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Peter Ford Dominey - One of the best experts on this subject based on the ideXlab platform.

  • Reservoir Computing Properties of Neural Dynamics in Prefrontal Cortex
    PLoS Computational Biology, 2016
    Co-Authors: Pierre Enel, Emmanuel Procyk, René Quilodran, Peter Ford Dominey
    Abstract:

    Primates display a remarkable ability to adapt to novel situations. Determining what is most pertinent in these situations is not always possible based only on the current sensory inputs, and often also depends on recent inputs and behavioral outputs that contribute to internal states. Thus, one can ask how cortical dynamics generate representations of these Complex situations. It has been observed that mixed selectivity in cortical neurons contributes to represent diverse situations defined by a combination of the current stimuli, and that mixed selectivity is readily obtained in randomly connected recurrent networks. In this context, these reservoir networks reproduce the highly recurrent nature of local cortical connectivity. Recombining present and past inputs, random recurrent networks from the reservoir computing framework generate mixed selectivity which provides pre-coded representations of an essentially universal set of contexts. These representations can then be selectively amplified through learning to solve the Task at hand. We thus explored their representational power and dynamical properties after training a reservoir to perform a Complex Cognitive Task initially developed for monkeys. The reservoir model inherently displayed a dynamic form of mixed selectivity, key to the representation of the behavioral context over time. The pre-coded representation of context was amplified by training a feedback neuron to explicitly represent this context, thereby reproducing the effect of learning and allowing the model to perform more robustly. This second version of the model demonstrates how a hybrid dynamical regime combining spatio-temporal processing of reservoirs, and input driven attracting dynamics generated by the feedback neuron, can be used to solve a Complex Cognitive Task. We compared reservoir activity to neural activity of dorsal anterior cingulate cortex of monkeys which revealed similar network dynamics. We argue that reservoir computing is a pertinent framework to model local cortical dynamics and their contribution to higher Cognitive function.

Eugene G Daquili - One of the best experts on this subject based on the ideXlab platform.

  • the measurement of regional cerebral blood flow during the Complex Cognitive Task of meditation a preliminary spect study
    Psychiatry Research-neuroimaging, 2001
    Co-Authors: Andrew B. Newberg, Abass Alavi, Michael J. Baime, Michael Pourdehnad, Jill Santanna, Eugene G Daquili
    Abstract:

    This study measured changes in regional cerebral blood flow (rCBF) during the Complex Cognitive Task of meditation using single photon emission computed tomography. Eight experienced Tibetan Buddhist meditators were injected at baseline with 7 mCi HMPAO and scanned 20 min later for 45 min. The subjects then meditated for 1 h at which time they were injected with 25 mCi HMPAO and scanned 20 min later for 30 min. Values were obtained for regions of interest in major brain structures and normalized to whole brain activity. The percentage change between meditation and baseline was compared. Correlations between structures were also determined. Significantly increased rCBF (P<0.05) was observed in the cingulate gyrus, inferior and orbital frontal cortex, dorsolateral prefrontal cortex (DLPFC), and thalamus. The change in rCBF in the left DLPFC correlated negatively (P<0.05) with that in the left superior parietal lobe. Increased frontal rCBF may reflect focused concentration and thalamic increases overall increased cortical activity during meditation. The correlation between the DLPFC and the superior parietal lobe may reflect an altered sense of space experienced during meditation. These results suggest a Complex rCBF pattern during the Task of meditation.

Catherine M Sweeneyreed - One of the best experts on this subject based on the ideXlab platform.

  • neural correlates of true and false memory in mild Cognitive impairment
    PLOS ONE, 2012
    Co-Authors: Catherine M Sweeneyreed, Judi A Ellis, Jayne E Freeman, Patricia M. Riddell, Slawomir J Nasuto
    Abstract:

    The goal of this research was to investigate the changes in neural processing in mild Cognitive impairment. We measured phase synchrony, amplitudes, and event-related potentials in veridical and false memory to determine whether these differed in participants with mild Cognitive impairment compared with typical, age-matched controls. Empirical mode decomposition phase locking analysis was used to assess synchrony, which is the first time this analysis technique has been applied in a Complex Cognitive Task such as memory processing. The technique allowed assessment of changes in frontal and parietal cortex connectivity over time during a memory Task, without a priori selection of frequency ranges, which has been shown previously to influence synchrony detection. Phase synchrony differed significantly in its timing and degree between participant groups in the theta and alpha frequency ranges. Timing differences suggested greater dependence on gist memory in the presence of mild Cognitive impairment. The group with mild Cognitive impairment had significantly more frontal theta phase locking than the controls in the absence of a significant behavioural difference in the Task, providing new evidence for compensatory processing in the former group. Both groups showed greater frontal phase locking during false than true memory, suggesting increased searching when no actual memory trace was found. Significant inter-group differences in frontal alpha phase locking provided support for a role for lower and upper alpha oscillations in memory processing. Finally, fronto-parietal interaction was significantly reduced in the group with mild Cognitive impairment, supporting the notion that mild Cognitive impairment could represent an early stage in Alzheimer’s disease, which has been described as a ‘disconnection syndrome’.

