Reappraisal of the effect of electrode property on recording slow potentials

Physiological paradigm for assessing reward prediction and extinction using cortical direct current potential responses in rats

Anticipating positive outcomes is a core cognitive function in the process of reward prediction. However, no neurophysiological method objectively assesses reward prediction in basic medical research. In the present study, we established a physiological paradigm using cortical direct current (DC) potential responses in rats to assess reward prediction. This paradigm consisted of five daily 1-h sessions with two tones, wherein the rewarded tone was followed by electrical stimulation of the medial forebrain bundle (MFB) scheduled at 1000 ms later, whereas the unrewarded tone was not. On day 1, both tones induced a negative DC shift immediately after auditory responses, persisting up to MFB stimulation. This negative shift progressively increased and peaked on day 4. Starting from day 3, the negative shift from 600 to 1000 ms was significantly larger following the rewarded tone than that following the unrewarded tone. This negative DC shift was particularly prominent in the frontal cortex, suggesting its crucial role in discriminative reward prediction. During the extinction sessions, the shift diminished significantly on extinction day 1. These findings suggest that cortical DC potential is related to reward prediction and could be a valuable tool for evaluating animal models of depression, providing a testing system for anhedonia.

Direct current electrocorticography for clinical neuromonitoring of spreading depolarizations

Spreading depolarizations cause cortical electrical potential changes over a wide spectral range that includes slow potentials approaching the direct current (or 0 Hz) level. The negative direct current shift (<0.05 Hz) is an important identifier of cortical depolarization and its duration is a measure of potential tissue injury associated with longer lasting depolarizations. To determine the feasibility of monitoring the full signal bandwidth of spreading depolarizations in patients, we performed subdural electrocorticography using platinum electrode strips and direct current-coupled amplifiers in 27 patients with acute brain injury at two neurosurgical centers. While large baseline direct current offsets developed, loss of data due to amplifier saturation was minimal and rates of baseline drift throughout recordings were generally low. Transient negative direct current shifts of spreading depolarizations were easily recognized and in 306/551 (56%) cases had stereotyped, measurable characteristics. Following a standardized training session, novice scorers achieved a high degree of accuracy and interobserver reliability in identifying depolarizations, suggesting that direct current-coupled recordings can facilitate bedside diagnosis for future trials or clinical decision-making. We conclude that intracranial monitoring of slow potentials can be achieved with platinum electrodes and that unfiltered, direct current-coupled recordings are advantageous for identifying and assessing the impact of spreading depolarizations.

Recording, analysis, and interpretation of spreading depolarizations in neurointensive care: Review and recommendations of the COSBID research group

Spreading depolarizations (SD) are waves of abrupt, near-complete breakdown of neuronal transmembrane ion gradients, are the largest possible pathophysiologic disruption of viable cerebral gray matter, and are a crucial mechanism of lesion development. Spreading depolarizations are increasingly recorded during multimodal neuromonitoring in neurocritical care as a causal biomarker providing a diagnostic summary measure of metabolic failure and excitotoxic injury. Focal ischemia causes spreading depolarization within minutes. Further spreading depolarizations arise for hours to days due to energy supply-demand mismatch in viable tissue. Spreading depolarizations exacerbate neuronal injury through prolonged ionic breakdown and spreading depolarization-related hypoperfusion (spreading ischemia). Local duration of the depolarization indicates local tissue energy status and risk of injury. Regional electrocorticographic monitoring affords even remote detection of injury because spreading depolarizations propagate widely from ischemic or metabolically stressed zones; characteristic patterns, including temporal clusters of spreading depolarizations and persistent depression of spontaneous cortical activity, can be recognized and quantified. Here, we describe the experimental basis for interpreting these patterns and illustrate their translation to human disease. We further provide consensus recommendations for electrocorticographic methods to record, classify, and score spreading depolarizations and associated spreading depressions. These methods offer distinct advantages over other neuromonitoring modalities and allow for future refinement through less invasive and more automated approaches.

Interictal Infraslow Activity in Stereoelectroencephalography: From Focus to Network

PURPOSE

Infraslow activity (ISA) occurring during the interictal state in focal epilepsy is largely unstudied. In this exploratory analysis, the authors aimed to characterize features of interictal ISA in a cohort of patients studied by stereoelectroencephography.

METHODS

The interictal stereoelectroencephography records for 15 consecutive adult patients were retrospectively analyzed, after application of both conventional (1.6-70 Hz) and infraslow (0.01-0.1 Hz) bandpass filters. Visual analysis was complemented by time-frequency analysis to quantify the change in ISA power over hours. Linear correlation coefficient (R) calculations were used to map interictal connectivity in the infraslow band.

RESULTS

Interictal ISA background fluctuations were present throughout the interictal state in all patients, manifesting as recurrent and stereotyped oscillations. These oscillations had an apparent modulatory effect on conventional-band activities and spikes ("spike-crested oscillations"). In the infraslow band, the correlations between electrode contacts were shown to have a stable structure over time.

