Functional optical hemodynamic imaging of the olfactory cortex in normosmia subjects and dysosmia subjects.
CONCLUSIONS
These activated areas may be related to the orbitofrontal cortex, corresponding to olfactory cortices. This study shows that multichannel near-infrared spectroscopy (NIRS) enables the evaluation of brain activity of normosmia subjects and dysosmia subjects by olfactory stimulation.


OBJECTIVE
Objective olfactory testing is not common. NIRS has beenused before to study functional activations in various areas of the brain, but we wanted to investigate the difference in brain olfactory activity in normosmia subjects and dysosmia subjects using multi-channel NIRS (MNIRS).


METHODS
This study was conducted on eight normosmia subjects and five dysosmia subjects. We employed a 22-channel near-infrared spectroscopy device with eight light incident fibers and seven light detector fibers, each with an inter-optode distance of 2.5 cm on the frontal head. Isovaleric acid was used as the odor stimulant. We measured the change in oxyhemoglobin concentrations [oxyHb], deoxyhemoglobin concentrations [deoxyHb], and total hemoglobin concentrations [totalHb] from pre-baseline values. Furthermore, we divided the frontal cortex into four areas (right upper, left upper, right lower, left lower) and measured the activity in each area. Then, the changes in [oxyHb], [deoxyHb], and [totalHb] of normosmia subjects and dysosmia subjects were compared in each area.


RESULTS
In all normosmia subjects, isovaleric acid caused remarkable changes, especially in the lower areas of the frontal cortex. However, in all dysosmia subjects, isovaleric acid caused no changes.
Kobayashi
Eiji
E
Department of Otorhinolaryngology, Faculty of Medicine, Kagawa University, Kagawa, Japan. weston7d@yahoo.co.jp
Karaki
Masayuki
M
Kusaka
Takashi
T
Kobayashi
Ryuichi
R
Itoh
Susumu
S
Mori
Nozomu
N
D000293:Adolescent; D000328:Adult; D000368:Aged; D016022:Case-Control Studies; D005260:Female; D005625:Frontal Lobe / Q000378:metabolism; D045782:Hemiterpenes; D006454:Hemoglobins / Q000378:metabolism*; D006801:Humans; D008297:Male; D008875:Middle Aged; D000857:Olfaction Disorders / Q000378:metabolism*; D009833:Olfactory Pathways / Q000378:metabolism*; D010421:Pentanoic Acids; D019265:Spectroscopy, Near-Infrared
D045782:Hemiterpenes; D006454:Hemoglobins; D010421:Pentanoic Acids; C008216:isovaleric acid