Effect of meditation on intracerebral EEG in a patient with temporal lobe epilepsy: A case report.

Meditation has been deemed a miracle cure for a wide range of neurological disorders. However, it is unclear whether meditation practice would be beneficial for patients suffering from epilepsy. Here we report on the comparison of the effects of focused-attention meditation and a control task on electroencephalographic (EEG) activity in a patient undergoing stereoencephalographic (SEEG) investigation for drug-resistant epilepsy. The patient routinely practiced focused-attention meditation and reported that she found it beneficial. During the SEEG investigation, intracerebral EEG data were recorded during meditation as well as during mind-wandering task. The EEG data were analyzed for type of electrical activity (labeled) by two expert epileptologists. We found that the proportion of EEG segments containing activity classified as interictal epileptiform discharges (IEDs; abnormal electrical activity that occurs between seizures) increased significantly during meditation practice. Although the finding was surprising, this increase in IEDs may not correlate with an increase in seizure frequency, and the patient might still benefit from practicing meditation. The finding does, however, warrant further studies on the influence of meditation on epileptic activity.

Accuracy and neural correlates of blinded mediumship compared to controls on an image classification task.

In this study, a classification task asked participants to look at 180 facial photographs of deceased individuals (photographs were taken years prior to their deaths) and guess the cause of death from three equiprobable categories: heart attack; death by firearm; or car accident. Electroencephalogram (EEG) and electrocardiogram (ECG) data were simultaneously collected during the task. The participants included individuals who claimed "mediumistic" (psychic) abilities and controls who claimed no mediumistic ability. Pooled data showed accurate guesses for the cause of death (partial η2 = 0.12; p = 0.004), and control subjects were primarily responsible for this effect (partial η2 = 0.11; p = 0.005). EEG and ECG differences were found between the mediums and controls. Control participants had larger amplitude event-related potentials (ERP) following the presentation of the images than the mediums, between 80 and 110 ms, and between 200 and 350 ms. This could be interpreted as reflecting greater attention and less response inhibition by controls as compared to the mediums. Participants in the control group also had lower average heart rates than the mediums, possibly indicating less stress during the task. Speculations and limits regarding why controls performed better than mediums are discussed.

Comparative effectiveness and safety of antipsychotic drugs in schizophrenia treatment: a real-world observational study.

OBJECTIVE: The objective was to compare, in a real-world setting, the risk of mental and physical health events associated with different antipsychotic drugs (clozapine, olanzapine, risperidone, quetiapine and first-generation antipsychotics) in patients with SZ. METHODS: This is a retrospective cohort study using administrative data. Outcome measures included any mental health event (suicide, hospitalization or emergency visit for mental disorders) and physical health event (death other than suicide, hospitalization or emergency visit for physical disorders). Cox proportional hazard models were used to estimate the hazard ratios of the events associated with the use of the different antipsychotic drugs. RESULTS: The cohort included 18 869 adult patients living in the province of Quebec (Canada) with SZ and starting antipsychotic drugs between January 1998 and December 2005. Results show that quetiapine and not using any antipsychotics were associated with an increased risk of mental and physical health events as compared to other drugs. The second finding is the confirmation of better performance of clozapine. The results were robust across sensitivity analyses. CONCLUSION: Both findings call for an international public health and drug agencies surveillance of 'real-world' antipsychotic medication to ensure the optimal choices in treatment guidelines for SZ.

Extraction of the average and differential dynamical response in stimulus-locked experimental data.

In optical imaging experiments of primary visual cortex, visual stimuli evoke a complicated dynamics. Typically, any stimulus with sufficient contrast evokes a response. Much of the response is the same regardless of which stimulus is presented. For instance, when oriented drifting gratings are presented to the visual system, over 90% of the response is the same from orientation to orientation. Small differences may be seen, however, between the responses to different orientations. A problem in the analysis of optical measurements of the response to stimulus in cortical tissue is the distinction of the 'global' or 'non-specific' response from the 'differential' or 'stimulus-specific' response. This problem arises whenever the signal of interest is the difference in response to various stimuli and is evident in many kinds of uni- and multivariate data. To this end, we present enhancements to a frequency-based method that we previously introduced called the periodic stacking method. These enhancements allow us to separately estimate the dynamics of both the average signal across all stimuli (the 'global' response) and deviations from the average amongst the various stimuli (the 'stimulus-specific' response) evoked in response to a set of stimuli. We also discuss improvements in the signal-to-noise ratio, relative to standard trial averaging methods, that result from the data-adaptive smoothing in our method.

Early cortical orientation selectivity: how fast inhibition decodes the order of spike latencies.

