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Results: 1 to 10 of 113

Publication Record

Connections

Accumulators, Neurons, and Response Time.
Schall JD
(2019) Trends Neurosci 42: 848-860
MeSH Terms: Animals, Brain, Decision Making, Humans, Mind-Body Relations, Metaphysical, Models, Neurological, Models, Psychological, Neurons, Psychophysiology, Reaction Time
Show Abstract · Added March 18, 2020
The marriage of cognitive neurophysiology and mathematical psychology to understand decision-making has been exceptionally productive. This interdisciplinary area is based on the proposition that particular neurons or circuits instantiate the accumulation of evidence specified by mathematical models of sequential sampling and stochastic accumulation. This linking proposition has earned widespread endorsement. Here, a brief survey of the history of the proposition precedes a review of multiple conundrums and paradoxes concerning the accuracy, precision, and transparency of that linking proposition. Correctly establishing how abstract models of decision-making are instantiated by particular neural circuits would represent a remarkable accomplishment in mapping mind to brain. Failing would reveal challenging limits for cognitive neuroscience. This is such a vigorous area of research because so much is at stake.
Copyright © 2019 Elsevier Ltd. All rights reserved.
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10 MeSH Terms
Disruption of Neural Homeostasis as a Model of Relapse and Recurrence in Late-Life Depression.
Andreescu C, Ajilore O, Aizenstein HJ, Albert K, Butters MA, Landman BA, Karim HT, Krafty R, Taylor WD
(2019) Am J Geriatr Psychiatry 27: 1316-1330
MeSH Terms: Aged, Allostasis, Autonomic Nervous System, Brain, Circadian Rhythm, Cognitive Dysfunction, Depressive Disorder, Major, Homeostasis, Humans, Hypothalamo-Hypophyseal System, Models, Neurological, Models, Psychological, Neural Pathways, Pituitary-Adrenal System, Recurrence, Stress, Psychological
Show Abstract · Added March 3, 2020
The significant public health burden associated with late-life depression (LLD) is magnified by the high rates of recurrence. In this manuscript, we review what is known about recurrence risk factors, conceptualize recurrence within a model of homeostatic disequilibrium, and discuss the potential significance and challenges of new research into LLD recurrence. The proposed model is anchored in the allostatic load theory of stress. We review the allostatic response characterized by neural changes in network function and connectivity and physiologic changes in the hypothalamic-pituitary-adrenal axis, autonomic nervous system, immune system, and circadian rhythm. We discuss the role of neural networks' instability following treatment response as a source of downstream disequilibrium, triggering and/or amplifying abnormal stress response, cognitive dysfunction and behavioral changes, ultimately precipitating a full-blown recurrent episode of depression. We propose strategies to identify and capture early change points that signal recurrence risk through mobile technology to collect ecologically measured symptoms, accompanied by automated algorithms that monitor for state shifts (persistent worsening) and variance shifts (increased variability) relative to a patient's baseline. Identifying such change points in relevant sensor data could potentially provide an automated tool that could alert clinicians to at-risk individuals or relevant symptom changes even in a large practice.
Published by Elsevier Inc.
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16 MeSH Terms
Functional MRI and resting state connectivity in white matter - a mini-review.
Gore JC, Li M, Gao Y, Wu TL, Schilling KG, Huang Y, Mishra A, Newton AT, Rogers BP, Chen LM, Anderson AW, Ding Z
(2019) Magn Reson Imaging 63: 1-11
MeSH Terms: Anisotropy, Brain Mapping, Cerebrovascular Circulation, Gray Matter, Hemodynamics, Humans, Magnetic Resonance Imaging, Models, Neurological, Reproducibility of Results, Vasodilation, White Matter
Show Abstract · Added March 3, 2020
Functional MRI (fMRI) signals are robustly detectable in white matter (WM) but they have been largely ignored in the fMRI literature. Their nature, interpretation, and relevance as potential indicators of brain function remain under explored and even controversial. Blood oxygenation level dependent (BOLD) contrast has for over 25 years been exploited for detecting localized neural activity in the cortex using fMRI. While BOLD signals have been reliably detected in grey matter (GM) in a very large number of studies, such signals have rarely been reported from WM. However, it is clear from our own and other studies that although BOLD effects are weaker in WM, using appropriate detection and analysis methods they are robustly detectable both in response to stimuli and in a resting state. BOLD fluctuations in a resting state exhibit similar temporal and spectral profiles in both GM and WM, and their relative low frequency (0.01-0.1 Hz) signal powers are comparable. They also vary with baseline neural activity e.g. as induced by different levels of anesthesia, and alter in response to a stimulus. In previous work we reported that BOLD signals in WM in a resting state exhibit anisotropic temporal correlations with neighboring voxels. On the basis of these findings, we derived functional correlation tensors that quantify the correlational anisotropy in WM BOLD signals. We found that, along many WM tracts, the directional preferences of these functional correlation tensors in a resting state are grossly consistent with those revealed by diffusion tensors, and that external stimuli tend to enhance visualization of specific and relevant fiber pathways. These findings support the proposition that variations in WM BOLD signals represent tract-specific responses to neural activity. We have more recently shown that sensory stimulations induce explicit BOLD responses along parts of the projection fiber pathways, and that task-related BOLD changes in WM occur synchronously with the temporal pattern of stimuli. WM tracts also show a transient signal response following short stimuli analogous to but different from the hemodynamic response function (HRF) characteristic of GM. Thus there is converging and compelling evidence that WM exhibits both resting state fluctuations and stimulus-evoked BOLD signals very similar (albeit weaker) to those in GM. A number of studies from other laboratories have also reported reliable observations of WM activations. Detection of BOLD signals in WM has been enhanced by using specialized tasks or modified data analysis methods. In this mini-review we report summaries of some of our recent studies that provide evidence that BOLD signals in WM are related to brain functional activity and deserve greater attention by the neuroimaging community.
