Abstract
Background/aims
Abnormal visceral sensory function in diabetes mellitus (DM) leads to neuronal changes in the enteric, peripheral and/or central nervous system (CNS). To explore the role of ...diabetic autonomic neuropathy (DAN) in patients with long-standing DM, we investigated psychophysical responses and neuronal activity recorded as evoked brain potentials (EPs) and dipolar source modelling.
Methods
Fifteen healthy volunteers and 14 type-1 DM patients with DAN were assessed with a symptom score index characterizing upper GI abnormalities. Multi-channel (62) electroencephalography was recorded during painful electrical stimulation of the lower oesophagus. Brain activity to painful stimulations was modelled by use of Brain Electrical Source Analysis (BESA).
Results
Diabetic patients had higher stimulus intensities to evoke painful sensation (
P
<0.001), longer latencies of N2 and P2 components (both
P
<0.001), lower amplitudes of P1–N2 and N2–P2 complexes (
P
<0.001;
P
= 0.02). Inverse modelling of brain sources showed deeper bilateral insular dipolar source localization (
P
= 0.002). Symptom score index was negatively correlated to the depth of insular activity (
P
= 0.004) and positively correlated to insular dipole strength (
P
= 0.03).
Conclusion
DM patients show neuroplastic changes in the central nervous system. The role of abnormal insular processing may explain the development and persistence of upper GI-symptoms related to DAN. This enhanced understanding of DAN may have clinical and therapeutical implications.
Objective: To record somatosensory evoked potentials (SEPs) to median nerve stimulation by chronically implanted electrodes in the parieto-rolandic opercular area of 9 epileptic patients, in order to ...evaluate whether somatosensory evoked responses could be generated in the second somatosensory area (SII) earlier than 40 ms after stimulus.
Methods: Nine patients (4 males, 5 females) with drug-resistant partial epileptic seizures were investigated using stereotactically implanted electrodes in the parietal cortex, posterior to vertical anterior commissure plane and in the frontal opercular region rostral to vertical anterior commissure (VAC).
Results: The main finding of this study is the recording of an early somatosensory evoked potential, (N30op), by chronically implanted electrodes in the SII area of 8 epileptic patients. In 3 patients where SEPs were performed after ipsilateral median nerve (MN) stimulation, a N30op was recorded 5.8±2 ms later than contralateral one.
Conclusions: This is the first report of early SEPs recorded by electrodes implanted in SII area. The N30op potential, even if less consistent than later potentials, confirmed the important role of the SII area in the early processing of somatosensory inputs.
Recent studies aimed at investigating artificial analogs of bacterial colonies have shown that low-density suspensions of self-propelled particles confined in two dimensions can assemble into finite ...aggregates that merge and split, but have a typical size that remains constant (living clusters). In this Letter we address the problem of the formation of living clusters and crystals of active particles in three dimensions. We study two systems: self-propelled particles interacting via a generic attractive potential and colloids that can move towards each other as a result of active agents (e.g. by molecular motors). In both cases fluid-like `living' clusters form. We explain this general feature in terms of the balance between active forces and regression to thermodynamic equilibrium. This balance can be quantified in terms of a dimensionless number that allows us to collapse the observed clustering behaviour onto a universal curve. We also discuss how active motion affects the kinetics of crystal formation.
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