Electrophysiological decomposition of attentional factors on the hypercorrection effect of false lexical representations.

False memories endorsed with higher confidence are more likely to be corrected by feedback than those endorsed with lower confidence (hypercorrection effect). Errors made with high confidence and correct responses made with low confidence are both associated with large meta-memory mismatches. Therefore, they both represent a type of unexpected event which automatically captures participant attention, such that correct information provided via feedback is well-encoded. On the other hand, a study that measured participants' perceived practical value for items suggested that voluntary allocation of attention might involve the hypercorrection effect. The present study involved a lexical learning task with 28 undergraduate student participants and measurement of automatic and voluntary attentional allocations via P3a/novelty P3 and P3b respectively, both of which are event-related potentials (ERPs). Behavioral results replicated the hypercorrection effect in a lexical learning task and showed modulation of the effect with regard to perceived practical value. In addition, ERP measurement results demonstrated that both automatic and voluntary allocations of attentional resources were independently involved in the hypercorrection phenomenon.

After-effect induced by microwave radiation in human electroencephalographic signal: a feasibility study.

PURPOSE: This feasibility study is aimed to clarify the possibility of detection of microwave radiation (MWR)-induced event related potential (ERP) in electroencephalographic (EEG) signal. METHODS: To trigger onset and offset effects in EEG, repetitive MWR stimuli were used. Four 30-channel EEG recordings on a single subject were performed, each about one month apart. The subject was exposed to 450 MHz MWR modulated at 40 Hz at the 1 g peak spatial average specific absorption rate of 0.3 W/kg. During a recording, 40 cycles of 30 s on-off MWR exposure were used. The artifact-free responses to 126 MWR-ON stimuli and 134 MWR-OFF stimuli were averaged over stimuli and channels. RESULTS: Regarding EEG signals locked to MWR-OFF stimulus, the enhanced signal level at alpha frequency band and about twice higher signal to noise ratio at 200 to 440 ms after the stimulus have been detected. No remarkable response in EEG signals locked to MWR-ON stimulus. CONCLUSIONS: The detection of offset effect confirms that there should be an imprint generated by MWR in brain. The results of this preliminary study provide evidence for the detection of MWR-induced ERP in EEG signal and encourage further research in this direction.

Reducing Pericyte-Derived Scarring Promotes Recovery after Spinal Cord Injury.

CNS injury often severs axons. Scar tissue that forms locally at the lesion site is thought to block axonal regeneration, resulting in permanent functional deficits. We report that inhibiting the generation of progeny by a subclass of pericytes led to decreased fibrosis and extracellular matrix deposition after spinal cord injury in mice. Regeneration of raphespinal and corticospinal tract axons was enhanced and sensorimotor function recovery improved following spinal cord injury in animals with attenuated pericyte-derived scarring. Using optogenetic stimulation, we demonstrate that regenerated corticospinal tract axons integrated into the local spinal cord circuitry below the lesion site. The number of regenerated axons correlated with improved sensorimotor function recovery. In conclusion, attenuation of pericyte-derived fibrosis represents a promising therapeutic approach to facilitate recovery following CNS injury.

Evoked bioelectrical brain activity following exposure to ionizing radiation. / VYKLYKANA BIOELEKTRYChNA AKTYVNIST' GOLOVNOGO MOZKU PISLIa VPLYVU IONIZUIuChOÏ RADIATsIÏ.

