| Sexual activity is of great significance to the survival and reproduction of both human being and other species.Meanwhile,sexual activity has animal and social attributes,whose underpinning neural mechanisms are extremely complex,involving components of cognition,emotion,motivation,inhibition and mediated by the autonomic nervous system.The male sexual dysfunction is a common male functional disorder.Erectile dysfunction(ED)is a highly prevalent male sexual dysfunction in China.It is characterized in the disability to gain or maintain adequate penile erection during sexual intercourses.ED does serious harm to suffers' physical and mental health.It also has serious negative impact on their family relationships and social life.Clinically,ED can be divided into organic erectile dysfunction and psychogenic erectile dysfunction(pED)according to the existence of organic lesions.Epidemiological survey showed that pED patients consist of 90% of ED population in youth,and compose of more than half of the population in middle-aged ED group.Nowadays,the studies on pED are still in its infancy and its pathogenesis has not been explicitly elucidated.Accordingly,no satisfactory treatment has been identified for pED and drug therapy did not show good effects in its clinical efficacy.Previous studies exploring the neural mechanism of pED focused on brain activity under visual tasks.By comparing the differences in brain response patterns between normal controls(NC)and pED patients under visual sexual stimulation,these studies initiated to investigate the possible neural mechanism in pED.However,our group hold a different view.After a thorough literature review on pED,no empirical data and previous studies on pED report impairment in the low order processing of sexual stimulus.Therefore,we suggest that pED patients may have defects in the high-level cognitive processing of sexual information.However,the high-level cognitive processing of sexual information is not limited to any specific sensory input modality,in this paper,we adopted the resting-state functional magnetic resonance imaging(f MRI),which is free of sensory input and investigated the neural mechanism of pED from multiple perspectives based on the resting-state brain activity in pED patients and matched NC.In our study,after rigorous participant inclusion procedure,27 pED patients and 27 NC were enrolled in this study.Previous studies show that the baseline issue is rudimentary in f MRI studies,particularly for studies adopting tasks,in that the changes in baseline brain activity may smear the spatial activation under task and bring biased results.Therefore,in this study,we started from the investigation of the baseline brain activity.Firstly,amplitude of lowfrequency fluctuation(ALFF)was used to investigate the baseline brain activity in pED patients,and significantly reduced baseline activity was observed in the right anterior insula(a INS).Secondly,in view that sexual response is mediated by spread brain regions rather than a single region,the region whose baseline changed,i.e.the right a INS,was used as the seed for further examination of the alterations in functional connectivity(FC),results elucidated the disrupted homogeneity within the right a INS and aberrant connection patterns between the right a INS and the right dorsolateral prefrontal cortex(dl PFC),as well as the right a INS and the right temporoparietal junction(TPJ)respectively in pED group,as compared with the NC group.Subsequently,in accordance with the changed functional connectivity pattern within the right a INS in pED group,we speculated that pED may be accompanied by changes in functional homogeneity in some brain regions.Therefore,we used the regional homogeneity(Re Ho)method and investigated the difference of functional regional homogeneity between pED and NC groups through the whole brain.Significant group-wise difference was observed in right a INS and right operculum.Finally,for all the aforementioned finding were happen to located in the right hemisphere of brain but previous studies show that laterality was not an issue in pED,we adopted the voxel-mirrored homotopic connectivity(VMHC)method and investigated the interaction pattern of homologous brain regions between hemispheres and significant erectile function related VMHC alteration was observed in caudate.In conclusion,our results demonstrated the aberrant baseline brain activity,disrupted insulacentered functional connectivity,changed functional homogeneity and interaction pattern of homologous brain regions between bilateral cerebral hemispheres in pED patients.We suggest that pED is likely to be related to the abnormal representation of internal bodily state or needs in the sexual context,which may lead to excessive inhibitory control of sexual responses.Last but not least,we propose that findings in this study may shed new light on the central mechanism of pED. |
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