, 1989).     

Beyond drug effects and dependent variables: the use of the Poisson-Erlang model to assess the effects of D-amphetamine on information processing

Several studies have shown that d-amphetamine (DAMP) speeds mean reaction time (RT). However, the use of mean RT may obscure important aspects of the drug response. Therefore we applied the Poisson-Erlang (PE) stochastic model of choice reaction time proposed by Pieters (1985) to the RT distribution. This model proposes that the RT distribution is generated by two states: Processing (P) and Distraction (D). RT represents the sum of the time spent in each of these states. P is the time taken to complete a set of cognitive operations which are required to give a correct response. D represents the time taken by all other activities. RTs were collected using a task (SERS) in which stimulus and response complexity each had two levels, easy and hard. Subjects were tested pre- and postdrug. Drug conditions were: placebo, 10 mg d-amphetamine (DAMP), 4 mg of the dopamine agonist, pimozide, and a combination of DAMP and pimozide (COMBO). Parameters of the model were derived using methods described by Pieters. Four measures were analyzed: Processing Time (PT); Mean Time per distraction (XTD); Distraction Rate (DR); and Total Distraction Time per trial (TDT). Mean RT is also presented. Analyses of the effects of task conditions on the parameters of the model were made using the predrug sessions. Mean RT was increased by both stimulus and response complexities as was PT. TDT was increased by the task conditions. The PE measures did not change over days. DAMP speeded mean RT. However, this effect did not interact with the task factors. DAMP speeded processing and reduced distraction. Processing was speeded only in the hard response condition, distraction time was reduced only in the easy response condition. The results indicate that the PE model can be successfully applied to fast RT tasks. More importantly, the parameters of the model revealed important pharmacological effects that were not apparent in mean RT. DAMP speeds cognitive operations related to motor preparation and reduces the effects of distraction. Consistent with past studies there are no indications that DAMP interacted with stimulus processing. The distraction effect appears to be mediated by an increase in the rate of distraction and a decrease in the average time of these distractions.     

Extinction of a heterogeneous chain after several reinforcement schedules

Rats were conditioned to emit the following two-member chain of responses on two different operanda always available: responses on a vertical bar produced a discriminative stimulus for food-reinforced responding on a horizontal bar. Responses on the vertical bar produced a discriminative stimulus on a variable-interval 1-min schedule, and the horizontal bar produced food on a variable ratio of 10 responses. Control conditions were included in which vertical bar responses were also food-reinforced simultaneous with the onset of the discriminative stimulus for the horizontal bar response and a tandem schedule which had the same response requirements but without different exteroceptive stimuli associated with the separate components of the response chain. The latter condition greatly retarded acquisition of the response chain compared to the other schedules studied here and compared to reports in the literature on homogeneous (single operandum) response chains. Intermittent reinforcement of the chain led to greater resistance to extinction of both members and the chain remained intact longer in the sense that stimulus control was maintained.     

Changes in the magnitude of the eyeblink startle response during habituation of sexual arousal

Modulation of the startle response was used to examine emotional processing of sexual stimulation across trials within a session. Eyeblink startle was elicited by a probe (burst of intense white noise) presented intermittently while men were viewing an erotic film segment. Repeated display of the film segment resulted in a progressive decrease in sexual arousal. Habituation of sexual arousal was accompanied by a reduction over trials in the extent the men felt absorbed when viewing the erotic stimulus and by an increase over trials in the magnitude of the eyeblink startle response. Replacing the familiar stimulus by a novel erotic stimulus increased in sexual arousal and absorption and reduced startle (novelty effect), while dishabituation was evident for all three response measures when the familiar stimulus was reintroduced. This pattern of results indicates that with repeated presentation an erotic stimulus is experienced not only as less sexually arousing but also as less appetitive and absorbing. The question of whether habituation of sexual arousal is mediated by changes in attentional and affective processing over trials is discussed, as are clinical contexts in which eyeblink startle can be used in studying aspects of sexual functioning.     

Progressive relaxation and meditation : A study of psychophysiological and therapeutic differences between two techniques

Physiological and self-report data were collected on anxious subjects who participated in a study comparing progressive relaxation, meditation and a waiting-list control. The data provide some support for the Schwartz, Davidson and Goleman (1978) hypothesis of specific effects for different relaxation procedures, superimposed upon a generalized relaxation response. The similarities between techniques, however, were greater than the differences, both on physiological and self-report measures. Both techniques generated positive expectancies and produced decreases in a variety of self-reported symptoms and on EMG: but no skin conductance or frontal EEG effects were observed. Progressive relaxation produced bigger decreases in forearm EMG responsiveness to stressful stimulation and a generally more powerful therapeutic effect than meditation. Meditation produced greater cardiac orienting responses to stressful stimuli, greater absorption in the task and better motivation to practice than progressive relaxation; but it also produced more reports of increased transient anxiety. We found no significant differences between conditions in the therapeutic expectancies they generated. The clinical implications of these findings are discussed.     