The article provides an overview of modern physiological evidence to support the hypothesis on cortico limbic sys tem dysfunction due to the hippocampal neurogenesis impairment as a basis of the brain interhemispheric asym metry and neurocognitive deficit after radiation exposure. The importance of the research of both evoked poten tials and fields as a highly sensitive and informative method is emphasized.Particular attention is paid to cerebral sensor systems dysfunction as a typical effect of ionizing radiation. Changes in functioning of the central parts of sensory analyzers of different modalities as well as the violation of brain integrative information processes under the influence of small doses of ionizing radiation can be critical when determining the radiation risks of space flight. The possible long term prospects for manned flights into space, including to Mars, given the effects identified are discussed. Potential risks to the central nervous system during space travel comprise cognitive functions impairment, including the volume of short term memory short ening, impaired motor functions, behavioral changes that could affect human performance and health. The remote risks for CNS are considered to be the following possible neuropsychiatric disorders: accelerated brain aging, Alzheimer's disease and other types of dementia. The new radiocerebral dose dependent effect, when applied cog nitive auditory evoked potentials P300 technique with a possible threshold dose of 0.05 Gy, manifesting in a form of disruption of information processing in the Wernicke's area is under discussion. In order to identify neurophys iological biological markers of ionizing radiation further international researches with adequate dosimetry support are necessary.

Utilidad de la monitorización electrofisiológica transoperatoria en el abordaje de las lesiones de plexo braquial / Usefulness of transoperative electrophysiological monitoring in the treatment of brachial plexus injuries

Antecedentes y Objetivo. Las lesiones del plexo braquial son devastadoras para los pacientes. La baja especificidad y el valor predictivo positivo en los estudios de electrofisiología prequirúrgicos son la principal indicación para la realización de una monitorización electrofiológica intraoperatoria. A pesar de los grandes avances logrados, los resultados del tratamiento quirúrgico en los pacientes con lesión de plexo braquial están lejos de un panorama ideal. Sin embargo, la terapia quirúrgica actual logra mejores resultados que los tratamientos sin reconstrucción nerviosa. El objetivo de este trabajo es analizar los resultados postquirúrgicos de los pacientes sometidos a cirugía de plexo braquial con y sin monitorización electrofiosológica transoperatoria. Material y Método. Evaluamos los expedientes y videos pre y postoperatorios de nuestros pacientes con lesión de plexo braquial entre 2007 y 2014 sometidos a neurolisis, injertos nerviosos y/o transferencias nerviosas. Excluimos a los pacientes con transferencias musculares o artrodesis, y divididos el total en 2 grupos dependiendo de la realización o no de monitorización electrofiológica transoperatoria. Analizamos los videos mediante una escala de evaluación basada en la tabla de valoración de Narakas y Raimondi. Resultados. Obtuvimos 25 pacientes. Todas las evaluaciones postquirúrgicas presentaron mejoría (p <0.05) independientemente de la realización o no de monitorización electrofisiológica transoperatoria. La evaluación postquirúrgica con monitorización transoperatoria de la rotación externa del hombro y el movimiento de los dedos centrales obtuvieron mejoría (p <0.05), en comparación con aquellos en los que no se realizó monitorización. En la evaluación postquirúrgica, 53.3% de los pacientes con monitorización presentó ascenso en 1 o más de los rangos de la escala; mientras que en los pacientes sin monitorización solo el 20% presentó incremento. Ninguno presentó menor puntaje en la evaluación postquirúrgica con respecto a la preoperatoria. Conclusiones. A pesar de no lograr reestablecer la función del miembro afectado, todos los pacientes presentaron mejoría clínica en el periodo postoperatorio. Cabe resaltar que los pacientes con monitorización electrofisiológica transoperatoria obtuvieron mejores resultados clínicos en el periodo postquirúrgico (AU)

