Effects of olfactory stimulation with isovaleric acid on brain activation in informed and naïve conditions: a functional MRI study.
OBJECTIVE
To investigate the differences in regions of brain activation in response to olfactory stimulation by functional magnetic resonance imaging in conditions of prior warning of an odor and without.


METHODS
Participants were 17 normal right-handed volunteers; 8 participants received prior warning of the odor (informed condition) and 9 participants were not pre-warned (naïve condition). The odorant used was isovaleric acid.


RESULTS
In the informed condition with prior warning, activation was observed in the putamen extending to the insula, amygdala, and inferior frontal gyrus, and there was instant reification of the odor, while in the naïve condition without prior warning, activation was observed in the anterior cingulate cortex, entorhinal cortex, putamen and inferior frontal gyrus, and recognition of the odor was difficult.


CONCLUSIONS
These results suggest that the condition prior to olfactory stimulation, i.e., with or without prior warning, can affect recognition and regions of brain activation in response to olfactory stimulation using isovaleric acid. Differences in recognition and regions of brain activation between both conditions could be associated with response latencies, or degree of attention, expectation and/or concentration.
Murata
Yoriko
Y
Department of Radiology, Kochi Medical School, Japan. muratay@kochi-u.ac.jp
Okutani
Fumino
F
Nakahira
Mitsuhiko
M
Ushida
Takahiro
T
Ikemoto
Tatsunori
T
Yokoe
Isamu
I
Takeda
Taizo
T
Kaba
Hideto
H
Tani
Toshikazu
T
Ogawa
Yasuhiro
Y
D000293:Adolescent; D000328:Adult; D001288:Attention / Q000502:physiology*; D001921:Brain / Q000503:physiopathology*; D001931:Brain Mapping; D002540:Cerebral Cortex / Q000503:physiopathology; D003463:Cues; D004292:Dominance, Cerebral / Q000502:physiology; D018728:Entorhinal Cortex / Q000503:physiopathology; D005260:Female; D005625:Frontal Lobe / Q000503:physiopathology; D006179:Gyrus Cinguli / Q000503:physiopathology; D045782:Hemiterpenes; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008279:Magnetic Resonance Imaging; D008297:Male; D009415:Nerve Net / Q000503:physiopathology; D009812:Odorants; D010421:Pentanoic Acids; D011699:Putamen / Q000503:physiopathology; D012903:Smell / Q000502:physiology*
D045782:Hemiterpenes; D010421:Pentanoic Acids; C008216:isovaleric acid