Ebb and Flow of Norepinephrine Colors Emotion

Press play on your earliest happy memory.  Your presence is transported to the past, where you feel temperature change, see younger versions of family members interact and even smell the succulent aromas around you.  A vivid experience drenches the senses and embosses an indelible memory on the brain's surface. Why do some remember (and even dream) in exquisite sensory detail, while others watch only monochromatic versions of their past? The answer lies in their genes.

Specifically, a mutation.  The ADRA2b gene codes for a specific receptor on which  the neurotransmitter and hormone norepinephrine (NE) attaches.  Like a key in a lock, NE unlocks the brain's ability to concentrate, increasing focus and preserving an exact memory of the event.   Usually, an emotionally evocative one.  The mutated ADRA2b gene alters the shape of the lock, such that NE no longer fits. 

The mutation allows large amounts of NE to affect other parts of the brain, which in turn increase perceptual vividness, a phenomenon dubbed by researchers as "emotionally enhanced vividness" (EEV).  

The question a recent study investigated is, does this mutation affect neural activity and contribute to EEV? Previous research suggests an abundance of NE arouses the visual cortex and in turn the eyes, veritably flushing the world with color.  To test this theory, participants with and without the receptor mutation were placed in an MRI scanner and given the following task.

Standard images were scrambled and blurred (or had noise added) by a certain percentage. The participant was asked to look at the scrambled picture then at the original, and finally compare the amount of noise between the first and second.  In essence, the researchers were testing how well participants with the mutation could see the blurred picture, contrasted to the ones without the mutation.  What scientists observed was incredible.  

Those with the mutated ADRA2b gene mentally lifted the photo out of the noise and focused on its colors, shapes and size, indicating a drastically different perceptual experience as compared to the others.

Seeing the world though a vastly more colorful filter is just the beginning. Increased activation in the frontal cortex further proves that NE modulates the emotional response and localizes attention to encode the memory in precise detail.

The graph above shows a striking difference between the ventral medial prefrontal cortex (VMPFC) brain activation in participants with no receptor mutation (left) and those with the mutation (right).

The graph above shows a striking difference between the ventral medial prefrontal cortex (VMPFC) brain activation in participants with no receptor mutation (left) and those with the mutation (right).

Further, an overabundance of NE in the amygdala increase its activity, allowing for heightened emotions.  You know, goose-bump type feelings while watching the sunset. Previous research indicates possessing this mutation also enhances emotional memory of traumatic experiences, coalescing sensory details into enduring and intrusive flashes.  Finding that individual genetic differences account for a drastic difference in how emotional experiences are registered (and thus recorded) could suggest a targeted future treatment through gene therapy.

Until then, those with the mutation can enjoy the sublime effect of their plight: awe-inspiring feelings in the smallest of details. 

ResearchBlogging.org Todd, R., Ehlers, M., Muller, D., Robertson, A., Palombo, D., Freeman, N., Levine, B., & Anderson, A. (2015). Neurogenetic Variations in Norepinephrine Availability Enhance Perceptual Vividness Journal of Neuroscience, 35 (16), 6506-6516 DOI: 10.1523/JNEUROSCI.4489-14.2015