Exposure to Certain Fragrances During Sleep Dramatically Increases Cognitive Function: ScienceAlert

Of all the senses we love to indulge, scent is often neglected – but the right smells can be just what your brain needs to keep it spinning in old age.

Researchers at the University of California, Irvine have recently uncovered strong evidence that enriching the air with fragrances improves cognitive performance by strengthening a critical link between neurological areas involved in memory and decision-making.

Their experiment, involving 43 men and women aged 60 to 85, suggests cognitive decline and conditions such as dementia can be slowed by simply diffusing a different choice of perfume through the bedroom before bed each night.

Keeping the old gray matter stimulated as we age is critical to maintaining good cognitive health. This doesn’t just mean that we have to keep up with the daily crossword – it means that we have to spice up our surroundings with all kinds of sights and sounds that the brain can chew on.

For other animals, enriching the environment with odors has been shown to stimulate neuroplasticity, especially in tests involving animals with human-like symptoms for neurological disorders.

It is not exactly a stretch to think that humans could also benefit from experiencing a complex ‘fragrance landscape’. Physiologically speaking, our ability to detect smells deteriorate before our cognitive abilities begins to fall.

Losing this sense too correlates with a loss in brain cells, suggesting a strong link between smell and neurological function.

“The sense of air has the special privilege of being directly connected to the memory circuits of the brain,” say neurobiologist Michael Yassa.

“All the other senses are first routed through the thalamus. Everyone has experienced how powerful aromas are in evoking memories, even from a very long time ago. But unlike vision changes, which we treat with glasses and hearing aids for hearing loss, there have been no intervention for loss of smell.”

To determine whether cognitive decline can be rescued with this kind of sensory stimulation, Yassa and his colleagues provided 20 of the study’s recruits with a selection of natural oils containing fragrances of rose, orange, eucalyptus, lemon, peppermint, rosemary and lavender.

The rest of the group were provided with a ‘sham’ containing trace amounts of an odorant. All participants had to use one of the oils with a diffuser to perfume their home for two hours each night over a six-month period, rotating through their menu of scents.

A battery of neuropsychological tests was then used to compare the volunteers’ memory, verbal learning, planning and attention-shifting skills before and after the six-month trial.

Amazingly, there was a clear difference of 226 percent between the responses given by those exposed to a variety of scents and individuals in the control group. A scan of their brains also revealed a significant change in anatomy connects areas of the brain critical in memory and thinking in the test group.

As all the volunteers had similar healthy mental health, the researchers now aim to see if the results continue to hold for people who have already been diagnosed with some degree of cognitive loss.

Regardless of age or state of mind, giving your nose something to do when the lights go out and silence sets in isn’t exactly an unpleasant way to exercise the mind at night.

This study was published in Frontiers in Neuroscience.