Alterations of hypoglossal motoneuronal activities during pulmonary inflations

Preventing pulmonary inflation during inspiration results in greater augmentations in activity of the hypoglossal nerve than in the phrenic nerve. Our purpose was to characterize the hypoglossal motoneuronal activities which underlie these augmentations. Activities of the phrenic and hypoglossal nerves and single hypoglossal fibers were recorded in decerebrate and paralyzed cats. Ventilation was by a servo-respirator which produced changes in lung volume in parallel with phrenic activity. The number of motoneurons that discharged during cycles in which the lungs were inflated increased with elevations of end-tidal fractional concentrations of CO2 (FETCO2) from 0.05 to 0.06 and 0.09. At each FETCO2, the discharge frequency increased when pulmonary inflation was withheld. In addition, withholding inflation resulted in the recruitment of other motoneuronal activities. Most motoneurons discharged during the period of the phrenic burst (inspiratory neurons). Lesser numbers of inspiratory-expiratory, expiratory-inspiratory, and tonic motoneuronal activities were also recorded. Results are considered in the context of the inhibition of respiratory motoneuronal activity by vagal pulmonary afferent fibers. The possible role of such inhibition, and release from this inhibition, in maintenance of patency of the upper airways is discussed.     

Strategies of intention formation are reflected in continuous MEG activity

Abstract

Self-regulation of intention formation is pivotal for achieving behavior change. Fantasy realization theory (Oettingen, 2000) assumes that mentally contrasting a desired positive future with present negative reality turns high expectations of success into strong intentions to realize the desired future, while indulging in the positive future fails to do so. The present study tests the theory's process assumption that mental contrasting is a cognitively demanding, purposeful problem-solving strategy involving working and episodic memory, whereas indulging is a mindless daydreaming strategy involving the free flow of thought, by investigating the neural correlates of the two strategies via continuous magnetoencephalographic (MEG) activity. We observed greater activity during mental contrasting (but not indulging) compared to resting in prefrontal, frontal, parietal, and temporal areas, indicating that mental contrasting involves strong intention formation, working memory, and episodic memory. In addition, heightened activity of occipital areas was observed during mental contrasting compared to resting and indulging, suggesting that mental contrasting, more than indulging and resting, entails purposefully creating mental images. Taken together, these findings indicate that mental contrasting is indeed a purposeful problem-solving strategy based on past performance history, whereas indulging is a purposeless daydreaming strategy that is oblivious to past experiences.     

Strategies of intention formation are reflected in continuous MEG activity

Self-regulation of intention formation is pivotal for achieving behavior change. Fantasy realization theory (Oettingen, 2000) assumes that mentally contrasting a desired positive future with present negative reality turns high expectations of success into strong intentions to realize the desired future, while indulging in the positive future fails to do so. The present study tests the theory's process assumption that mental contrasting is a cognitively demanding, purposeful problem-solving strategy involving working and episodic memory, whereas indulging is a mindless daydreaming strategy involving the free flow of thought, by investigating the neural correlates of the two strategies via continuous magnetoencephalographic (MEG) activity. We observed greater activity during mental contrasting (but not indulging) compared to resting in prefrontal, frontal, parietal, and temporal areas, indicating that mental contrasting involves strong intention formation, working memory, and episodic memory. In addition, heightened activity of occipital areas was observed during mental contrasting compared to resting and indulging, suggesting that mental contrasting, more than indulging and resting, entails purposefully creating mental images. Taken together, these findings indicate that mental contrasting is indeed a purposeful problem-solving strategy based on past performance history, whereas indulging is a purposeless daydreaming strategy that is oblivious to past experiences.     

Generator sites of spontaneous MEG activity during sleep.

We have recorded spontaneous magnetoencephalographic (MEG) activity during overnight natural sleep in 4 healthy adults with a 24-channel SQUID gradiometer, mainly over the sides of the head. All sleep stages were obtained. The MEG wave forms resembled the EEG phenomena recorded simultaneously from the scalp midline, but the electric and magnetic signals did not always coincide. The source locations of different signals were studied by using a current dipole model. The equivalent sources of magnetic transients, resembling and often coinciding with the electric vertex waves and K-complexes, as well as the transients during REM sleep, were concentrated within a volume of 4 x 4 x 3 cm3 in the inferior parietal lobe. For spindles and slow waves, no such focal generators were found.     

