Abnormal Spontaneous Neural Activity Research Articles

Altered spontaneous neuronal activity and functional connectivity pattern in primary angle-closure glaucoma: a resting-state fMRI study.

To explore the alterations of spontaneous neuronal activity and functional connectivity pattern using fractional amplitude of low-frequency fluctuation (fALFF) and functional connectivity (FC) in patients with primary angle-closure glaucoma (PACG) and fALFF relationship with the glaucoma clinical indices. Forty-two PACG patients and 21 normal controls were enrolled in this study. Resting-state functional magnetic resonance imaging was firstly analyzed by fALFF and brain regions with altered fALFF between groups were selected as seeds for the further FC analysis. The relationships between fALFF/FC values of abnormal regions and ophthalmological measures, including mean deviation of visual field (MDVF) and retinal nerve fiber layer (RNFL) thickness, were also analyzed. Compared with NC, PACG had significant lower fALFF values in the left cuneus, left middle temporal gyrus, right middle temporal gyrus, and right precentral gyrus, while higher fALFF values in the bilateral superior frontal gyrus (P < 0.05 after correction). Furthermore, PACG showed increased FC between left cuneus and bilateral superior frontal gyrus/bilateral posterior cingulate gyrus; between left middle temporal gyrus and bilateral superior frontal gyrus; and between right middle temporal gyrus and bilateral insular (P < 0.05 after correction). In addition, in the PACG group, the mean fALFF values of the left cuneus were positively correlated with MDVF (R = 0.419, P = 0.005) and RNFL thickness (R = 0.322, P = 0.038). Meanwhile, the mean fALFF values of bilateral superior frontal gyrus were negatively correlated with MDVF (R = - 0.454, P = 0.003) and RNFL thickness (R = - 0.556, P < 0.001). PACG exhibited abnormal spontaneous neural activity and connectivity in several brain regions mainly associated with visual and visual-related functions. In addition, the fALFF values of the left cuneus and bilateral superior frontal gyrus may be complementary biomarkers for assessing the disease severity.

Fractional amplitude of low-frequency fluctuations in retinal vein occlusion: a resting-state fMRI study

Objective: To investigate the altered spontaneous brain activity in patients with retinal vein occlusion (RVO) during the resting state. Methods: A case-control study. Forty-five patients with RVO [24 males and 21 females; age, (51.24±5.86) years] diagnosed from May 2018 to July 2019 in Renmin Hospital of Wuhan University were recruited in the RVO group. Meanwhile, forty-three healthy controls [19 males and 24 females; age, (49.79±7.31) years] who were closely matched in age and sex to patients with RVO were recruited in the healthy control group. Each subject underwent a whole-brain resting-state functional magnetic resonance imaging scan to detect the values of fractional amplitude of low-frequency fluctuations (fALFF). The altered spontaneous brain activity between RVO patients and healthy controls were analyzed. The intra-and inter-group comparisons of two sets of fALFF values were conducted using one-sample t-test and two-sample t-test, respectively. Results: Compared with the healthy control group, the fALFF values of RVO patients were significantly changed. The fALFF values of left cerebellum (-0.68±0.48, t=3.8081), right cerebellum (-0.79±0.47, t=4.590), right brainstem (-0.57±0.50, t=3.964) and left insula (-0.22±0.27, t=3.587) increased, while the fALFF values of right calcarinesulcus (0.60±0.72, t=-3.521), right thalamus (-0.68±0.43, t=-3.846) and left lingual gyrus (-0.12±0.33, t=-3.876) decreased. The differences were statistically significant (voxel-level P<0.01, Gaussian random field correction, cluster-level P<0.05). Conclusions: Patients with RVO have abnormal spontaneous neural activity in multiple brain areas, including visual pathways and emotion-cognition processing regions. Moreover, there may be compensatory brain function enhancement in local brain areas. The results provide new insights into the understanding of the mechanism for the occurrence and development of RVO.(Chin J Ophthalmol, 2020, 56:266-271).

Abnormal Spontaneous Neural Activity of the Central Auditory System Changes the Functional Connectivity in the Tinnitus Brain: A Resting-State Functional MRI Study.

