Neural connectivity of alexithymia: Specific association with major depressive disorder

Emotion Processing in Peripheral Neuropathic Pain: An Observational Study

BACKGROUND

In clinical practice, the implementation of tailored treatment is crucial for assessing the patient's emotional processing profile. Here, we investigate all three levels of analysis characterizing emotion processing, i.e., recognition, representation, and regulation, in patients with peripheral neuropathic pain (PNP).

METHODS

Sixty-two patients and forty-eight healthy controls underwent quantitative sensory testing, i.e., psychophysical tests to assess somatosensory functions such as perception of cold (CDT), heat-induced pain (HPT), and vibration (VDT), as well as three standardized tasks to assess emotional processing: (1) the Ekman 60-Faces Test (EK-60F) to assess recognition of basic facial emotions, (2) the Reading the Mind in the Eyes Test (RME) to assess the ability to represent the feelings of another person by observing their eyes, and (3) the 20-item Toronto Alexithymia Scale (TAS-20) to assess emotional dysregulation, i.e., alexithymia.

RESULTS

General Linear Model analysis revealed a significant relationship between left index finger VDT z-scores in PNP patients with alexithymia. The RME correlated with VDT z-scores of the left little finger and overall score for the EK-60F.

CONCLUSIONS

In patients with PNP, emotion processing is impaired, which emphasizes the importance of assessing these abilities appropriately in these patients. In this way, clinicians can tailor treatment to the needs of individual patients.

Basolateral Amygdala Functional Connectivity in Alexithymia: Linking Interoceptive Sensibility and Cognitive Empathy

Emotions rely on bodily states, and perceiving the emotions of others depends on awareness of one's own emotional state. However, the intercorrelations among interoception, alexithymia, and empathy are not well understood, and the neural mechanisms behind this connection are also largely unknown. To address these issues, 297 college students participated in this study, completing measures of interoceptive sensibility (IS), empathy and alexithymia and undergoing resting-state fMRI scans. The functional connectivity of the amygdala was analysed to identify the neural substrates of alexithymia, and mediation analyses were conducted to examine the mediation effect of alexithymia and alexithymia-specific amygdala functional connectivity on the relationship between IS and empathy. The results showed that higher levels of IS were associated with increased cognitive empathy through weakened alexithymia. Functional connectivity analysis indicated that right basolateral amygdala (BLA)-left precuneus connectivity was negatively related to alexithymia, while right BLA-left precentral gyrus connectivity was positively related to alexithymia. Furthermore, right BLA-left precuneus connectivity was found to mediate the impact of interoception on cognitive empathy. In conclusion, this study provides valuable insights into the relationships among IS, alexithymia, and empathy. The right BLA-left precuneus connectivity may serve as a shared neural substrate between interoception and cognitive empathy.

Functional Activity in the Effect of Transcranial Magnetic Stimulation Therapy for Patients with Depression: A Meta-Analysis

Depression is a long-lasting mental disorder that affects more than 264 million people worldwide. Transcranial magnetic stimulation (TMS) can be a safe and effective choice for the treatment of depression. Functional neuroimaging provides unique insights into the neuropsychiatric effects of antidepressant TMS. In this meta-analysis, we aimed to assess the functional activity of brain regions caused by TMS for depression. A literature search was conducted from inception to 5 January 2022. Studies were then selected according to predetermined inclusion and exclusion criteria. Activation likelihood estimation was applied to analyze functional activation. Five articles were ultimately included after selection. The main analysis results indicated that TMS treatment for depression can alter the activity in the right precentral gyrus, right posterior cingulate, left inferior frontal gyrus and left middle frontal gyrus. In resting-state studies, increased activation was shown in the right precentral gyrus, right posterior cingulate, left inferior frontal gyrus and left superior frontal gyrus associated with TMS treatment. In task-related studies, clusters in the right middle frontal gyrus, left sub-gyrus, left middle frontal gyrus and left posterior cingulate were hyperactivated post-treatment. Our study offers an overview of brain activity changes in patients with depression after TMS treatment.

