28 results on '"Trujillo-Barreto, Nelson J."'
Search Results
2. Explicit modeling of brain state duration using hidden semi Markov models in EEG data
- Author
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Trujillo-Barreto, Nelson J, Galvez, David Araya, Astudillo, Aland, El-Deredy, Wael, Trujillo-Barreto, Nelson J, Galvez, David Araya, Astudillo, Aland, and El-Deredy, Wael
- Abstract
We consider the detection and characterization of brain state transitions based on ongoing electroencephalography (EEG). Here, a brain state represents a specific brain dynamical regime or mode of operation that produces a characteristic quasi-stable pattern of activity at the topography, sources, or network levels. These states and their transitions over time can reflect fundamental computational properties of the brain, shaping human behavior and brain function. The hidden Markov model (HMM) has emerged as a useful tool for uncovering the hidden dynamics of brain state transitions based on observed data. However, the limitations of the Geometric distribution of states' durations (dwell times) implicit in the standard HMM, make it sub-optimal for modeling brain states in EEG. We propose using hidden semi Markov models (HSMM), a generalization of HMM that allows modeling the brain states duration distributions explicitly. We present a Bayesian formulation of HSMM and use the variational Bayes framework to efficiently estimate the HSMM parameters, the number of brain states, and select among candidate brain state duration distributions. We assess HSMM performance against HMM on simulated data and demonstrate that the accurate modeling of state durations is paramount for making reliable inference when the task at hand requires accurate model predictions. Finally, we use actual resting-state EEG data to illustrate the benefits of the approach in practice. We demonstrate that the possibility of modeling brain state durations explicitly provides a new way for investigating the nature of the neural dynamics that generated the EEG data.
- Published
- 2024
3. Test–retest reliability of Bayesian estimations of the effects of stimulation, prior information and individual traits on pain perception
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Delgado-Sanchez, Ariane, Charalambous, Christiana, Trujillo-Barreto, Nelson J, Safi, Hannah, Jones, Anthony, Sivan, Manoj, Talmi, Deborah, Brown, Christopher, Delgado-Sanchez, Ariane, Charalambous, Christiana, Trujillo-Barreto, Nelson J, Safi, Hannah, Jones, Anthony, Sivan, Manoj, Talmi, Deborah, and Brown, Christopher
- Abstract
Background: There is inter-individual variability in the influence of different components (e.g. nociception and expectations) on pain perception. Identifying the individual effect of these components could serve for patient stratification, but only if these influences are stable in time. Methods: In this study, 30 healthy participants underwent a cognitive pain paradigm in which they rated pain after viewing a probabilistic cue informing of forthcoming pain intensity and then receiving electrical stimulation. The trial information was then used in a Bayesian probability model to compute the relative weight each participant put on stimulation, cue, cue uncertainty and trait-like bias. The same procedure was repeated 2 weeks later. Relative and absolute test–retest reliability of all measures was assessed. Results: Intraclass correlation results showed good reliability for the effect of the stimulation (0.83), the effect of the cue (0.75) and the trait-like bias (0.75 and 0.75), and a moderate reliability for the effect of the cue uncertainty (0.55). Absolute reliability measures also supported the temporal stability of the results and indicated that a change in parameters corresponding to a difference in pain ratings ranging between 0.47 and 1.45 (depending on the parameters) would be needed to consider differences in outcomes significant. The comparison of these measures with the closest clinical data we possess supports the reliability of our results. Conclusions: These findings support the hypothesis that inter-individual differences in the weight placed on different pain factors are stable in time and could therefore be a possible target for patient stratification. Significance: Our results demonstrate the temporal stability of the weight healthy individuals place on the different factors leading to the pain response. These findings give validity to the idea of using Bayesian estimations of the influence of different factors on pain as a way to stratify patients
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- 2024
4. GABA Modulates Frequency-Dependent Plasticity in Humans
- Author
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Lea-Carnall, Caroline A., Williams, Stephen R., Sanaei-Nezhad, Faezeh, Trujillo-Barreto, Nelson J., Montemurro, Marcelo A., El-Deredy, Wael, and Parkes, Laura M.
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- 2020
- Full Text
- View/download PDF
5. A tutorial and tool for exploring feature similarity gradients with MRI data
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Bajada, Claude J., Costa Campos, Lucas Q., Caspers, Svenja, Muscat, Richard, Parker, Geoff J.M., Lambon Ralph, Matthew A., Cloutman, Lauren L., and Trujillo-Barreto, Nelson J.
