From Rachel Herz's quite interesting The Scent of Desire:
In one study that contrasted the trauma of being blinded or becoming anosmic [losing you sense of smell] after an accident, it was found that those who were blinded initially felt much more traumatized by their loss than those who had lost their sense of smell. But follow-up analyses on the emotional health of these patients one year later showed that the anosmics were faring much more poorly than the blind. The emotional health of anosmic patients typically continues to deteriorate with passing time, in some cases requiring hospitalization.
I cite some of Herz's work in my own book, including her charming experiment "A Naturalistic Study of Autobiographical Memories Evoked By Olfactory and Visual Cues: Testing the Proustian Hypothesis". As you can probably guess, the French novelist was right: there is something uniquely sentimental about the buttery whiff of a seashell-shaped cookie (or any other odor). This is because smell and taste are the only senses that connect directly to the hippocampus, the center of the brain's long-term memory. Their mark is primal and indelible. All our other senses (sight, touch and hearing) are first processed by the thalamus and only then sent along to the hippocampus. As a result, these senses are much less efficient at summoning up our past.
My wife lost most, if not all, of her sense of smell in an accident more than 20 years ago. She retains the sense of taste from her tongue, but has little or no sense of the flavors of food. Thus she usually strongly seasons food with salt or sugar before they taste right to her. However, she apparently relies on the memory of the flavors of food, and judges food taste similarly to the way she did before her injury. Some foods do not taste good to her, a judgement that might usually be expected to come from the odor of food. Maybe she has some remaining sense that works at an unconscious level.
The last line of your post caused me to recall a remark from someone I did work for years ago. It's a little on the sentimental side.
Although this man was a non-smoker, his mother asked him to light up a cigar at holiday gatherings--something he did obligingly. It seems that his father, by then deceased, had smoked cigars, and the mother actively wished to create the illusion, however fleeting, that the father was there among them.
Another glancing general thought: I have to wonder about the prevalence of advertising featuring the terms "home style" or "home cooking." This seems to me, as a non-Madison Avenue type, to be an obvious case of attempting to link a product with remembered fragrances that trigger positive emotional responses. Any thoughts?
During my neuroscience studies, I became fascinated by the emotional impact of smell. A couple of anecdotes added to my interest:
1. When walking down a street and encountering a woman wearing the same perfume as an ex-girlfriend, I was always amazed at how that smell would stir old memories of my ex, whom I hadn't seen for years.
2. After talking about the olfaction with an acquaintance of mine and relating the previous story, she told a similar one. She was diagnosed with breast cancer about 15 years back, and underwent treatment at the time. Everytime she went to the clinic, she would park in the same parking garage. And to this day, whenever she parks in a parking garage that smells similar to that one, she gets flashbacks of an obviously stressful period of her life.