The Association of White Matter Tracts with Alexithymia among Individuals with Major Depressive Disorder

Alexithymia is characterized by impairments in the processing of emotions. Although the disruptions in the white matter (WM) integrity in Major depressive disorder (MDD) has frequently been reported, the underlying relationship with alexithymia remains unclear. In the present study, we investigated WM tracts with Tracts Constrained by UnderLying Anatomy approach to discover potential associations between alexithymia and WM integrity to identify the neural basis of impaired emotional self-awareness in MDD. 101 patients with MDD and 99 healthy sex- and age-matched individuals underwent diffusion-weighted imaging. All participants were assessed with the 20-item Toronto Alexithymia Scale (TAS). TAS scores were significantly higher in MDD patients than in controls. Patients with MDD exhibited significantly lower FA values in the left inferior longitudinal fasciculus and it also showed negative associations with TAS. These results contribute to the neurobiological evidence on the association between MDD and alexithymia. Additionally, they suggest that reduced white matter integrity in the regions constitutes a principal pathophysiology underlying impaired emotional recognition and description in MDD.

Paradoxical somatic information processing for interoception and anxiety in alexithymia

The concept of alexithymia has garnered much attention in an attempt to understand the psychological mechanisms underlying the experience of feeling an emotion. In this study, we aimed to understand how the interoceptive processing in an emotional context relates to problems of alexithymia in recognizing self‐emotions. Therefore, we prepared experimental conditions to induce emotional awareness based on interoceptive information. As such, we asked participants to be aware of interoception under an anxiety‐generating situation anticipating pain, having them evaluate their subjective anxiety levels in this context. High alexithymia participants showed attenuated functional connectivity within their ‘interoception network’, particularly between the insula and the somatosensory areas when they focused on interoception. In contrast, they had enhanced functional connectivity between these regions when they focused on their anxiety about pain. Although access to somatic information is supposed to be more strongly activated while attending to interoception in the context of primary sensory processing, high alexithymia individuals were biased as this process was activated when they felt emotions, suggesting they recognize primitive and unprocessed bodily sensations as emotions. The paradoxical somatic information processing may reflect their brain function pathology for feeling emotions and their difficulty with context‐dependent emotional control.

Relationship between alexithymia and depression: A narrative review

Alexithymia has been described as difficulty in expressing as well as experiencing feelings. It has been studied in relation with medical as well as psychological conditions and has been seen to impact treatment outcomes. The current review focuses on the relationship of alexithymia with depression and the role of culture in this relationship. The keywords for literature included terms such as depression, alexithymia, depression and alexithymia, Toronto Alexithymia Scale, assessing alexithymia and depression, and alexithymia as a trait. The main findings of the review were that alexithymia and depression are highly correlated, and severity of depression and gender are independently associated with alexithymia and may interfere with treatment outcomes.

The relationship between alexithymia, sensory phenotype and neurophysiological parameters in patients with chronic upper limb neuropathy

In this study, we investigated the relationship between sensory abnormalities evaluated by quantitative sensory testing (QST) and alexithymia, depression and anxiety in patients with neuropathic pain involving the upper limbs. We enrolled 62 patients (34 with carpal tunnel syndrome, 7 with brachial plexopathy, 3 with cervical painful radiculopathy, 5 with ulnar entrapment neuropathy at elbow and 13 with post-burn hypertrophic scars) and 48 healthy controls. All underwent nerve conduction studies (NCS), evaluation of cold, heat pain and vibration detection threshold (VDT) by QST and evaluation of alexithymia by Toronto Alexithymia Scale (TAS-20), depression by Beck Depression Inventory II (BDI-II), anxiety by State-Trait Anxiety Inventory (STAI-Y), level of psychological distress by 12-item General Health Questionnaire (GHQ-12) and perceived social support by the Multidimensional Scale of Perceived Social Support (MSPSS). The general linear model analysis revealed a significant relationship between TAS-20 overall and TAS-20 sub-score for difficulty identifying feelings and VDT z-scores in the left index with no interaction by year of education and sensory NCS results. Our results demonstrated the association between impairment of vibratory sensation of the left hand, reflecting cutaneous mechanoceptor dysfunction, and alexithymia, particularly the difficulty to identify feelings. The importance of delivering to patients with neuropathic pain personalized care that takes into account not only the neurophysiological aspects but also the aspects of mental functioning is discussed.

