Emotions tag our experiences and act as waypoints in how we steer our behavior, but they seem to be subjective. Avoiding danger and pursuing rewards is essential for successful navigation through a complex environment, and thus for survival, but why are some people afraid of harmless spiders yet most are not afraid of incredibly dangerous horses?

The search for the neural correlate of emotions fascinates neuroscientists and psychologists – emotions are a central part of our mental selves.

Researchers have set out to understand how emotions are generated in the brain. Just like seeing or hearing, they believe our feelings are based on the activity of nerve cells or neurons and can be established commonly in all people the way physical senses are. They note that emotions are characterized by the activity of multiple areas of the brain: the neocortex, brain stem and an almond-shaped region in the limbic system called amygdala, and they believe together these components form a complex network of neuronal circuits whose detailed structure and function are not yet understood. But can be.

The Research Institute of Molecular Pathology (IMP) in Vienna is using mice as an experimental model and they seek to map the emotional circuitry within this network and to study how activity in these circuits gives rise to emotions. Mice are able to show basic emotional behaviors and have a brain-anatomy sufficiently similar to ours, which will allow them to draw conclusions that might be relevant for humans as well.

Cartography of the Brain May Lead To Circuit Therapies for the Future

To address the origin of emotions, neuroscientists will visualize neuronal circuit elements by taking advantage of the characteristics of certain viruses, such as the rabies pathogen. These viruses infect specific nerve cells and migrate along them to the brain. A fluorescent protein, engineered into the virus in advance, leaves a visible trace of light. This “viral circuit mapping” is able to highlight networks of interacting neurons with cartographic precision.

For a functional analysis of the tagged circuits, the scientists then employ optogenetic technology. These methods make it possible to selectively switch groups of neurons on or off, using visible light like a remote control.
The project will also address the question of how genes and pharmaceutical substances affect the activity of neuronal circuits and influence emotions. The researchers hope to gain valuable insights into emotional dysfunctions such as post-traumatic stress or anxiety disorders. Ultimately, this could lead to the development of specific “circuit therapies” to treat psychiatric disorders more selectively and with less side effects.