A new study in mice and rats, led by researchers from NYU Grossman School of Medicine and University of Szeged in Hungary, found that restoring certain signals in a brain region that processes smells could counter depression.
The study, which was published online on May 9 in the journal Neuron, focused on nerve cells in the brain that emit electrical signals to transmit information. Researchers discovered that effective communication between brain regions requires groups of neurons to synchronize their activity patterns in repetitive periods called “gamma” oscillations, which are an important timing pattern for the encoding of complex information, potentially including emotions.
Depression is reflected in gamma oscillation changes in brain regions that manage the sense of smell, which have also been tied to emotions. To test this theory, the study authors shut down the function of the olfactory bulb using genetic and cell signaling techniques and observed a related increase in depression-like behaviors in study rodents. They then reversed these behaviors using a device that boosted gamma signals of the brain at their natural pace.
“Moving forward, we will be working to better understand this link in the bulb, and in the regions it connects to, as behavior changes,” says senior study author György Buzsáki, MD, PhD.
The researchers designed a reversible method to avert damage by using a single, engineered strand of DNA encapsulated in a harmless virus, which when injected into neurons in the olfactory bulbs of rodents caused the cells to build certain protein receptors on their surfaces. This allowed the researchers to selectively and reversibly switch off the communication between the olfactory bulb and partner brain regions. These tests revealed that chronic suppression of olfactory bulb signals, including gamma, not only induced depressive behaviors during the intervention, but for days afterward.
The researchers next used a custom-made device that recorded the natural gamma oscillations from the olfactory bulb and sent those paced signals back into the rodents’ brains as closed-loop electrical stimulation. The device was able to suppress gamma in healthy animals or amplify it. Feeding an amplified olfactory bulb signal back into the brains of depressed rats restored normal gamma function in the limbic system and reduced depressive behaviors by 40 percent.
The study was led by Orrin Devinsky, MD, professor in the Department of Neurology at NYU Langone, and director of its Comprehensive Epilepsy Center. Funding for the study was provided through grants from various sources.
Q: What is depression?
A: Depression is a common, severe psychiatric illness that affects a person’s mood and the way they think and feel. It can make it difficult for someone to carry out their day-to-day activities.
Q: What causes depression?
A: The causes of depression are not fully understood, but it is believed to be a combination of genetic, biological, environmental, and psychological factors.
Q: Can depression be cured?
A: Depression can be treated, but it is not always curable. Treatment options include medications, therapy, lifestyle changes, and other interventions.
Q: How can smelling scents help with depression?
A: The study found that restoring certain signals in a brain region that processes smells could counter depression. Researchers discovered that effective communication between brain regions requires groups of neurons to synchronize their activity patterns in repetitive periods called “gamma” oscillations, which are an important timing pattern for the encoding of complex information, potentially including emotions. Depression is reflected in gamma oscillation changes in brain regions that manage the sense of smell, which have also been tied to emotions.
