Implicit but not explicit extinction to threat‐conditioned stimulus prevents spontaneous recovery of threat‐potentiated startle responses in humans

Abstract

IntroductionIt 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.MethodsTwo 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.ResultsOn 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 electrodermal activity.ConclusionOur results suggest that implicit extinction using CFS might facilitate the modulation of the affective 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 psychotherapies.

Alpha-band EEG suppression as a neural marker of sustained attentional engagement to conditioned threat stimuli

“…top-down driven mechanisms. This might be an interesting topic for future research, testing whether there are differences in attention-related neural activity between implicit vs explicit extinction learning and the effects on phenomena such as extinction retrieval, spontaneous recovery, fear reinstatement and renewal ( Maren and Holmes, 2016 ; Oyarzun et al. , 2019 ).…”

Systematic Review of Studies on Subliminal Exposure to Phobic Stimuli: Integrating Therapeutic Models for Specific Phobias

“…The lack of a decrease in brain responses to subliminal phobic stimuli following CBT suggests that this approach does not impact on the regulation of automatic attentional processes (Lipka et al, 2014) and could explain the significant vulnerability to relapse that persists following successful elimination of fear via CBT (LeDoux, 1994;Vervliet et al, 2013). Actually, subliminal stimulations have a role in activating (and properly habituating) non-conscious stimulus-processing mechanisms and in fact recent evidence supports the idea that subliminal stimulus exposure may be an effective means of reducing relapse (Oyarzún et al, 2019). As a summary, there are hints that responses to subliminal stimuli survive standard interventions involving overt stimuli exposure only, and paradigms integrating also subliminal stimuli exposure might be more effective.…”

“All we have to fear is fear itself”: Paradigms for reducing fear by preventing awareness of it.

“…Unlike the catastrophic consequences of exposure that phobic persons believe will happen, these aversive arousal and subjective fear responses are sure to happen, acting like the electric shocks (the UCS) in fear conditioning experiments. These initial, but inevitable and highly aversive fear responses to exposure are naturally occurring, internal UCSs that powerfully reinforce "Stimulus → Fear" associations-a positive feedback loop that, as studies have repeatedly shown, interferes with extinction learning (Figure 4; Hauner et al, 2013;Norrholm et al, 2015;Oyarzún et al, 2019;Siegel et al, 2017Siegel et al, , 2022Siegel & Weinberger, 2012).…”

“…Nonconscious extinction studies based on unconscious exposure to the fear CS yielded direct evidence of extinction learning during late extinction (Bachar-Avnieli et al, 2023), fear reinstatement , spontaneous recovery (Bachar-Avnieli et al, 2023;Oyarzún et al, 2019), and during the unconscious state of SWS (Gvozdanovic et al, 2023;Hauner et al, 2013;.…”

“…Unconscious exposure studies based on fear conditioning may have similarly demonstrated reconsolidation in humans. Unconscious exposure to fear CSs significantly reduced conditioned SCRs during both extinction and spontaneous recovery (Bachar-Avnieli et al, 2023), and it similarly reduced the recovery of fear-potentiated startle 1 day after extinction (Oyarzún et al, 2019). Thus, unconscious exposure to the fear CS may reduce conditioned fear by reducing physiological arousal associated with the conditioned fear memory (reconsolidation).…”