ObjectiveAn abnormal state of the central auditory system (CAS) likely plays a large role in the occurrence of phantom sound of tinnitus. Various tinnitus studies using resting-state functional MRI (RS-fMRI) have reported aberrant spontaneous brain activity in the non-auditory system and altered functional connectivity between the CAS and non-auditory system. This study aimed to investigate abnormal functional connections between the aberrant spontaneous activity in the CAS and the whole brain in tinnitus patients, compared to healthy controls (HC) using RS-fMRI.Materials and MethodsRS-fMRI from 16 right-ear tinnitus patients with normal hearing (TNHs) and 15 HC individuals was collected, and the time series were extracted from different clusters of a CAS template, supplied by the Anatomy Toolbox of the Statistical Parametric Mapping software. These data were used to derive the smoothed mean amplitude of low-frequency fluctuation (smALFF) values and calculate the relationship between such values and the corresponding clinical data. In addition, clusters in the CAS identified by the smALFF maps were set as seed regions for calculating and comparing the brain-wide connectivity between TNH and HC.ResultsWe identified the different clusters located in the left higher auditory cortex (HAC) and the right inferior colliculus (IC) from the smALFF maps that contained increased (HAC) and decreased (IC) activity when the TNH group was compared to the HC group, respectively. The value of increased smALFF cluster in the HAC was positively correlated with the tinnitus score, but the decreased smALFF cluster in the IC was not correlated with any clinical characters of tinnitus. The TNH group displayed increased connectivity, compared to the HC group, in brain regions that encompassed the left IC, bilateral Heschl gyrus, bilateral supplementary motor area, right insula, bilateral superior temporal gyrus, right middle temporal gyrus, left hippocampus, left amygdala, and right supramarginal gyrus.ConclusionTinnitus may be linked to abnormal spontaneous activity in the HAC, which can arise from the neural plasticity induced from the increased functional connectivity between the auditory network, cerebellum, and limbic system.

Assessment of cerebral low-frequency oscillations in patients with retinal vein occlusion: a preliminary functional MRI study.

There is increasing evidence that patients with retinal vein occlusion exhibit cerebral vascular changes and are at an increased risk of stroke. However, it remains unknown whether patients with retinal vein occlusion exhibit changes in intrinsic brain activity. This study investigated intrinsic brain activity changes in patients with retinal vein occlusion by assessing the amplitude of low-frequency fluctuations. Forty-five patients with retinal vein occlusion (22 men, 23 women, mean age 56.55 ± 6.97 years) and 43 healthy controls (13 men, 30 women; mean age 53.53 ± 8.19 years) closely matched in age, sex, and education level underwent resting-state MRI scans. The amplitude of low-frequency fluctuation method was used to compare intrinsic brain activity between the two groups. Compared with healthy controls, patients with retinal vein occlusion exhibited significantly lower amplitude of low-frequency fluctuation values in the left middle occipital gyrus, right middle occipital gyrus, and right calcarine. However, patients with retinal vein occlusion showed significantly higher amplitude of low-frequency fluctuations in the bilateral cerebellum 6, right hippocampus, left insula, and left fusiform (voxel-level P < 0.01, Gaussian random field correction, cluster-level P < 0.05). Our results demonstrated that patients with retinal vein occlusion showed abnormal spontaneous neural activities in the visual cortices, cerebellum, and Papez circuit, which might indicate impaired vision, cognition, and emotional function in patients with retinal vein occlusion. These findings offer important insights into the neural mechanism of retinal vein occlusion.

Abnormal spontaneous neural activity in the medial prefrontal cortex and right superior temporal gyrus correlates with anhedonia severity in obsessive-compulsive disorder