Copyright © 2019 Elsevier Inc. All rights reserved.
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11 MeSH Terms
Neurally constrained modeling of speed-accuracy tradeoff during visual search: gated accumulation of modulated evidence.
Servant M, Tillman G, Schall JD, Logan GD, Palmeri TJ
(2019) J Neurophysiol 121: 1300-1314
MeSH Terms: Animals, Decision Making, Macaca, Models, Neurological, Saccades, Sensorimotor Cortex, Sensory Gating, Stochastic Processes, Visual Fields, Visual Perception
Show Abstract · Added March 18, 2020
Stochastic accumulator models account for response times and errors in perceptual decision making by assuming a noisy accumulation of perceptual evidence to a threshold. Previously, we explained saccade visual search decision making by macaque monkeys with a stochastic multiaccumulator model in which accumulation was driven by a gated feed-forward integration to threshold of spike trains from visually responsive neurons in frontal eye field that signal stimulus salience. This neurally constrained model quantitatively accounted for response times and errors in visual search for a target among varying numbers of distractors and replicated the dynamics of presaccadic movement neurons hypothesized to instantiate evidence accumulation. This modeling framework suggested strategic control over gate or over threshold as two potential mechanisms to accomplish speed-accuracy tradeoff (SAT). Here, we show that our gated accumulator model framework can account for visual search performance under SAT instructions observed in a milestone neurophysiological study of frontal eye field. This framework captured key elements of saccade search performance, through observed modulations of neural input, as well as flexible combinations of gate and threshold parameters necessary to explain differences in SAT strategy across monkeys. However, the trajectories of the model accumulators deviated from the dynamics of most presaccadic movement neurons. These findings demonstrate that traditional theoretical accounts of SAT are incomplete descriptions of the underlying neural adjustments that accomplish SAT, offer a novel mechanistic account of decision-making mechanisms during speed-accuracy tradeoff, and highlight questions regarding the identity of model and neural accumulators. NEW & NOTEWORTHY A gated accumulator model is used to elucidate neurocomputational mechanisms of speed-accuracy tradeoff. Whereas canonical stochastic accumulators adjust strategy only through variation of an accumulation threshold, we demonstrate that strategic adjustments are accomplished by flexible combinations of both modulation of the evidence representation and adaptation of accumulator gate and threshold. The results indicate how model-based cognitive neuroscience can translate between abstract cognitive models of performance and neural mechanisms of speed-accuracy tradeoff.
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MeSH Terms
A practical protocol for measurements of spinal cord functional connectivity.
Barry RL, Conrad BN, Smith SA, Gore JC
(2018) Sci Rep 8: 16512
MeSH Terms: Adult, Female, Healthy Volunteers, Humans, Image Interpretation, Computer-Assisted, Magnetic Resonance Imaging, Male, Models, Neurological, Rest, Spinal Cord, Young Adult
Show Abstract · Added March 26, 2019
Resting state functional magnetic resonance imaging (fMRI) has been used to study human brain function for over two decades, but only recently has this technique been successfully translated to the human spinal cord. The spinal cord is structurally and functionally unique, so resting state fMRI methods developed and optimized for the brain may not be appropriate when applied to the cord. This report therefore investigates the relative impact of different acquisition and processing choices (including run length, echo time, and bandpass filter width) on the detectability of resting state spinal cord networks at 3T. Our results suggest that frequencies beyond 0.08 Hz should be included in resting state analyses, a run length of ~8-12 mins is appropriate for reliable detection of the ventral (motor) network, and longer echo times - yet still shorter than values typically used for fMRI in the brain - may increase the detectability of the dorsal (sensory) network. Further studies are required to more fully understand and interpret the nature of resting state spinal cord networks in health and in disease, and the protocols described in this report are designed to assist such studies.
