Gamma-band synchronous oscillations: recent evidence regarding their functional significance.

How do our brains represent distinct objects in consciousness? In order to consciously distinguish between objects, our brains somehow selectively bind together activity patterns of spatially intermingled neurons that simultaneously represent similar and dissimilar features of distinct objects. Gamma-band synchronous oscillations (GSO) of neuroelectrical activity have been hypothesized to be a mechanism used by our brains to generate and bind conscious sensations to represent distinct objects. Most experiments relating GSO to specific features of consciousness have been published only in the last several years. This brief review focuses on a wide variety experiments in which animals, including humans, discriminate between sensory stimuli and make these discriminations evident in their behavior. Performance of these tasks, in humans, is invariably accompanied by conscious awareness of both stimuli and behavior. Results of these experiments indicate that specific patterns of GSO correlate closely with specific aspects of conscious sensorimotor processing. That is, GSO appear to be closely correlated with neural generation of our most paradigmatic cognitive state: consciousness.     

Alpha and theta oscillations in mental addition for high and low performers

Cognitive Processing - While many contemporary studies aim to explore the sources of notable individual differences in arithmetic skills, this study specifically aims to highlight cognitive...     

A theory of alpha/theta neurofeedback,creative performance enhancement,long distance functional connectivity and psychological integration

Professionally significant enhancement of music and dance performance and mood has followed training with an EEG-neurofeedback protocol which increases the ratio of theta to alpha waves using auditory feedback with eyes closed. While originally the protocol was designed to induce hypnogogia, a state historically associated with creativity, the outcome was psychological integration, while subsequent applications focusing on raising the theta–alpha ratio, reduced depression and anxiety in alcoholism and resolved post traumatic stress syndrome (PTSD). In optimal performance studies we confirmed associations with creativity in musical performance, but effects also included technique and communication. We extended efficacy to dance and social anxiety. Diversity of outcome has a counterpart in wide ranging associations between theta oscillations and behaviour in cognitive and affective neuroscience: in animals with sensory-motor activity in exploration, effort, working memory, learning, retention and REM sleep; in man with meditative concentration, reduced anxiety and sympathetic autonomic activation, as well as task demands in virtual spatial navigation, focussed and sustained attention, working and recognition memory, and having implications for synaptic plasticity and long term potentiation. Neuroanatomical circuitry involves the ascending mescencephalic-cortical arousal system, and limbic circuits subserving cognitive as well as affective/motivational functions. Working memory and meditative bliss, representing cognitive and affective domains, respectively, involve coupling between frontal and posterior cortices, exemplify a role for theta and alpha waves in mediating the interaction between distal and widely distributed connections. It is posited that this mediation in part underpins the integrational attributes of alpha–theta training in optimal performance and psychotherapy, creative associations in hypnogogia, and enhancement of technical, communication and artistic domains of performance in the arts.     

A theory of alpha/theta neurofeedback, creative performance enhancement, long distance functional connectivity and psychological integration

Professionally significant enhancement of music and dance performance and mood has followed training with an EEG-neurofeedback protocol which increases the ratio of theta to alpha waves using auditory feedback with eyes closed. While originally the protocol was designed to induce hypnogogia, a state historically associated with creativity, the outcome was psychological integration, while subsequent applications focusing on raising the theta–alpha ratio, reduced depression and anxiety in alcoholism and resolved post traumatic stress syndrome (PTSD). In optimal performance studies we confirmed associations with creativity in musical performance, but effects also included technique and communication. We extended efficacy to dance and social anxiety. Diversity of outcome has a counterpart in wide ranging associations between theta oscillations and behaviour in cognitive and affective neuroscience: in animals with sensory-motor activity in exploration, effort, working memory, learning, retention and REM sleep; in man with meditative concentration, reduced anxiety and sympathetic autonomic activation, as well as task demands in virtual spatial navigation, focussed and sustained attention, working and recognition memory, and having implications for synaptic plasticity and long term potentiation. Neuroanatomical circuitry involves the ascending mescencephalic-cortical arousal system, and limbic circuits subserving cognitive as well as affective/motivational functions. Working memory and meditative bliss, representing cognitive and affective domains, respectively, involve coupling between frontal and posterior cortices, exemplify a role for theta and alpha waves in mediating the interaction between distal and widely distributed connections. It is posited that this mediation in part underpins the integrational attributes of alpha–theta training in optimal performance and psychotherapy, creative associations in hypnogogia, and enhancement of technical, communication and artistic domains of performance in the arts.     

