The effect of propofol on effective brain networks

Objective: We compared the effective networks derived from Single Pulse Electrical Stimulation (SPES) in intracranial electrocorticography (ECoG) of awake epilepsy patients and while under general propofol-anesthesia to investigate the effect of propofol on these brain networks. Methods: We included nine patients who underwent ECoG for epilepsy surgery evaluation. We performed SPES when the patient was awake (SPES-clinical) and repeated this under propofol-anesthesia during the surgery in which the ECoG grids were removed (SPES-propofol). We detected the cortico-cortical evoked potentials (CCEPs) with an automatic detector. We constructed two effective networks derived from SPES-clinical and SPES-propofol. We compared three network measures (indegree, outdegree and betweenness centrality), the N1-peak-latency and amplitude of CCEPs between the two effective networks. Results: Fewer CCEPs were observed during SPES-propofol (median: 6.0, range: 0–29) compared to SPES-clinical (median: 10.0, range: 0–36). We found a significant correlation for the indegree, outdegree and betweenness centrality between SPES-clinical and SPES-propofol (respectively rs = 0.77, rs = 0.70, rs = 0.55, p < 0.001). The median N1-peak-latency increased from 22.0 ms during SPES-clinical to 26.4 ms during SPES-propofol. Conclusions: Our findings suggest that the number of effective network connections decreases, but network measures are only marginally affected. Significance: The primary network topology is preserved under propofol

DeltaScan for the Assessment of Acute Encephalopathy and Delirium in ICU and non-ICU Patients, a Prospective Cross-Sectional Multicenter Validation Study

Objectives: To measure the diagnostic accuracy of DeltaScan: a portable real-time brain state monitor for identifying delirium, a manifestation of acute encephalopathy (AE) detectable by polymorphic delta activity (PDA) in single-channel electroencephalograms (EEGs). Design: Prospective cross-sectional study. Setting: Six Intensive Care Units (ICU's) and 17 non-ICU departments, including a psychiatric department across 10 Dutch hospitals. Participants: 494 patients, median age 75 (IQR:64-87), 53% male, 46% in ICUs, 29% delirious. Measurements: DeltaScan recorded 4-minute EEGs, using an algorithm to select the first 96 seconds of artifact-free data for PDA detection. This algorithm was trained and calibrated on two independent datasets. Methods: Initial validation of the algorithm for AE involved comparing its output with an expert EEG panel's visual inspection. The primary objective was to assess DeltaScan's accuracy in identifying delirium against a delirium expert panel's consensus. Results: DeltaScan had a 99% success rate, rejecting 6 of the 494 EEG's due to artifacts. Performance showed and an Area Under the Receiver Operating Characteristic Curve (AUC) of 0.86 (95% CI: 0.83-0.90) for AE (sensitivity: 0.75, 95%CI=0.68-0.81, specificity: 0.87 95%CI=0.83-0.91. The AUC was 0.71 for delirium (95%CI=0.66-0.75, sensitivity: 0.61 95%CI=0.52-0.69, specificity: 72, 95%CI=0.67-0.77). Our validation aim was an NPV for delirium above 0.80 which proved to be 0.82 (95%CI: 0.77-0.86). Among 84 non-delirious psychiatric patients, DeltaScan differentiated delirium from other disorders with a 94% (95%CI: 87-98%) specificity. Conclusions: DeltaScan can diagnose AE at bedside and shows a clear relationship with clinical delirium. Further research is required to explore its role in predicting delirium-related outcomes.</p

Bewust van kleine epileptische aanvallen

Not all epileptic seizures are accompanied by loss of awareness. Focal aware seizures provide an opportunity to predict the location of the epileptic source in the brain. The impact of these seizures is often underestimated, especially if someone has previously had seizures with loss of awareness

Towards human BCI applications based on cognitive brain systems: An investigation of neural signals recorded from the dorsolateral prefrontal cortex

One of the critical issues in brain-computer interface (BCI) research is how to translate a person's intention into brain signals for controlling computer programs. The motor system is currently the primary focus, where signals are obtained during imagined motor responses. However, cognitive brain systems are also attractive candidates, in that they may be more amenable to conscious control, yielding better regulation of magnitude and duration of localized brain activity. We report on a proof of principle study for the potential use of a higher cognitive system for BCI, namely the working memory (WM) system. We show that mental calculation reliably activates the WM network as measured with functional magnetic resonance imaging (fMRI). Moreover, activity in the dorsolateral prefrontal cortex (DLPFC) indicates that this region is active for the duration of mental processing. This supports the notion that DLPFC can be activated, and remains active, at will. Further confirmation is obtained from a patient with an implanted electrode grid for diagnostic purposes, in that gamma power within DLPFC increases during mental calculation and remains elevated for the duration thereof. These results indicate that cortical regions involved in higher cognitive functions may serve as a readily self-controllable input for BCI applications. It also shows that fMRI is an effective tool for identifying function-specific foci in individual subjects for subsequent placement of cortical electrodes. The fact that electrocorticographic (ECoG) signal confirmed the functional localization of fMRI provides a strong argument for incorporating fMRI in BCI research

Chronic social stress does not affect behavioural habituation in male CD1 mice.