BackgroudConverging evidence indicated the presence of clinically significant anhedonia in patients with obsessive-compulsive disorder (OCD). Studying anhedonia and its neural correlates in OCD may be beneficial in understanding the pathophysiology and treatment of OCD. However, the neural mechanisms that underlie anhedonia in OCD still remain unclear. The present study was designed to bridge this research gap by using resting-state functional magnetic resonance imaging (fMRI). Methods29 OCD patients with anhedonia (OCD-AH), 31 OCD patients with normal hedonia (OCD-NH), and 30 healthy controls (HC) received the fMRI scan. The low-frequency fluctuation (ALFF) approach was applied to compare spontaneous neural activity among the three groups. Relationships between the regional ALFFs and anhedonia levels were examined in OCD patients. ResultOCD-AH and OCD-NH manifested overlapping but partially distinct brain alterations. Notably, compared to OCD-NH, the OCD-AH showed decreased ALFF in right superior temporal gyrus (STG) and increased ALFF in medial prefontal cortex (MPFC). Moreover, ALFF values in the right STG were negatively correlated with social anhedonia severity, and ALFFs in the MPFC were positively correlated with both physical and social anhedonia severity in patients with OCD. LimitationsRelatively small sample size; ALFF could not provide more holistic information of brain network. ConclusionThe present study revealed that abnormal spontaneous neural activity in MPFC is associated with both physical and social anhedonia, while altered intrinsic brain function in right STG is specifically associated with social anhedonia in OCD. These findings contribute to our understandings of the neurobiological mechanisms underlying anhedonia in OCD

Abnormal spontaneous neural activity of brain regions in patients with primary blepharospasm at rest

BackgroundPrimary blepharospasm (BSP) is characterized by excessive involuntary eyelid spasms without significant morphological brain abnormalities. Its neural bases remain unclear. Resting-state functional magnetic resonance imaging (rs-fMRI) is a powerful tool for exploring cerebral function mechanisms in BSP. MethodsTwo subject groups (24 patients with BSP and 24 healthy controls) underwent rs-fMRI scans. The rs-fMRI images were analyzed using the regional homogeneity (ReHo) method to assess the local features of spontaneous brain activity. Correlation analysis was carried out to explore the relationship between the ReHo values of abnormal brain areas and clinical variables including illness duration, symptom severity, and depression/anxiety symptoms. ResultsRelative to healthy controls, patients with BSP showed significantly decreased ReHo in the left superior temporal pole/left insula, left calcarine cortex, and bilateral superior medial frontal gyrus (mSFG), and increased ReHo in the bilateral supplementary motor area (SMA). There were no significant correlations between ReHo values in these brain regions and clinical variables in the patients. ConclusionsOur results suggest that abnormal spontaneous brain activity in multiple brain regions not limited to the basal ganglia may be trait alterations in the patients, which provides more insights into the pathogenesis of BSP.

Frequency-dependent neural activity in primary angle-closure glaucoma.

ObjectiveIn this study, we aimed to investigate the frequency-dependent spontaneous neural activity in primary angle-closure glaucoma (PACG) using the amplitude of low-frequency fluctuations (ALFF) method.Patients and methodsIn total, 52 PACG individuals (24 males and 28 females) and 52 normal-sighted controls (NS; 24 males and 28 females) who were closely matched in age, sex, and education underwent resting-state magnetic resonance imaging scans. A repeated-measures ANOVA and post hoc two-sample t-tests were conducted to analyze the different ALFF values in two different frequency bands (slow-4, 0.027–0.073 Hz and slow-5, 0.010–0.027 Hz) between the two groups. Pearson’s correlation analysis was conducted to reveal the relationship between the mean ALFF values and clinical variables in the PACG group.ResultsCompared to the NS group, the PACG group had high ALFF values in the right inferior occipital gyrus and low ALFF values in the left middle occipital gyrus, left precentral gyrus, and left postcentral gyrus in the slow-4 band. The PACG group had high ALFF values in the right inferior occipital gyrus and low ALFF values in the left inferior parietal lobule, left postcentral gyrus, and right precentral/postcentral gyrus in the slow-5 band. Specifically, we found that the abnormal ALFF values in the bilateral posterior cingulate gyrus and bilateral precuneus were higher in the slow-4 than in the slow-5 band, whereas ALFF in the bilateral frontal lobe, right fusiform, and right cerebellum posterior lobe were higher in the slow-5 than in the slow-4 band. The greater mean ALFF values of the right inferior occipital gyrus were associated with smaller retinal nerve fiber layer thickness and greater visual fields in PACG group in the slow-4 band.ConclusionOur results highlighted that individuals in the PACG group showed abnormal spontaneous neural activities in the visual cortices, sensorimotor cortices, frontal lobe, frontoparietal network, and default mode network at two frequency bands, which might indicate impaired vision and cognition and emotion function in PACG individuals. These findings offer important insight into the understanding of the neural mechanism of PACG.