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- 2020
- Full Text
- View/download PDF
6. Evidence for frequency-dependent cortical plasticity in the human brain
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Lea-Carnall, Caroline A., Trujillo-Barreto, Nelson J., Montemurro, Marcelo A., El-Deredy, Wael, and Parkes, Laura M.
- Published
- 2017
7. A mean-field model of glutamate and GABA synaptic dynamics for functional MRS
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Lea-Carnall, Caroline A, El-Deredy, Wael, Stagg, Charlotte J, Williams, Stephen R, Trujillo-Barreto, Nelson J, Lea-Carnall, Caroline A, El-Deredy, Wael, Stagg, Charlotte J, Williams, Stephen R, and Trujillo-Barreto, Nelson J
- Abstract
Advances in functional magnetic resonance spectroscopy (fMRS) have enabled the quantification of activity-dependent changes in neurotransmitter concentrations in vivo. However, the physiological basis of the large changes in GABA and glutamate observed by fMRS (>10%) over short time scales of less than a minute remain unclear as such changes cannot be accounted for by known synthesis or degradation metabolic pathways. Instead, it has been hypothesized that fMRS detects shifts in neurotransmitter concentrations as they cycle from presynaptic vesicles, where they are largely invisible, to extracellular and cytosolic pools, where they are detectable. The present paper uses a computational modelling approach to demonstrate the viability of this hypothesis. A new mean-field model of the neural mechanisms generating the fMRS signal in a cortical voxel is derived. The proposed macroscopic mean-field model is based on a microscopic description of the neurotransmitter dynamics at the level of the synapse. Specifically, GABA and glutamate are assumed to cycle between three metabolic pools: packaged in the vesicles; active in the synaptic cleft; and undergoing recycling and repackaging in the astrocytic or neuronal cytosol. Computational simulations from the model are used to generate predicted changes in GABA and glutamate concentrations in response to different types of stimuli including pain, vision, and electric current stimulation. The predicted changes in the extracellular and cytosolic pools corresponded to those reported in empirical fMRS data. Furthermore, the model predicts a selective control mechanism of the GABA/glutamate relationship, whereby inhibitory stimulation reduces both neurotransmitters, whereas excitatory stimulation increases glutamate and decreases GABA. The proposed model bridges between neural dynamics and fMRS and provides a mechanistic account for the activity-dependent changes in the glutamate and GABA fMRS signals. Lastly, these results indicate
- Published
- 2023
8. Frontal alpha asymmetry: A potential biomarker of approach-withdrawal motivation towards pain
- Author
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Silva-Passadouro, Bárbara, primary, Delgado-Sanchez, Ariane, additional, Henshaw, James, additional, Lopez-Diaz, Karen, additional, Trujillo-Barreto, Nelson J., additional, Jones, Anthony K. P., additional, and Sivan, Manoj, additional
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- 2022
- Full Text
- View/download PDF
9. Frontal alpha asymmetry: a potential biomarker of approach-withdrawal motivation towards pain
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Silva-Passadouro, Bárbara, Delgado-Sanchez, Ariane, Henshaw, James, Lopez-Diaz, Karen, Trujillo-Barreto, Nelson J, Jones, Anthony K P, Sivan, Manoj, Silva-Passadouro, Bárbara, Delgado-Sanchez, Ariane, Henshaw, James, Lopez-Diaz, Karen, Trujillo-Barreto, Nelson J, Jones, Anthony K P, and Sivan, Manoj
- Abstract
Pain-related catastrophising is a maladaptive coping strategy known to have a strong influence on clinical pain outcomes and treatment efficacy. Notwithstanding, little is known about its neurophysiological correlates. There is evidence to suggest catastrophising is associated with resting-state EEG frontal alpha asymmetry (FAA) patterns reflective of greater relative right frontal activity, which is known to be linked to withdrawal motivation and avoidance of aversive stimuli. The present study aims to investigate whether such a relationship occurs in the situational context of experimental pain. A placebo intervention was also included to evaluate effects of a potential pain-relieving intervention on FAA. 35 participants, including both chronic pain patients and healthy subjects, completed the Pain Catastrophising Scale (PCS) questionnaire followed by EEG recordings during cold pressor test (CPT)-induced tonic pain with or without prior application of placebo cream. There was a negative correlation between FAA and PCS-subscale helplessness scores, but not rumination or magnification, during the pre-placebo CPT condition. Moreover, FAA scores were shown to increase significantly in response to pain, indicative of greater relative left frontal activity that relates to approach-oriented behaviours. Placebo treatment elicited a decrease in FAA in low helplessness scorers, but no significant effects in individuals scoring above the mean on PCS-helplessness. These findings suggest that, during painful events, FAA may reflect the motivational drive to obtain reward of pain relief, which may be diminished in individuals who are prone to feel helpless about their pain. This study provides valuable insights into biomarkers of pain-related catastrophising and prospects of identifying promising targets of brain-based therapies for chronic pain management.