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11 MeSH Terms
Modulation of thalamocortical oscillations by TRIP8b, an auxiliary subunit for HCN channels.
Zobeiri M, Chaudhary R, Datunashvili M, Heuermann RJ, Lüttjohann A, Narayanan V, Balfanz S, Meuth P, Chetkovich DM, Pape HC, Baumann A, van Luijtelaar G, Budde T
(2018) Brain Struct Funct 223: 1537-1564
MeSH Terms: Action Potentials, Adenine, Adenylyl Cyclase Inhibitors, Animals, Cardiovascular Agents, Cerebral Cortex, Cyclic AMP, Cyclic GMP, Female, Hyperpolarization-Activated Cyclic Nucleotide-Gated Channels, Male, Membrane Proteins, Mice, Mice, Inbred C57BL, Mice, Transgenic, Models, Neurological, Neural Pathways, Peroxins, Pyrimidines, Sodium Channel Blockers, Tetrodotoxin, Thalamus, Thionucleotides
Show Abstract · Added April 2, 2019
Hyperpolarization-activated cyclic nucleotide-gated cation (HCN) channels have important functions in controlling neuronal excitability and generating rhythmic oscillatory activity. The role of tetratricopeptide repeat-containing Rab8b-interacting protein (TRIP8b) in regulation of hyperpolarization-activated inward current, I , in the thalamocortical system and its functional relevance for the physiological thalamocortical oscillations were investigated. A significant decrease in I current density, in both thalamocortical relay (TC) and cortical pyramidal neurons was found in TRIP8b-deficient mice (TRIP8b). In addition basal cAMP levels in the brain were found to be decreased while the availability of the fast transient A-type K current, I , in TC neurons was increased. These changes were associated with alterations in intrinsic properties and firing patterns of TC neurons, as well as intrathalamic and thalamocortical network oscillations, revealing a significant increase in slow oscillations in the delta frequency range (0.5-4 Hz) during episodes of active-wakefulness. In addition, absence of TRIP8b suppresses the normal desynchronization response of the EEG during the switch from slow-wave sleep to wakefulness. It is concluded that TRIP8b is necessary for the modulation of physiological thalamocortical oscillations due to its direct effect on HCN channel expression in thalamus and cortex and that mechanisms related to reduced cAMP signaling may contribute to the present findings.
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MeSH Terms
Models of inhibitory control.
Schall JD, Palmeri TJ, Logan GD
(2017) Philos Trans R Soc Lond B Biol Sci 372:
MeSH Terms: Animals, Humans, Inhibition, Psychological, Models, Neurological, Models, Psychological, Reaction Time, Synaptic Transmission
Show Abstract · Added April 14, 2017
We survey models of response inhibition having different degrees of mathematical, computational and neurobiological specificity and generality. The independent race model accounts for performance of the stop-signal or countermanding task in terms of a race between GO and STOP processes with stochastic finishing times. This model affords insights into neurophysiological mechanisms that are reviewed by other authors in this volume. The formal link between the abstract GO and STOP processes and instantiating neural processes is articulated through interactive race models consisting of stochastic accumulator GO and STOP units. This class of model provides quantitative accounts of countermanding performance and replicates the dynamics of neural activity producing that performance. The interactive race can be instantiated in a network of biophysically plausible spiking excitatory and inhibitory units. Other models seek to account for interactions between units in frontal cortex, basal ganglia and superior colliculus. The strengths, weaknesses and relationships of the different models will be considered. We will conclude with a brief survey of alternative modelling approaches and a summary of problems to be addressed including accounting for differences across effectors, species, individuals, task conditions and clinical deficits.This article is part of the themed issue 'Movement suppression: brain mechanisms for stopping and stillness'.
© 2017 The Author(s).
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7 MeSH Terms
Realistic models of apparent dynamic changes in resting-state connectivity in somatosensory cortex.
