Differences in anosmic and normosmic group in bimodal odorant perception: a functional- MRI study

Area of Science:

• Neuroscience
• Sensory Science
• Olfactory Research

Background:

• Bimodal odorants activate both olfactory and trigeminal systems.
• Understanding the cerebral interaction between these systems is crucial for sensory perception.
• Previous research has not fully elucidated the neural basis of this interaction.

Purpose of the Study:

• To investigate the cerebral interaction between the olfactory and trigeminal systems.
• To determine how olfactory input modulates trigeminally mediated sensory information.
• To examine the effect of stimulus intensity on neural activation patterns.

Main Methods:

• Utilized menthol as a bimodal odorant at low and high concentrations.
• Employed a computer-controlled air-dilution olfactometer for precise stimulus delivery.
• Assessed brain activity using functional magnetic resonance imaging (fMRI) in normosmic and anosmic participants.
• Analyzed fMRI data using SPM5.

Main Results:

• Normosmic subjects showed activation in the anterior cingulate cortex (ACC), posterior cingulate cortex (PCC), prefrontal cortex (PFC), and cerebellum.
• Anosmic subjects activated the ACC and showed additional activation in the left parahippocampal gyrus.
• In controls, stimulus intensity modulated activation in the ACC, medial frontal gyrus, and cerebellum, which was absent in anosmic subjects.

Conclusions:

• The olfactory system significantly modulates trigeminally mediated information.
• Neural processing of stimulus intensity differs between individuals with and without olfactory function.
• These findings highlight the integrated nature of sensory processing in the brain.