Background and Objective. Brachial plexus injuries are one of the most devastating lesions for the patient. The presurgical low specificity and positive predicted value in the electrophysiology studies are the main indication to perform an intraoperative nerve recording. Despite the great progress obtained, the surgical treatment results in patients with brachial plexus lesions are fare from an ideal scenario. Nevertheless, the surgical management obtains better results than nonsurgical treatment. The aim of this study is to analyze the postoperative results of patients with brachial plexus surgery with and without transoperative electrophysiological monitoring. Methods. From 2007 to 2014 medical files and preoperative and postoperative videos of our patients with brachial plexus injury were evaluated, those patients underwent neurolysis, nerve grafts and/or nerve transfer. Patients with muscle transfer or arthrodesis were excluded. Two groups were formed, depending on the performance or absence of intraoperative nerve recording. Their pre and post-surgery videos were reviewed and rated according to a scale based on the Narakas and Raimondi valuation. Results. Twenty five patients were obtained. All postoperative assessments showed a statistically significant improvement (p <0.05) regardless either of the presence or the absence of intraoperative nerve recording. During the postoperative evaluation of the group with intraoperative monitoring, shoulder external rotation and movement of the middle fingers obtained statistically significant improvement (p <0.05), in comparison to the group without nerve recording. In the postoperative evaluation, 53.3% of patients presented with intraoperative nerve recording arose in 1 or more of the ranges of the rating scale; whereas in patients without it only 20% had increased. None of the patients gave a lower score while postoperative assessment. Conclusions. Even though the surgical treatment did not reestablish the complete patient movement, it reached better postsurgical outcomes. Draws attention to intraoperative nerve monitoring studies provide better clinical outcomes in the postoperative period in patients with brachial plexus inju (AU)

Preparation of Horizontal Slices of Adult Mouse Retina for Electrophysiological Studies.

Vertical slice preparations are well established to study circuitry and signal transmission in the adult mammalian retina. The plane of sectioning in these preparations is perpendicular to the retinal surface, making it ideal for the study of radially oriented neurons like photoreceptors and bipolar cells. However, the large dendritic arbors of horizontal cells, wide-field amacrine cells, and ganglion cells are mostly truncated, leaving markedly reduced synaptic activity in these cells. Whereas ganglion cells and displaced amacrine cells can be studied in a whole-mounted preparation of the retina, horizontal cells and amacrine cells located in the inner nuclear layer are only poorly accessible for electrodes in whole retina tissue. To achieve maximum accessibility and synaptic integrity, we developed a horizontal slice preparation of the mouse retina, and studied signal transmission at the synapse between photoreceptors and horizontal cells. Horizontal sectioning allows (1) easy and unambiguous visual identification of horizontal cell bodies for electrode targeting, and (2) preservation of the extended horizontal cell dendritic fields, as a prerequisite for intact and functional cone synaptic input to horizontal cell dendrites. Horizontal cells from horizontal slices exhibited tonic synaptic activity in the dark, and they responded to brief flashes of light with a reduction of inward current and diminished synaptic activity. Immunocytochemical evidence indicates that almost all cones within the dendritic field of a horizontal cell establish synapses with its peripheral dendrites. The horizontal slice preparation is therefore well suited to study the physiological properties of horizontally extended retinal neurons as well as sensory signal transmission and integration across selected synapses.

Optogenetic Modulation of Urinary Bladder Contraction for Lower Urinary Tract Dysfunction.

As current clinical approaches for lower urinary tract (LUT) dysfunction such as pharmacological and electrical stimulation treatments lack target specificity, thus resulting in suboptimal outcomes with various side effects, a better treatment modality with spatial and temporal target-specificity is necessary. In this study, we delivered optogenetic membrane proteins, such as channelrhodopsin-2 (ChR2) and halorhodopsin (NpHR), to bladder smooth muscle cells (SMCs) of mice using either the Cre-loxp transgenic system or a viral transfection method. The results showed that depolarizing ChR2-SMCs with blue light induced bladder contraction, whereas hyperpolarizing NpHR-SMCs with yellow light suppressed PGE2-induced overactive contraction. We also confirmed that optogenetic contraction of bladder smooth muscles in this study is not neurogenic, but solely myogenic, and that optogenetic light stimulation can modulate the urination in vivo. This study thus demonstrated the utility of optogenetic modulation of smooth muscle as a means to actively control the urinary bladder contraction with spatial and temporal accuracy. These features would increase the efficacy of bladder control in LUT dysfunctions without the side effects of conventional clinical therapies.