Missing the forest because of the trees: slower alternations during binocular rivalry are associated with lower levels of visual detail during ongoing thought

Conscious awareness of the world fluctuates, either through variation in how vividly we perceive the environment, or when our attentional focus shifts away from information in the external environment towards information that we generate via imagination. Our study combined individual differences in experience sampling, psychophysical reports of perception and neuroimaging descriptions of structural connectivity to better understand these changes in conscious awareness. In particular, we examined (i) whether aspects of ongoing thought—indexed via multi-dimensional experience sampling during a sustained attention task—are associated with the white matter fibre organization of the cortex as reflected by their relative degree of anisotropic diffusion and (ii) whether these neurocognitive descriptions of ongoing experience are related to a more constrained measure of visual consciousness through analysis of bistable perception during binocular rivalry. Individuals with greater fractional anisotropy in right hemisphere white matter regions involving the inferior fronto-occipital fasciculus, the superior longitudinal fasciculus and the cortico-spinal tract, described their ongoing thoughts as lacking external details. Subsequent analysis indicated that the combination of low fractional anisotropy in these right hemisphere regions, with reports of thoughts with high levels of external details, was associated with the shortest periods of dominance during binocular rivalry. Since variation in binocular rivalry reflects differences between bottom-up and top-down influences on vision, our study suggests that reports of ongoing thoughts with vivid external details may occur when conscious precedence is given to bottom-up representation of perceptual information.

Brain structural correlates of alexithymia in patients with major depressive disorder

BACKGROUND

Alexithymia is a risk factor for major depressive disorder (MDD) and has been associated with diminished treatment response. Neuroimaging studies have revealed structural aberrations of the anterior cingulate cortex and the fusiform gyrus in healthy controls with high levels of alexithymia. The present study tried to corroborate and extend these results to patients with MDD compared with healthy controls.

METHODS

We investigated the relationship between alexithymia, depression and grey matter volume in 63 patients with MDD (mean age ± standard deviation = 42.43 yr ± 11.91; 33 female) and 46 healthy controls (45.35 yr ± 8.37; 22 female). We assessed alexithymia using the Toronto Alexithymia Scale. We conducted an alexithymia × group analysis of covariance; we used a region-of-interest approach, including the fusiform gyrus and anterior cingulate cortex, and conducted whole brain analysis using voxelbased morphometry.

RESULTS

Our analysis revealed a significant alexithymia × group interaction in the fusiform gyrus (left, pFWE = 0.031; right, pFWE = 0.010). Higher alexithymia scores were associated with decreased grey matter volume in patients with MDD (pFWE = 0.009), but with increased grey matter volume of the fusiform gyrus in healthy controls (pFWE = 0.044). We found no significant main effects in the region-of-interest analysis.

LIMITATIONS

Owing to the naturalistic nature of our study, patients with MDD and healthy controls differed significantly in their alexithymia scores.

CONCLUSION

Our results showed the fusiform gyrus as a correlate of alexithymia. We also found differences related to alexithymia between patients with MDD and healthy controls in the fusiform gyrus. Our study encourages research related to the transition from risk to MDD in people with alexithymia.

Alexithymia and frontal-amygdala functional connectivity in North Korean refugees

BACKGROUND

Refugees commonly experience difficulties with emotional processing, such as alexithymia, due to stressful or traumatic experiences. However, the functional connectivity of the amygdala, which is central to emotional processing, has yet to be assessed in refugees. Thus, the present study investigated the resting-state functional connectivity of the amygdala and its association with emotional processing in North Korean (NK) refugees.

