Effective Connectivity of Beta Oscillations in Endometriosis-Related Chronic Pain During rest and Pain-Related Mental Imagery.

Using the EEG recordings of patients with endometriosis-related chronic pelvic pain, we have examined the effective connectivity within the cortical pain-related network during rest and during pain-related imagery. During rest, an altered connectivity was hypothesized between cortical somatosensory pain areas and regions involved in emotional and cognitive modulation of pain. During pain-related imagery, alterations in prefrontal-temporal connectivity were expected. The effective connectivity was estimated using the Directed Transfer Function method. Differences between endometriosis patients and controls were found in the beta band (14-25 Hz). During rest, endometriosis was associated with an increased connectivity from the left dorsolateral prefrontal cortex to the left somatosensory cortex and also from the left somatosensory cortex to the orbitofrontal cortex and the right temporal cortex. These results might be related to sustained activation of the somatosensory pain system caused by the ongoing pain. During pain-related imagery, endometriosis patients showed an increased connectivity from the left dorsolateral prefrontal cortex to the right temporal cortex. This finding might point to impaired emotional regulation when processing pain-related stimuli, or it might be related to altered memorization of pain experiences. Results of this study open up new directions in chronic pain research aimed at exploring the beta band connectivity alterations. PERSPECTIVE: This study examined the pain system's dynamics in endometriosis patients with chronic pelvic pain during resting-state and pain-related mental imagery. The results could contribute to the development of new therapies using guided mental imagery.

Pain catastrophizing is associated with altered EEG effective connectivity during pain­related mental imagery.

Pain catastrophizing - defined as a tendency to exaggerate the threat value or seriousness of experienced pain ­ has been shown to be a risk factor for pain chronification. However, the neural basis of pain catastrophizing remains unclear and requires thorough investigation. This study aimed to explore the relationship between pain catastrophizing and effective connectivity of the pain systems in healthy participants. EEG data were collected during an induced state of pain­related negative, depressive, positive and neutral mental imagery conditions, and pain catastrophizing tendencies were measured by the Pain Catastrophizing Scale. The Directed Transfer Function, a method based on Granger causality principles, was used to assess the effective connectivity. Linear mixed effects analyses revealed a negative relationship between pain catastrophizing and beta information flow from the right temporal cortex to the frontal regions and a positive relationship between pain catastrophizing and increased beta information flow from the right somatosensory cortices to the right temporal cortices when thinking about pain. These patterns were not found in other imagery conditions. Taken together, this study suggests that individual differences in pain catastrophizing might be related to an altered frontotemporal regulatory loop and increased connectivity between pain and affective systems. Our study reveals connectivity patterns related to pain catastrophizing tendencies that are detectable even in pain­free, healthy individuals.

Cortical functional connectivity is associated with the valence of affective states.

The study investigates the relationships between the valence of affective states and the cortical patterns of functional connectivity. The information flow rate and direction were estimated by means of Directed Transfer Function (DTF), a multivariate method based on Granger causality. It was calculated on EEG activity recorded during mental imagery tasks. As a result, three regions were revealed as main network hubs, where the information outflow changed specifically with valence: the anterior orbitofrontal cortex, and the right posterior and right temporal area. The role of these structures in synchronizing the cortical affective network as well as in mediating different aspects of emotional state is discussed.

Does magnetic resonance spectroscopy identify patients with minimal hepatic encephalopathy?

BACKGROUND AND PURPOSE: The results of a few studies suggest that magnetic resonance spectroscopy of the brain could allow detection of minimal hepatic encephalopathy. The goal of this study was to assess the ability of magnetic resonance spectroscopy to differentiate between cirrhotic patients with and without minimal hepatic encephalopathy. MATERIAL AND METHODS: Localized magnetic resonance spectroscopy was performed in the basal ganglia, occipital gray matter and frontal white matter in 46 patients with liver cirrhosis without overt encephalopathy and in 45 controls. Neurological and neuropsychological examination was performed in each participant. RESULTS: The patients with liver cirrhosis had a decreased ratio of myoinositol to creatine in occipital gray matter and frontal white matter (mean: 0.17 ± 0.05 vs. 0.20 ± 0.04, p = 0.01 and 0.15 ± 0.05 vs. 0.19 ± 0.04, p < 0.01, respectively) and a decreased ratio of choline to creatine in occipital gray matter (mean: 0.32 ± 0.07 vs. 0.36 ± 0.08, p = 0.03). Minimal hepatic encephalopathy was diagnosed in 7 patients. Metabolite ratios did not differ significantly between patients with and without minimal hepatic encephalopathy. Metabolite ratios did not differ significantly between patients with Child-Pugh A and those with Child-Pugh B. CONCLUSIONS: Magnetic resonance spectroscopy does not allow accurate diagnosis of minimal hepatic encephalopathy. A similar profile of metabolites in the brain is observed in cirrhotic patients without cognitive impairment.