The Experts below are selected from a list of 56778 Experts worldwide ranked by ideXlab platform
Xin Tian - One of the best experts on this subject based on the ideXlab platform.
-
Dynamic trajectory of multiple single-unit activity during Working Memory Task in rats.
Frontiers in Computational Neuroscience, 2015Co-Authors: Xiaofan Zhang, Wenwen Bai, Xin TianAbstract:Working Memory plays an important role in complex cognitive Tasks. A popular theoretical view is that transient properties of neuronal dynamics underlie cognitive processing. The question raised here as to how the transient dynamics evolve in Working Memory. To address this issue, we investigated the multiple single-unit activity dynamics in rat medial prefrontal cortex (mPFC) during a Y-maze Working Memory Task. The approach worked by reconstructing state space from delays of the original single-unit firing rate variables, which were further analyzed using kernel principal component analysis (KPCA). Then the neural trajectories were obtained to visualize the multiple single-unit activity. Furthermore, the maximal Lyapunov exponent (MLE) was calculated to quantitatively evaluate the neural trajectories during the Working Memory Task. The results showed that the neuronal activity produced stable and reproducible neural trajectories in the correct trials while showed irregular trajectories in the incorrect trials, which may establish a link between the neurocognitive process and behavioral performance in Working Memory. The MLEs significantly increased during Working Memory in the correctly performed trials, indicating an increased divergence of the neural trajectories. In the incorrect trials, the MLEs were nearly zero and remained unchanged during the Task. Taken together, the trial-specific neural trajectory provides an effective way to track the instantaneous state of the neuronal population during the Working Memory Task and offers valuable insights into Working Memory function. The MLE describes the changes of neural dynamics in Working Memory and may reflect different neuronal population states in Working Memory.
-
Functional connectivity in a rat model of Alzheimer's disease during a Working Memory Task.
Current Alzheimer research, 2014Co-Authors: Tiaotiao Liu, Wenwen Bai, Tao Tan, Jing Wei, Ju Wang, Xin TianAbstract:Alzheimer's disease (AD) is a neurodegenerative disease characterized by progressive loss of Memory. Impairment of Working Memory was typically observed in AD. The concept of brain functional connectivity plays an important role in neuroscience as a useful tool to understand the organized behavior of brain. Hence, the purpose of this study is to investigate the possible mechanism of Working Memory deficits in AD from a new perspective of functional connectivity. Rats were randomly divided into 2 groups: Aβ injection group (Aβ 1-42 -induced toxicity rat model) and control group. Multi-channel local field potentials (LFPs) were obtained from rat prefrontal cortex with implanted microelectrode arrays while the rats performed a Y-maze Working Memory Task. The short-time Fourier transform was utilized to analyze the power changes in LFPs and sub-bands (in particular theta and low gamma bands) were extracted via band filtering. Then the Directed transfer function (DTF) method was applied to calculate the functional connections among LFPs. From the DTF calculation, the causal networks in the sub-bands were identified. DTF mean (mean of connectivity matrix elements) was used to quantify connection strength as well as global efficiency (E glob ) was calculated to quantitatively describe the efficient of information transfer in the network. Our results showed that both connection strength and efficient of information transfer increased during the Working Memory Task in the control group; by contrast, there was no significantly change in the Aβ injection group. These findings could lead to improve the understanding of the mechanism of Working Memory deficits in AD.
-
Anticipatory activity in rat medial prefrontal cortex during a Working Memory Task
Neuroscience bulletin, 2012Co-Authors: Wenwen Bai, Tiaotiao Liu, Xin TianAbstract:Objective Working Memory is a key cognitive function in which the prefrontal cortex plays a crucial role. This study aimed to show the firing patterns of a neuronal population in the prefrontal cortex of the rat in a Working Memory Task and to explore how a neuronal ensemble encodes a Working Memory event.
-
Increases of theta-low gamma coupling in rat medial prefrontal cortex during Working Memory Task.