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- 2022
10. Using EEG Alpha States to Understand Learning During Alpha Neurofeedback Training for Chronic Pain
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Patel, Kajal, primary, Henshaw, James, additional, Sutherland, Heather, additional, Taylor, Jason R., additional, Casson, Alexander J., additional, Lopez-Diaz, Karen, additional, Brown, Christopher A., additional, Jones, Anthony K. P., additional, Sivan, Manoj, additional, and Trujillo-Barreto, Nelson J., additional
- Published
- 2021
- Full Text
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11. GABA modulates frequency-dependent plasticity in humans
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Lea-Carnall, Caroline A, Williams, Stephen R, Sanaei-Nezhad, Faezeh, Trujillo-Barreto, Nelson J, Montemurro, Marcelo A, El-Deredy, Wael, Parkes, Laura M, Lea-Carnall, Caroline A, Williams, Stephen R, Sanaei-Nezhad, Faezeh, Trujillo-Barreto, Nelson J, Montemurro, Marcelo A, El-Deredy, Wael, and Parkes, Laura M
- Abstract
Frequency-dependent reorganization of the primary somatosensory cortex, together with perceptual changes, arises following repetitive sensory stimulation. Here, we investigate the role of GABA in this process. We co-stimulated two finger tips and measured GABA and Glx using magnetic resonance (MR) spectroscopy at the beginning and end of the stimulation. Participants performed a perceptual learning task before and after stimulation. There were 2 sessions with stimulation frequency either at or above the resonance frequency of the primary somatosensory cortex (23 and 39 Hz, respectively). Perceptual learning occurred following above resonance stimulation only, while GABA reduced during this condition. Lower levels of early GABA were associated with greater perceptual learning. One possible mechanism underlying this finding is that cortical disinhibition “unmasks” lateral connections within the cortex to permit adaptation to the sensory environment. These results provide evidence in humans for a frequency-dependent inhibitory mechanism underlying learning and suggest a mechanism-based approach for optimizing neurostimulation frequency.
- Published
- 2020
12. Entraining Alpha Activity Using Visual Stimulation in Patients With Chronic Musculoskeletal Pain: A Feasibility Study
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Arendsen, Laura J., primary, Henshaw, James, additional, Brown, Christopher A., additional, Sivan, Manoj, additional, Taylor, Jason R., additional, Trujillo-Barreto, Nelson J., additional, Casson, Alexander J., additional, and Jones, Anthony K. P., additional
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- 2020
- Full Text
- View/download PDF
13. Random Fields—Union Intersection Tests for Detecting Functional Connectivity in EEG/MEG Imaging
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Carbonell, Felix, Worsley, Keith J., Trujillo-Barreto, Nelson J., and Sotero, Roberto C.
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- 2009
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14. Early correlates of visual awareness following orientation and colour rivalry
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Veser, Sandra, OʼShea, Robert P., Schröger, Erich, Trujillo-Barreto, Nelson J., and Roeber, Urte
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- 2008
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15. Cortical Resonance Frequencies Emerge from Network Size and Connectivity
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Lea-Carnall, Caroline A., Montemurro, Marcelo A., Trujillo-Barreto, Nelson J., Parkes, Laura M., El-Deredy, Wael, and Hilgetag, Claus C.
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- 2016
16. Brain Signals of Face Processing as Revealed by Event-Related Potentials
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Olivares, Ela I., Iglesias, Jaime, Saavedra, Cristina, Trujillo-Barreto, Nelson J., and Valdés-Sosa, Mitchell
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Article Subject - Abstract
We analyze the functional significance of different event-related potentials (ERPs) as electrophysiological indices of face perception and face recognition, according to cognitive and neurofunctional models of face processing. Initially, the processing of faces seems to be supported by early extrastriate occipital cortices and revealed by modulations of the occipital P1. This early response is thought to reflect the detection of certain primary structural aspects indicating the presence grosso modo of a face within the visual field. The posterior-temporal N170 is more sensitive to the detection of faces as complex-structured stimuli and, therefore, to the presence of its distinctive organizational characteristics prior to within-category identification. In turn, the relatively late and probably more rostrally generated N250r and N400-like responses might respectively indicate processes of access and retrieval of face-related information, which is stored in long-term memory (LTM). New methods of analysis of electrophysiological and neuroanatomical data, namely, dynamic causal modeling, single-trial and time-frequency analyses, are highly recommended to advance in the knowledge of those brain mechanisms concerning face processing.
