Synaptic integration in the periaqueductal grey circuit of defensive behaviour

• Applicant: Dr. Sabine Rühle
• Subject Area: Cognitive, Systems and Behavioural Neurobiology ; Sensory and Behavioural Biology ; Molecular Biology and Physiology of Neurons and Glial Cells
• Term: from 2014 to 2016
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 259603355

One of the main challenges in Neuroscience is to understand how neural circuits implement computations during behaviour. For example, how is incoming sensory information transformed into the appropriate behavioural output? Answering this question requires detailed knowledge on how individual neurons process information and convert synaptic input into action potential output. Neurons receive a plethora of synaptic inputs onto their dendritic tree, and recent in vitro experiments have shown that dendrites pre-process synaptic input before it reaches the action potential initiation site. This independent implementation of computations should allow individual neurons in vivo to perform highly complex information processing. In this project, I aim to investigate synaptic integration in a circuit underlying defensive behaviour in the mouse, and analyse how single neurons in the periaqueductal grey (PAG) contribute to the computations leading to defensive freezing behaviour. The PAG is part of a large network that includes the hypothalamus and the amygdala, and acts as a common path where ascending and descending information directing defensive behaviour converges. PAG neurons have a simpler structure compared to cells carrying out higher cognitive functions, yet have a prominent dendritic tree with a small number of branches. Neuronal activation in the PAG is a crucial step in the implementation of defensive responses, but little is known about what drives PAG neurons to fire. By combining behavioural, genetic, electrophysiological and optical techniques, I aim to address three specific questions: (1) How do PAG neurons active during defensive behaviour integrate excitatory signals? (2) How do inhibitory synapses set the excitability level of PAG neurons? (3) How does activation of the amygdala modulate the input-output transformation of PAG neurons active during freezing behaviour? The results of this study on dendritic integration in the PAG will advance our understanding of how neurons in a circuit critical for implementing basic behaviours process information and generate defensive responses.

• DFG Programme: Research Fellowships
• International Connection: United Kingdom
• Host: Tiago Branco, Ph.D.