Ncm, a Photolabile Group for Preparation of Caged Molecules: Synthesis and Biological Application.

Ncm, 6-nitrocoumarin-7-ylmethyl, is a photolabile protective group useful for making "caged" molecules. Ncm marries the reliable photochemistry of 2-nitrobenzyl systems with the excellent stability and spectroscopic properties of the coumarin chromophore. From simple, commercially available starting materials, preparation of Ncm and its caged derivatives is both quick and easy. Photorelease of Ncm-caged molecules occurs on the microsecond time scale, with quantum efficiencies of 0.05-0.08. We report the synthesis and physical properties of Ncm and its caged derivatives. The utility of Ncm-caged glutamate for neuronal photostimulation is demonstrated in cultured hippocampal neurons and in brain slice preparations.

Corregistro de la actividad eléctrica cerebral y oculomotora: una alternativa para la investigación en dislexia / Simultaneous recording of electrical brain activity and eye movements: an alternative for research into dyslexia

La dislexia es uno de los trastornos del desarrollo más comunes en la etapa escolar y afecta aproximadamente del 5 a 15% de la población. La comprensión en «tiempo real» de un texto requiere del procesamiento de la información visual entrante a través de una compleja serie de fijaciones cortas de la mirada y movimientos sacádicos de los ojos, así como de la recuperación, actualización e integración de los elementos almacenados en la memoria. Esto ha provocado que numerosas investigaciones hayan hecho un gran uso de 2 métodos en particular para su estudio: los potenciales cerebrales relacionados a eventos (PRE) y el rastreo ocular (RO). Sin embargo, los resultados todavía son muy variables y, por tanto, el origen de la dislexia, desde el punto de vista neurobiológico, continúa siendo aún un tema muy debatido. En este trabajo se realiza una revisión exhaustiva de la literatura donde se abordan los hallazgos de los diferentes estudios neurofisiológicos publicados en el tema, así como sus limitaciones. Luego se analiza la factibilidad del registro simultáneo de la actividad eléctrica cerebral y los movimientos oculares mediante la revisión detallada de los aspectos metodológicos a considerar. Por último, se fundamentan las posibles ventajas de este enfoque para los estudios de la lectura, así como sus aplicaciones potenciales en la investigación en dislexia (AU)

Dyslexia is one of the most common developmental disorders at school age and affects approximately 5-15% of the population. Reading is a complex cognitive task and its comprehension requires the processing of visual input across a complex series of brief fixation pauses and saccadic eye movements, as well as retrieving, updating, and integrating contents of memory. This has led to current research making heavy use of two methods: recording eye movement (EMs) and event-related brain potentials (ERPs). However, results are still equivocal, and therefore, the neurobiology of dyslexia remains hotly debated. This paper presents a comprehensive review of the literature in which the findings of different neurophysiological studies published on the subject are addressed, as well as their limitations. The feasibility of simultaneously recording electrical brain activity and eye movements is then analysed by a detailed review of methodological challenges to consider. Finally, the possible benefits of this approach to reading studies and its potential applications in research into dyslexia are described (AU)

Optogenetic control of human neurons in organotypic brain cultures.

Optogenetics is one of the most powerful tools in neuroscience, allowing for selective control of specific neuronal populations in the brain of experimental animals, including mammals. We report, for the first time, the application of optogenetic tools to human brain tissue providing a proof-of-concept for the use of optogenetics in neuromodulation of human cortical and hippocampal neurons as a possible tool to explore network mechanisms and develop future therapeutic strategies.

The Processing of Attended and Predicted Sounds in Time.