Abnormal regional spontaneous neural activity in visual pathway in retinal detachment patients: a resting-state functional MRI study.

ObjectiveThe aim of the study was to investigate changes of brain neural homogeneity in retinal detachment (RD) patients using the regional homogeneity (ReHo) method to understand their relationships with clinical features.Materials and methodsA total of 30 patients with RD (16 men and 14 women), and 30 healthy controls (HCs) (16 men and 14 women) closely matched in age and sex were recruited. Resting-state functional magnetic resonance imaging scans were performed for all subjects. The ReHo method was used to investigate the brain regional neural homogeneity. Patients with RD were distinguished from HCs by receiver operating characteristic curve. The relationships between the mean ReHo signal values in many brain regions and clinical features in RD patients were calculated by Pearson correlation analysis.ResultsCompared with HCs, RD patients had significantly decreased ReHo values in the right occipital lobe, right superior temporal gyrus, bilateral cuneus and left middle frontal gyrus. Moreover, we found that the mean ReHo signal of the bilateral cuneus showed positive relationships with the duration of the RD (r=0.392, P=0.032).ConclusionThe RD patients showed brain neural homogeneity dysfunction in the visual pathway, which may underline the pathological mechanism of RD patients with acute vision loss. Besides, the ReHo values can reflect the progress of the RD disease.

Relationship between function and resting state functional magnetic resonance imaging amplitude of low-frequency fluctuations in childhood and adolescence-first-onset obsessive-compulsive disorder

Objective To investigate the characteristics and relationship of cognitive function and resting state functional magnetic resonance imaging(fMRI) amplitude of low-frequency fluctuations (ALFF)in childhood and adolescence-first-onset obsessive-compulsive disorder(OCD). Methods Twenty-four childhood and adolescence-first-onset OCD patients (patient group) and thirty-three age/gender/education-matched healthy controls (healthy control group) were enrolled in this study.The participants′ cognitive function was tested with trail making test (TMT), symbol coding, Hopkins verbal learning test-revised (HVLT-R), brief visuospatial memory test-revised (BVMT-R), verbal fluency test (VF), digital span test, maze test and Stroop test.Then a resting-state fMRI scan was conducted for each participant.Amplitude of low-frequency fluctuation approach was used to explore the diffe-rences of resting-state brain function between patients and controls, and analyze the significant brain regions by adopting t test.The cognitive functions of patients and healthy control group in the significant brain regions were compared by using Pearson correlation analysis. Results The patient group had lower scores than healthy control group in symbol coding, BVMT-R and digital span test, and the differences were statistically significant [(45.24±10.32)scores vs.(56.85±9.57) scores, (21.94±6.99)scores vs.(30.58±3.92) scores, (64.06±20.00) scores vs.(78.03±18.08) scores; t=3.96, 4.90, 2.50; all P<0.05]. Corrected by Alphasim, patient group showed significantly increased ALFF in the left and right temporal lobe, left and right posterior lobe of cerebellum, right middle temporal gyrus, but ALFF decreased in the area of left and right lenticula, left putamen compared with the healthy control group (all P<0.05 ). The patients group showed that TMT scores were positively correlated with the value of ALFF in the right temporal lobe (r=0.67), and color scores were positively correlated with the value of ALFF in the right middle temporal gyrus (r=0.53), but colour scores were negatively correlated with the value of ALFF in the right temporal lobe (r=-0.54); the healthy control group showed that BVMT-R and digital span test scores were positively correlated with the value of ALFF in the left temporal lobe (r=0.47, 0.41), but digital span test scores were negatively correlated with the value of ALFF in the right temporal lobe (r=-0.49), and colour scores were negatively correlated with the value of ALFF in the left temporal lobe (r=-0.35), while word and color-word scores were negatively correlated with the value of ALFF in the right middle temporal gyrus (r=-0.39, -0.36); the correlation coefficient above had statistical significance (all P<0.05). Conclusions The childhood and adolescence-first-onset OCD patients had cognitive impairment, including speed of processing, visual learning and memory, working memory; and the patients showed abnormal spontaneous neural activity at some brain regions.The cognitive dysfunction may be associated with abnormal spontaneous neuronal activity in childhood and adolescence-first-onset OCD. Key words: Obsessive-compulsive disorder; Child; Adolescent; Cognitive function; Functional magnetic resonance imaging; Amplitude of low-frequency fluctuation