Application of an MEG eigenspace beamformer to reconstructing spatio-temporal activities of neural sources

We have applied the eigenspace-based beamformer to reconstruct spatio-temporal activities of neural sources from MEG data. The weight vector of the eigenspace-based beamformer is obtained by projecting the weight vector of the minimum-variance beamformer onto the signal subspace of a measurement covariance matrix. This projection removes the residual noise-subspace component that considerably degrades the signal-to-noise ratio (SNR) of the beamformer output when errors in estimating the sensor lead field exist. Therefore, the eigenspace-based beamformer produces a SNR considerably higher than that of the minimum-variance beamformer in practical situations. The effectiveness of the eigenspace-based beamformer was validated in our numerical experiments and experiments using auditory responses. We further extended the eigenspace-based beamformer so that it incorporates the information regarding the noise covariance matrix. Such a prewhitened eigenspace beamformer was experimentally demonstrated to be useful when large background activity exists.     

蛛网膜下腔出血腰池持续引流前后脑脊液中NO浓度的变化

目的 探讨腰池持续引流防治脑血管痉挛的效果及其对脑脊液中一氧化氮（NO）浓度的影响。方法 50例破裂动脉瘤蛛网膜下腔出血患，随机分为引流组25例。对照组25例。引流组在电解可脱弹簧圈（GDC）栓塞术后立即实施腰池持续引流，对照组行间断腰椎穿刺。脑脊液NO浓度采用镉粒子还原法测定。结果 引流组中发生症状性脑血管痉挛2例。对照组7例。血管痉挛患的NO浓度明显降低，引流组脑脊液中NO浓度在出血后第5d起明显高于对照组。结论 腰池持续引流可有效清除蛛网膜下腔积血，提高脑脊液中NO的浓度。     

连续性结果测量的效应度

我们在上一期栏目中已经讨论了效应度是评估治疗效果的重要指标[1]接下来我们讨论几种广泛使用的方法来计算连续性结果测量值的效应度(以后将讨论二分结果测量值的效应度).     

A qualitative and quantitative analysis of rhythmic activities during a mental task and sleep spindles

The frequency, configuration, and distribution of sleep spindles are similar to some of the rhythmic activities seen during task performance. In the present study, the relationship between rhythmic activities during sleep and arithmetic addition was investigated in male university students with (n = 10) and without (n = 10) frontal midline theta activity (Fmtheta). Electroencephalograms (EEGs) during addition in both groups were compared at frontal and central areas on three consecutive days. Polysomnograms were recorded at the same regions on four consecutive nights for each group. The amount of theta rhythm during a mental task (Fmtheta) and in nocturnal sleep at Fz and Cz electrodes was greater for the Fmtheta group than for the non-Fmtheta group, while the amount of beta rhythm at both sites was smaller in the Fmtheta group than in the non-Fmtheta group. There were no differences between the groups in the amount of alpha rhythm at either site. The frequency of alpha rhythm at Fz and Cz in both situations was slower for the Fmtheta group than for the non-Fmtheta group, but there were no differences in the frequency of theta and beta rhythms between the groups at either site. These results suggest that rhythmic activities during a mental task and in sleep may correlate with each other.     

Modulation of the auditory cortex during speech: an MEG study

Several behavioral and brain imaging studies have demonstrated a significant interaction between speech perception and speech production. In this study, auditory cortical responses to speech were examined during self-production and feedback alteration. Magnetic field recordings were obtained from both hemispheres in subjects who spoke while hearing controlled acoustic versions of their speech feedback via earphones. These responses were compared to recordings made while subjects listened to a tape playback of their production. The amplitude of tape playback was adjusted to match the amplitude of self-produced speech. Recordings of evoked responses to both self-produced and tape-recorded speech were obtained free of movement-related artifacts. Responses to self-produced speech were weaker than were responses to tape-recorded speech. Responses to tones were also weaker during speech production, when compared with responses to tones recorded in the presence of speech from tape playback. However, responses evoked by gated noise stimuli did not differ for recordings made during self-produced speech versus recordings made during tape-recorded speech playback. These data suggest that during speech production, the auditory cortex (1) attenuates its sensitivity and (2) modulates its activity as a function of the expected acoustic feedback.     

Survey of New York City mental hygiene activities

Psychiatric Quarterly -     

Modulation of spatial orientation processing by mental imagery instructions: a MEG study of representational momentum