METHODS

This study included 45 NK refugees and 40 native South Koreans (SK). All participants were administered the Toronto Alexithymia Scale (TAS), Beck Depression Inventory (BDI), and Clinician-administered PTSD Scale (CAPS), and differences between NK refugees and native SK in terms of resting-state functional connectivity of the amygdala were assessed. Additionally, the association between the strength of amygdala connectivity and the TAS score was examined.

RESULTS

Resting-state connectivity values from the left amygdala to the bilateral dorsolateral prefrontal cortex (dlPFC) and dorsal anterior cingulate cortex (dACC) were higher in NK refugees than in native SK. Additionally, the strength of connectivity between the left amygdala and right dlPFC was positively associated with TAS score after controlling for the number of traumatic experiences and BDI and CAPS scores.

CONCLUSIONS

The present study found that NK refugees exhibited heightened frontal-amygdala connectivity, and that this connectivity was correlated with alexithymia. The present results suggest that increased frontal-amygdala connectivity in refugees may represent frontal down-regulation of the amygdala, which in turn may produce alexithymia.

Neuro-cognitive correlates of alexithymia in patients with circumscribed prefrontal cortex damage

Alexithymia has been extensively reported in studies of psychiatric patients. However, little attention has been paid regarding its occurrence in the context of patients with circumscribed prefrontal cortex lesions. Moreover, the neuro-cognitive impairments that lead to alexithymia remain unclear and limited numbers of studies have addressed these issues. The authors investigated the impact of prefrontal cortex lesions on alexithymia and its neuro-cognitive correlates in a population of 20 patients with focal frontal lesions, 10 patients with parietal lesions and 34 matched control participants. Alexithymia was screened using the Toronto Alexithymia Scale (TAS-20) and executive functions were assessed using a large battery of executive tasks that address inhibition, flexibility and the planning process. Results showed that patients with prefrontal cortex damage showed significantly increased difficulty in facets of identifying feelings (DIF) and externally oriented thinking (EOT) on TAS-20, compared to parietal patients and control participants. Moreover, both correlation and regression analysis revealed that higher alexithymia levels on the three facets of TAS-20 were consistently but differentially associated with impairment in inhibition, flexibility and planning tasks for frontal patients and both control groups. These findings provide clinical evidence of the implication of prefrontal cortex damage and executive control in alexithymia. Our results were also discussed in the light of the cognitive appraisal concept as a mechanism involved in emotion episode processing. This study suggests that increased neuropsychological attention should be directed to the relation between the neuro-cognitive model of executive functions and cognitive appraisal theory in processing emotion.

Functional Magnetic Resonance Imaging (fMRI) of Neural Responses to Visual and Auditory Food Stimuli Pre and Post Roux-en-Y Gastric Bypass (RYGB) and Sleeve Gastrectomy (SG)

Of current obesity treatments, bariatric surgery induces the most weight loss. Given the marked increase in the number of bariatric surgeries performed, elucidating the mechanisms of action is a key research goal. We compared whole brain activation in response to high-energy dense (HED) vs. low-energy dense (LED) visual and auditory food cues before and approximately 4 months after Roux-en-Y Gastric Bypass (RYGB) (n = 16) and Sleeve Gastrectomy (SG) (n = 9). We included two control groups: a low-calorie diet weight loss group (WL) (n = 14) and a non-treatment group (NT) (n = 16). Relative to the control groups, the surgery groups showed increased dorsolateral prefrontal cortex (dlPFC) and decreased parahippocampal/fusiform gyrus (PHG/fusiform) activation in response to HED vs. LED, suggesting greater cognitive dietary inhibition and decreased rewarding effects and attention related to HED foods. dlPFC activation was significantly more increased in RYGB vs. SG. We also found that postprandial increases in GLP-1 concentrations (pre to postsurgery) correlated with postsurgical decreases in RYGB brain activity in the inferior temporal gyrus and the right middle occipital gyrus in addition to increases in the right medial prefrontal gyrus/paracingulate for HED > LED stimuli, suggesting involvement of these attention and inhibitory regions in satiety signaling postsurgery.