Reward feedback processing in children and adolescents: Medial frontal theta oscillations

We examined event-related electroencephalography (EEG) oscillations, including event-related spectral perturbations (ERSP) and intertrial coherence (ITC), to compare feedback processing during a chance-based reward vs. non-reward task in groups of 10–12-year-old (n = 42), 13–14-year-old (n = 34) and 15–17-year-olds (n = 32). Because few, if any studies have applied these analytic methods to examine feedback processing in children or adolescents, we used a fine-grained approach that explored one half hertz by 16 ms increments during feedback (no win vs. win events) in the theta (4–8 Hz) frequency band. Complex wavelet frequency decomposition revealed that no win feedback was associated with enhanced theta power and phase coherence. We observed condition and age-based differences for both ERSP and ITC, with stronger effects for ITC. The transition from childhood to early adolescence (13–14 yrs.) was a point of increased differentiation of ITC favoring no win vs. wins feedback and also compared to children or older adolescents, a point of heightened ITC for no win feedback (quadratic effect).     

Interindividual differences in alpha and theta power reflect memory performance

Previous research from our laboratory has shown that phasic or event-related changes in alpha and theta band power are related to memory performance. In this study, we test the hypothesis, whether tonic or ‘baseline’ power too is related to memory performance. The ongoing EEG was analyzed for a sample of 60 subjects during five experimental conditions: eyes closed, eyes open, memorizing words and counting backward in steps of 3 and 7. The results show that subjects with good memory performance have significantly larger upper alpha, but less theta and lower alpha power. In contrast to memory, good calculation performers have more beta and theta power than bad performers. These findings were obtained during actual task performance, but in a similar way also during the resting conditions eyes closed and open.     

Remembering specific features of emotional events across time: The role of REM sleep and prefrontal theta oscillations

When an episode of emotional significance is encountered, it often results in the formation of a highly resistant memory representation that is easily retrieved for many succeeding years. Recent research shows that beyond generic consolidation processes, rapid eye movement (REM) sleep importantly contributes to this effect. However, the boundary conditions of consolidation processes during REM sleep, specifically whether these extend to source memory, have not been examined extensively. The current study tested the effects of putative consolidation processes emerging during REM sleep and slow wave sleep (SWS) on item and source memory of negative and neutral images, respectively. Results demonstrate superior emotional relative to neutral item memory retention after both late night REM sleep and early night SWS. Emotional source memory, on the other hand, exhibited an attenuated decline following late night REM sleep, whereas neutral source memory was selectively preserved across early night SWS. This pattern of results suggests a selective preservation of emotional source memory during REM sleep that is functionally dissociable from SWS-dependent reprocessing of neutral source memory. This was further substantiated by a neurophysiological dissociation: Postsleep emotional source memory was selectively correlated with frontal theta lateralization (REM sleep), whereas postsleep neutral item memory was correlated with SWS spindle power. As such, the present results contribute to a more comprehensive characterization of sleep-related consolidation mechanisms underlying emotional and neutral memory retention. Subsidiary analysis of emotional reactivity to previously encoded material revealed an enhancing rather than attenuating effect of late night REM sleep on emotional responses.     

The significance and future of functional analysis methodologies

Iwata, Dorsey, Slifer, Bauman, and Richman (1982) presented the first comprehensive and standardized methodology for identifying operant functions of aberrant behavior. This essay discusses the significance functional analysis has had for applied behavior analysis. The methodology has lessened the field's reliance on default technologies and promoted analysis of environment-behavior interactions maintaining target responses as the basis for selecting treatments. It has also contributed to the integration of basic and applied research. Future directions for this research are suggested.     

The role of alpha oscillations in deriving and maintaining spatial relations in working memory

Previous research has demonstrated distinct neural correlates for maintenance of abstract, relational versus concrete, sensory information in working memory (WM). Storage of spatial relations in WM results in suppression of posterior sensory regions, which suggests that sensory information is task-irrelevant when relational representations are maintained in WM. However, the neural mechanisms by which abstract representations are derived from sensory information remain unclear. Here, using electroencephalography, we investigated the role of alpha oscillations in deriving spatial relations from a sensory stimulus and maintaining them in WM. Participants encoded two locations into WM, then after an initial maintenance period, a cue indicated whether to convert the spatial information to another sensory representation or to a relational representation. Results revealed that alpha power increased over posterior electrodes when sensory information was converted to a relational representation, but not when the information was converted to another sensory representation. Further, alpha phase synchrony between posterior and frontal regions increased for relational compared to sensory trials during the maintenance period. These results demonstrate that maintaining spatial relations and locations in WM rely on distinct neural oscillatory patterns.     