Neural responses to an attended event are typically enhanced relative to those from an unattended one (attention enhancement). Conversely, neural responses to a predicted event are typically reduced relative to those from an unpredicted one (prediction suppression). What remains to be established is what happens with attended and predicted events. To examine the interaction between attention and prediction, we combined two robust paradigms developed for studying attention and prediction effects on ERPs into an orthogonal design. Participants were presented with sounds in attended or unattended intervals with onsets that were either predicted by a moving visual cue or unpredicted (no cue was provided). We demonstrated an N1 enhancement effect for attended sounds and an N1 suppression effect for predicted sounds; furthermore, an interaction between these effects was found that emerged early in the N1 (50-95 msec), indicating that attention enhancement only occurred when the sound was unpredicted. This pattern of results can be explained by the precision of the predictive cue that reduces the need for attention selection in the attended and predicted condition.

Terrestrial Trunked Radio (TETRA) exposure and its impact on slow cortical potentials.

BACKGROUND: Studies have shown that exposure to radiofrequency electromagnetic fields (RF-EMF) in the mobile communication frequency range may induce physiological modifications of both spontaneous as well as event-related human electroencephalogram. So far, there are very few peer-reviewed studies on effects of Terrestrial Trunked Radio (TETRA), which is a digital radio communication standard used by security authorities and organizations in several European countries, on the central nervous system. OBJECTIVES: To analyze the impact of simulated TETRA handset signals at 385 MHz on slow cortical potentials (SCPs). METHODS: 30 young healthy males (25.2±2.7 years) were exposed in a double-blind, counterbalanced, cross-over design to one of three exposure levels (TETRA with 10 g averaged peak spatial SAR: 1.5 W/kg, 6.0 W/kg and sham). Exposure was conducted with a body worn antenna (especially designed for this study), positioned at the left side of the head. Subjects had 9 test sessions (three per exposure condition) in which three SCPs were assessed: SCP related to a clock monitoring task (CMT), Contingent negative variation (CNV) and Bereitschaftspotential (BP). RESULTS: Neither behavioral measures nor the electrophysiological activity was significantly affected by exposure in the three investigated SCP paradigms. Independent of exposure, significant amplitude differences between scalp regions could be observed for the CMT-related SCP and for the CNV. CONCLUSIONS: The present results reveal no evidence of RF-EMF exposure-dependent brain activity modifications investigated at the behavioral and the physiological level.

Sleep loss, circadian mismatch, and abnormalities in reorienting of attention in night workers with shift work disorder.

STUDY OBJECTIVES: Permanent night-shift workers may develop shift-work disorder (SWD). In the current study, we evaluated neurophysiological and behavioral indices of distractibility across times prior to the night shift (T1), during night hours (T2), and after acute sleep deprivation (T3) in permanent hospital night workers with and without SWD. METHODS: Ten asymptomatic night workers (NW) and 18 NW with SWD participated in a 25-h sleep deprivation study. Circadian phase was evaluated by dim-light salivary melatonin onset (DLMO). Objective sleepiness was evaluated using the Multiple Sleep Latency Test (MSLT). Electrophysiological distractibility was evaluated by brain event-related potentials (ERP), whereas behavioral distractibility was evaluated by performance on a visual task in an auditory-visual distraction paradigm. STATISTICAL ANALYSES: Comparisons of ERP results were performed by repeated-measures analysis of variance, and t-tests were used where appropriate. A Mann-Whitney U test was used for comparison of variables (MLST, Stanford Sleepiness Scale, and DLMO) that deviated from normal. RESULTS: First, in the SWD group, the reorienting negativity ERP amplitude was significantly attenuated compared to that in the NW group. Second, the SWD group had shorter MSLT during night shift hours (4.8 ± 4.9 min) compared to that in NW (7.8 ± 3.7 min; U = 47; z = -2.1; P < 0.03). Third, NW with SWD had a DLMO at 20:27 ± 5.0 h, whereas healthy NW had a DLMO at 05:00 ± 3.4 h (U = 43.5; z = -2.22, P < 0.03). Finally, acute sleep deprivation impaired behavioral performance and the P3a ERP in both groups. CONCLUSIONS: Our results demonstrate specific deficits in neurophysiological activity in the attentional domain among the shift-work disorder group relative to night workers.