Network-wide oscillations in the parkinsonian state: alterations in neuronal activities occur in the premotor cortex in parkinsonian nonhuman primates

A number of studies suggest that Parkinson's disease (PD) is associated with alterations of neuronal activity patterns in the basal-ganglia-thalamocortical circuit. There are limited electrophysiological data, however, describing how the premotor cortex, which is involved in movement and decision-making, is likely impacted in PD. In this study, spontaneous local field potential (LFP) and single unit neuronal activity were recorded in the dorsal premotor area of nonhuman primates in both the naïve and parkinsonian state using the 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) model of parkinsonism. In both animals, we observed a shift of power in LFP power spectral densities (1-350 Hz) from higher to lower frequency bands; parkinsonism resulted in increased power in frequencies <8 Hz and decreased power at frequencies >30 Hz. A comparable but not identical trend was observed in the power spectral analysis of single unit spike trains: alpha power increased in both animals and gamma power decreased in one; power in other frequency bands remaining unchanged. Although not consistent across animals, we also observed changes in discharge rates and bursting activity. Overall, the LFP and single unit analysis suggest that abnormalities in premotor neural activity are a feature of parkinsonism, although specific details of those abnormalities may differ between subjects. This study further supports the concept that PD is a network disorder that induces abnormal spontaneous neural activities across the basal-ganglia-thalamocortical circuit including the premotor cortex and provides foundational knowledge for future studies regarding the relationship between changes in neuronal activity in this region and the development of motor deficits in PD.NEW & NOTEWORTHY This study begins to fill a gap in knowledge regarding how Parkinson's disease (PD) may cause abnormal functioning of the premotor cortex. It is novel as the premotor activity is examined in both the naïve and parkinsonian states, in the same subjects, at the single unit and LFP level. It provides foundational knowledge on which to build future studies to explore the relationships between premotor activities and specific parkinsonian motor and cognitive deficits.

Resting-state functional MRI of abnormal baseline brain activity in young depressed patients with and without suicidal behavior

BackgroundSuicide among youth is a major public health challenge, attracting increasing attention. However, the neurobiological mechanisms and the pathophysiology underlying suicidal behavior in depressed youths are still unclear. The fMRI enables a better understanding of functional changes in the brains of young suicide attempters with depressive disorder through detecting spontaneous neural activity. The purpose of this study was to identify the relationship between abnormalities involving local brain function and suicidal attempts in depressed youths using resting-state fMRI (RS-fMRI). MethodThirty-five depressed youths aged between 15 and 29 years with a history of suicidal attempts (SU group), 18 patients without suicidal attempts (NSU group) and 47 gender-, age- and education-matched healthy controls (HC) underwent psychological assessment and R-fMRI. The differences in fractional amplitude of low-frequency fluctuation (ALFF) among the three groups were compared. The clinical factors correlated with z-score ALFF in the regions displaying significant group differences were investigated. The ROC method was used to evaluate these clusters as markers to screen patients with suicidal behavior. ResultsCompared with the NSU and HC groups, the SU group showed increased zALFF in the right superior temporal gyrus (r-STG), left middle temporal gyrus (L-MTG) and left middle occipital gyrus (L-MOG). Additionally, significantly decreased zALFF values in the L-SFG and L-MFG were found in the SU group compared with the NSU group, which were negatively correlated with BIS scores in the SU group. Further ROC analysis revealed that the mean zALFF values in these two regions (sensitivity=83.3% and specificity=71.4%) served as markers to differentiate the two patient subtypes. ConclusionThe SU group had abnormal spontaneous neural activity during the resting state, and decreased activity in L-SFG and L-MFG was associated with increased impulsivity in SU group. Our results suggested that abnormal neural activity in these brain regions may represent a potential neurobiological diathesis or predisposition to suicidal behavior in youth depression.