Coarse threat images reveal theta oscillations in the amygdala: A magnetoencephalography study

Neurocognitive models propose a specialized neural system for processing threat-related information, in which the amygdala plays a key role in the analysis of threat cues. fMRI research indicates that the amygdala is sensitive to coarse visual threat relevant information—for example, low spatial frequency (LSF) fearful faces. However, fMRI cannot determine the temporal or spectral characteristics of neural responses. Consequently, we used magnetoencephalography to explore spatiotemporal patterns of activity in the amygdala and cortical regions with blurry (LSF) and normal angry, fearful, and neutral faces. Results demonstrated differences in amygdala activity between LSF threat-related and LSF neutral faces (50–250 msec after face onset). These differences were evident in the theta range (4–8 Hz) and were accompanied by power changes within visual and frontal regions. Our results support the view that the amygdala is involved in the early processing of coarse threat related information and that theta is important in integrating activity within emotion-processing networks.     

The role of midfrontal theta oscillations across the development of cognitive control in preschoolers and school‐age children

The development of cognitive control enables children to better resist acting based on distracting information that interferes with the current action. Cognitive control improvement serves different functions that differ in part by the type of interference to resolve. Indeed, resisting to interference at the task‐set level or at the response‐preparation level is, respectively, associated with cognitive flexibility and inhibition. It is, however, unknown whether the same neural mechanism underlies these two functions across development. Studies in adults have revealed the contribution of midfrontal theta (MFT) oscillations in interference resolution. This study investigated whether MFT is involved in the resolution of different types of interference in two age groups identified as corresponding to different latent structures of executive functions. Preschool (4–6 years) and school children (6–8 years) were tested with a task involving interference at the response level and/or the task‐set level while (electroencephalogram) EEG was recorded. Behaviorally, response time and accuracy were affected by task‐set. Both age groups were less accurate when the interference occurred at the task‐set level and only the younger group showed decreased accuracy when interference was presented at the response‐preparation level. Furthermore, MFT power was increased, relative to the baseline, during the resolution of both types of interference and in both age groups. These findings suggest that MFT is involved in immature cognitive control (i.e., preschool and school‐ages), by orchestrating its different cognitive processes, irrespective of the interference to resolve and of the level of cognitive control development (i.e., the degree of differentiation of executive functions).     

Validity and reliability of electroencephalographic frontal alpha asymmetry and frontal midline theta as biomarkers for depression

Electroencephalographic (EEG) frontal alpha asymmetry (FAA) and frontal midline (FM) theta have been suggested as biomarkers for depression and anxiety, but have mostly been assessed in small and non‐clinical studies. In a clinical sample of 79 adults with depression (ICD‐10: F32), resting EEG and scales of depression (MADRS) and anxiety (HADS‐A) were measured at intake and after 3 months. FAA and FM theta values were referenced to a normative population database. Internal consistency, test‐retest reliability, and correlations with psychiatric tests were examined. Reliability was sufficient. However, FAA and FM theta values were close to the general population, and correlations with psychiatric tests were mostly small and non‐significant, with the exception of FAA on F7–F8 z‐scores and HADS‐A. We conclude that the validity of FAA and FM theta and therefore their potential as biomarkers for depression and anxiety remain unclear.     

Dynamics of alpha oscillations elucidate facial affect recognition in schizophrenia

Impaired facial affect recognition is characteristic of schizophrenia and has been related to impaired social function, but the relevant neural mechanisms have not been fully identified. The present study sought to identify the role of oscillatory alpha activity in that deficit during the process of facial emotion recognition. Neuromagnetic brain activity was monitored while 44 schizophrenia patients and 44 healthy controls viewed 5-s videos showing human faces gradually changing from neutral to fearful or happy expressions or from the neutral face of one poser to the neutral face of another. Recognition performance was determined separately by self-report. Relative to prestimulus baseline, controls exhibited a 10- to 15-Hz power increase prior to full recognition and a 10- to 15-Hz power decrease during the postrecognition phase. These results support recent proposals about the function of alpha-band oscillations in normal stimulus evaluation. The patients failed to show this sequence of alpha power increase and decrease and also showed low 10- to 15-Hz power and high 10- to 15-Hz connectivity during the prestimulus baseline. In light of the proposal that a combination of alpha power increase and functional disconnection facilitates information intake and processing, the finding of an abnormal association of low baseline alpha power and high connectivity in schizophrenia suggests a state of impaired readiness that fosters abnormal dynamics during facial affect recognition.     