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- 2015
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- View/download PDF
17. Timing matters: the processing of pitch relations
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Weise, Annekathrin, Grimm, Sabine, Trujillo-Barreto, Nelson J., Schröger, Erich, Universität Leipzig, University of Barcelona, and Cuban Neuroscience Centre
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ddc:150 ,temporal window of integration ,abstract regularities ,mismatch negativity ,abstract regularities, automatic processing, frontal generators, mismatch negativity, supratemporal generators, temporal window of integration ,frontal generators ,Original Research Article ,Hörwahrnehmung, Tonhöhe, Mismatch Negativity (MMN) ,automatic processing ,supratemporal generators ,Neuroscience - Abstract
The human central auditory system can automatically extract abstract regularities from a variant auditory input. To this end, temporarily separated events need to be related. This study tested whether the timing between events, falling either within or outside the temporal window of integration (~350 ms), impacts the extraction of abstract feature relations. We utilized tone pairs for which tones within but not across pairs revealed a constant pitch relation (e.g., pitch of second tone of a pair higher than pitch of first tone, while absolute pitch values varied across pairs). We measured the mismatch negativity (MMN; the brain’s error signal to auditory regularity violations) to second tones that rarely violated the pitch relation (e.g., pitch of second tone lower). A Short condition in which tone duration (90 ms) and stimulus onset asynchrony between the tones of a pair were short (110 ms) was compared to two conditions, where this onset asynchrony was long (510 ms). In the Long Gap condition, the tone durations were identical to Short (90 ms), but the silent interval was prolonged by 400 ms. In Long Tone, the duration of the first tone was prolonged by 400 ms, while the silent interval was comparable to Short (20 ms). Results show a frontocentral MMN of comparable amplitude in all conditions. Thus, abstract pitch relations can be extracted even when the within-pair timing exceeds the integration period. Source analyses indicate MMN generators in the supratemporal cortex. Interestingly, they were located more anterior in Long Gap than in Short and Long Tone. Moreover, frontal generator activity was found for Long Gap and Long Tone. Thus, the way in which the system automatically registers irregular abstract pitch relations depends on the timing of the events to be linked. Pending that the current MMN data mirror established abstract rule representations coding the regular pitch relation, neural processes building these templates vary with timing.:Introduction; Materials and methods; Results; Discussion; Conclusion
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- 2014
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18. Cortical Resonance Frequencies Emerge from Network Size and Connectivity
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Lea-Carnall, Caroline A., primary, Montemurro, Marcelo A., additional, Trujillo-Barreto, Nelson J., additional, Parkes, Laura M., additional, and El-Deredy, Wael, additional
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- 2016
- Full Text
- View/download PDF
19. Timing matters: the processing of pitch relations
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Universität Leipzig, University of Barcelona, Cuban Neuroscience Centre, Weise, Annekathrin, Grimm, Sabine, Trujillo-Barreto, Nelson J., Schröger, Erich, Universität Leipzig, University of Barcelona, Cuban Neuroscience Centre, Weise, Annekathrin, Grimm, Sabine, Trujillo-Barreto, Nelson J., and Schröger, Erich
- Abstract
The human central auditory system can automatically extract abstract regularities from a variant auditory input. To this end, temporarily separated events need to be related. This study tested whether the timing between events, falling either within or outside the temporal window of integration (~350 ms), impacts the extraction of abstract feature relations. We utilized tone pairs for which tones within but not across pairs revealed a constant pitch relation (e.g., pitch of second tone of a pair higher than pitch of first tone, while absolute pitch values varied across pairs). We measured the mismatch negativity (MMN; the brain’s error signal to auditory regularity violations) to second tones that rarely violated the pitch relation (e.g., pitch of second tone lower). A Short condition in which tone duration (90 ms) and stimulus onset asynchrony between the tones of a pair were short (110 ms) was compared to two conditions, where this onset asynchrony was long (510 ms). In the Long Gap condition, the tone durations were identical to Short (90 ms), but the silent interval was prolonged by 400 ms. In Long Tone, the duration of the first tone was prolonged by 400 ms, while the silent interval was comparable to Short (20 ms). Results show a frontocentral MMN of comparable amplitude in all conditions. Thus, abstract pitch relations can be extracted even when the within-pair timing exceeds the integration period. Source analyses indicate MMN generators in the supratemporal cortex. Interestingly, they were located more anterior in Long Gap than in Short and Long Tone. Moreover, frontal generator activity was found for Long Gap and Long Tone. Thus, the way in which the system automatically registers irregular abstract pitch relations depends on the timing of the events to be linked. Pending that the current MMN data mirror established abstract rule representations coding the regular pitch relation, neural processes building these templates vary with timing.:Introduction; Mat