Under appropriate conditions, an observer's memory for the final position of an abruptly halted moving object is distorted in the direction of the represented motion. This phenomenon is called "representational momentum" (RM). We examined the effect of mental imagery instructions on the modulation of spatial orientation processing by testing for RM under conditions of picture versus body rotation perception and imagination. Behavioral data were gathered via classical reaction time and error measurements, whereas brain activity was recorded with the help of magnetoencephalography (MEG). Due to the so-called inverse problem and to signal complexity, results were described at the signal level rather than with the source location modeling. Brain magnetic field strength and spatial distribution, as well as latency of P200m evoked fields were used as neurocognitive markers. A task was devised where a subject examined a rotating sea horizon as seen from a virtual boat in order to extrapolate either the picture motion or the body motion relative to the picture while the latter disappeared temporarily until a test-view was displayed as a final orientation candidate. Results suggest that perceptual interpretation and extrapolation of visual motion in the roll plane capitalize on the fronto-parietal cortical networks involving working memory processes. Extrapolation of the rotational dynamics of sea horizon revealed a RM effect simulating the role of gravity in rotational equilibrium. Modulation of the P200m component reflected spatial orientation processing and a non-voluntary detection of an incongruity between displayed and expected final orientations given the implied motion. Neuromagnetic properties of anticipatory (Contingent Magnetic Variation) and evoked (P200m) brain magnetic fields suggest, respectively, differential allocation of attentional resources by mental imagery instructions (picture vs. body tilt), and a communality of neural structures (in the right centro-parietal region) for the control of both RM and mental rotation processes. Finally, the RM of the body motion is less prone to forward shifts than that of picture motion evidencing an internalization of the implied mass of the virtual body of the observer.     

The relationship between rhythmic activities during a mental task and sleep spindles: a correlative analysis

In a previous study, we suggested that the characteristics of theta, alpha, and beta rhythms during a mental task were similar to those during sleep. Building upon the previous data, correlations between rhythmic activities during a mental task and during sleep were investigated in the present study. Patterns of correlation and no correlation between rhythmic activities during the mental task were similar to those during sleep for subjects with and without frontal midline theta (Fmtheta) activity. In the Fmtheta group, there were no correlations between rhythmic activities in the two situations, while in the non-Fmtheta subjects, theta and alpha rhythms showed a positive correlation with one another, and theta and beta rhythms correlated negatively during sleep. In both groups, there were many correlations between rhythmic activities during the mental task and those in Sleep Stage 2, while there were few correlations between rhythmic activities during the mental task and those in other sleep stages. These results suggest that the mechanism generating rhythmic activities during the appearance of rhythmic activities induced by a mental task may be closely related to those of rhythmic activities during sleep, and that the membrane potentials in reticular thalamic (RE) neurons during the appearance of rhythmic activities induced by a mental task may be nearly equivalent to that in Sleep Stage 2, and that the correlation pattern between the rhythmic activities in each group may be well explained by the appearance pattern of each rhythm in the previous report.     

EEG and MEG coherence: measures of functional connectivity at distinct spatial scales of neocortical dynamics

We contrasted coherence estimates obtained with EEG, Laplacian, and MEG measures of synaptic activity using simulations with head models and simultaneous recordings of EEG and MEG. EEG coherence is often used to assess functional connectivity in human cortex. However, moderate to large EEG coherence can also arise simply by the volume conduction of current through the tissues of the head. We estimated this effect using simulated brain sources and a model of head tissues (cerebrospinal fluid (CSF), skull, and scalp) derived from MRI. We found that volume conduction can elevate EEG coherence at all frequencies for moderately separated (<10 cm) electrodes; a smaller levation is observed with widely separated (>20 cm) electrodes. This volume conduction effect was readily observed in experimental EEG at high frequencies (40-50 Hz). Cortical sources generating spontaneous EEG in this band are apparently uncorrelated. In contrast, lower frequency EEG coherence appears to result from a mixture of volume conduction effects and genuine source coherence. Surface Laplacian EEG methods minimize the effect of volume conduction on coherence estimates by emphasizing sources at smaller spatial scales than unprocessed potentials (EEG). MEG coherence estimates are inflated at all frequencies by the field spread across the large distance between sources and sensors. This effect is most apparent at sensors separated by less than 15 cm in tangential directions along a surface passing through the sensors. In comparison to long-range (>20 cm) volume conduction effects in EEG, widely spaced MEG sensors show smaller field-spread effects, which is a potentially significant advantage. However, MEG coherence estimates reflect fewer sources at a smaller scale than EEG coherence and may only partially overlap EEG coherence. EEG, Laplacian, and MEG coherence emphasize different spatial scales and orientations of sources.     

The feasibility of routine outcome measures in mental health

Background: Standardised outcome measures are not being used in routine mental health care. Method: The importance of routine use of standardised outcome measures is argued, and reasons for their lack of use suggested. Results: One reason for standardised outcome measures not being used routinely is the lack of appropriate instruments. This property of being suitable for routine use is often called feasibility, but there is no consensus about the meaning of feasibility, or how it should be measured. We propose a definition of feasibility as a psychometric property of a standardised outcome measure, provide criteria for assessing feasibility, and then present a framework for changing practice to increase the routine use of standardised outcome measures. Conclusions: If mental health care is to maximise outcome, then more attention needs to be paid both to the process of developing and to facilitating the routine clinical use of feasible outcome measures. Accepted: 20 January 1999     

