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Enhancing brain health in older adults: Olfactory stimulation via aromatherapy shows promise in cognitive function preservation. neurosciencenews.com
The limbic system – a complex system of nerves and networks in the brain – supports many brain functions, including memory, emotion, and learning. The olfactory system is the only sensory system directly linked to this critical brain region. A new study shows that olfactory stimulation via aromatherapy may enhance limbic system function, potentially preserving or improving cognitive function in older adults.
Researchers assigned 23 older adults (aged 60 to 85) to an olfactory-enriched or control group. Using an aromatherapy diffuser, they exposed the enriched group to seven essential oil scents (rose, orange, eucalyptus, lemon, peppermint, rosemary, and lavender – one per night) for two hours per night for six months. They exposed the control group to a similar routine but with minimal amounts of scent. The participants underwent neuropsychological assessments and functional magnetic resonance imaging (fMRI) scans at the study’s outset and again after six months.
The assessments revealed that the participants who received olfactory enrichment demonstrated a 226 percent improvement on learning and memory tests. Notably, only six of the 12 participants improved, five stayed the same, and one did worse, calling the data into question. The fMRIs showed that the enriched group also exhibited enhanced function in the left uncinate fasciculus – an area of the brain that plays a crucial role in memory, language, emotion, and memory retrieval.
These findings suggest that olfactory enrichment administered at night improves cognitive and neural functioning and may provide an effective and low-effort means to improve brain health. This study was very small, so larger trials are needed to confirm the benefits of aromatherapy on cognitive health.
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A Western diet impairs odor-related learning and memory in mice. www.sciencedaily.com
Loss of olfactory system function – the sense of smell – is an early indicator of cognitive decline in people with type 2 diabetes and obesity. A new study in mice demonstrates the negative effects of a high-fat, high-sugar Western dietary pattern on odor-related learning and memory.
Smell is an important regulator of behavior and memory, especially in non-human animals like mice. Olfactory system dysfunction may be due to decreased neurogenesis in the olfactory regions of the brains. In this way, changes in smell may signal decreased neurogenesis in other areas of the brain, which may indicate cognitive decline and Alzheimer’s disease progression.
The investigators fed mice either standard chow, a high-fat diet (54 percent of calories from fat), or a Western diet (42 percent of calories from fat, 34 percent of calories from sugar) for eight months. They measured body weight, blood glucose, olfactory learning and memory, and cellular mechanisms of smell.
After just three months of consuming a Western diet, mice showed declines in odor-related learning and memory. Weight gain and loss of glucose control were similar between the mice eating the Western and high-fat diets, but higher than among the mice eating the standard chow. After eight months, the mice consuming the Western and high-fat diets exhibited a diminished sense of smell and impaired olfactory learning and memory. However, the authors were unable to detect cellular changes related to this outcome.
These findings add to a growing number of studies investigating the role of diet and obesity in cognitive decline. The authors encourage future researchers to investigate the interactions between olfactory and endocrine systems in people with obesity and type 2 diabetes.