Shi Z, Rogers BP, Chen LM, Morgan VL, Mishra A, Wilkes DM, Gore JC
(2016) Hum Brain Mapp 37: 3897-3910
MeSH Terms: Animals, Brain Mapping, Computer Simulation, Magnetic Resonance Imaging, Models, Neurological, Models, Statistical, Neural Pathways, Rest, Saimiri, Somatosensory Cortex
Show Abstract · Added April 10, 2017
Variations over time in resting-state correlations in blood oxygenation level-dependent (BOLD) signals from different cortical areas may indicate changes in brain functional connectivity. However, apparent variations over time may also arise from stationary signals when the sample duration is finite. Recently, a vector autoregressive (VAR) null model has been proposed to simulate real functional magnetic resonance imaging (fMRI) data, which provides a robust stationary model for identifying possible temporal dynamic changes in functional connectivity. In this work, we propose a simpler model that uses a filtered stationary dataset. The filtered stationary model generates statistically stationary time series from random data with a single prescribed correlation coefficient that is calculated as the average over the entire time series. In addition, we propose a dynamic model, which is better able to replicate real fMRI connectivity, estimated from monkey brain studies, than the two stationary models. We compare simulated results using these three models with the behavior of primary somatosensory cortex (S1) networks in anesthetized squirrel monkeys at high field (9.4 T), using a sliding window correlation analysis. We found that at short window sizes, both stationary models reproduced the distribution of correlations of real signals well, but at longer window sizes, a dynamic model reproduced the distribution of correlations of real signals better than the stationary models. While stationary models replicate several features of real data, a close representation of the behavior of resting-state data acquired from somatosensory cortex of non-human primates is obtained only when a dynamic correlation is introduced, suggesting dynamic variations in connectivity are real. Hum Brain Mapp 37:3897-3910, 2016. © 2016 Wiley Periodicals, Inc.
© 2016 Wiley Periodicals, Inc.
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2 Members
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10 MeSH Terms
Reproducibility of resting state spinal cord networks in healthy volunteers at 7 Tesla.
Barry RL, Rogers BP, Conrad BN, Smith SA, Gore JC
(2016) Neuroimage 133: 31-40
MeSH Terms: Adolescent, Adult, Brain Mapping, Computer Simulation, Female, Humans, Magnetic Resonance Imaging, Male, Models, Neurological, Nerve Net, Reference Values, Reproducibility of Results, Rest, Sensitivity and Specificity, Spinal Cord, Young Adult
Show Abstract · Added April 6, 2017
We recently reported our findings of resting state functional connectivity in the human spinal cord: in a cohort of healthy volunteers we observed robust functional connectivity between left and right ventral (motor) horns and between left and right dorsal (sensory) horns (Barry et al., 2014). Building upon these results, we now quantify the within-subject reproducibility of bilateral motor and sensory networks (intraclass correlation coefficient=0.54-0.56) and explore the impact of including frequencies up to 0.13Hz. Our results suggest that frequencies above 0.08Hz may enhance the detectability of these resting state networks, which would be beneficial for practical studies of spinal cord functional connectivity.
Copyright © 2016 Elsevier Inc. All rights reserved.
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2 Members
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16 MeSH Terms
Phase-amplitude coupling, an indication of bursting in parkinsonism, is masked by periodic pulses.
Sanders TH
(2016) J Neurophysiol 115: 1587-95
MeSH Terms: Animals, Brain Waves, Macaca mulatta, Male, Mice, Mice, Inbred C57BL, Models, Neurological, Neurons, Parkinsonian Disorders, Thalamic Nuclei
Show Abstract · Added August 8, 2017
Interactions between neural oscillations in the brain have been observed in many structures including the hippocampus, amygdala, motor cortex, and basal ganglia. In this study, one popular approach for quantifying oscillation interactions was considered: phase-amplitude coupling. The goals of the study were to use simulations to examine potential causes of elevated phase-amplitude coupling in parkinsonism, to compare simulated parkinsonian signals with recorded local field potentials from animal models of parkinsonism, to investigate possible relationships between increased bursting in parkinsonian single cells and elevated phase-amplitude coupling, and to uncover potential noise and artifact effects. First, a cell model that integrates incremental input currents and fires at realistic voltage thresholds was modified to allow control of stochastic parameters related to firing and burst rates. Next, the input currents and distribution of integration times were set to reproduce firing patterns consistent with those from parkinsonian subthalamic nucleus cells. Then, local field potentials were synthesized from the output of multiple simulated cells with varying degrees of synchronization and compared with subthalamic nucleus recordings from animal models of parkinsonism. The results showed that phase-amplitude coupling can provide important information about underlying neural activity. In particular, signals synthesized from synchronized bursting neurons showed increased oscillatory interactions similar to those observed in parkinsonian animals. Additionally, changes in bursting parameters such as the intraburst rate, the mean interburst period, and the amount of synchronization between neurons influenced the phase-amplitude coupling in predictable ways. Finally, simulation results revealed that small periodic signals can have a surprisingly large masking effect on phase-amplitude coupling.
Copyright © 2016 the American Physiological Society.
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10 MeSH Terms