Exploring brain functional connectivity in patients with taste loss: a pilot study

Purpose: In a previous neuroimaging study, patients with taste loss showed stronger activations in gustatory cortices compared to people with normal taste function during taste stimulations. The aim of the current study was to examine whether there are changes in central-nervous functional connectivity in patients with taste loss. Methods: We selected 26 pairs of brain regions related to taste processing as our regions of interests (ROIs). Functional magnetic resonance imaging (fMRI) was used to measure brain responses in seven patients with taste loss and 12 healthy controls as they received taste stimulations (taste condition) and water (water condition). The data were analysed using ROI-to-ROI functional connectivity analysis (FCA). Results: We observed weaker functional connectivity in the patient group between the left and right orbitofrontal cortex in the taste condition and between the left frontal pole and the left superior frontal gyrus in the water condition. Conclusion: These results suggested that patients with taste loss experience changes of functional connectivity between brain regions not only relevant to taste processing but also to cognitive functions. While further studies are needed, fMRI might be helpful in diagnosing taste loss as an additional tool in exceptional cases

Novel methods to assess olfactory processing

Research in olfaction is been quite diverse, for example with studies on semantics, brain activations, or distorted smells. Olfactory dysfunction can lead to reduced quality of life, poor dietary habits, sexual and/or mental dysfunctions. Especially in terms of the investigation of olfactory loss it is not only important to assess olfactory function with ratings subjectively assess but more objective measures should be considered. Use of EEG and fMRI has been quite well studied. I have focused my thesis on the use of newer or updated use of existing processing pipelines in order to understand olfaction in a better way

Novel methods to assess olfactory processing

Research in olfaction is been quite diverse, for example with studies on semantics, brain activations, or distorted smells. Olfactory dysfunction can lead to reduced quality of life, poor dietary habits, sexual and/or mental dysfunctions. Especially in terms of the investigation of olfactory loss it is not only important to assess olfactory function with ratings subjectively assess but more objective measures should be considered. Use of EEG and fMRI has been quite well studied. I have focused my thesis on the use of newer or updated use of existing processing pipelines in order to understand olfaction in a better way

Novel methods to assess olfactory processing

Research in olfaction is been quite diverse, for example with studies on semantics, brain activations, or distorted smells. Olfactory dysfunction can lead to reduced quality of life, poor dietary habits, sexual and/or mental dysfunctions. Especially in terms of the investigation of olfactory loss it is not only important to assess olfactory function with ratings subjectively assess but more objective measures should be considered. Use of EEG and fMRI has been quite well studied. I have focused my thesis on the use of newer or updated use of existing processing pipelines in order to understand olfaction in a better way

Subtle Differences in Brain Architecture in Patients with Congenital Anosmia

People suffering from congenital anosmia show normal brain architecture although they do not have functional sense of smell. Some studies in this regard point to the changes in secondary olfactory cortex, orbitofrontal cortex (OFC), in terms of gray matter volume increase. However, diffusion tensor imaging has not been explored so far. We included 13 congenital anosmia subjects together with 15 controls and looked into various diffusion parameters like FA. Increased FA in bilateral OFC confirms the earlier studies reporting increased gray matter thickness. However, it is quite difficult to interpret FA in terms of gray matter volume. Increased FA has been seen with recovery after traumatic brain injury. Such changes in OFC point to the plastic nature of the brain

Subtle Differences in Brain Architecture in Patients with Congenital Anosmia

People suffering from congenital anosmia show normal brain architecture although they do not have functional sense of smell. Some studies in this regard point to the changes in secondary olfactory cortex, orbitofrontal cortex (OFC), in terms of gray matter volume increase. However, diffusion tensor imaging has not been explored so far. We included 13 congenital anosmia subjects together with 15 controls and looked into various diffusion parameters like FA. Increased FA in bilateral OFC confirms the earlier studies reporting increased gray matter thickness. However, it is quite difficult to interpret FA in terms of gray matter volume. Increased FA has been seen with recovery after traumatic brain injury. Such changes in OFC point to the plastic nature of the brain.Funding Agencies|Projekt DEAL</p

Tractography indicates lateralized differences between trigeminal and olfactory pathways

Odorous sensations are based on trigeminal and olfactory perceptions. Both trigeminal and olfactory stimuli generate overlapping as well as distinctive activations in the olfactory cortex including the piriform cortex. Orbitofrontal cortex (OFC), an integrative center for all senses, is directly activated in the presence of olfactory stimulations. In contrast, the thalamus, a very important midbrain structure, is not directly activated in the presence of odors, but rather acts as a relay for portions of olfactory information between primary olfactory cortex and higher-order processing centers. The aims of the study were (1) to examine the number of streamlines between the piriform cortex and the OFC and also between the piriform cortex and the thalamus and (2) to explore potential correlations between these streamlines and trigeminal and olfactory chemosensory perceptions. Thirtyeight healthy subjects were recruited for the study and underwent diffusion MRI using a 3T MRI scanner with 67 diffusion directions. ROIs were adapted from two studies looking into olfaction in terms of functional and structural properties of the olfactory system. The "waytotal number" was used which corresponds to number of streamlines between two regions of interests. We found the number of streamlines between the piriform cortex and the thalamus to be higher in the left hemisphere, whereas the number of streamlines between the piriform cortex and the OFC were higher in the right hemisphere. We also found streamlines between the piriform cortex and the thalamus to be positively correlated with the intensity of irritating (trigeminal) odors. On the other hand, streamlines between the piriform cortex and the OFC were correlated with the threshold scores for these trigeminal odors. This is the first studying the correlations between streamlines and olfactory scores using tractography. Results suggest that different chemosensory stimuli are processed through different networks in the chemosensory system involving the thalamus.Funding Agencies|Takasago International Cooperation, Paris, France; DAAD (Deutscher Akademischer Austauschdienst/German Academic Exchange Service)</p

Functional connectivity patterns in parosmia

Abstract Objective Parosmia is a qualitative olfactory dysfunction presenting as “distorted odor perception” in presence of an odor source. Aim of this study was to use resting state functional connectivity to gain more information on the alteration of olfactory processing at the level of the central nervous system level. Methods A cross sectional study was performed in 145 patients with parosmia (age range 20–76 years; 90 women). Presence and degree of parosmia was diagnosed on the basis of standardized questionnaires. Participants also received olfactory testing using the “Sniffin’ Sticks”. Then they underwent resting state scans using a 3 T magnetic resonance imaging scanner while fixating on a cross. Results Whole brain analyses revealed reduced functional connectivity in salience as well as executive control networks. Region of interest-based analyses also supported reduced functional connectivity measures between primary and secondary olfactory eloquent areas (temporal pole, supramarginal gyrus and right orbitofrontal cortex; dorso-lateral pre-frontal cortex and the right piriform cortex). Conclusions Participants with parosmia exhibited a reduced information flow between memory, decision making centers, and primary and secondary olfactory areas