Altered Intrinsic Coupling between Functional Connectivity Density and Amplitude of Low-Frequency Fluctuation in Mild Cognitive Impairment with Depressive Symptoms

Neuroimaging studies have demonstrated that major depressive disorder increases the risk of dementia in older individuals with mild cognitive impairment. We used resting-state functional magnetic resonance imaging to explore the intrinsic coupling patterns between the amplitude and synchronisation of low-frequency brain fluctuations using the amplitude of low-frequency fluctuations (ALFF) and the functional connectivity density (FCD) in 16 patients who had mild cognitive impairment with depressive symptoms (D-MCI) (mean age: 69.6 ± 6.2 years) and 18 patients with nondepressed mild cognitive impairment (nD-MCI) (mean age: 72.1 ± 9.7 years). Coupling was quantified as the correlations between the ALFF values and their associated FCDs. The results showed that the ALFF values in the D-MCI group were higher in the left medial prefrontal cortex (mPFC) and lower in the right precentral gyrus (preCG), and the FCD values were higher in the left medial temporal gyrus (MTG) than those in the nD-MCI group. Further, correlation analyses demonstrated that, in the D-MCI group, the mPFC was negatively correlated with the MTG. These findings may relate to the characteristics of mood disorders in patients with MCI, and they offer further insight into the neuropathophysiology of MCI with depressive symptoms.

The functional and structural characteristics of the emotion network in alexithymia

BACKGROUND

Alexithymia is a multifaceted personality trait characterized by emotional dysfunction.

METHODS

In this study, the functional and structural features of the emotion network in alexithymia were investigated using resting-state functional MRI (rsfMRI), voxel-based morphometry (VBM), functional connectivity (FC) analysis, and diffusion tensor imaging (DTI). Alexithymic and non-alexithymic students were recruited from the local university. The intrinsic neural activity and gray matter density of the brain regions in the emotion network were measured using rsfMRI and VBM; the FC and structural connectivity of the brain regions in the emotion network were measured using FC analysis and DTI.

RESULTS

The altered intrinsic neural activity in V1, rostral dorsal anterior cingulate cortex, and left amygdala, and the weak FC between V1 and left superior temporal gyrus and V1 and left paracentral lobule in alexithymia subjects were identified. However, no alteration of the structure and structural connectivity of the emotion network was identified.

CONCLUSION

The results indicated that the development of alexithymia might have been caused only by slight alteration of the neural activity. Furthermore, the results suggest that noninvasive treatment technologies for improving the brain activity are suitable for alexithymic individuals.

Characteristics of brain functional and structural connectivity in alexithymic students

BACKGROUND

Alexithymia is a multifaceted personality trait and a risk factor for several mental and physical diseases.

METHODS

In this study, 21 alexithymic students and 21 nonalexithymic students were recruited from the local university and assigned to the alexithymic group and the control group, respectively. Then, the functional connectivity and the structural connectivity among the brain regions of the students were investigated using resting-state functional magnetic resonance imaging (rsfMRI), function connection (FC) analysis, and diffusion tensor imaging (DTI).

RESULTS

The rsfMRI results revealed 14 brain regions showing significant differences in the amplitude of low-frequency fluctuations between the two groups. Comparative analysis of the FC and DTI data in these brain regions between the two groups identified altered levels of functional and structural connectivity between the following four pairs of regions in the alexithymic subjects: the right inferior temporal gyrus and the central posterior gyrus, the left temporal gyrus and the insula, and the bilateral superior frontal gyrus and the anterior cingulate gyrus.

CONCLUSION

Compared with single MRI analysis, the multiple MRI analysis identified more precisely the brain regions that could play a key role in the development of alexithymia.

