The relationship between self-awareness of attentional status, behavioral performance and oscillatory brain rhythms

High-level cognitive factors, including self-awareness, are believed to play an important role in human visual perception. The principal aim of this study was to determine whether oscillatory brain rhythms play a role in the neural processes involved in self-monitoring attentional status. To do so we measured cortical activity using magnetoencephalography (MEG) and functional magnetic resonance imaging (fMRI) while participants were asked to self-monitor their internal status, only initiating the presentation of a stimulus when they perceived their attentional focus to be maximal. We employed a hierarchical Bayesian method that uses fMRI results as soft-constrained spatial information to solve the MEG inverse problem, allowing us to estimate cortical currents in the order of millimeters and milliseconds. Our results show that, during self-monitoring of internal status, there was a sustained decrease in power within the 7-13 Hz (alpha) range in the rostral cingulate motor area (rCMA) on the human medial wall, beginning approximately 430 msec after the trial start (p < 0.05, FDR corrected). We also show that gamma-band power (41-47 Hz) within this area was positively correlated with task performance from 40-640 msec after the trial start (r = 0.71, p < 0.05). We conclude: (1) the rCMA is involved in processes governing self-monitoring of internal status; and (2) the qualitative differences between alpha and gamma activity are reflective of their different roles in self-monitoring internal states. We suggest that alpha suppression may reflect a strengthening of top-down interareal connections, while a positive correlation between gamma activity and task performance indicates that gamma may play an important role in guiding visuomotor behavior. © 2013 Yamagishi et al.

Rhythms of life:antecedents and outcomes of work-family balance among employed parents

This study examined antecedents and outcomes of a fourfold taxonomy of work-family balance in terms of the direction of influence (work-family vs. family-work) and type of effect (conflict vs. facilitation). Respondents were full-time employed parents in India. Confirmatory factor analysis results provided evidence for the discriminant validity of M. R. Frone's (2003) fourfold taxonomy of work-family balance. Results of moderated regression analysis revealed that different processes underlie the conflict and facilitation components. Furthermore, gender had only a limited moderating influence on the relationships between the antecedents and the components of work-family balance. Last, work-family facilitation was related to the work outcomes of job satisfaction and organizational commitment.

Circannual rhythms of maturation in the female rainbow trout and their entrainment by changes in photoperiod

The importance of endogenous rhythms in the photoperiodic control of the annual reproduction cycle in female rainbow trout was investigated. The effect of photoperiod regimes on the different stages of maturation was assessed by recording the timing of ovulation and from quantifying associated changes in serum oestradiol-17,testosterone and total calcium. Maintained under constant 6L:18D and constant temperature for up to four years, rainbow trout exhibited an endogenous rhythm of maturation with a periodicity of approximately one year. This rhythm of maturation appears to be driven by an autonomous circannual oscillator or clock which can be dissociated from the neuroendocrine mechanisms controlling gonadal maturation. Under conditions of constant 18L:6D or LL the periodicity of the maturation rhythm was 5.5-6 months; it is suggested that this periodicity may be caused by a splitting or uncoupling of at least two circannual clocks involved in the control of maturation. Abrupt changes in the length of the photoperiod act as a zeitgeber to entrain the endogenous rhythm of maturation. Whether the timing of maturation is advanced or delayed depends primarily on the direction of the change in photoperiod and its timing in relation to the phase of the rhythm, with the magnitude of the alteration in photoperiod having only a supplementary effect. The effect of specific changes in photoperiod on the entrainment of the maturation cycle can be described in terms of a phase-response curve. Photic information is transduced, probably by the pineal gland, into a daily rhythm of melatonin; exposure of rainbow trout to skeleton and resonance photoperiod regimes indicated that daylength measurement is effected by endogenous circadian clock(s) rather than by hour-glass mechanisms. A gating mechanism is closely associated with the circannual clock which determines the timing of onset of maturation in virgin female rainbow trout, only allowing fish that have attained a threshold stage of development to undergo gonadal maturation. Collectively the results support the hypothesis that the female rainbow trout exhibits an endogenous circannual rhythm of maturation which can be entrained by changes in photoperiod.

