Abstract
this study was conducted with the aim of neural representation of olfactory words in the conceptual metaphors of the sense of smell. For this purpose, a database of48 sentences related to the conceptual metaphors of the sense of smell and 48 sentences related to literal sentences was formed, and the processing of these sentences in the brain was investigated using functional magnetic resonance imaging. In this study, twenty-six subjects between the ages of20 to35, all healthy right-handed women participated, and their brain activities were recorded while facing the pictures of sentences. The statistical comparison between the brain function during the encounter with metaphors and literal sentences indicated that only during the processing of metaphors, the areas of the secondary sense of smell show activities in sensory-motor and perceptual representations. The activity of the orbitofrontal cortex (secondary olfactory area) in order to converge the information of olfactory, gustatory and visual modalities has been seen in other studies. Considering the lack of significant activity in the areas related to emotion processing as well as the primary olfactory areas, we believe that perhaps the lack of pleasantness of the sense of smell in metaphorical sentences is the reason for this.

1. Introduction 

People often like to use metaphorical expressions, for example, instead of "he constantly violates the rules of the deal" they use "his behavior in the deal reeks of fraud".Conceptual metaphor theory was first proposed by Lakoff and Johnson in 1980(1).
It has been reported that during olfactory processing, olfactory information go from the primary olfactory area to the orbitofrontal cortex (2). The way of brain processing related to the verbalization of the sense of smell in Persian sentences, especially metaphors, still needs a better understanding. The main hypothesis of this research is that the processing of olfactory words in olfactory metaphors relies on sensory-motor processes and activates the secondary olfactory areas, which will be different from reading verbal expressions.
Method
26women with Persian mother tongue with an average age of 24.32 years and a standard deviation of 4.82 years in the age range of 18-35 years participated in this experiment. This research has been approved and issued in accordance with the principles determined by the Declaration of Helsinki. The code of ethics of this research has been approved with the code of ethicsIR.UT.IRICSS.REC.1401.033. Forty-eight metaphorical sentences related to the sense of smell and forty-eight literal sentences were created by substituting related words that retain the same meaning. After structural imaging, imaging was performed at rest(with eyes open) for5 minutes. The test started on the monitor screen with a positive sign (+) for a fixed duration of 2 seconds. Each sentence appears in the center of the monitor for 4 seconds. Data were acquired using a 3-Tesla Siemens Magnetom Prisma MRI scanner. In functionalT2-weighted, the field of view is 196 mm and the size and phase images (field maps) are 35 slices per image with a thickness of 3 mm. and with voxel size:3x 3x3.5 mm, with a rotation angle of 90°,TR =2040 ms andTE =30 ms. Statistical analysis in this research was implemented bySPM12 software(3) in MATLAB version R2022b. In the SPM software, to find the desired significant areas in the whole brain analysis, P <0.001 in each condition and distinct areas between both conditions, voxel level threshold P <0.05 and cluster level threshold with Voxel number equal to30was proposed and this threshold value was obtained based on multiple comparison correction using FWE method. For each region of interest, theMNI coordinates of the voxel with the maximum t value are reported. See Table 1
Table 1. Example sentences of each condition

Note. The visual baseline is matched to the olfactory metaphor

2. Findings

Comparisons between both literal and metaphorical sentences conditions were examined for two lexical versus visual baseline conditions (olfactory metaphors and literal sentences>sequences with hashtags). Analysis in the contrast of literal sentences < olfactory metaphors lead to significant changes in the gyrus Right posterior/lateral orbit, right fusiform gyrus, right precentral, right insula, left posterior/middle occipital, left/right angular gyrus, left posterior and middle cingulate gyrus, right inferior frontal gyrus, right/left superior gyrus The frontal opercular part is straightened. In the analysis of the contrast of literal sentences>olfactory metaphors only the activity in the left and right fusiform gyrus, middle and upper temporal areas left/right middle/inferior occipital gyrus and left angular gyrus, left pereconeus were seen.

3. Discussion

The purpose of testing was whether the processing of metaphors relies on sensorimotor representations. In addition, our goal was to examine this case in Persian language, which has been less discussed. Three main findings related to our hypotheses:1- olfactory word processing activates the second olfactory region(2-4). 2- in comparison between olfactory metaphorical sentences and literal sentences, activation was seen in more areas for metaphors 3- No activity was observed in the fields related to emotions for the metaphorical sentences of the sense of smell. This research has examined neuroimaging findings based on olfactory-language cortical interactions, and orbitofrontal areas showed activity, which indicates a connection between olfactory and language cortices.The lack of activation of the primary olfactory cortex may be because, in general, sensorimotor simulations during language comprehension do not involve the primary cortex(2).

4. Ethical considerations

Compliance with ethical guidelines
The code of ethics of this research isIR.UT.IRICSS.REC.1401.033.
Contribution of authors
The experimental design was done byR.KH. Programming and data collection was done byM.A. Data processing and statistical analyzes were done by M.A and A.T.J. The initial version of the article was written byM.A and A.T.J and R.KH edited and reviewed the manuscript.
Funding
This research did not receive any specific funding from funding
Acknowledgments
We express our gratitude to Mrs. Ghaem Panah for her assistance in data collection and Mr. Mohsen Mobasseri for his assistance in data processing and to all the participants in this research.
Conflict of interest
There is no conflict of interest between the authors.