Brain research bulletin, 2012Co-Authors: Wenwen Bai, Tiaotiao Liu, Xin TianAbstract:Cross-frequency coupling (CFC) between the theta (4-12Hz) phase and the amplitude of gamma (30-100Hz) oscillations occurs frequently in brain. However, the function of theta-gamma coupling in rat medial prefrontal cortex (mPFC) in Working Memory remains unclear. To address this issue, we studied 16-channel CFC in local field potentials (LFPs) recorded from the mPFC of over-trained rats as they performed a Y-maze Working Memory Task. During this course, the amplitude of the low gamma subband (30-60Hz) was more strongly modulated by theta phase during the correct trials than in the error ones. Meanwhile, more channels showed higher theta-low gamma coupling levels during the correct performance. By contrast, the strength of theta-high gamma coupling did not significantly increase during the Working Memory Task in both correct and error trials, indicating an insignificant correlation with the performance validity. These findings suggest a role of mPFC theta-low gamma coupling in Working Memory.
-
Effect of propofol on local field potential in rat prefrontal cortex during Working Memory Task
World Journal of Neuroscience, 2012Co-Authors: Guolin Wang, Wenwen Bai, Tiaotiao Liu, Wenqian Zhai, Xin TianAbstract:Propofol may produce Memory impairment during anesthesia procedure. Local field potentials (LFPs) are used with increasing frequency in recent years to link neural activity to perception and cognition. In this study, effect of propofol on LFPs in rat’s prefrontal cortex during Working Memory Task was evaluated. Young (approximately 3 month) male Sprague-Dawley rats were divided into two group: propofol rats and control rats. Propofol rats received propofol at 0.9 mg/Kg·min intravenously for 2 h. After 12 h, LFPs of all rats were measured simultaneously from multiple electrodes placed in prefrontal cortex while rats were performing a Working Memory Task in Y-maze. LFPs instantaneous phase were obtained by applying Hilbert transform, and cross-correlation coherence of LFPs was calculated. The results indicate that propofol decreased the correct rate and crosscorrelation coherence of LFPs on the first two days (p 0.05). Our results suggest that propofol can impair cross-correlation coherence of LFPs in the first two days, but not long time.
Wenwen Bai - One of the best experts on this subject based on the ideXlab platform.
-
Dynamic trajectory of multiple single-unit activity during Working Memory Task in rats.
Frontiers in Computational Neuroscience, 2015Co-Authors: Xiaofan Zhang, Wenwen Bai, Xin TianAbstract:Working Memory plays an important role in complex cognitive Tasks. A popular theoretical view is that transient properties of neuronal dynamics underlie cognitive processing. The question raised here as to how the transient dynamics evolve in Working Memory. To address this issue, we investigated the multiple single-unit activity dynamics in rat medial prefrontal cortex (mPFC) during a Y-maze Working Memory Task. The approach worked by reconstructing state space from delays of the original single-unit firing rate variables, which were further analyzed using kernel principal component analysis (KPCA). Then the neural trajectories were obtained to visualize the multiple single-unit activity. Furthermore, the maximal Lyapunov exponent (MLE) was calculated to quantitatively evaluate the neural trajectories during the Working Memory Task. The results showed that the neuronal activity produced stable and reproducible neural trajectories in the correct trials while showed irregular trajectories in the incorrect trials, which may establish a link between the neurocognitive process and behavioral performance in Working Memory. The MLEs significantly increased during Working Memory in the correctly performed trials, indicating an increased divergence of the neural trajectories. In the incorrect trials, the MLEs were nearly zero and remained unchanged during the Task. Taken together, the trial-specific neural trajectory provides an effective way to track the instantaneous state of the neuronal population during the Working Memory Task and offers valuable insights into Working Memory function. The MLE describes the changes of neural dynamics in Working Memory and may reflect different neuronal population states in Working Memory.
-
Functional connectivity in a rat model of Alzheimer's disease during a Working Memory Task.
