title: Updating freeze: aligning animal and human research.
abstract: Freezing is widely used as the main outcome measure for fear in animal studies. Freezing is also getting attention more frequently in human stress research, as it is considered to play an important role in the development of psychopathology. Human models on defense behavior are largely based on animal models. Unfortunately, direct translations between animal and human studies are hampered by differences in definitions and methods. The present review therefore aims to clarify the conceptualization of freezing. Neurophysiological and neuroanatomical correlates are discussed and a translational model is proposed. We review the upcoming research on freezing in humans that aims to match animal studies by using physiological indicators of freezing (bradycardia and objective reduction in movement). Finally, we set the agenda for future research in order to optimize mutual animal-human translations and stimulate consistency and systematization in future empirical research on the freezing phenomenon.
authors.affiliation: Behavioural Science Institute (BSI), Radboud University Nijmegen, PO Box 9104, 6500 HE Nijmegen, The Netherlands. Electronic address: m.hagenaars@psych.ru.nl.
authors.forename: Muriel A
authors.initials: MA
authors.lastname: Hagenaars
authors.affiliation: SILS-CNS, University of Amsterdam, The Netherlands. Electronic address: m.s.oitzl@uva.nl.
authors.forename: Melly
authors.initials: M
authors.lastname: Oitzl
authors.affiliation: Behavioural Science Institute (BSI), Radboud University Nijmegen, PO Box 9104, 6500 HE Nijmegen, The Netherlands; Donders Institute for Brain, Cognition and Behaviour, Radboud University Nijmegen, The Netherlands. Electronic address: k.roelofs@donders.ru.nl.
authors.forename: Karin
authors.initials: K
authors.lastname: Roelofs
mesh_terms: D000818:Animals; D001008:Anxiety Disorders / Q000503:physiopathology* / Q000523:psychology; D005239:Fear / Q000502:physiology* / Q000523:psychology; D046352:Freezing Reaction, Cataleptic / Q000502:physiology*; D006801:Humans; D013315:Stress, Psychological / Q000503:physiopathology* / Q000523:psychology
keywords: Anxiety; Body sway; Freezing; Immobility; Orienting; Stabilometric platform; Stress