Frequency-dependent alterations in regional homogeneity in major depression

Previous studies using resting-state functional magnetic resonance imaging (fMRI) have found abnormal spontaneous neural activity in patients with major depressive disorder (MDD). Yet, the frequency-dependent neural activity in MDD is largely unknown. Here, we used resting-state fMRI and regional homogeneity (ReHo) methods to investigate spontaneous neural activity in specific frequency bands of 31 MDD patients and 31 age-, gender- and education-matched healthy controls. We examined spontaneous neural activity in three frequency bands: slow-4 (0.027–0.073Hz), slow-5 (0.010–0.027Hz), and the typical band (0.01–0.08Hz). Compared to controls, MDD patients showed increased ReHo in the middle frontal gyrus (MFG) and decreased ReHo in the fusiform and postcentral gyrus at the typical band. Importantly, MDD patients showed increased ReHo in the middle occipital gyrus (MOG) and decreased ReHo in the anterior cingulate cortex (ACC), inferior frontal gyrus (IFG), superior frontal gyrus (SFG) and the bilateral thalamus in the slow-4 band, while they showed increased ReHo in the medial prefrontal cortex (mPFC) in the slow-5 band. Our results suggest that the abnormality of ReHo in MDD is associated with the frequency band and that future studies should take frequency band effect into account when examining spontaneous neural activity.

Amplitude of low frequency fluctuation in primary open angle glaucoma: a resting state fMRI study.

Primary open angle glaucoma (POAG) is a kind of progressive neuropathy with no clear cause. In the present fMRI study, a data-driven approach was employed to map the alteration of regional spontaneous activity in POAG patients by measuring the amplitude of low-frequency fluctuation (ALFF) of the blood oxygen level-dependent (BOLD) signal. Twenty one POAG patients and 22 age and gender matched healthy subjects participated in this study. We found that the abnormal ALFF values in the POAG patients compared with healthy controls were not only detected in the visual regions but also across the whole brain. We also found the correlations between ALFF values and the POAG stages for POAG patients. We concluded that the abnormality of spontaneous brain activity in patients with POAG existed in visual cortex as well as in distal brain regions associated with sensation, motion, emotion and psychology. And the abnormal spontaneous neural activity in different brain regions could be better detected by specific frequency bands. These findings might contribute to a better understanding of the pathophysiology of POAG.

Abnormal Spontaneous Neural Activity in Obsessive-Compulsive Disorder: A Resting-State Functional Magnetic Resonance Imaging Study

Neuroimaging studies of obsessive-compulsive disorder have found abnormalities in orbitofronto-striato-thalamic circuitry, including the orbitofrontal cortex, anterior cingulate cortex, caudate, and thalamus, but few studies have explored abnormal intrinsic or spontaneous brain activity in the resting state. We investigated both intra- and inter-regional synchronized activity in twenty patients with obsessive-compulsive disorder and 20 healthy controls using resting-state functional magnetic resonance imaging. Regional homogeneity (ReHo) and functional connectivity methods were used to analyze the intra- and inter-regional synchronized activity, respectively. Compared with healthy controls, patients with obsessive-compulsive disorder showed significantly increased ReHo in the orbitofrontal cortex, cerebellum, and insula, and decreased ReHo in the ventral anterior cingulate cortex, caudate, and inferior occipital cortex. Based on ReHo results, we determined functional connectivity differences between the orbitofrontal cortex and other brain regions in both patients with obsessive-compulsive disorder and controls. We found abnormal functional connectivity between the orbitofrontal cortex and ventral anterior cingulate cortex in patients with obsessive-compulsive disorder compared with healthy controls. Moreover, ReHo in the orbitofrontal cortex was correlated with the duration of obsessive-compulsive disorder. These findings suggest that increased intra- and inter-regional synchronized activity in the orbitofrontal cortex may have a key role in the pathology of obsessive-compulsive disorder. In addition to orbitofronto-striato-thalamic circuitry, brain regions such as the insula and cerebellum may also be involved in the pathophysiology of obsessive-compulsive disorder.