Joseph Ciorciari - One of the best experts on this subject based on the ideXlab platform.

  • Source-based neurofeedback methods using EEG recordings: training altered brain activity in a functional brain source derived from blind source separation
    Frontiers in Behavioral Neuroscience, 2014
    Co-Authors: David J White, Marco Congedo, Joseph Ciorciari
    Abstract:

    A developing literature explores the use of neurofeedback in the treatment of a range of clinical conditions, particularly ADHD and epilepsy, whilst neurofeedback also provides an experimental tool for studying the functional significance of endogenous brain activity. A critical component of any neurofeedback method is the underlying physiological signal which forms the basis for the feedback. While the past decade has seen the emergence of fMRI-based protocols training spatially confined BOLD activity, traditional neurofeedback has utilized a small number of electrode sites on the scalp. As scalp EEG at a given electrode site reflects a linear mixture of activity from multiple brain sources and artifacts, efforts to successfully acquire some level of control over the signal may be confounded by these extraneous sources. Further, in the event of successful training, these traditional neurofeedback methods are likely influencing multiple brain regions and processes. The present work describes the use of source-based signal processing methods in EEG neurofeedback. The feasibility and potential utility of such methods were explored in an experiment training increased theta oscillatory activity in a source derived from Blind Source Separation (BSS) of EEG data obtained during completion of a Complex Cognitive Task (spatial navigation). Learned increases in theta activity were observed in two of the four participants to complete 20 sessions of neurofeedback targeting this individually defined functional brain source. Source-based EEG neurofeedback methods using BSS may offer important advantages over traditional neurofeedback, by targeting the desired physiological signal in a more functionally and spatially specific manner. Having provided preliminary evidence of the feasibility of these methods, future work may study a range of clinically and experimentally relevant brain processes where individual brain sources may be targeted by source-based EEG neurofeedback.

Andrew B. Newberg - One of the best experts on this subject based on the ideXlab platform.

  • the measurement of regional cerebral blood flow during the Complex Cognitive Task of meditation a preliminary spect study
    Psychiatry Research-neuroimaging, 2001
    Co-Authors: Andrew B. Newberg, Abass Alavi, Michael J. Baime, Michael Pourdehnad, Jill Santanna, Eugene G Daquili
    Abstract:

    This study measured changes in regional cerebral blood flow (rCBF) during the Complex Cognitive Task of meditation using single photon emission computed tomography. Eight experienced Tibetan Buddhist meditators were injected at baseline with 7 mCi HMPAO and scanned 20 min later for 45 min. The subjects then meditated for 1 h at which time they were injected with 25 mCi HMPAO and scanned 20 min later for 30 min. Values were obtained for regions of interest in major brain structures and normalized to whole brain activity. The percentage change between meditation and baseline was compared. Correlations between structures were also determined. Significantly increased rCBF (P<0.05) was observed in the cingulate gyrus, inferior and orbital frontal cortex, dorsolateral prefrontal cortex (DLPFC), and thalamus. The change in rCBF in the left DLPFC correlated negatively (P<0.05) with that in the left superior parietal lobe. Increased frontal rCBF may reflect focused concentration and thalamic increases overall increased cortical activity during meditation. The correlation between the DLPFC and the superior parietal lobe may reflect an altered sense of space experienced during meditation. These results suggest a Complex rCBF pattern during the Task of meditation.

  • The measurement of regional cerebral blood flow during the Complex Cognitive Task of meditation: a preliminary SPECT study.
    Psychiatry Research: Neuroimaging, 2001
    Co-Authors: Andrew B. Newberg, Abass Alavi, Michael J. Baime, Michael Pourdehnad, Jill Santanna, Eugene G. D'aquili
    Abstract:

    This study measured changes in regional cerebral blood flow (rCBF) during the Complex Cognitive Task of meditation using single photon emission computed tomography. Eight experienced Tibetan Buddhist meditators were injected at baseline with 7 mCi HMPAO and scanned 20 min later for 45 min. The subjects then meditated for 1 h at which time they were injected with 25 mCi HMPAO and scanned 20 min later for 30 min. Values were obtained for regions of interest in major brain structures and normalized to whole brain activity. The percentage change between meditation and baseline was compared. Correlations between structures were also determined. Significantly increased rCBF (P