Autonomic nervous system, circadian rhythms, and primary open-angle glaucoma

The etiology of primary open-angle glaucoma (POAG) remains the subject of continuing investigation. Despite the many known risk factors and mechanism of damage, the principal treatment objectives in POAG still consist of reduction of intraocular pressure, which although straightforward in many cases, often leaves the clinician with the question of how far to pursue a sufficiently low pressure to prevent further damage. Other risk factors such as hemodynamic insufficiency due to vascular dysregulation and abnormal blood pressure are often overlooked in the day-to-day practice; their harmful effects for glaucoma are, it seems, more potent at night while the patient sleeps and when clinical investigation is most difficult. Although the status of autonomic nervous system is an important determinant of the systemic hemodynamic parameters, this issue is usually ignored by the clinician in the process of glaucoma diagnosis. Consequently, there is a lack of alternative therapies tailored to address associated systemic risk factors for POAG on a case and chronological basis; this approach could be more effective in preventing the progression and visual loss in selected glaucoma cases. © 2004 Elsevier Inc. All rights reserved.

The role of oscillatory brain activity in object processing and figure-ground segmentation in human vision

The perception of an object as a single entity within a visual scene requires that its features are bound together and segregated from the background and/or other objects. Here, we used magnetoencephalography (MEG) to assess the hypothesis that coherent percepts may arise from the synchronized high frequency (gamma) activity between neurons that code features of the same object. We also assessed the role of low frequency (alpha, beta) activity in object processing. The target stimulus (i.e. object) was a small patch of a concentric grating of 3c/°, viewed eccentrically. The background stimulus was either a blank field or a concentric grating of 3c/° periodicity, viewed centrally. With patterned backgrounds, the target stimulus emerged--through rotation about its own centre--as a circular subsection of the background. Data were acquired using a 275-channel whole-head MEG system and analyzed using Synthetic Aperture Magnetometry (SAM), which allows one to generate images of task-related cortical oscillatory power changes within specific frequency bands. Significant oscillatory activity across a broad range of frequencies was evident at the V1/V2 border, and subsequent analyses were based on a virtual electrode at this location. When the target was presented in isolation, we observed that: (i) contralateral stimulation yielded a sustained power increase in gamma activity; and (ii) both contra- and ipsilateral stimulation yielded near identical transient power changes in alpha (and beta) activity. When the target was presented against a patterned background, we observed that: (i) contralateral stimulation yielded an increase in high-gamma (>55 Hz) power together with a decrease in low-gamma (40-55 Hz) power; and (ii) both contra- and ipsilateral stimulation yielded a transient decrease in alpha (and beta) activity, though the reduction tended to be greatest for contralateral stimulation. The opposing power changes across different regions of the gamma spectrum with 'figure/ground' stimulation suggest a possible dual role for gamma rhythms in visual object coding, and provide general support of the binding-by-synchronization hypothesis. As the power changes in alpha and beta activity were largely independent of the spatial location of the target, however, we conclude that their role in object processing may relate principally to changes in visual attention.

Cortical oscillatory activity associated with the perception of illusory and real visual contours

We used magnetoencephalography (MEG) to examine the nature of oscillatory brain rhythms when passively viewing both illusory and real visual contours. Three stimuli were employed: a Kanizsa triangle; a Kanizsa triangle with a real triangular contour superimposed; and a control figure in which the corner elements used to form the Kanizsa triangle were rotated to negate the formation of illusory contours. The MEG data were analysed using synthetic aperture magnetometry (SAM) to enable the spatial localisation of task-related oscillatory power changes within specific frequency bands, and the time-course of activity within given locations-of-interest was determined by calculating time-frequency plots using a Morlet wavelet transform. In contrast to earlier studies, we did not find increases in gamma activity (> 30 Hz) to illusory shapes, but instead a decrease in 10–30 Hz activity approximately 200 ms after stimulus presentation. The reduction in oscillatory activity was primarily evident within extrastriate areas, including the lateral occipital complex (LOC). Importantly, this same pattern of results was evident for each stimulus type. Our results further highlight the importance of the LOC and a network of posterior brain regions in processing visual contours, be they illusory or real in nature. The similarity of the results for both real and illusory contours, however, leads us to conclude that the broadband (< 30 Hz) decrease in power we observed is more likely to reflect general changes in visual attention than neural computations specific to processing visual contours.