Programming Time as a Function of Response Duration

Reaction time was longer prior to longer-lasting pressing responses for low probability, unanticipated movements. By contrast, reaction time was independent of response duration for high probability, anticipated movements. This replicates and extends previous findings for choice and simple reaction time in the “dit-dah” paradigm. The present results (unanticipated responses) cannot be given a selective anticipation interpretation because the comparison is between responses which are never anticipated. The previous paradigm was open to an alternative interpretation in which selective anticipation of dit rather than dah could have produced the differences in choice reaction time. Confirmation of the finding that variations in required response duration lead to differences in reaction time supports the view that the underlying parameter of “complexity” in the “memory drum theory” may be response duration.     

Programming time as a function of response duration: a replication of "dit-dah" without possible guessing artifacts

Reaction time was longer prior to longer-lasting pressing responses for low probability, unanticipated movements. By contrast, reaction time was independent of response duration for high probability, anticipated movements. This replicates and extends previous findings for choice and simple reaction time in the "dit-dah" paradigm. The present results (unanticipated responses) cannot be given a selective anticipation interpretation because the comparison is between responses which are never anticipated. The previous paradigm was open to an alternative interpretation in which selective anticipation of dit rather than dah could have produced the differences in choice reaction time. Confirmation of the finding that variations in required response duration lead to differences in reaction time supports the view that the underlying parameter of "complexity" in the "memory drum theory" may be response duration.     

Defensive physiological reactions to rejection: the effect of self-esteem and attentional control on startle responses

We examined the hypothesis that rejection automatically elicits defensive physiological reactions in people with low self-esteem (SE) but that attentional control moderates this effect. Undergraduates (N= 67) completed questionnaire measures of SE and attentional control. Their eye-blink responses to startle probes were measured while they viewed paintings related to rejection and acceptance themes. The stimuli also included positive-, negative-, and neutral-valence control paintings unrelated to rejection. As predicted, compared with people high in SE, those low in SE showed stronger startle eye-blink responses to paintings related to rejection, but not to negative paintings. Paintings related to acceptance did not attenuate their physiological reactivity. Furthermore, attentional control moderated their sensitivity to rejection, such that low SE was related to greater eye-blink responses to rejection only among individuals who were low in attentional control. Implications of the role of attentional control as a top-down process regulating emotional reactivity in people with low SE are discussed.     

Measuring anxious responses to predictable and unpredictable threat in children and adolescents

Research has highlighted the need for new methods to assess emotions in children on multiple levels to gain better insight into the complex processes of emotional development. The startle reflex is a unique translational tool that has been used to study physiological processes during fear and anxiety in rodents and in human participants. However, it has been challenging to implement developmentally appropriate startle experiments in children. This article describes a procedure that uses predictable and unpredictable aversive events to distinguish between phasic fear and sustained anxiety in children and adolescents. We investigated anxious responses, as measured with the startle reflex, in youths (N = 36, mean age = 12.63 years, range = 7-17) across three conditions: no aversive events (N), predictable aversive events (P), and unpredictable aversive events (U). Short-duration cues were presented several times in each condition. Aversive events were signaled by the cues in the P condition but were presented randomly in the U condition. Participants showed fear-potentiated startle to the threat cue in the P condition. Startle responses were also elevated between cues in the U condition compared with the N condition, suggesting that unpredictable aversive events can evoke a sustained state of anxiety in youths. This latter effect was influenced by sex, being greater in girls than in boys. These findings indicate the feasibility of this experimental induction of the startle reflex in response to predictable and unpredictable events in children and adolescents, enabling future research on interindividual differences in fear and anxiety and their development in youths.     

Facilitating eyewitness memory in adults and children with context reinstatement and focused meditation

This study examined the comparative efficacy of two brief techniques for facilitating eyewitness memory in police investigations. Adult and child participants (N = 126; 64 children and 62 adults) who had viewed a videotape of a crime were subsequently tested for their memory of the event following either a focused meditation procedure (FM, derived from hypnotic interviewing techniques), a context reinstatement procedure (CR, a component of the cognitive interview), or a control procedure (no memory facilitation instructions). For both adults and children, the FM and CR procedures enhanced performance on both open‐ended and closed questions to levels above those achieved by controls, although those in the CR condition produced significantly more correct responses than those in the FM condition. However, only those in the CR group displayed elevated levels of confidence in relation to incorrect responses on closed questions. Implications for the possible use of such procedures are discussed. Copyright © 2006 John Wiley & Sons, Ltd.