Sensitization and aversive conditioning: Effects on the startle reflex and electrodermal responding (original) (raw)
Related papers
Startle potentiation: Shock sensitization, aversive learning, and affective picture modulation
Behavioral Neuroscience, 1998
This study investigated the size of, and relationship between, different modulatory effects of aversive stimulation on the acoustic startle reflex. This reflex is potentiated by shock exposure and associative shock conditioning (in animals and human volunteers) and unpleasant pictures (in human volunteers). In this study, dramatic sensitization of the probe-startle response was observed after shock exposure but not after a control task. Magnitude of sensitization was significantly larger than associative shock conditioning and picture modulation effects (also significant). Sensitization and conditioning scores showed modest, significant correlations with one another but not with picture modulation scores, consistent with animal data showing that partially overlapping brain mechanisms (i.e., amygdaloid-reticular projections) mediate these effects. The present results also indicate that sensitization of startle in human volunteers is a relatively more robust defensive response to aversive stimulation.
The fear potentiated startle effect
Integrative Physiological and Behavioral Science, 1991
A differential conditioning study examined whether an acoustic startle probe, presented during extinction of an aversively conditioned visual stimulus, potentiated the reflex eyeblink response in humans and whether this potentiation varied with the change in affective valence of the conditioned stimulus. Sixty college students were randomly assigned to view a series of two slides, depicting either tmpleasant/highly arousing, unpleasant/moderate arousing, neutral/calm, pleasant/moderate arousing or pleasant/hlghly arousing scenes and objects (duration: 8 see). During preconditioning (8 trials) and extinction (24 trials) acoustic startle probes (white noise bursts [50 ms; 95 dBA] were administered during and between slide presentation). During acquisition (16 trials) CS+ was reinforced by an electric shock. Startle response magnitudes significantly increased from preconditioning to extinction and were substantially larger to CS+. Conditioned startle reflex augmentation linearly increased with the pleasantness of the slides. Furthermore, subjects showed a greater post-conditioning increase of judged aversiveness to slides that they had previously reported to be more pleasant, exactly paralleling the startle reflex results.
Aversive associative conditioning of prepulses in a startle inhibition paradigm
Psychophysiology, 2009
Prepulse inhibition of startle (PPI) represents an automatic mechanism that reflects sensorimotor gating and early attention processes. PPI neither is the consequence of conscious behavioral modulation nor does it depend on learning and conditioning. However, pairing of weak tones and aversive startle stimuli during PPI testing may induce associative learning. Thus, in the present study (n 5 60) we tested whether prepulses may be subject to aversive conditioning. Eyeblink EMG and electrodermal responses to intense (100 dB) acoustic stimuli, presented either alone or preceded by weak tones (prepulses, 50 ms, 70 dB, SOA 5 120 ms), were measured. We found that after strong contingent pairing of weak tones with startle stimuli (PPI paradigm) intense versions of these tones induced significantly larger eyeblink and skin conductance responses than did never paired control tones. We conclude that during PPI testing, prepulses may be subject to aversive conditioning.
Extinction in fear conditioning: Effects on startle modulation and evaluative self-reports
Psychophysiology, 1998
A basic feature of human evaluative conditioning is that the reported acquired valence of a previously neutral conditioned stimulus~CS! that has been paired with a valenced unconditioned stimulus~US!, is resistant to extinction. The present study investigated whether startle modulation, sometimes presented as an index of acquired valence, reflected this basic feature. In a differential fear conditioning paradigm~n ϭ 38! with an electrocutaneous stimulus as the US, a strong extinction manipulation was conducted by removing the US-electrodes and by extended extinction trials. At the end of extinction, the results corroborated previous findings of evaluative conditioning in that the reported valence for CSϩ was still more negative than for CSϪ, despite disappearance of the differential skin conductance responses. However, startle modulation did not show resistance-to-extinction. Results were discussed in terms of recent conceptualizations of extinction.
Startle reactivity and anxiety disorders: aversive conditioning, context, and neurobiology
Biological Psychiatry, 2002
The aim of this article is to review studies on human anxiety using the startle reflex methodology and to apply the literature on context conditioning in rats to interpret the results. A distinction is made between cued fear (as in specific phobia), a phasic response to an explicit threat cue, and anxiety, a more sustained and future-oriented response not linked to a specific discrete cue. Experimentally, contextual fear, as opposed to cued fear, may best reflect the feeling of aversive expectation about potential future dangers that characterizes anxiety. Following a brief description of the neurobiology of cued fear and context conditioning, evidence is presented showing that anxious patients are overly sensitive to threatening contexts. It is then argued that the degree to which contextual fear is prompted by threat depends on whether the danger is predictable or unpredictable. Consistent with animal data, unpredictable shocks in humans result in greater context conditioning compared to predictable shocks. Because conditioning promotes predictability, it is proposed to use conditioning procedures to study the development of appropriate and inappropriate aversive expectations. Cued fear learning is seen as an adaptive process by which undifferentiated fear becomes cue-specific. Deficits in cued fear learning lead to the development of nonadaptive aversive expectancies and an attentional bias toward generalized threat. Lacking a cue for threat, the organism cannot identify periods of danger and safety and remains in a chronic state of anxiety. Factors that may affect conditioning are discussed.