Attentional shifts towards an expected visual target alter the level of alpha-band oscillatory activity in the human calcarine cortex

Neuronal operations associated with the top-down control process of shifting attention from one locus to another involve a network of cortical regions, and their influence is deemed fundamental to visual perception. However, the extent and nature of these operations within primary visual areas are unknown. In this paper, we used magnetoencephalography (MEG) in combination with magnetic resonance imaging (MRI) to determine whether, prior to the onset of a visual stimulus, neuronal activity within early visual cortex is affected by covert attentional shifts. Time/frequency analyses were used to identify the nature of this activity. Our results show that shifting attention towards an expected visual target results in a late-onset (600 ms postcue onset) depression of alpha activity which persists until the appearance of the target. Independent component analysis (ICA) and dipolar source modeling confirmed that the neuronal changes we observed originated from within the calcarine cortex. Our results further show that the amplitude changes in alpha activity were induced not evoked (i.e., not phase-locked to the cued attentional task). We argue that the decrease in alpha prior to the onset of the target may serve to prime the early visual cortex for incoming sensory information. We conclude that attentional shifts affect activity within the human calcarine cortex by altering the amplitude of spontaneous alpha rhythms and that subsequent modulation of visual input with attentional engagement follows as a consequence of these localized changes in oscillatory activity. © 2005 Elsevier B.V. All rights reserved.

Attentional modulation of oscillatory activity in human visual cortex

The effects of attentional modulation on activity within the human visual cortex were investigated using magnetoencephalography. Chromatic sinusoidal stimuli were used to evoke activity from the occipital cortex, with attention directed either toward or away from the stimulus using a bar-orientation judgment task. For five observers, global magnetic field power was plotted as a function of time from stimulus onset. The major peak of each function occurred at about 120 ms latency and was well modeled by a current dipole near the calcarine sulcus. Independent component analysis (ICA) on the non-averaged data for each observer also revealed one component of calcarine origin, the location of which matched that of the dipolar source determined from the averaged data. For two observers, ICA revealed a second component near the parieto-occipital sulcus. Although no effects of attention were evident using standard averaging procedures, time-varying spectral analyses of single trials revealed that the main effect of attention was to alter the level of oscillatory activity. Most notably, a sustained increase in alpha-band (7-12 Hz) activity of both calcarine and parieto-occipital origin was evident. In addition, calcarine activity in the range of 13-21 Hz was enhanced, while calcarine activity in the range of 5-6 Hz was reduced. Our results are consistent with the hypothesis that attentional modulation affects neural processing within the calcarine and parieto-occipital cortex by altering the amplitude of alpha-band activity and other natural brain rhythms. © 2003 Elsevier Inc. All rights reserved.

Pharmacologically induced and stimulus evoked rhythmic neuronal oscillatory activity in the primary motor cortex in vitro

Parkinson's disease (PD) is associated with enhanced synchronization of neuronal network activity in the beta (15-30 Hz) frequency band across several nuclei of the basal ganglia (BG). Deep brain stimulation of the subthalamic nucleus (STN) appears to reduce this pathological oscillation, thereby alleviating PD symptoms. However, direct stimulation of primary motor cortex (M1) has recently been shown to be effective in reducing symptoms in PD, suggesting a role for cortex in patterning pathological rhythms. Here, we examine the properties of M1 network oscillations in coronal slices taken from rat brain. Oscillations in the high beta frequency range (layer 5, 27.8 +/- 1.1 Hz, n=6) were elicited by co-application of the glutamate receptor agonist kainic acid (400 nM) and muscarinic receptor agonist carbachol (50 mu M). Dual extracellular recordings, local application of tetrodotoxin and recordings in M1 micro-sections indicate that the activity originates within deep layers V/VI. Beta oscillations were unaffected by specific AMPA receptor blockade, abolished by the GABA type A receptor (GABAAR) antagonist picrotoxin and the gap-junction blocker carbenoxolone, and modulated by pentobarbital and zolpidem indicating dependence on networks of GABAergic interneurons and electrical coupling. High frequency stimulation (HFS) at 125 Hz in superficial layers, designed to mimic transdural/transcranial stimulation, generated gamma oscillations in layers 11 and V (incidence 95%, 69.2 +/- 7.3 Hz, n=17) with very fast oscillatory components (VFO; 100-250 Hz). Stimulation at 4 Hz, however, preferentially promoted theta activity (incidence 62.5%, 5.1 +/- 0.6 Hz, n=15) that effected strong amplitude modulation of ongoing beta activity. Stimulation at 20 Hz evoked mixed theta and gamma responses. These data suggest that within M1, evoked theta, gamma and fast oscillations may coexist with and in some cases modulate pharmacologically induced beta oscillations.

