Foraging for foundations in decision neuroscience: insights from ethology

Modern decision neuroscience offers a powerful and broad account of human behaviour using computational techniques that link psychological and neuroscientific approaches to the ways that individuals can generate near-optimal choices in complex controlled environments. However, until recently, relatively little attention has been paid to the extent to which the structure of experimental environments relates to natural scenarios, and the survival problems that individuals have evolved to solve. This situation not only risks leaving decision-theoretic accounts ungrounded but also makes various aspects of the solutions, such as hard-wired or Pavlovian policies, difficult to interpret in the natural world. Here, we suggest importing concepts, paradigms and approaches from the fields of ethology and behavioural ecology, which concentrate on the contextual and functional correlates of decisions made about foraging and escape and address these lacunae

Induction and Expression of Fear Sensitization Caused by Acute Traumatic Stress

Fear promotes adaptive responses to threats. However, when the level of fear is not proportional to the level of threat, maladaptive fear-related behaviors characteristic of anxiety disorders result. Post-traumatic stress disorder develops in response to a traumatic event, and patients often show sensitized reactions to mild stressors associated with the trauma. Stress-enhanced fear learning (SEFL) is a rodent model of this sensitized responding, in which exposure to a 15-shock stressor nonassociatively enhances subsequent fear conditioning training with only a single trial. We examined the role of corticosterone (CORT) in SEFL. Administration of the CORT synthesis blocker metyrapone prior to the stressor, but not at time points after, attenuated SEFL. Moreover, CORT co-administered with metyrapone rescued SEFL. However, CORT alone without the stressor was not sufficient to produce SEFL. In these same animals, we then looked for correlates of SEFL in terms of changes in excitatory receptor expression. Western blot analysis of the basolateral amygdala (BLA) revealed an increase in the GluA1 AMPA receptor subunit that correlated with SEFL. Thus, CORT is permissive to trauma-induced changes in BLA function

Midbrain circuits for defensive behaviour

Survival in threatening situations depends on the selection and rapid execution of an appropriate active or passive defensive response, yet the underlying brain circuitry is not understood. Here we use circuit-based optogenetic, in vivo and in vitro electrophysiological, and neuroanatomical tracing methods to define midbrain periaqueductal grey circuits for specific defensive behaviours. We identify an inhibitory pathway from the central nucleus of the amygdala to the ventrolateral periaqueductal grey that produces freezing by disinhibition of ventrolateral periaqueductal grey excitatory outputs to pre-motor targets in the magnocellular nucleus of the medulla. In addition, we provide evidence for anatomical and functional interaction of this freezing pathway with long-range and local circuits mediating flight. Our data define the neuronal circuitry underlying the execution of freezing, an evolutionarily conserved defensive behaviour, which is expressed by many species including fish, rodents and primates. In humans, dysregulation of this 'survival circuit' has been implicated in anxiety-related disorders