Graduate Student, National Centre for Biological Sciences
Stress has debilitating effects on the physiology on an animal – often leading to conditions like Post-Traumatic Disorder (PTSD), where exposure to a single episode of severe stress or trauma leads to delayed symptoms including increase in anxiety and hyper-function of the amygdala. In a pre-clinical translational model of PTSD, a single, acute episode of stress in male rats causes a like-wise increase in anxiety and dendritic spines in the amygdala, 10 days after stress but not 1 day later. This suggests that the effects develop over time, hence prompting the question if the delayed effects in this model could be prevented by intervening after exposure to acute stress. We found that a single-dose intervention with a classical anxiolytic after stress prevented both behavioural and cellular changes from happening 10 days later. In addition, when acute stress was followed by another brief stress-exposure immediately afterwards, it showed similar preventive effects as well. The mechanism of these dual modes of prevention are currently being examined to better understand the possible approaches that could eventually translate to therapeutic intervention strategies.
Abstract: Tremendous progress has been made in basic neuroscience in recent decades. One area that has been especially successful is research on how the brain detects and responds to threats. Such studies have demonstrated comparable patterns of brain-behavior relationships underlying threat processing across a range of mammalian species, including humans. This would seem to be an ideal body of information for advancing our understanding of disorders in which altered threat processing is a key factor, namely, fear and anxiety disorders. But research on threat processing has not led to significant improvements in clinical practice. The authors propose that in order to take advantage of this progress for clinical gain, a conceptual reframing is needed. Key to this conceptual change is recognition of a distinction between circuits underlying two classes of responses elicited by threats: 1) behavioral responses and accompanying physiological changes in the brain and body and 2) conscious feeling states reflected in self-reports of fear and anxiety. This distinction leads to a "two systems" view of fear and anxiety. The authors argue that failure to recognize and consistently emphasize this distinction has impeded progress in understanding fear and anxiety disorders and hindered attempts to develop more effective pharmaceutical and psychological treatments. The two-system view suggests a new way forward.
Pub.: 10 Sep '16, Pinned: 23 Jun '17
Abstract: The amygdala has long been associated with emotion and motivation, playing an essential part in processing both fearful and rewarding environmental stimuli. How can a single structure be crucial for such different functions? With recent technological advances that allow for causal investigations of specific neural circuit elements, we can now begin to map the complex anatomical connections of the amygdala onto behavioural function. Understanding how the amygdala contributes to a wide array of behaviours requires the study of distinct amygdala circuits.
Pub.: 17 Jan '15, Pinned: 23 Jun '17
Abstract: In this review, we discuss the usefulness of the distinction between fear and anxiety. The clinical use of the labels is ambiguous, often defining one in terms of the other. We first consider what a useful, objective, and scientifically valid definition would entail and then evaluate several fear/anxiety distinctions that have been made in the neurobiological literature. A strong distinction should specify the difference in conditions that lead to fear versus anxiety. Additionally, fear and anxiety should generate distinct sets of behaviors. Ideally, the two states should be supported by distinguishable neuroanatomical circuits. Such a conceptualization would be consistent with the National Institute of Mental Health's Research Domain Criteria (RDoc). The majority of neurobiological approaches to the fear versus anxiety distinction fail to differentiate the two states in terms of behavior, often using the exact same behavioral measures as indicators. Of the two that do, only Predatory Imminence Theory provides a distinction both in terms of cause and effect. Indeed, that approach provides a ready distinction of anxiety, fear, and panic in terms of both antecedent conditions and response selection rules. Additionally, it appeals to distinct neural circuits to generate these modes of action.
Pub.: 20 Aug '15, Pinned: 23 Jun '17