Aspects of the feeding behaviour of intensively reared trout

Feeding behaviour of trained rainbow trout was investigated by the use of demand feeders, under different light conditions. The effects of the energy content of diet, and the size, colour and texture of feed pellets, on the feeding behaviour, were studied. An attempt was made to locate the assumed centres for feeding and satiety in the hypothalamus of brain by the intraperitoneal injections of goldthioglucose. Feeding under nine different constant photoperiods at 160 lux, at a temperature of 13.5°C, showed that trout exhibit a rhythmic pattern of feeding behaviour in all photoperiods except in continuous darkness.Feeding rhythms of trout attributable to the degree of gut distension were formed every eight to ten hours. Further studies by varying levels of light intensity revealed the interaction of light intensity and photoperiod. At shorter photoperiods lower levels of light intensity decreased the feeding activity in terms of food intake but by increasing the photoperiod the same feeding activity was accomplished as by the fish subject to a short photoperiod but under higher light intensity.Simulated effect of increasing and decreasing daylengths did not affect the overall food intake and growth performance. Trout are quite efficient in adjusting their food intake in terms of energy content. Colour, size and texture of feed pellets affect the feeding responses and elicit preferential food selection behaviour in trout. Goldthioglucose induced some reversable toxic effects upon general physiology of trout and did not produce any lesions in the assumed areas of feeding and satiety centres in the brain.  It was concluded that the feeding behaviour of trout exhibited selective preferences according to the physical nature of food items and those preferences could be further influenced by the biotic and abiotic factors, light being one of the most important abiotic factors.

Synchronization processes in nonlinear systems and their relation to cortical oscillatory dynamics

This thesis was focused on theoretical models of synchronization to cortical dynamics as measured by magnetoencephalography (MEG). Dynamical systems theory was used in both identifying relevant variables for brain coordination and also in devising methods for their quantification. We presented a method for studying interactions of linear and chaotic neuronal sources using MEG beamforming techniques. We showed that such sources can be accurately reconstructed in terms of their location, temporal dynamics and possible interactions. Synchronization in low-dimensional nonlinear systems was studied to explore specific correlates of functional integration and segregation. In the case of interacting dissimilar systems, relevant coordination phenomena involved generalized and phase synchronization, which were often intermittent. Spatially-extended systems were then studied. For locally-coupled dissimilar systems, as in the case of cortical columns, clustering behaviour occurred. Synchronized clusters emerged at different frequencies and their boundaries were marked through oscillation death. The macroscopic mean field revealed sharp spectral peaks at the frequencies of the clusters and broader spectral drops at their boundaries. These results question existing models of Event Related Synchronization and Desynchronization. We re-examined the concept of the steady-state evoked response following an AM stimulus. We showed that very little variability in the AM following response could be accounted by system noise. We presented a methodology for detecting local and global nonlinear interactions from MEG data in order to account for residual variability. We found crosshemispheric nonlinear interactions of ongoing cortical rhythms concurrent with the stimulus and interactions of these rhythms with the following AM responses. Finally, we hypothesized that holistic spatial stimuli would be accompanied by the emergence of clusters in primary visual cortex resulting in frequency-specific MEG oscillations. Indeed, we found different frequency distributions in induced gamma oscillations for different spatial stimuli, which was suggestive of temporal coding of these spatial stimuli. Further, we addressed the bursting character of these oscillations, which was suggestive of intermittent nonlinear dynamics. However, we did not observe the characteristic-3/2 power-law scaling in the distribution of interburst intervals. Further, this distribution was only seldom significantly different to the one obtained in surrogate data, where nonlinear structure was destroyed. In conclusion, the work presented in this thesis suggests that advances in dynamical systems theory in conjunction with developments in magnetoencephalography may facilitate a mapping between levels of description int he brain. this may potentially represent a major advancement in neuroscience.