Pulsed 808-nm infrared laser stimulation of the auditory nerve in guinea pig cochlea.

Pulsed near-infrared radiation has been proposed as an alternative stimulus for auditory nerve stimulation and could be potentially used in the design of cochlear implant. Although the infrared with high absorption coefficient of water (i.e., wavelength ranged from 1.8 to 2.2 µm) has been widely investigated, the lymph in the cochlea absorbs most of the infrared energies, and only a small part can arrive at the target auditory nerves. The present study is aimed to test whether the short-wavelength near-infrared irradiation with lower absorption coefficients can penetrate the lymph fluid to stimulate the auditory nerves. An 808-nm near-infrared laser was chosen to stimulate the auditory nerve in the guinea pig cochlea. The infrared pulse was delivered by an optical fiber that was surgically inserted near the round window membrane and oriented toward the spiral ganglion cells in the basal turn of the cochlea. The 2-Hz infrared pulses were used to stimulate the cochlea before and after the deafness with different pulse durations (100-1,000 µs). Optically evoked compound action potentials (oCAPs) were recorded during the infrared radiation. We successfully recorded oCAPs from both normal hearing animals and deafened animals. The oCAP amplitude increased with the infrared radiation energy. The preliminary experiment suggests that the near-infrared with lower absorption coefficients can effectively pass through the lymph filled in the cochlea and stimulate the auditory nerve. Further studies will optimize the deafness animal model and determine the optimal stimulation parameters.

Effects of strobe light stimulation on postnatal developing rat retina.

The nature and intensity of visual stimuli have changed in recent years because of television and other dynamic light sources. Although light stimuli accompanied by contrast and strength changes are thought to have an influence on visual system development, little information is available on the effects of dynamic light stimuli such as a strobe light on visual system development. Thus, this study was designed to evaluate changes caused by dynamic light stimuli during retinal development. This study used 80 Sprague-Dawley rats. From eye opening (postnatal day 14), half of the rats were maintained on a daily 12-h light/dark cycle (control group) and the remaining animals were raised under a 12-h strobe light (2 Hz)/dark cycle (strobe light-reared group). Morphological analyses and electroretinogram (ERG) were performed at postnatal weeks 3, 4, 6, 8, and 10. Among retinal neurons, tyrosine hydroxylase-immunoreactive (TH-IR, dopaminergic amacrine cells) cells showed marked plastic changes, such as variations in numbers and soma sizes. In whole-mount preparations at 6, 8, and 10 weeks, type I TH-IR cells showed a decreased number and larger somata, while type II TH-IR cells showed an increased number in strobe-reared animals. Functional assessment by scotopic ERG showed that a-wave and b-wave amplitudes increased at 6 and 8 weeks in strobe-reared animals. These results show that exposure to a strobe light during development causes changes in TH-IR cell number and morphology, leading to a disturbance in normal visual functions.

Age-related differences in enhancement and suppression of neural activity underlying selective attention in matched young and old adults.

Selective attention reflects the top-down control of sensory processing that is mediated by enhancement or inhibition of neural activity. ERPs were used to investigate age-related differences in neural activity in an experiment examining selective attention to color under Attend and Ignore conditions, as well as under a Neutral condition in which color was task-irrelevant. We sought to determine whether differences in neural activity between old and young adult subjects were due to differences in age rather than executive capacity. Old subjects were matched to two groups of young subjects on the basis of neuropsychological test performance: one using age-appropriate norms and the other using test scores not adjusted for age. We found that old and young subject groups did not differ in the overall modulation of selective attention between Attend and Ignore conditions, as indexed by the size of the anterior Selection Positivity. However, in contrast to either young adult group, old subjects did not exhibit reduced neural activity under the Ignore relative to Neutral condition, but showed enhanced activity under the Attend condition. The onset and peak of the Selection Positivity occurred later for old than young subjects. In summary, older adults execute selective attention less efficiently than matched younger subjects, with slowed processing and failed suppression under Ignore. Increased enhancement under Attend may serve as a compensatory mechanism.