Sequential audiovisual interactions during speech perception: a whole-head MEG study

Using whole-head magnetoencephalography (MEG), audiovisual (AV) interactions during speech perception (/ta/- and /pa/-syllables) were investigated in 20 subjects. Congruent AV events served as the 'standards' of an oddball design. The deviants encompassed incongruent /ta/-/pa/ configurations differing from the standards either in the acoustic or the visual domain. As an auditory non-speech control condition, the same video signals were synchronized with either one of two complex tones. As in natural speech, visual movement onset preceded acoustic signals by about 150 ms. First, the impact of visual information on auditorily evoked fields to non-speech sounds was determined. Larger facial movements (/pa/ versus /ta/) yielded enhanced early responses such as the M100 component, indicating, most presumably, anticipatory pre-activation of auditory cortex by visual motion cues. As a second step of analysis, mismatch fields (MMF) were calculated. Acoustic deviants elicited a typical MMF, peaking ca. 180 ms after stimulus onset, whereas visual deviants gave rise to later responses (220 ms) of a more posterior-medial source location. Finally, a late (275 ms), left-lateralized visually-induced MMF component, resembling the acoustic mismatch response, emerged during the speech condition, presumably reflecting phonetic/linguistic operations. There is mounting functional imaging evidence for an early impact of visual information on auditory cortical regions during speech perception. The present study suggests at least two successive AV interactions in association with syllable recognition tasks: early activation of auditory areas depending upon visual motion cues and a later speech-specific left-lateralized response mediated, conceivably, by backward-projections from multisensory areas.     

Brain activation during reading in deep dyslexia: an MEG study

Magnetoencephalographic (MEG) changes in cortical activity were studied in a chronic Finnish-speaking deep dyslexic patient during single-word and sentence reading. It has been hypothesized that in deep dyslexia, written word recognition and its lexical-semantic analysis are subserved by the intact right hemisphere. However, in our patient, as well as in most nonimpaired readers, lexical-semantic processing as measured by sentence-final semantic-incongruency detection was related to the left superior-temporal cortex activation. Activations around this same cortical area could be identified in single-word reading as well. Another factor relevant to deep dyslexic reading, the morphological complexity of the presented words, was also studied. The effect of morphology was observed only during the preparation for oral output. By performing repeated recordings 1 year apart, we were able to document significant variability in both the spontaneous activity and the evoked responses in the lesioned left hemisphere even though at the behavioural level, the patient's performance was stable. The observed variability emphasizes the importance of estimating consistency of brain activity both within and between measurements in brain-damaged individuals.     

Alterations in pain during adolescence and puberty

During adolescence and puberty, alterations in pain, both experimental and clinical, are observed. In addition, adolescents undergo extensive biopsychosocial changes as they transition from childhood to adulthood. However, a better understanding of how the biopsychosocial changes during adolescence impact pain is needed to improve pain management and develop targeted pain interventions for adolescents. This review synthesizes the literature on alterations in pain during adolescence in humans, describes the potential biopsychosocial factors impacting pain during adolescence, and suggests future research directions to advance the understanding of the impact of adolescent development on pain.     

Effects of GSM electromagnetic field on the MEG during an encoding-retrieval task

Potential effects of GSM 1800 electromagnetic fields (EMF) on verbal memory encoding were investigated by recording event-related magnetic fields (ERMF) from the brain during subsequent memory retrieval. Twelve normal subjects participated in the study. After encoding words from a study list presented in the first phase they had to discriminate old from new words mixed together in a test list presented during the second phase. All subjects performed two experimental sessions, one with exposure to EMF during the study phase, and one without. Exposure to EMF changed an early (350-400 ms) task-specific component of the ERMF indicating an interference of EMF and item encoding. Behavioural measures were not significantly affected. Adverse health effects cannot be derived from these data.     

Assessment and diagnosis of mental illness in persons with mental retardation. Methods and measures

The assessment and diagnosis of psychiatric disorders in individuals with mental retardation has been a neglected area of research. However, current research indicates that these individuals suffer from the same range of psychiatric disorders that is evident in those who are not mentally retarded. A model of assessment and diagnosis of mental illness in this population is presented that incorporates psychiatric as well as behavioral methods. The emphasis is on the comprehensive assessment of an individual's behavior, based on family history, self and informant clinical interviews, rating scales, direct observations, and an experimental analysis of the target behaviors. The model provides the basis for making differential diagnoses in terms of related psychiatric disorders and between psychiatric disorders and behavior problems. Depression and schizophrenia are used as illustrative disorders to describe the application of this model. Given the paucity of literature on the assessment and diagnosis of mental illness in individuals with mental retardation, a number of suggestions are made regarding future research and refinement of the model.