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Fear circuits

Summary: Who’s afraid of the big, bad wolf? Fear processing circuit connectivity strength and anxiety changes across the lifespan

Recent diffusion tensor imaging (DTI) research has demonstrated a subcortical pathway in the human brain proposed to mediate fast orienting of visual attention to fearful emotion (e.g. Tammietto, Pullens, De Gelder, Weiskrantz & Goebel, 2012). One challenge faced when proposing novel white matter pathways in the healthy human brain, is to validate pathway anatomy functionally with behaviour. DTI data from our lab has demonstrated this proposed threat-processing pathway, forming connections between the superior colliculus and the amygdala, via the pulvinar nucleus of the thalamus. We are now interested in finding new ways to functionally link pathway anatomy with behaviour. Using DTI data and questionnaire measures of anxiety from the public NKI-RS dataset, this project aims to confirm the function of the proposed threat-mediating pathway in healthy humans (across young and older age groups) by investigating a link between pathway connection strength (using fractional anisotropy measures) and individual differences in fear processing behaviour (using anxiety scores in the State-Trait Anxiety Inventory).

A bit of background to the study:

Patients with unconscious blindsight show intact responses to emotionally valenced stimuli, proposing that fear may be processed via a subcortical connection, bypassing the cortex (De Gelder, Morris & Dolan, 2005; Morris, Ohman, & Dolan, 1999). Convincing evidence of an accurate fear processing circuit remains to be established in humans. A circuit connecting white matter axons between the superior colliculus (SC) and the amygdala, via the pulvinar nucleus of the thalamus has been proposed to be a candidate subcortical threat-mediating channel (Tammietto, Pullens, De Gelder, Weiskrantz & Goeberl, 2012). Challenges of Diffusion Tensor Imaging (DTI) tractography (e.g. crossing fibres connecting spurious fibres) renders it ambitious to conclude that a pathway authentically exists in the healthy human brain solely based on DTI results and without relating structure to function. Therefore, this project aims to functionally validate fear processing pathway anatomy with behaviour.

Project Aims:

The first aim of this project is to virtually dissect the proposed threat pathway with probabilistic DTI tractography in humans. Secondly, this project aims to validate the proposed pathway by confirming its function in humans. Potential links between pathway connection strength and individual differences in fear processing behaviour will be investigated. This will be done by investigating whether high levels of anxiety correlate with stronger pathway connectivity. Furthermore, older adults demonstrate lower levels of anxiety in comparison to young adults (Brenes, 2006). Hence, the final aim of this project is to investigate whether younger adults possess a stronger threat-processing pathway in comparison to older adults.

Outcomes and implications:

Behavioural correlates of the virtually dissected threat pathway will allow for a possible link to be established between the anatomy of threat processing pathways and threat processing behavior, further providing a greater insight into age-related changes in anatomy and behaviour across the life span.

What can I do?

You can come to Brainhack and collaborate on this project by helping with the following: 1) provide new ideas on functionally validating novel DTI anatomical tracts with behaviour 2) help with virtual dissection of pathways using DTI tractography 3) offer expertise advice on the anatomy of fear processing circuits in the brain

How can I join?

Brainhack attendees or anyone who is interested are welcome to collaborate! Please e-mail Kristin Koller (kristinkoller1@gmail.com).

Who are the members?

Kristin Koller & Brainhack attendees

Submitted by: Kristin Koller
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