Arc length coding by interference of theta frequency oscillations may underlie context-dependent hippocampal unit data and episodic memory function

Many memory models focus on encoding of sequences by excitatory recurrent synapses in region CA3 of the hippocampus. However, data and modeling suggest an alternate mechanism for encoding of sequences in which interference between theta frequency oscillations encodes the position within a sequence based on spatial arc length or time. Arc length can be coded by an oscillatory interference model that accounts for many features of the context-dependent firing properties of hippocampal neurons observed during performance of spatial memory tasks. In continuous spatial alternation, many neurons fire selectively depending on the direction of prior or future response (left or right). In contrast, in delayed non-match to position, most neurons fire selectively for task phase (sample vs. choice), with less selectivity for left versus right. These seemingly disparate results are effectively simulated by the same model, based on mechanisms similar to a model of grid cell firing in entorhinal cortex. The model also simulates forward shifting of firing over trials. Adding effects of persistent firing with reset at reward locations addresses changes in context-dependent firing with different task designs. Arc length coding could contribute to episodic encoding of trajectories as sequences of states and actions.     

The functional significance of autistic behaviors for the psychotic child

Physiological, cognitive, and emotional factors were examined throughout the treatment of a psychotic child. Heart rate, latency and accuracy in task performance, behavioral indices of stress (e.g., muscular tension, facial expression), and frequency of autistic mannerisms were measured concurrently. Both contemporaneous relationships and patterns of change suggested that autistic behaviors were organized and psychologically meaningful. Self-stimulation, conflict, and negativism (deliberate erroneous performance) occurred predictably, were intimately related, and were associated with specific patterns of heart-rate change. The changing function of self-stimulation across treatment and the centrality of negativism in this child's disturbance were discussed.This research was supported in part by a Program Project Grant from the National Institute of Child Health and Human Development to the Institute of Child Development, University of Minnesota (1 PO1 IID05027).     

An inexpensive circuit for beta,alpha, theta,or delta EEG biofeedback

An inexpensive circuit is described for EEG biofeedback or measurement. The circuit is designed to interface easily with most basic EEG machines. It taps the output from a single recording channel of the basic EEG instrument and provides the following for each EEG band (beta, alpha, theta, and delta): (a) very selective bandpass discrimination, (b) variable center frequency, (c) variable threshold at which feedback will be provided, or the measurement made, and (d) use with any biofeedback stimulus or measurement device that one wishes to switch contingent with S’s EEG rhythms.     

A k-sample significance test for independent alpha coefficients

The earlier two-sample procedure of Feldt [1969] for comparing independent alpha reliability coefficients is extended to the case ofK 2 independent samples. Details of a normalization of the statistic under consideration are presented, leading to computational procedures for the overallK-group significance test and accompanying multiple comparisons. Results based on computer simulation methods are presented, demonstrating that the procedures control Type I error adequately. The results of a power comparison of the case ofK=2 with Feldt's [1969]F test are also presented. The differences in power were negligible. Some final observations, along with suggestions for further research, are noted.The authors gratefully acknowledge the assistance of Michael E. Masson, in the computations performed, and of Leonard S. Feldt, in suggesting the data generation procedures used in the study. In addition, the authors thank James Zidek and the Institute of Applied Mathematics and Statistics, University of British Columbia, for advice concerning some of the theoretical development.     

Awareness in the crowd: Beta power and alpha phase of prestimulus oscillations predict object discrimination in visual crowding

Visual crowding is among the factors that most hamper conscious object perception. However, we currently ignore the neural states that predispose to an accurate perception within different crowding regimes. Here, we performed single-trial analyses of the electroencephalographical (EEG) oscillations, evaluating the prestimulus power and phase differences between correct and incorrect discrimination during a letter-crowding task, where irrelevant letters were placed nearby (strong crowding) or far (mid crowding) relative to the target. Results show that prestimulus alpha (8–12 Hz) power was related to target discrimination in the mid, but not in the strong, crowding condition. Importantly, accurate discrimination in the strong crowding condition was predicted by the phase of alpha and by the power of beta (13–20 Hz) oscillations. These evidence suggest that both periodic visual sampling mechanisms, reflected in the alpha phase, and network predisposition to extract local information, reflected in the beta power, predispose to object discrimination in a crowded scene.