Intrinsic functional connectivity in late-life depression: trajectories over the course of pharmacotherapy in remitters and non-remitters

Previous studies in late-life depression (LLD) have found that patients have altered intrinsic functional connectivity in the dorsal default mode network (DMN) and executive control network (ECN). We aimed to detect connectivity differences across a treatment trial among LLD patients as a function of remission status. LLD patients (N=37) were enrolled into a 12-week trial of venlafaxine and underwent five functional magnetic resonance imaging resting state scans during treatment. Patients had no history of drug abuse, psychosis, dementia/neurodegenerative diseases or medical conditions with known effects on mood. We investigated whether there were differences in three networks: DMN, ECN and anterior salience network connectivity, as well as a whole brain centrality measure (eigenvector centrality). We found that remitters showed increases in ECN connectivity in the right precentral gyrus and decreases in DMN connectivity in the right inferior frontal gyrus and supramarginal gyrus. The ECN and DMN had regions (middle temporal gyrus and bilateral middle/inferior temporal/fusiform gyrus, respectively) that showed reversed effects (decreased ECN and increased DMN, respectively). Early changes in functional connectivity can occur after initial medication exposure. This study offers new data, indicating that functional connectivity changes differ depending on treatment response and can occur shortly after exposure to antidepressant medication.

Frontal EEG asymmetry in borderline personality disorder is associated with alexithymia

BACKGROUND

Frontal EEG asymmetry is a widely studied correlate of emotion processing and psychopathology. Recent research suggests that frontal EEG asymmetry during resting state is related to approach/withdrawal motivation and is also found in affective disorders such as major depressive disorder. Patients with borderline personality disorder (BPD) show aberrant behavior in relation to both approach and withdrawal motivation, which may arguably be associated with their difficulties in emotion processing. The occurrence and significance of frontal EEG asymmetry in BPD, however, has received little attention.

RESULTS

Thirty-seven BPD patients and 39 controls underwent resting EEG and completed several psychometric questionnaires. While there were no between-group differences in frontal EEG asymmetry, in BPD frontal EEG asymmetry scores correlated significantly with alexithymia. That is, higher alexithymia scores were associated with relatively lower right-frontal activity. A subsequent analysis corroborated the significant interaction between frontal EEG asymmetry and alexithymia, which was moderated by group.

CONCLUSIONS

Our findings reveal that lower right frontal EEG asymmetry is associated with alexithymia in patients with BPD. This finding is in accordance with neurophysiological models of alexithymia that implicate a right hemisphere impairment in emotion processing, and could suggest frontal EEG asymmetry as a potential biomarker of relevant psychopathology in these patients.

Abnormal degree centrality in Alzheimer's disease patients with depression: A resting-state functional magnetic resonance imaging study

Depression is common in Alzheimer's disease (AD) and occurs in AD patients with a prevalence of up to 40%. It reduces cognitive function and increases the burden on caregivers. Currently, there are very few medications that are useful for treating depression in AD patients. Therefore, understanding the brain abnormalities in AD patients with depression (D-AD) is crucial for developing effective interventions. The aim of this study was to investigate the intrinsic dysconnectivity pattern of whole-brain functional networks at the voxel level in D-AD patients based on degree centrality (DC) as measured by resting-state functional magnetic resonance imaging (R-fMRI). Our study included 32 AD patients. All patients were evaluated using the Neuropsychiatric Inventory and Hamilton Depression Rating Scale and further divided into two groups: 15 D-AD patients and 17 non-depressed AD (nD-AD) patients. R-fMRI datasets were acquired from these D-AD and nD-AD patients. First, we performed a DC analysis to identify voxels that showed altered whole brain functional connectivity (FC) with other voxels. We then further investigated FC using the abnormal DC regions to examine in more detail the connectivity patterns of the identified DC changes. D-AD patients had lower DC values in the right middle frontal, precentral, and postcentral gyrus than nD-AD patients. Seed-based analysis revealed decreased connectivity between the precentral and postcentral gyrus to the supplementary motor area and middle cingulum. FC also decreased in the right middle frontal, precentral, and postcentral gyrus. Thus, AD patients with depression fit a 'network dysfunction model' distinct from major depressive disorder and AD.