- Published
- 2014
20. A formal model of interpersonal inference
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Moutoussis, Michael, primary, Trujillo-Barreto, Nelson J., additional, El-Deredy, Wael, additional, Dolan, Raymond J., additional, and Friston, Karl J., additional
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- 2014
- Full Text
- View/download PDF
21. Experimental Placebo Analgesia Changes Resting-State Alpha Oscillations
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Huneke, Nathan T. M., primary, Brown, Christopher A., additional, Burford, Edward, additional, Watson, Alison, additional, Trujillo-Barreto, Nelson J., additional, El-Deredy, Wael, additional, and Jones, Anthony K. P., additional
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- 2013
- Full Text
- View/download PDF
22. A Sparse Neural Code for Some Speech Sounds but Not for Others
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Scharinger, Mathias, primary, Bendixen, Alexandra, additional, Trujillo-Barreto, Nelson J., additional, and Obleser, Jonas, additional
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- 2012
- Full Text
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23. Early correlates of visual awareness in the human brain: Time and place from event-related brain potentials
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Roeber, Urte, primary, Widmann, Andreas, additional, Trujillo-Barreto, Nelson J., additional, Herrmann, Christoph S., additional, O'Shea, Robert P., additional, and Schröger, Erich, additional
- Published
- 2008
- Full Text
- View/download PDF
24. Processing of Abstract Rule Violations in Audition
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Schröger, Erich, primary, Bendixen, Alexandra, additional, Trujillo-Barreto, Nelson J., additional, and Roeber, Urte, additional
- Published
- 2007
- Full Text
- View/download PDF
25. Evidence for frequency-dependent cortical plasticity in the human brain
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Lea-Carnall, Caroline A., Trujillo-Barreto, Nelson J., Montemurro, Marcelo A., El-Deredy, Wael, Parkes, Laura M., Lea-Carnall, Caroline A., Trujillo-Barreto, Nelson J., Montemurro, Marcelo A., El-Deredy, Wael, and Parkes, Laura M.
- Abstract
Frequency-dependent plasticity (FDP) describes adaptation at the synapse in response to stimulation at different frequencies. Its consequence on the structure and function of cortical networks is unknown. We tested whether cortical “resonance,” favorable stimulation frequencies at which the sensory cortices respond maximally, influenced the impact of FDP on perception, functional topography, and connectivity of the primary somatosensory cortex using psychophysics and functional imaging (fMRI). We costimulated two digits on the hand synchronously at, above, or below the resonance frequency of the somatosensory cortex, and tested subjects’ accuracy and speed on tactile localization before and after costimulation. More errors and slower response times followed costimulation at above- or below-resonance, respectively. Response times were faster after at-resonance costimulation. In the fMRI, the cortical representations of the two digits costimulated above-resonance shifted closer, potentially accounting for the poorer performance. Costimulation at-resonance did not shift the digit regions, but increased the functional coupling between them, potentially accounting for the improved response time. To relate these results to synaptic plasticity, we simulated a network of oscillators incorporating Hebbian learning. Two neighboring patches embedded in a cortical sheet, mimicking the two digit regions, were costimulated at different frequencies. Network activation outside the stimulated patches was greatest at above-resonance frequencies, reproducing the spread of digit representations seen with fMRI. Connection strengths within the patches increased following at-resonance costimulation, reproducing the increased fMRI connectivity. We show that FDP extends to the cortical level and is influenced by cortical resonance.
26. GABA Modulates Frequency-Dependent Plasticity in Humans
- Author
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Lea-Carnall, Caroline A., Williams, Stephen R., Sanaei-Nezhad, Faezeh, Trujillo-Barreto, Nelson J., Montemurro, Marcelo A., El-Deredy, Wael, Parkes, Laura M., Lea-Carnall, Caroline A., Williams, Stephen R., Sanaei-Nezhad, Faezeh, Trujillo-Barreto, Nelson J., Montemurro, Marcelo A., El-Deredy, Wael, and Parkes, Laura M.