Strain differences in illumination-dependent structural changes at mouse photoreceptor ribbon synapses.

Photoreceptor cells encode light signals over a wide range of intensities with graded changes in their membrane potential. At their highly specialized ribbon synapses they transmit the signals to the postsynaptic neurons by the tonic release of glutamate, which is continuously adjusted to changes in light intensity. Such a level of performance requires adaptive mechanisms, and it is suggested that illumination-dependent changes in ribbon shape and size are one of these adaptive processes. In this study we compared structural properties of synaptic ribbons under various illumination conditions between three mouse strains: the pigmented C57BL/6 and the two albino strains Balb/c and B6(Cg)-Tyr(c-2J) /J (coisogenic to C57BL/6). In addition, electroretinograms (ERGs) recorded in the same groups were compared. In the C57BL/6 mouse a change in illumination did not result in structural alterations of the synaptic ribbon. Similarly, in the B6(Cg)-Tyr(c-2J) /J mouse only minor structural changes were detected. In contrast, the state of adaptation had a large influence on the ribbon structure of the Balb/c mouse. The ERG recordings showed only small functional differences between C57BL/6 and B6(Cg)-Tyr(c-2J) /J mice, but the retinal function of Balb/c mice was strongly compromised. We conclude that illumination-dependent changes of photoreceptor ribbon structure differ between strains and thus cannot be regarded as a general mechanism for light adaptation.

Effects of transcranial electrical stimulation on cognition.

Alterations of cortical excitability, oscillatory as well as non-oscillatory, are physiological derivates of cognitive processes, such as perception, working memory, learning, and long-term memory formation. Since noninvasive electrical brain stimulation is capable of inducing alterations in the human brain, these stimulation approaches might be attractive tools to modulate cognition. Transcranial direct current stimulation (tDCS) alters spontaneous cortical activity, while transcranial alternating current stimulation (tACS) and transcranial random noise stimulation (tRNS) are presumed to induce or interfere with oscillations of cortical networks. Via these mechanisms, the respective stimulation techniques have indeed been shown to modulate cognitive processes in a multitude of studies conducted during the last years. In this review, we will gather knowledge about the potential of noninvasive electrical brain stimulation to study and modify cognitive processes in healthy humans and discuss directions of future research.

Functional neuroimaging and transcranial electrical stimulation.

Transcranial electrical stimulation (tES) is a noninvasive tool for inducing local and widespread neuroplastic changes in brain networks. The combination of tES with various neuroimaging techniques provides whole brain data on the working mechanisms of tES, in particular on the development of large-scale activation patterns of interconnected neuronal regions induced by tES. This review focuses on the combined usage of a noninvasive application of transcranial direct current stimulation and functional magnetic resonance imaging and on magnetic resonance spectroscopy.

Optogenetic field potential recording in cortical slices.

We introduce a method that uses optogenetic stimulation to evoke field potentials in brain slices prepared from transgenic mice expressing channelrhodopsin-2-YFP. Cortical slices in a recording chamber were stimulated with a 473 nm blue laser via either a laser scanning photostimulation setup or by direct guidance of a fiber optic. Field potentials evoked by either of the two optogenetic stimulation methods had stable amplitude, consistent waveform, and similar components as events evoked with a conventional stimulating electrode. The amplitude of evoked excitatory postsynaptic potentials increased with increasing laser intensity or pulse duration. We further demonstrated that optogenetic stimulation can be used for the induction and monitoring of long-term depression. We conclude that this technique allows for efficient and reliable activation of field potentials in brain slice preparation, and will be useful for studying short and long term synaptic plasticity.