Current Alzheimer research, 2014Co-Authors: Tiaotiao Liu, Wenwen Bai, Tao Tan, Jing Wei, Ju Wang, Xin TianAbstract:Alzheimer's disease (AD) is a neurodegenerative disease characterized by progressive loss of Memory. Impairment of Working Memory was typically observed in AD. The concept of brain functional connectivity plays an important role in neuroscience as a useful tool to understand the organized behavior of brain. Hence, the purpose of this study is to investigate the possible mechanism of Working Memory deficits in AD from a new perspective of functional connectivity. Rats were randomly divided into 2 groups: Aβ injection group (Aβ 1-42 -induced toxicity rat model) and control group. Multi-channel local field potentials (LFPs) were obtained from rat prefrontal cortex with implanted microelectrode arrays while the rats performed a Y-maze Working Memory Task. The short-time Fourier transform was utilized to analyze the power changes in LFPs and sub-bands (in particular theta and low gamma bands) were extracted via band filtering. Then the Directed transfer function (DTF) method was applied to calculate the functional connections among LFPs. From the DTF calculation, the causal networks in the sub-bands were identified. DTF mean (mean of connectivity matrix elements) was used to quantify connection strength as well as global efficiency (E glob ) was calculated to quantitatively describe the efficient of information transfer in the network. Our results showed that both connection strength and efficient of information transfer increased during the Working Memory Task in the control group; by contrast, there was no significantly change in the Aβ injection group. These findings could lead to improve the understanding of the mechanism of Working Memory deficits in AD.
-
Anticipatory activity in rat medial prefrontal cortex during a Working Memory Task
Neuroscience bulletin, 2012Co-Authors: Wenwen Bai, Tiaotiao Liu, Xin TianAbstract:Objective Working Memory is a key cognitive function in which the prefrontal cortex plays a crucial role. This study aimed to show the firing patterns of a neuronal population in the prefrontal cortex of the rat in a Working Memory Task and to explore how a neuronal ensemble encodes a Working Memory event.
-
Increases of theta-low gamma coupling in rat medial prefrontal cortex during Working Memory Task.
Brain research bulletin, 2012Co-Authors: Wenwen Bai, Tiaotiao Liu, Xin TianAbstract:Cross-frequency coupling (CFC) between the theta (4-12Hz) phase and the amplitude of gamma (30-100Hz) oscillations occurs frequently in brain. However, the function of theta-gamma coupling in rat medial prefrontal cortex (mPFC) in Working Memory remains unclear. To address this issue, we studied 16-channel CFC in local field potentials (LFPs) recorded from the mPFC of over-trained rats as they performed a Y-maze Working Memory Task. During this course, the amplitude of the low gamma subband (30-60Hz) was more strongly modulated by theta phase during the correct trials than in the error ones. Meanwhile, more channels showed higher theta-low gamma coupling levels during the correct performance. By contrast, the strength of theta-high gamma coupling did not significantly increase during the Working Memory Task in both correct and error trials, indicating an insignificant correlation with the performance validity. These findings suggest a role of mPFC theta-low gamma coupling in Working Memory.
-
Effect of propofol on local field potential in rat prefrontal cortex during Working Memory Task
World Journal of Neuroscience, 2012Co-Authors: Guolin Wang, Wenwen Bai, Tiaotiao Liu, Wenqian Zhai, Xin TianAbstract:Propofol may produce Memory impairment during anesthesia procedure. Local field potentials (LFPs) are used with increasing frequency in recent years to link neural activity to perception and cognition. In this study, effect of propofol on LFPs in rat’s prefrontal cortex during Working Memory Task was evaluated. Young (approximately 3 month) male Sprague-Dawley rats were divided into two group: propofol rats and control rats. Propofol rats received propofol at 0.9 mg/Kg·min intravenously for 2 h. After 12 h, LFPs of all rats were measured simultaneously from multiple electrodes placed in prefrontal cortex while rats were performing a Working Memory Task in Y-maze. LFPs instantaneous phase were obtained by applying Hilbert transform, and cross-correlation coherence of LFPs was calculated. The results indicate that propofol decreased the correct rate and crosscorrelation coherence of LFPs on the first two days (p 0.05). Our results suggest that propofol can impair cross-correlation coherence of LFPs in the first two days, but not long time.
Tiaotiao Liu - One of the best experts on this subject based on the ideXlab platform.
-
Functional connectivity in a rat model of Alzheimer's disease during a Working Memory Task.