Additive effects of threat-of-shock and picture valence on startle reflex modulation
PloS one
The present study examined the effects of sustained anticipatory anxiety on the affective modulation of the eyeblink startle reflex. Towards this end, pleasant, neutral and unpleasant pictures were presented as a continuous stream during alternating threat-of-shock and safety periods, which were cued by colored picture frames. Orbicularis-EMG to auditory startle probes and electrodermal activity were recorded. Previous findings regarding affective picture valence and threat-ofshock modulation were replicated. Of main interest, anticipating aversive events and viewing affective pictures additively modulated defensive activation. Specifically, despite overall potentiated startle blink magnitude in threat-of-shock conditions, the startle reflex remained sensitive to hedonic picture valence. Finally, skin conductance level revealed sustained sympathetic activation throughout the entire experiment during threat-compared to safety-periods. Overall, defensive activation by physical threat appears to operate independently from reflex modulation by picture media. The present data confirms the importance of simultaneously manipulating phasic-fear and sustained-anxiety in studying both normal and abnormal anxiety.
Biological Psychology, 2006
Previous research has shown that the startle reflex is potentiated during experimentally induced anxiety (fear-potentiated startle). In the present study, the magnitude and time course of the startle blink reflex were examined among 35 undergraduates scoring one standard deviation above (n = 14) or below (n = 21) the mean in a self-report measure of sensitivity to punishment (SP) in a paradigm involving the anticipation of electric shocks. Contrary to our predictions, SP did not relate to differences in the magnitude or in the time course of fear-potentiated startle. Our data do not support an association between this individual differences variable and the fear-potentiated startle.
Frontiers in Behavioral Neuroscience, 2014
There is conflicting evidence as to whether awareness is required for conditioning of the skin conductance response (SCR). Recently, Schultz and Helmstetter (2010) reported SCR conditioning in contingency unaware participants by using difficult to discriminate stimuli. These findings are in stark contrast with other observations in human fear conditioning research, showing that SCR predominantly reflects contingency learning. Therefore, we repeated the study by Schultz and Helmstetter and additionally measured conditioning of the startle response, which seems to be less sensitive to declarative knowledge than SCR. While we solely observed SCR conditioning in participants who reported awareness of the contingencies (n = 16) and not in the unaware participants (n = 18), we observed startle conditioning irrespective of awareness. We conclude that SCR but not startle conditioning depends on conscious discriminative fear learning.
Conditioned fear extinction and reinstatement in a human fear-potentiated startle paradigm
Learning & Memory, 2006
The purpose of this study was to analyze fear extinction and reinstatement in humans using fear-potentiated startle. Participants were fear conditioned using a simple discrimination procedure with colored lights as the conditioned stimuli (CSs) and an airblast to the throat as the unconditioned stimulus (US). Participants were extinguished 24 h after fear conditioning. Upon presentation of unsignaled USs after extinction, participants displayed significant fear reinstatement. In summary, these procedures produced robust fear-potentiated startle, significant CS+/CS− discrimination, within-session extinction, and significant reinstatement. This is the first demonstration of fear extinction and reinstatement in humans using startle measures.
Implicit extinction, 2018
INTRODUCTION: It has long been posited that threat learning operates and forms under an affective and a cognitive learning system that is supported by different brain circuits. A primary drawback in exposure-based therapies is the high rate of relapse that occurs when higher order areas fail to inhibit responses driven by the defensive circuit. It has been shown that implicit exposure of fearful stimuli leads to a long-lasting reduction in avoidance behavior in patients with phobia. Despite the potential benefits of this approach in the treatment of phobias and posttraumatic stress disorder, implicit extinction is still underinvestigated. Methods: Two groups of healthy participants were threat conditioned. The following day, extinction training was conducted using a stereoscope. One group of participants was explicitly exposed with the threat‐conditioned image, while the other group was implicitly exposed using a continuous flash suppression (CFS) technique. On the third day, we tested the spontaneous recovery of defensive responses using explicit presentations of the images. Results: On the third day, we found that only the implicit extinction group showed reduced spontaneous recovery of defensive responses to the threat‐conditioned stimulus, measured by threat‐potentiated startle responses but not by the electro-dermal activity. Conclusion: Our results suggest that implicit extinction using CFS might facilitate the modulation of the effective component of fearful memories, attenuating its expression after 24 hr. The limitations of the CFS technique using threatful stimuli urge the development of new strategies to improve implicit presentations and circumvent such limitations. Our study encourages further investigations of implicit extinction as a potential therapeutic target to further advance exposure‐based psychotherapy.