Following a flashed stimulus, I show that a simple neurophysiological mechanism in the primary visual system can generate orientation selectivity based on the first incoming spikes. A biological model of the lateral geniculate nucleus generates an asynchronous wave of spikes, with the most strongly activated neurons firing first. Geniculate activation leads to both the direct excitation of a cortical pyramidal cell and disynaptic feed-forward inhibition. The mechanism provides automatic gain control, so the cortical neurons respond over a wide range of stimulus contrasts. It also demonstrates the biological plausibility of a new computationally efficient neural code: latency rank order coding.

Determination of the absolute mobility and the equivalent ionic conductivity of NpO2+ at 25 degrees C and at infinite dilution by capillary electrophoresis-inductively coupled plasma-mass spectrometry.

The absolute mobility of NpO2+ and its equivalent ionic conductivity were extrapolated at 25 degrees C and at infinite dilution using a set of experimental data obtained at various ionic strengths. The separation was carried out by capillary electrophoresis (CE) at various concentrations of creatinine at a pH of 5. The detection of NpO2+ was performed by inductively coupled plasma mass spectrometry coupled on-line with CE. The following values have been found: mu0NpO2+ (25 degrees C) = (2.94 +/- 0.07) x 10(-4) cm2 V(-1) s(-1) and lambda0NpO2+ (x 10(4), 25 degrees C) = 28.3 +/- 0.7 m2 S mol(-1).

Spike-based strategies for rapid processing.

Most experimental and theoretical studies of brain function assume that neurons transmit information as a rate code, but recent studies on the speed of visual processing impose temporal constraints that appear incompatible with such a coding scheme. Other coding schemes that use the pattern of spikes across a population a neurons may be much more efficient. For example, since strongly activated neurons tend to fire first, one can use the order of firing as a code. We argue that Rank Order Coding is not only very efficient, but also easy to implement in biological hardware: neurons can be made sensitive to the order of activation of their inputs by including a feed-forward shunting inhibition mechanism that progressively desensitizes the neuronal population during a wave of afferent activity. In such a case, maximum activation will only be produced when the afferent inputs are activated in the order of their synaptic weights.

Face identification using one spike per neuron: resistance to image degradations.

The short response latencies of face selective neurons in the inferotemporal cortex impose major constraints on models of visual processing. It appears that visual information must essentially propagate in a feed-forward fashion with most neurons only having time to fire one spike. We hypothesize that flashed stimuli can be encoded by the order of firing of ganglion cells in the retina and propose a neuronal mechanism, that could be related to fast shunting inhibition, to decode such information. Based on these assumptions, we built a three-layered neural network of retino-topically organized neuronal maps. We showed, by using a learning rule involving spike timing dependant plasticity, that neuronal maps in the output layer can be trained to recognize natural photographs of faces. Not only was the model able to generalize to novel views of the same faces, it was also remarkably resistant to image noise and reductions in contrast.

A limit to the speed of processing in ultra-rapid visual categorization of novel natural scenes.

The processing required to decide whether a briefly flashed natural scene contains an animal can be achieved in 150 msec (Thorpe, Fize, & Marlot, 1996). Here we report that extensive training with a subset of photographs over a 3-week period failed to increase the speed of the processing underlying such Rapid Visual Categorizations: Completely novel scenes could be categorized just as fast as highly familiar ones. Such data imply that the visual system processes new stimuli at a speed and with a number of stages that cannot be compressed. This rapid processing mode was seen with a wide range of visual complex images, challenging the idea that short reaction times can only be seen with simple visual stimuli and implying that highly automatic feed-forward mechanisms underlie a far greater proportion of the sophisticated image analysis needed for everyday vision than is generally assumed.

Dopamine-synthesizing neurons include the putative H-cell homologue in the moth Manduca sexta.

The catecholamine dopamine (DA) plays a fundamental role in the regulation of behavior and neurodevelopment across animal species. Uncovering the embryonic origins of neurons that express DA opens a path for a deeper understanding of how DA expression is regulated and, in turn, how DA regulates the activities of the nervous system. In a well-established insect model, Manduca sexta, we identified the putative homologue of the embryonic grasshopper "H-cell" using intracellular techniques, laser scanning confocal microscopy, and immunohistochemistry. In both species, this neuron possesses four axons and has central projections resembling the letter H. The H-cell in grasshoppers is known to be derived from the midline precursor 3 cell (MP3) and to pioneer the pathways of the longitudinal connectives; in Drosophila, the H-cell is also known to be derived from MP3. In the current study, we demonstrate that the Manduca H-cell is immunoreactive to antibodies raised against DA and its rate-limiting synthetic enzyme, tyrosine hydroxylase (TH). In larvae and adults, one DA/TH-immunoreactive (-ir) H-cell per ganglion is present. In embryos, individual ganglia contain a single midline TH-ir cell body positioned along side its putative sibling. Such observations are consistent with the known secondary transformation (in grasshoppers) of only one of the two MP3 progeny during early development. Although a hallmark feature of invertebrate neurons is the fairly stereotypical position of neuronal somata, we found that the H-cell somata can "flip-flop" by 180 degrees between an anterior and posterior position. This variability appears to be random and is not restricted to any particular ganglion. Curiously, what is segment-specific is the absence of the DA/TH-ir H-cell in the metathoracic (T3) ganglion as well as the unique structure of the H-cell in the subesophageal ganglion. Because this is the first immunohistochemical study of DA neurons in Manduca, we have provided the distribution pattern and morphologies of dopaminergic neurons, in addition to the H-cells, within the ventral nerve cord during development.

