The birth, death and resurrection of avoidance: a reconceptualization of a troubled paradigm

Abstract

Research on avoidance conditioning began in the late 1930s as a way to use laboratory experiments to better understand uncontrollable fear and anxiety. Avoidance was initially conceived of as a two-factor learning process in which fear is initially acquired through Pavlovian aversive conditioning (so-called fear conditioning), and then behaviors that reduce the fear aroused by the Pavlovian conditioned stimulus are reinforced through instrumental conditioning. Over the years, criticisms of both the avoidance paradigm and the two-factor fear theory arose. By the mid 1980s, avoidance had fallen out of favor as an experimental model relevant to fear and anxiety. However recent progress in understanding the neural basis of Pavlovian conditioning has stimulated a new wave of research on avoidance. The new work has fostered new insights into contributions of not only Pavlovian and instrumental learning, but also habit learning, to avoidance, and has suggested that the reinforcing event underlying the instrumental phase should be conceived in terms of cellular and molecular events in specific circuits rather than in terms of vague notions of fear reduction. In our approach, defensive reactions (freezing), actions (avoidance) and habits (habitual avoidance) are viewed as being controlled by unique circuits that operate non-consciously in the control of behavior, and that are distinct from the circuits that give rise to conscious feelings of fear and anxiety. These refinements, we suggest, overcome older criticisms, justifying the value of the new wave of research on avoidance, and offering a fresh perspective on the clinical implications of this work.

Prefrontal circuits signaling active avoidance retrieval and extinction

“…Thus, PL may be in direct communication with BLA to express avoidance memories, similar to Pavlovian fear conditioning (Cho et al 2013). Projections from basal amygdala to VS have been shown to mediate active avoidance (Ramirez et al 2015), supporting the idea that BLA is a central hub for defensive reactions (LeDoux et al 2017). What then might be the function of PL inputs to BLA?…”

Noradrenergic Regulation of Central Amygdala in Aversive Pavlovian-to-Instrumental Transfer

“…The underlying psychological nature of avoidance behavior is not very well understood (LeDoux et al, 2016). While this form of learning is sensitive to elements of negative reinforcement such as response feedback and shock omission (Kamin, 1956), other nonreinforcement based accounts have been proposed.…”

“…This is likely because control subjects in this study also showed very little freezing to the CS, as is commonly observed in aversive PIT (Campese et al, 2013). Many published reports find that over the course of avoidance training, freezing CRs are attenuated as avoidance behavior emerges (LeDoux et al, 2016). This is true when avoidance training includes an explicit signal (Cain and LeDoux, 2007; Choi et al, 2010; Moscarello and LeDoux, 2013) as well as in unsignaled avoidance learning paradigms such as that used in the current paper where freezing to the context is reduced over training (Fig.…”

Brain circuit dysfunction in post-traumatic stress disorder: from mouse to man

“…A growing literature describes the brain circuits involved in determining whether an animal will respond to a threat-associated stimulus with passive avoidance (freezing; see also the dissociative subtype of PTSD, Box 2) or more active avoidance strategies (such as running towards a safe chamber) 59 . Both strategies can be maladaptive if used excessively or in a fashion in which the individual has no control; however, there is evidence to suggest that active avoidance strategies can dampen responses to subsequent stressors 60 .…”