Tonic Immobility and Freezing

Freeze for action: neurobiological mechanisms in animal and human freezing
Karin Roelofs
Donders Institute for Brain Cognition and Behaviour and Behavioural Science Institute, Radboud University Nijmegen, Kapittelweg 29, 6525 EN, Nijmegen, The Netherlands KR, 0000-0002-8863-8978
Abstract
Upon increasing levels of threat, animals activate qualitatively different defen- sive modes, including freezing and active fight-or-flight reactions. Whereas freezing is a form of behavioural inhibition accompanied by parasympatheti- cally dominated heart rate deceleration, fight-or-flight reactions are associated with sympathetically driven heart rate acceleration. Despite the potential relevance of freezing for human stress-coping, its phenomenology and neuro- biological underpinnings remain largely unexplored in humans. Studies in rodents have shown that freezing depends on amygdala projections to the brainstem (periaqueductal grey). Recent neuroimaging studies in humans have indicated that similar brain regions may be involved in human freezing. In addition, flexibly shifting between freezing and active defensive modes is critical for adequate stress-coping and relies on fronto-amygdala connections. This review paper presents a model detailing these neural mechanisms involved in freezing and the shift to fight-or-flight action. Freezing is not a pas- sive state but rather a parasympathetic brake on the motor system, relevant to perception and action preparation. Study of these defensive responses in humans may advance insights into human stress-related psychopathologies characterized by rigidity in behavioural stress reactions. The paper therefore concludes with a research agenda to stimulate translational animal–human research in this emerging field of human defensive stress responses.  This article is part of the themed issue ‘Movement suppression: brain mechanisms for stopping and stillness’.

Freeze, Flight, Fight, Fright, Faint: Adaptationist Perspectives on the Acute Stress Response Spectrum
Stefan Bracha, MD
CNS Spectr. 2004;9(9):679-685
ABSTRACT
This article reviews the existing evolutionary perspectives on the acute stress response habitual faintness and blood-injection-injury type-specific phobia (BIITS phobia). In this article, an alternative evolutionary perspective, based on recent advances in evolutionary psychology, is proposed. Specifically, that fear–induced faintness (eg, fainting following the sight of a syringe, blood, or following a trivial skin injury) is a distinct Homo sapiens- specific extreme-stress survival response to an inescapable threat. The article suggests that faintness evolved in response to middle paleolithic intra-group and inter-group violence (of con-specifics) rather than as a pan-mammalian defense response, as is presently assumed. Based on recent literature, freeze, flight, fight, fright, faint provides a more complete description of the human acute stress response sequence than current descriptions. Faintness, one of three primary physiological reactions involved in BIITS phobia, is extremely rare in other phobias. Since heritability estimates are higher for faintness than for fears or phobias, the author suggests that trait-faintness may be a useful complement to trait-anxiety as an endophenotype in research on the human fear circuitry. Some implications for the forthcoming Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition as well as for clinical, health services, and transcriptomic research are briefly discussed.

Adult male rape and sexual assault: Prevalence, re-victimisation and the tonic immobility response.
Coxell, Adrian W. and King, Michael B.
Sexual and Relationship Therapy, Vol 25(4), Nov, 2010. pp. 372-379.
Abstract:
Fifteen years ago we summarised research on what was known about the sexual assault of men and its effects. Here we present evidence from epidemiological research that demonstrates that the sexual assault of men is observed in many countries—demonstrating the widespread existence of the sexual assault of men and the need for further research. We also present research to show that the association between child sexual abuse and sexual assault in adult females has also been found in a variety of studies on men. Finally, we also consider the phenomenon of tonic immobility as this has important implications for the well-being of victims of sexual assault.