Ultra-rapid categorisation of natural scenes does not rely on colour cues: a study in monkeys and humans.

In a rapid categorisation task, monkeys and humans had to detect a target (animal or food) in briefly flashed (32 ms) and previously unseen natural images. Removing colour cues had very little effect on average performance. Impairments were restricted to a mild accuracy drop (in some human subjects) and a small reaction time mean increase (10-15 ms) observed both in monkeys and humans but only in the detection of food targets. In both tasks, accuracy and latency of the fastest behavioural responses were unaffected, suggesting that such ultra-rapid categorizations could depend on feed-forward processing of early coarse achromatic magnocellular information.

Programmed cell death of an identified motoneuron examined in vivo: electrophysiological and morphological correlates.

A paucity of information exists about the electrophysiological and anatomical correlates of neurons committed to die in vivo. Thus, we examined how an identified neuron, motoneuron MN-12, dies during development in the intact moth Manduca sexta. The developmental programmed cell death of this motoneuron was examined because of its defined commitment point of death. In addition, its ability to be unambiguously identified between animals and its accessibility to recording and dye injection facilitated our examination. MN-12 becomes committed to die approximately 28-30 h after adult emergence. At this time, MN-12 can no longer be saved by manipulations of steroid hormone levels, protein synthesis, or removal of descending inputs. Our initial prediction was that within a few hours after the commitment point, MN-12 would begin showing a gradual loss of central arbors and alterations in membrane properties. Contrary to our expectations, we found the MN-12 motoneuron to exhibit a stable central morphology and electrophysiological profile for approximately 12 h, followed by a rapid dismantling that occurred within a 1- to 2-h period. Several hours prior to the commitment point, the target muscle of MN-12 was no longer viable; yet, this did not affect the death of MN-12 or cause retraction of its motor terminals. We conclude that the delayed (12-h) onset of rapid cell death is not preceded by a slow accumulation of damages to the neuronal membrane (e.g., ion channels or cytoskeletal components) as both the electrical activity and morphology of MN-12 remained measurably unaltered during this 12-h lag.

Face processing using one spike per neurone.

The speed with which neurones in the monkey temporal lobe can respond selectively to the presence of a face implies that processing may be possible using only one spike per neurone, a finding that is problematic for conventional rate coding models that need at least two spikes to estimate interspike interval. One way of avoiding this problem uses the fact that integrate-and-fire neurones will tend to fire at different times, with the most strongly activated neurones firing first (Thorpe, 1990, Parallel Processing in Neural Systems). Under such conditions, processing can be performed by using the order in which cells in a particular layer fire as a code. To test this idea, we have explored a range of architectures using SpikeNET (Thorpe and Gautrais, 1997, Neural Information Processing Systems, 9), a simulator designed for modelling large populations of integrate-and-fire neurones. One such network used a simple four-layer feed-forward architecture to detect and localise the presence of human faces in natural images. Performance of the model was tested with a large range of grey-scale images of faces and other objects and was found to be remarkably good by comparison with more classic image processing techniques. The most remarkable feature of these results is that they were obtained using a purely feed-forward neural network in which none of the neurones fired more than one spike (thus ruling out conventional rate coding mechanisms). It thus appears that the combination of asynchronous spike propagation and rank order coding may provide an important key to understanding how the nervous system can achieve such a huge amount of processing in so little time.

Prevention concerning mental health: the adolescent's perspective.

OBJECTIVE: To examine several subjective components of adolescents' behaviour concerning mental illness prevention. METHOD: Adolescents' knowledge, their attitudes and subjective norms, as well as their thoughts about how they would concretely handle a psychological problem were measured. A self-administered questionnaire was completed by 438 male and female adolescents in grades 8 and 11. RESULTS: Gender and age differences were revealed: girls and older adolescents were more attuned to prevention. Further, the influence on young people of peers and parents was also apparent. CONCLUSION: Adolescents perceive prevention concerning mental health as important.

A motoneuron spared from steroid-activated developmental death by removal of descending neural inputs exhibits stable electrophysiological properties and morphology.