Abnormal regional spontaneous neural activity in first-episode, treatment-naive patients with late-life depression: A resting-state fMRI study

The previous resting perfusion or task-based studies have provided evidence of functional changes in the brains of patients with late-life depression (LLD). Little is known, so far, about the changes in the spontaneous brain activity in LLD during the resting state. The aim of this study was to investigate the spontaneous neural activity in first-episode, treatment-naive patients with LLD by using resting-state functional magnetic resonance imaging (fMRI). A novel analytical method, coherence-based regional homogeneity (Cohe-ReHo), was used to assess regional spontaneous neural activity during the resting state in 15 first-episode, treatment-naive patients with LLD and 15 age- and gender-matched healthy controls. Compared to the healthy controls, the LLD group showed significantly decreased Cohe-ReHo in left caudate nucleus, right anterior cingulate gyrus, left dorsolateral prefrontal cortex, right angular gyrus, bilateral medial prefrontal cortex, and right precuneus, while significantly increased Cohe-ReHo in left cerebellum posterior lobe, left superior temporal gyrus, bilateral supplementary motor area, and right postcentral gyrus (p<0.005, corrected for multiple comparisons). These findings indicated abnormal spontaneous neural activity was distributed extensively in first-episode, treatment-naive patients with LLD during the resting state. Our results might supply a novel way to look into the underlying pathophysiology mechanisms of patients with LLD.

Abnormal regional spontaneous neural activity in treatment‐refractory depression revealed by resting‐state fMRI

Treatment-refractory depression (TRD) represents a large proportion of the depressive population, yet has seldom been investigated using advanced imaging techniques. To characterize brain dysfunction in TRD, we performed resting-state functional MRI (rs-fMRI) on 22 TRD patients, along with 26 matched healthy subjects and 22 patients who were depressed but not treatment-refractory (NDD) as comparison groups. Results were analyzed using a data-driven approach known as Regional Homogeneity (ReHo) analysis which measures the synchronization of spontaneous fMRI signal oscillations within spatially neighboring voxels. Relative to healthy controls, both depressed groups showed high ReHo primarily within temporo-limbic structures, and more widespread low ReHo in frontal, parietal, posterior fusiform cortices, and caudate. TRD patients showed more cerebral regions with altered ReHo than did NDD. Moderate but significant correlations between the altered regional ReHo and measures of clinical severity were observed in some identified clusters. These findings shed light on the pathophysiological mechanisms underlying TRD and demonstrate the feasibility of using ReHo as a research and clinical tool to monitor persistent cerebral dysfunction in depression, although further work is necessary to compare different measures of brain function to elucidate the neural substrates of these ReHo abnormalities.

The expression of deafferentation dysesthesias reduced by dorsal root entry zone lesions in the rat.

Extensive longitudinal lesions of the dorsal root entry zone (DREZ) are effective in relieving some chronic deafferentation pain in humans. A deafferentation syndrome follows C5-T2 dorsal root ganglionectomies in rats. The syndrome consists of biting and scratching the completely and partially denervated limb areas, respectively. This study examines the effect of DREZ lesions on the deafferentation syndrome in the rat. Of 37 rats, 24 underwent C5-T2 ganglionectomies only, five received C4-T3 micromechanical DREZ lesions only, and eight underwent ganglionectomies plus simultaneous DREZ lesions. The animals were observed for 45 days post-operatively. Histological analysis of the spinal cord lesions was performed. All rats with ganglionectomies alone exhibited the deafferentation syndrome; however, no rats with DREZ lesions alone showed this feature. Only 25% of rats with combined ganglionectomies and DREZ lesions exhibited the deafferentation syndrome in the first 30 days, whereas 80% of the animals with ganglionectomies only did so. Although 75% of the animals with combined lesions eventually bit the insensitive forepaw, this behavior was significantly attenuated: the day of onset was delayed and the extent of self-mutilation was reduced. Postmortem histological examination of the DREZ lesions indicated a close association between the completeness of the dorsal horn destruction and the reduction or prevention of self-mutilation. These data support the validity of the animal model and also the hypothesis stating that the deafferentation syndrome results from abnormal spontaneous neural activity in the dorsal horn. Moreover, the variability of the histological findings in these experiments stresses the importance of making contiguous and complete dorsal horn lesions in human DREZ surgery.