Current Alzheimer research, 2014Co-Authors: Tiaotiao Liu, Wenwen Bai, Tao Tan, Jing Wei, Ju Wang, Xin TianAbstract:Alzheimer's disease (AD) is a neurodegenerative disease characterized by progressive loss of Memory. Impairment of Working Memory was typically observed in AD. The concept of brain functional connectivity plays an important role in neuroscience as a useful tool to understand the organized behavior of brain. Hence, the purpose of this study is to investigate the possible mechanism of Working Memory deficits in AD from a new perspective of functional connectivity. Rats were randomly divided into 2 groups: Aβ injection group (Aβ 1-42 -induced toxicity rat model) and control group. Multi-channel local field potentials (LFPs) were obtained from rat prefrontal cortex with implanted microelectrode arrays while the rats performed a Y-maze Working Memory Task. The short-time Fourier transform was utilized to analyze the power changes in LFPs and sub-bands (in particular theta and low gamma bands) were extracted via band filtering. Then the Directed transfer function (DTF) method was applied to calculate the functional connections among LFPs. From the DTF calculation, the causal networks in the sub-bands were identified. DTF mean (mean of connectivity matrix elements) was used to quantify connection strength as well as global efficiency (E glob ) was calculated to quantitatively describe the efficient of information transfer in the network. Our results showed that both connection strength and efficient of information transfer increased during the Working Memory Task in the control group; by contrast, there was no significantly change in the Aβ injection group. These findings could lead to improve the understanding of the mechanism of Working Memory deficits in AD.
-
Anticipatory activity in rat medial prefrontal cortex during a Working Memory Task
Neuroscience bulletin, 2012Co-Authors: Wenwen Bai, Tiaotiao Liu, Xin TianAbstract:Objective Working Memory is a key cognitive function in which the prefrontal cortex plays a crucial role. This study aimed to show the firing patterns of a neuronal population in the prefrontal cortex of the rat in a Working Memory Task and to explore how a neuronal ensemble encodes a Working Memory event.
-
Increases of theta-low gamma coupling in rat medial prefrontal cortex during Working Memory Task.
Brain research bulletin, 2012Co-Authors: Wenwen Bai, Tiaotiao Liu, Xin TianAbstract:Cross-frequency coupling (CFC) between the theta (4-12Hz) phase and the amplitude of gamma (30-100Hz) oscillations occurs frequently in brain. However, the function of theta-gamma coupling in rat medial prefrontal cortex (mPFC) in Working Memory remains unclear. To address this issue, we studied 16-channel CFC in local field potentials (LFPs) recorded from the mPFC of over-trained rats as they performed a Y-maze Working Memory Task. During this course, the amplitude of the low gamma subband (30-60Hz) was more strongly modulated by theta phase during the correct trials than in the error ones. Meanwhile, more channels showed higher theta-low gamma coupling levels during the correct performance. By contrast, the strength of theta-high gamma coupling did not significantly increase during the Working Memory Task in both correct and error trials, indicating an insignificant correlation with the performance validity. These findings suggest a role of mPFC theta-low gamma coupling in Working Memory.
-
Effect of propofol on local field potential in rat prefrontal cortex during Working Memory Task
World Journal of Neuroscience, 2012Co-Authors: Guolin Wang, Wenwen Bai, Tiaotiao Liu, Wenqian Zhai, Xin TianAbstract:Propofol may produce Memory impairment during anesthesia procedure. Local field potentials (LFPs) are used with increasing frequency in recent years to link neural activity to perception and cognition. In this study, effect of propofol on LFPs in rat’s prefrontal cortex during Working Memory Task was evaluated. Young (approximately 3 month) male Sprague-Dawley rats were divided into two group: propofol rats and control rats. Propofol rats received propofol at 0.9 mg/Kg·min intravenously for 2 h. After 12 h, LFPs of all rats were measured simultaneously from multiple electrodes placed in prefrontal cortex while rats were performing a Working Memory Task in Y-maze. LFPs instantaneous phase were obtained by applying Hilbert transform, and cross-correlation coherence of LFPs was calculated. The results indicate that propofol decreased the correct rate and crosscorrelation coherence of LFPs on the first two days (p 0.05). Our results suggest that propofol can impair cross-correlation coherence of LFPs in the first two days, but not long time.
Douglas C. Noll - One of the best experts on this subject based on the ideXlab platform.