CONCLUSIONS

Infraslow activity exists as a fundamental component of wideband cortical dynamics in focal epilepsy, with features suggestive of scale-free (1/f) dynamics: evidence of phase-amplitude coupling and functional connectivity in the infraslow band. Rather than viewed as a focal paroxysmal activity, interictal ISA may be better understood as a network process, although this requires further study.

Recovery of slow potentials in AC-coupled electrocorticography: application to spreading depolarizations in rat and human cerebral cortex

Cortical spreading depolarizations (spreading depressions and peri-infarct depolarizations) are a pathology intrinsic to acute brain injury, generating large negative extracellular slow potential changes (SPCs) that, lasting on the order of minutes, are studied with DC-coupled recordings in animals. The spreading SPCs of depolarization waves are observed in human cortex with AC-coupled electrocorticography (ECoG), although SPC morphology is distorted by the high-pass filter stage of the amplifiers. Here, we present a signal processing method to reverse these distortions and recover approximate full-band waveforms from AC-coupled recordings. We constructed digital filters that reproduced the phase and amplitude distortions introduced by specific AC-coupled amplifiers and, based on this characterization, derived digital inverse filters to remove these distortions from ECoG recordings. Performance of the inverse filter was validated by its ability to recover both simulated and real low-frequency input test signals. The inverse filter was then applied to AC-coupled ECoG recordings from five patients who underwent invasive monitoring after aneurysmal subarachnoid hemorrhage. For 117 SPCs, the inverse filter recovered full-band waveforms with morphologic characteristics typical of the negative DC shifts recorded in animals. Compared with those recorded in the rat cortex with the same analog and digital methods, the negative DC shifts of human depolarizations had significantly greater durations (1:47 vs. 0:45 min:sec) and peak-to-peak amplitudes (10.1 vs. 4.2 mV). The inverse filter thus permits the study of spreading depolarizations in humans, using the same assessment of full-band DC potentials as that in animals, and suggests a particular solution for recovery of biosignals recorded with frequency-limited amplifiers.

Sound-induced changes of infraslow brain potential fluctuations in the medial geniculate nucleus and primary auditory cortex in anaesthetized rats

Recent publications indicate the presence of infraslow activity (<0.5 Hz) in subcortical and cortical sites of the auditory system of the brain. It has been reported that this activity might be sensitive to acoustic stimuli. Yet the dynamics of infraslow brain potential (ISBP) fluctuations in these structures and their potential sensitivity to auditory stimuli are unknown. The present study was performed in order to test the hypothesis that extracellular ISBP activity in the medial geniculate nucleus (MGN) and the primary auditory cortex (A1) responds concurrently to acoustic stimuli. The experimental subjects were 5 adult rats with chronic stereotaxic electrodes implanted in MGN and A1. The animals were anesthetized and recordings were made in both sites during both silence and rhythmical acoustic stimulation. Our results support the hypothesis that these fluctuations are sensitive to acoustic stimuli. There were similar changes in ISBP activity in the MGN and A1 in response to rhythmic acoustic stimulation. Specifically, there were significant increases in the frequency range of seconds. Based on these findings, we suggest that sound-correlated changes in infraslow activity in the range of seconds in the MGN and A1 reflect specific mechanisms of neural processing of acoustic information in the auditory system of the brain.

Very slow brain potential fluctuations (< 0.5 Hz) in visual thalamus and striate cortex after their successive electrical stimulation in lightly anesthetized rats

Recently accumulating evidence demonstrates the presence of very slow activity (< 0.5 Hz) in structures of the visual system of the brain. It was found in our laboratory earlier that specific and significant alterations of this activity (mainly in the domain of seconds) occurred in the visual system in response to illumination changes. The present study was performed in order to test the hypothesis that potentials in the domain of seconds reflect specific and direct interactions of the lateral geniculate nucleus (LGN) and the primary visual cortex (V1) during neural processing of sensory information. The experimental subjects were seven adult rats with chronic stereotaxic electrodes implanted in the LGN and V1. Animals were lightly anesthetized and the recordings were made in the LGN before and after electrical stimulation of V1 and also in the V1 before and after stimulation of LGN. The main findings were significant spectral changes in the domain of seconds in the V1 after LGN electrical stimulation and similar changes in the LGN after V1 electrical stimulation. These changes were manifested as significant increases in power in the domain of seconds (0.1-0.5 Hz). Significant responses were detected in the both LGN and V1 multisecond activities (pre- vs. post-stimulus recordings). The changes were opposite in direction in the LGN and V1. The obtained results support the conclusion that very slow activity in the domain of seconds reflects specific mechanisms of forward and backward interactions within the LGN-V1 thalamic-cortical-thalamic system, while multisecond activity relates to global neuronal activity fluctuations.

