Researchers have recently discovered that subjects report having more emotionally pleasant dreams when they smell the scent of roses while dreaming. Conversely, subjects who experienced the scent of rotten eggs while dreaming reported more negatively charged dreams. Actually, subjects tended to rate their dreams more positively when the aroma was pleasant.
Each subject was tested with three different odours; roses, rotten eggs, and no odour at all. Oddly, "there was hardly any kind of a dream dealing with smelling and tasting". And, it seemed that the more impacted your mood is by a smell while awake, the more so it affects you in dreamland.
Tubes were attached to the nostrils of 15 healthy women in their twenties where an olfactometer pumped constant streams of air into their noses and a ten second shot of a specific odour during REM periods.
How exactly does the brain smell?
Essentially, smell enters the nose and confronts the cell body dendrites of some 10,000 sensory neurons. The odour molecules bind to receptors on a few different classes of neurons, which are, in effect, randomly located in the nose. The binding of the scent alters the electrical properties of these neurons down their axons, which extend to the olfactory bulb. The axons from these activated neurons synapse to a few glomeruli (globular tangle of axons and dendrites) in the olfactory bulb. The synapsing of the activated axons at these glomeruli sends signals, which are transmitted to the brain areas such as the olfactory cortex, hippocampus, amygdala, and hypothalamus in the limbic system, which is involved with emotional behaviour and memory.
The following is an interesting article that explains the olfactory system in greater depth: How the olfactory system makes sense of scents
A few questions come to mind after reading about this new research. I wonder how this new information might differ for people with brain injuries to areas of the brain associated with smell or even those with nasal problems. Also, could this really mean that we could all sleep better with scented air fresheners in our bedrooms?