- Abstract
Frequency-dependent reorganization of the primary somatosensory cortex, together with perceptual changes, arises following repetitive sensory stimulation. Here, we investigate the role of GABA in this process. We co-stimulated two finger tips and measured GABA and Glx using magnetic resonance (MR) spectroscopy at the beginning and end of the stimulation. Participants performed a perceptual learning task before and after stimulation. There were 2 sessions with stimulation frequency either at or above the resonance frequency of the primary somatosensory cortex (23 and 39 Hz, respectively). Perceptual learning occurred following above resonance stimulation only, while GABA reduced during this condition. Lower levels of early GABA were associated with greater perceptual learning. One possible mechanism underlying this finding is that cortical disinhibition “unmasks” lateral connections within the cortex to permit adaptation to the sensory environment. These results provide evidence in humans for a frequency-dependent inhibitory mechanism underlying learning and suggest a mechanism-based approach for optimizing neurostimulation frequency.
27. Evidence for frequency-dependent cortical plasticity in the human brain
- Author
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Lea-Carnall, Caroline A., Trujillo-Barreto, Nelson J., Montemurro, Marcelo A., El-Deredy, Wael, Parkes, Laura M., Lea-Carnall, Caroline A., Trujillo-Barreto, Nelson J., Montemurro, Marcelo A., El-Deredy, Wael, and Parkes, Laura M.
- Abstract
Frequency-dependent plasticity (FDP) describes adaptation at the synapse in response to stimulation at different frequencies. Its consequence on the structure and function of cortical networks is unknown. We tested whether cortical “resonance,” favorable stimulation frequencies at which the sensory cortices respond maximally, influenced the impact of FDP on perception, functional topography, and connectivity of the primary somatosensory cortex using psychophysics and functional imaging (fMRI). We costimulated two digits on the hand synchronously at, above, or below the resonance frequency of the somatosensory cortex, and tested subjects’ accuracy and speed on tactile localization before and after costimulation. More errors and slower response times followed costimulation at above- or below-resonance, respectively. Response times were faster after at-resonance costimulation. In the fMRI, the cortical representations of the two digits costimulated above-resonance shifted closer, potentially accounting for the poorer performance. Costimulation at-resonance did not shift the digit regions, but increased the functional coupling between them, potentially accounting for the improved response time. To relate these results to synaptic plasticity, we simulated a network of oscillators incorporating Hebbian learning. Two neighboring patches embedded in a cortical sheet, mimicking the two digit regions, were costimulated at different frequencies. Network activation outside the stimulated patches was greatest at above-resonance frequencies, reproducing the spread of digit representations seen with fMRI. Connection strengths within the patches increased following at-resonance costimulation, reproducing the increased fMRI connectivity. We show that FDP extends to the cortical level and is influenced by cortical resonance.
28. GABA Modulates Frequency-Dependent Plasticity in Humans
- Author
-
Lea-Carnall, Caroline A., Williams, Stephen R., Sanaei-Nezhad, Faezeh, Trujillo-Barreto, Nelson J., Montemurro, Marcelo A., El-Deredy, Wael, Parkes, Laura M., Lea-Carnall, Caroline A., Williams, Stephen R., Sanaei-Nezhad, Faezeh, Trujillo-Barreto, Nelson J., Montemurro, Marcelo A., El-Deredy, Wael, and Parkes, Laura M.
- Abstract
Frequency-dependent reorganization of the primary somatosensory cortex, together with perceptual changes, arises following repetitive sensory stimulation. Here, we investigate the role of GABA in this process. We co-stimulated two finger tips and measured GABA and Glx using magnetic resonance (MR) spectroscopy at the beginning and end of the stimulation. Participants performed a perceptual learning task before and after stimulation. There were 2 sessions with stimulation frequency either at or above the resonance frequency of the primary somatosensory cortex (23 and 39 Hz, respectively). Perceptual learning occurred following above resonance stimulation only, while GABA reduced during this condition. Lower levels of early GABA were associated with greater perceptual learning. One possible mechanism underlying this finding is that cortical disinhibition “unmasks” lateral connections within the cortex to permit adaptation to the sensory environment. These results provide evidence in humans for a frequency-dependent inhibitory mechanism underlying learning and suggest a mechanism-based approach for optimizing neurostimulation frequency.
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