Abstract
The right orbitofrontal cortex (rOFC) has been proposed as the region where conscious olfactory perception arises; however, evidence supporting this hypothesis has all been collected from neuroimaging and lesion studies in which only correlation and not a temporal pattern can be established. Continuous theta burst stimulation (cTBS) causes a reversible disruption of cortical activity and has been used successfully to disrupt orbitofrontal activity. To overcome intrinsic limitations of current experimental research, a crossover, double-blind, prospective and longitudinal study was carried out in which cTBS was applied over the rOFC to evaluate its effect on odorant stimuli detection. All subjects received real and sham cTBS. Experimental procedures were done in two different sessions with a separation of at least one week between them to avoid carryover and learning effects. A total of 15 subjects completed the experiment, and their data were included in the final analysis (10 women, 5 men, mean age 22.40 ± 3.41). Every session consisted of two different measures of the conscious olfactory perception task: A baseline measure and one 5 min after cTBS/sham. Compared to baseline, marks in the olfactory task during the sham cTBS session increased (p = 0.010), while marks during the real cTBS session decreased (p = 0.017). Our results support the hypothesis that rOFC is an important node of a complex network required for conscious olfactory perception to arise. However, the exact mechanism that explains our results is unclear and could be explained by the disruption of other cognitive functions related to the rOFC.
Highlights
Crick and Koch (1990) first proposed the neural correlates of consciousness as a means to explain conscious experiences
It is theorized that the endpoint integration right orbitofrontal cortex (rOFC) and Conscious Olfactory Perception cortex of conscious olfactory perception is the three-layered piriform cortex (Merrick et al, 2014), which would set the neural correlate of olfactory consciousness in the paleocortex
Variables that could affect the outcome of the study did not differ between session type
Summary
Crick and Koch (1990) first proposed the neural correlates of consciousness as a means to explain conscious experiences. The correlation between rOFC activation and conscious olfactory perception was first described by Zatorre et al (1992); thereafter, evidence from multiple neuroimaging studies (Kringelbach and Rolls, 2004; Gottfried and Zald, 2005; Seubert et al, 2013) and lesion studies have supported this relationship (Zatorre and Jones-Gotman, 1991; Li et al, 2010). Contradictory evidence exists regarding rOFC and conscious olfactory perception: direct cortical electrical stimulation via subdural electrodes over rOFC failed to produce positive olfactory perception in children with epilepsy (Kumar et al, 2012); and not all subjects with rOFC damage have olfactory impairment (Jones-Gotman and Zatorre, 1988)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