Neurons die during the development of nervous systems. The death of specific, identified motoneurons during metamorphosis of the tobacco hornworm, Manduca sexta, provides an accessible model system in which to study the regulation of postembryonic neuronal death. Hormones and descending neural inputs have been shown to influence the survival of abdominal motoneurons during the first few days of adult life in this insect. Motoneurons prevented from undergoing the normal process of developmental degeneration by removal of neural inputs were examined at the physiological and structural levels using several cell imaging techniques. Although these neurons lost their muscle targets and experienced the endocrine cue that normally triggers death, they showed no overt electrophysiological or morphological signs of degeneration. Thus, by appropriate intervention, the MN-12 motoneuron can be spared from developmental neuronal death and remain as a functioning supernumerary element in the mature nervous system.

Dichoptically viewed colour aftereffects produced by monocular adaptation.

Colour aftereffects were observed in dichoptically viewed achromatic striped patterns after a 25 s period of monocular adaptation to an homogeneous coloured field of red, green, or blue. Three test conditions of dichoptic viewing were used. In condition 1, black line patterns were viewed dichoptically on fused white backgrounds. Stimuli used in condition 2 were similar except that they were white line patterns on black backgrounds. Last, condition 3 was realised with the same stimulus patterns utilised in condition 1, except that the mode of dichoptic viewing produced a juxtaposition rather than a fusion of the two white backgrounds containing the line patterns. Some colour aftereffect was obtained for each colour-adaptation condition and in each test condition. It consisted in a negative colour aftereffect (NCA) in the adapted eye (the colour seen was roughly the complementary of the adaptation colour) and/or a positive colour aftereffect (PCA) in the unadapted eye (the colour seen tended rather to be similar in hue to the adaptation colour). In fact, the following four kinds of responses were obtained: (i) two colour aftereffects, one seen by each eye, ie a NCA involving the adapted eye and a PCA involving the unadapted eye; (ii) a NCA involving the adapted eye only; (iii) a PCA involving the unadapted eye only; (iv) no colour aftereffect at all. Results obtained in different test conditions permitted us to assert that both kinds of colour aftereffect could be produced with white patterns on dark backgrounds as well as with black patterns on white backgrounds and did not require binocular fusion of the white backgrounds.(ABSTRACT TRUNCATED AT 250 WORDS)

Roll, pitch, longitudinal and yaw vection visually induced by optical flow in flight simulation conditions.

The present experiment was undertaken to study the effect of the addition of stimulation in the peripheral visual field on perceived self-motion (vection). The parameters were axes of motion, "Central + Peripheral" versus "Central vision, frequencies of sinusoidal motion (0.2 Hz to 1.0 Hz), and amplitudes. Vection generally increased with increased amplitudes and frequencies. In the "Central + Peripheral" condition, there was an interaction between frequencies and amplitudes. When stimuli were presented in "Central" vision only, vection was generally higher. It has been concluded that, for vection, the addition of visual stimulation in the periphery is more important at low sinusoidal frequencies and high amplitudes; at higher frequencies, this produces a decrease in vection probably attributable to an increase in object motion perception.

On performing experimental studies on transient states of continuous-flow methanogenic reactors.

One approach to exploring the behavior of microbial cultures during transient conditions of unbalanced growth is to experimentally observe continuous-flow biological reactors which have been subjected to perturbations in the influent flowrate and/or concentration of growth-limiting substrate. Proper interpretation of such experiments requires that appropriate account be taken of reaction stoichiometry, the distribution and abundance of microbial populations within the reactor, and the nonideality of mixing and flow distribution in the reactor. These aspects of proper experimental design are particularly critical when the system of interest involves methanogenic consortia and is not a completely-mixed, suspended-growth reactor.

Infants' reactions to visual movement of the environment.

It has been demonstrated many times that the posture of infants is affected by movement of the visual environment. However, in previous studies, measurements taken with infants less than 10 to 12 months of age have always been recorded with the infants in a sitting position. An experiment is reported in which the postural reactions to a sinusoidal movement of the visual environment were recorded in infants 7 months of age and older standing with support. Fifty subjects divided into five groups (mean age 7.15 to 48.6 months) participated in the experiment. The groups differed in age and motor ability. Movement of the visual environment was achieved by means of a floorless room that could be moved sinusoidally in the anteroposterior axis. The subjects had to stand holding a horizontal bar fixed to a force-measurement platform. For each subject, measurements were made during four 60 s intervals: two with movement of the room and two with the room stationary. For all groups, reactions in the anteroposterior axis were stronger than in the lateral axis and this was true for both stimulus conditions. Comparison of the differences between the movement and stationary conditions in the anteroposterior axis, as a function of age, shows that the youngest infants seemed paradoxically to give stronger reactions when the room was stationary than when it was moving; the inverse was true for older infants and this difference increased with age. An analysis of the data with fast Fourier transforms reveals that the majority of subjects showed a pattern of postural reactions where the dominant (peak) frequency was identical to the peak frequency of room movement.(ABSTRACT TRUNCATED AT 250 WORDS)