Disrupted Olfactory Integration in Schizophrenia: Functional Connectivity Study

Abstract

BackgroundEvidence for olfactory dysfunction in schizophrenia has been firmly established. However, in the typical understanding of schizophrenia, olfaction is not recognized to contribute to or interact with the illness. Despite the solid presence of olfactory dysfunction in schizophrenia, its relation to the rest of the illness remains largely unclear. Here, we aimed to examine functional connectivity of the olfactory bulb, olfactory tract, and piriform cortices and isolate the network that would account for the altered olfaction in schizophrenia.MethodsWe examined the functional connectivity of these specific olfactory regions in order to isolate other brain regions associated with olfactory processing in schizophrenia. Using the resting state functional MRI data from the Center for Biomedical Research Excellence in Brain Function and Mental Illness, we compared 84 patients of schizophrenia and 90 individuals without schizophrenia.ResultsThe schizophrenia group showed disconnectivity between the anterior piriform cortex and the nucleus accumbens, between the posterior piriform cortex and the middle frontal gyrus, and between the olfactory tract and the visual cortices.ConclusionsThe current results suggest functional disconnectivity of olfactory regions in schizophrenia, which may account for olfactory dysfunction and disrupted integration with other sensory modalities in schizophrenia.

Olfaction, among the First Senses to Develop and Decline

“…They observed that schizophrenic people appear to have a reduced assortment of pleasant odors compared to healthy subjects and they report smells as less good over the controls [193,196,198], being in line with other reports [66,193,196,198,199]. Functional and structural alterations of the olfactory circuitry have been observed in schizophrenic patients using fMRI analysis [200] and electro olfactogram (EOG) measuring olfactory evoked potentials (EP) [194,201]. At the biomarker level, cell culture preparations from nasal epithelium showed an alteration in G protein-coupled receptors (GPCRs) cascade, likely affecting the olfactory processing observed in this psychiatric disorder [202].…”

Association of cardiorespiratory fitness on interhemispheric hippocampal and parahippocampal functional connectivity

“…Data preprocessing and statistical analyses were conducted using FMRIB Software Library as well as Analysis of Functional NeuroImages (AFNI). The preprocessing stream has been described in our previous study (Kiparizoska & Ikuta, ). Briefly, skull stripping and segmentation were performed on the structural volume, as well as its co‐registration to the EPI volumes.…”

Estimation of Dynamic Bivariate Correlation Using a Weighted Graph Algorithm

“…We used Stroop task fMRI data ( ) [ 20 ], since activation patterns for the Stroop task is relatively well known. Preliminary data processing followed previous publication [ 23 ]. Using FMRIB Software Library (FSL) as well as Analysis of Functional NeuroImages (AFNI), anatomical volume was skull stripped, segmented (gray matter, white matter and CSF), and registered to the MNI 2mm standard brain.…”