Very slow potentials in the lateral geniculate complex and primary visual cortex during different illumination changes in freely moving rats

Previous literature has shown different forms of very slow oscillatory phenomena (0-0.5 Hz) in the structures of brain visual system. It was demonstrated in aforementioned publications that this infraslow activity might be sensitive to the level of environmental illumination. This study was performed to test the hypothesis that extracellular very slow brain potential (VSBP) oscillations or fluctuations in lateral geniculate complex (LGC) and primary visual cortex (PVC) are responding specifically and concurrently to different illumination changes. Experiments were conducted on five albino rats with chronically implanted stereotaxic electrodes in LGC and PVC brain sites. Our results support the aforementioned suggestion and revealed significant and similar patterns of VSBP modification within a frequency domain of seconds (0.1-0.25 Hz) in both the LGC and PVC in response to darkness, illumination and photostimulation. It is also documented here that significant and similar changes of multisecond activity (0.02-0.04 Hz) occur in both investigated brain sites in response to photostimulation only. Based on these findings, we propose that a possible role for VSBP oscillations in the LGC and PVC should be strongly considered in the CNS mechanisms of visual information processing.

Direct and mediated associations between P300 amplitude in childhood and substance use disorders outcome in young adulthood

BACKGROUND

Attenuated amplitude of the P300 wave has been frequently documented in youths at high risk for substance use disorders (SUDs). This investigation had two aims: 1) determine whether P300 amplitude in late childhood is a predictor of SUD outcome by age 19; and 2) evaluate whether neurobehavior disinhibition (ND) mediates this association.

METHODS

Boys (aged 10-12) were recruited through proband biological fathers with either a lifetime DSM-III-R diagnosis of SUD (N = 67) or no adult psychiatric disorder (N = 94). P300 amplitude was recorded during an auditory oddball task. Neurobehavior disinhibition was evaluated using tests of executive cognitive function, behavior under control, and emotion dysregulation. The relationship is assessed using multiple and logistic regressions.

RESULTS

Substance use disorder by age 19 was significantly predicted by P300 amplitude (odds ratio [OR] = .958; 95% confidence interval [CI] = .918-.999; Wald chi (2) = 3.992; df = 1; p = .045) and ND score (OR = 1.060; 95% CI = 1.023-1.098; Wald chi (2) = 10.267; df = 1; p = .0014) measured at age 10 to 12. P300 amplitude also significantly correlated with ND severity (beta = -.217; t = -2.412; df = 6,160; p = .017). Low P300 amplitudes were observed in children who succumbed to SUD by age 19.

CONCLUSIONS

These results indicate that ND mediates the association between attenuated P300 amplitude in childhood and SUD at age 19; however, P300 amplitude is not a specific childhood marker of SUD.

Very slow potential oscillations in locus coeruleus and dorsal raphe nucleus under different illumination in freely moving rats

Recent findings have revealed very slow (<0.5 Hz) oscillatory phenomena in the structures of the brain visual system. It has been proposed that very slow brain potentials in an extremely slow domain, less than 0.1 Hz, recorded from the lateral geniculate complex and primary visual cortex are associated with periodic influences originating from the locus coeruleus and dorsal raphe nucleus. The present study was performed to test the hypothesis that extremely slow brain potential oscillatory patterns in the locus coeruleus and dorsal raphe nucleus during several types of visual stimulation--light exposure, darkness, and photostimulation--are similar to those in the primary visual cortex and lateral geniculate complex under the same conditions of illumination. The results support this hypothesis. Specifically, spectral patterns of multisecond oscillations in the range of 0.02-0.04 Hz and fluctuations in the domain of minutes (below 0.002 Hz) were present in both the locus coeruleus and dorsal raphe nucleus and were similar to those found in the primary visual cortex and lateral geniculate complex. Additionally, we detected significant increases in the power spectra of multisecond oscillations in both nuclei in response to photostimulation (P<0.05). Our tentative conclusion is that extremely slow potentials in the locus coeruleus and dorsal raphe nucleus contribute to the regulation of extremely slow activity in the brain visual system.

Percutaneous peripheral neuromodulation in the treatment of fecal incontinence

BACKGROUND/AIMS

To assess the results of peripheral neuromodulation for the treatment of fecal incontinence (FI) resulting from uninhibited rectal contraction (URC) or uninhibited anal sphincter relaxation (UASR).

METHODS

The work comprised 32 patients (age 38.2 +/- 6.7 years; 22 women) with FI in whom conventional therapy had failed before enrollment in the study. Twenty-six had URC and 6 UASR. Peripheral neurostimulation was effected by posterior tibial nerve stimulation using a Stoller Afferent Nerve Stimulator (UroSurge, Coralville, lowa, USA). The needle was introduced into the skin cephalad to the medial malleolus. Stimulation (parameters: 0.5-10 mA, 200 micros, 20 Hz) was performed every other day for 4 weeks. Functional assessment was done by a questionnaire (incontinence score: 0-20) and physiologic studies.

RESULTS

Group 1: 17 patients (13 URC, 4 UASR) had FI improvement, recording a mean score of 1.7 of 20. Group 2: 10 patients (8 URC, 2 UASR) had fair improvement (score 8.6). Group 3: 5 patients had poor results (score 14.8). Rectometric recording showed improvement in groups 1 and 2. Recurrence of symptoms occurred in 8 patients; 6 improved after retreatment.

CONCLUSIONS

A percutaneous access to the S(3) spinal region was achieved through the posterior tibial nerve. Improvement of FI was achieved in 78.2%. The technique is simple, easy, without complications and cost-effective. It can be done as an outpatient procedure or by the patient at home. The results need to be reproduced on a large number of patients.