Item does not contain fulltextVarious protocols to induce chronic stress in rodents are being used to determine the effects and underlying mechanisms of prolonged stress experience. Recently, a novel chronic social stress (CSS) protocol has been developed for mice where social instability in adolescence and early adulthood is induced. This protocol has been shown to cause an increase in HPA-axis activity and acute avoidance behaviour in the elevated plus maze. The aim of the present study was to investigate the effect of this CSS protocol on habituation to an initially novel environment in CD1 mice, since it has been shown that initially high avoidance behaviour in mice can still be followed by rapid habituation, pointing towards an adaptive response. One group of male mice, the CSS group, was exposed to the CSS protocol for 7 weeks and we compared their behavioural and physiological responses with male mice that were housed in a stable social group, the SH group. The results reveal a decrease in body weight gain and fur condition, changes in adrenal weight and decreased GR mRNA expression in the CA1 and the dentate gyrus of the hippocampus in chronically stressed CD1 animals. Irrespective of such evidence for a significantly stressful effect of the protocol, CD 1 mice, after termination of the stress procedure, revealed habituation profiles that matched those of control animals. We conclude that the physiological and central-nervous effects caused by a CSS procedure as used in this experiment fall within the coping capacities of CD1 mice at the behavioural level

Chronic social stress does not affect behavioural habituation in male CD1 mice.

Various protocols to induce chronic stress in rodents are being used to determine the effects and underlying mechanisms of prolonged stress experience. Recently, a novel chronic social stress (CSS) protocol has been developed for mice where social instability in adolescence and early adulthood is induced. This protocol has been shown to cause an increase in HPA-axis activity and acute avoidance behaviour in the elevated plus maze. The aim of the present study was to investigate the effect of this CSS protocol on habituation to an initially novel environment in CD1 mice, since it has been shown that initially high avoidance behaviour in mice can still be followed by rapid habituation, pointing towards an adaptive response. One group of male mice, the CSS group, was exposed to the CSS protocol for 7 weeks and we compared their behavioural and physiological responses with male mice that were housed in a stable social group, the SH group. The results reveal a decrease in body weight gain and fur condition, changes in adrenal weight and decreased GR mRNA expression in the CA1 and the dentate gyrus of the hippocampus in chronically stressed CD1 animals. Irrespective of such evidence for a significantly stressful effect of the protocol, CD 1 mice, after termination of the stress procedure, revealed habituation profiles that matched those of control animals. We conclude that the physiological and central-nervous effects caused by a CSS procedure as used in this experiment fall within the coping capacities of CD1 mice at the behavioural level

Decoding four hand gestures with a single bipolar pair of electrocorticography electrodes

Objective. Electrocorticography (ECoG) based brain-computer interfaces (BCIs) can be used to restore communication in individuals with locked-in syndrome. In motor-based BCIs, the number of degrees-of-freedom, and thus the speed of the BCI, directly depends on the number of classes that can be discriminated from the neural activity in the sensorimotor cortex. When considering minimally invasive BCI implants, the size of the subdural ECoG implant must be minimized without compromising the number of degrees-of-freedom. Approach. Here we investigated if four hand gestures could be decoded using a single ECoG strip of four consecutive electrodes spaced 1 cm apart and compared the performance between a unipolar and a bipolar montage. For that we collected data of seven individuals with intractable epilepsy implanted with ECoG grids, covering the hand region of the sensorimotor cortex. Based on the implanted grids, we generated virtual ECoG strips and compared the decoding accuracy between (a) a single unipolar electrode (Unipolar Electrode), (b) a combination of four unipolar electrodes (Unipolar Strip), (c) a single bipolar pair (Bipolar Pair) and (d) a combination of six bipolar pairs (Bipolar Strip). Main results. We show that four hand gestures can be equally well decoded using 'Unipolar Strips' (mean 67.4 ± 11.7%), 'Bipolar Strips' (mean 66.6 ± 12.1%) and 'Bipolar Pairs' (mean 67.6 ± 9.4%), while 'Unipolar Electrodes' (61.6 ± 5.9%) performed significantly worse compared to 'Unipolar Strips' and 'Bipolar Pairs'. Significance. We conclude that a single bipolar pair is a potential candidate for minimally invasive motor-based BCIs and encourage the use of ECoG as a robust and reliable BCI platform for multi-class movement decoding

Intracranial Recordings Reveal Unique Shape and Timing of Responses in Human Visual Cortex during Illusory Visual Events

de Jong et al. find that the processing hierarchy of perceptual changes during binocular rivalry is reversed compared to processing of stimulus changes. Binocular rivalry responses in ventral regions precede those in early visual regions. They speculate top-down signals stabilize a new perceptual interpretation of a binocular rivalry stimulus