Circadian gene variants and susceptibility to type 2 diabetes:a pilot study

Disruption of endogenous circadian rhythms has been shown to increase the risk of developing type 2 diabetes, suggesting that circadian genes might play a role in determining disease susceptibility. We present the results of a pilot study investigating the association between type 2 diabetes and selected single nucleotide polymorphisms (SNPs) in/near nine circadian genes. The variants were chosen based on their previously reported association with prostate cancer, a disease that has been suggested to have a genetic link with type 2 diabetes through a number of shared inherited risk determinants.

Bromocriptine:old drug, new formulation and new indication

Bromocriptine is an ergot alkaloid dopamine D receptor agonist that has been used extensively in the past to treat hyperprolactinaemia, galactorrhoea and Parkinsonism. It is known that hypothalamic hypodopaminergic states and disturbed circadian rhythm are associated with the development of insulin resistance, obesity and diabetes in animals and humans. When administered in the early morning at the start of the light phase, a new quick release (QR) formulation of bromocriptine appears to act centrally to reset circadian rhythms of hypothalamic dopamine and serotonin and improve insulin resistance and other metabolic abnormalities. Phase II and III clinical studies show that QR-bromocriptine lowers glycated haemoglobin by 0.6-1.2% (7-13 mmol/mol) either as monotherapy or in combination with other antidiabetes medications. Apart from nausea, the drug is well tolerated. The doses used to treat diabetes (up to 4.8 mg daily) are much lower than those used to treat Parkinson's disease and have not been associated with retroperitoneal fibrosis or heart valve abnormalities. QR-bromocriptine (Cycloset™) has recently been approved in the USA for the treatment of type 2 diabetes mellitus (T2DM). Thus, a QR formulation of bromocriptine timed for peak delivery in the early morning may provide a novel neurally mediated approach to the control of hyperglycaemia in T2DM. © 2010 Blackwell Publishing Ltd.

Student morningness-eveningness type and performance:does class timing matter?

Circadian rhythms have often been linked to people’s performance outcomes, although this link has not been examined within the context of University students. We therefore sought to test whether students’ perceptions of their morning-evening (ME) type had an influence on their performance on modules. We tested this hypothesis using students from a number of modules at two UK Universities. Results indicated that, contrary to our hypothesis, the further the discrepancy between a student’s ME type and the teaching time of the class, the better the student’s performance. These results have implications for teaching as student ME type could be taken into account for timetabling especially if modules need to be taught multiple times. We also provide implications for those seeking to measure ME, as our results are consistent with a 5-item ME scale, a 3-item ME scale, and a single-item ME scale.

Rhythmic masking release:effects of asynchrony, temporal overlap, harmonic relations, and source separation on cross-spectral grouping

The rhythm created by spacing a series of brief tones in a regular pattern can be disguised by interleaving identical distractors at irregular intervals. The disguised rhythm can be unmasked if the distractors are allocated to a separate stream from the rhythm by integration with temporally overlapping captors. Listeners identified which of 2 rhythms was presented, and the accuracy and rated clarity of their judgment was used to estimate the fusion of the distractors and captors. The extent of fusion depended primarily on onset asynchrony and degree of temporal overlap. Harmonic relations had some influence, but only an extreme difference in spatial location was effective (dichotic presentation). Both preattentive and attentionally driven processes governed performance. (PsycINFO Database Record (c) 2012 APA, all rights reserved)