-
Reproducibility of fMRI Results across Four Institutions Using a Spatial Working Memory Task
NeuroImage, 1998Co-Authors: B. J. Casey, Jonathan D. Cohen, Kathy O'craven, Richard J. Davidson, William Irwin, Charles A. Nelson, Douglas C. Noll, Mark J. Lowe, Bruce R. RosenAbstract:Four U.S. sites formed a consortium to conduct a multisite study of fMRI methods. The primary purpose of this consortium was to examine the reliability and reproducibility of fMRI results. FMRI data were collected on healthy adults during performance of a spatial Working Memory Task at four different institutions. Two sets of data from each institution were made available. First, data from two subjects were made available from each site and were processed and analyzed as a pooled data set. Second, statistical maps from five to eight subjects per site were made available. These images were aligned in stereotactic space and common regions of activation were examined to address the reproducibility of fMRI results when both image acquisition and analysis vary as a function of site. Our grouped and individual data analyses showed reliable patterns of activation in dorsolateral prefrontal cortex and posterior parietal cortex during performance of the Working Memory Task across all four sites. This multisite study, the first of its kind using fMRI data, demonstrates highly consistent findings across sites.
-
temporal dynamics of brain activation during a Working Memory Task
Nature, 1997Co-Authors: Jonathan D. Cohen, Douglas C. Noll, Todd S Braver, William M Perlstein, Leigh E Nystrom, John Jonides, Edward E SmithAbstract:Working Memory is responsible for the short-term storage and online manipulation of information necessary for higher cognitive functions, such as language, planning and problem-solving. Traditionally, Working Memory has been divided into two types of processes: executive control (governing the encoding manipulation and retrieval of information in Working Memory) and active maintenance (keeping information available 'online'). It has also been proposed that these two types of processes may be subserved by distinct cortical structures, with the prefrontal cortex housing the executive control processes, and more posterior regions housing the content-specific buffers (for example verbal versus visuospatial) responsible for active maintenance. However, studies in non-human primates suggest that dorsolateral regions of the prefrontal cortex may also be involved in active maintenance. We have used functional magnetic resonance imaging to examine brain activation in human subjects during performance of a Working Memory Task. We used the temporal resolution of this technique to examine the dynamics of regional activation, and to show that prefrontal cortex along with parietal cortex appears to play a role in active maintenance.
-
Activation of prefrontal cortex in children during a nonspatial Working Memory Task with functional MRI.
NeuroImage, 1995Co-Authors: B. J. Casey, Jonathan D. Cohen, Douglas C. Noll, Peter Jezzard, Robert Turner, Rolf J. Trainor, Jay N. Giedd, Debra Kaysen, Lucy Hertz-pannier, Judith L. RapoportAbstract:Functional magnetic resonance imaging (fMRI) was used to examine the pattern of activity of prefrontal cortex in prepubertal children during performance of a nonspatial Working Memory Task. The children observed sequences of letters and responded whenever a letter repeated with exactly one nonidentical letter intervening. In a comparison Task, subjects monitored similar sequences of letters for any occurrence of a single, prespecified target letter. Location of activation closely approximated that observed in a recent fMRI study with adults using exactly the same Task. Activation of the inferior and middle frontal gyri was reliably observed within individual subjects during performance of the Working Memory Task relative to the comparison Task. Activation increased and decreased with a time course that was highly consistent with the Task manipulations and correlated with behavioral performance. To our knowledge, this study is one of the first to demonstrate the applicability of fMRI to a normative developmental population. Issues of age dependence of the hemodynamic responses of fMRI are discussed.
-
activation of the prefrontal cortex in a nonspatial Working Memory Task with functional mri
Human Brain Mapping, 1994Co-Authors: Jonathan D. Cohen, B. J. Casey, Douglas C. Noll, Steven D Forman, Todd S Braver, David ServanschreiberAbstract:Functional magnetic resonance imaging (fMRI) was used to examine the pattern of activity of the prefrontal cortex during performance of subjects in a nonspatial Working Memory Task. Subjects observed sequences of letters and responded whenever a letter repeated with exactly one nonidentical letter intervening. In a comparison Task, subjects monitored similar sequences of letters for any occurrence of a single, prespecified target letter. Functional scanning was performed using a newly developed spiral scan image acquisition technique that provides high-resolution, multislice scanning at approximately five times the rate usually possible on conventional equipment (an average of one image per second). Using these methods, activation of the middle and inferior frontal gyri was reliably observed within individual subjects during performance of the Working Memory Task relative to the comparison Task. Effect sizes (2–4%) closely approximated those that have been observed within primary sensory and motor cortices using similar fMRI techniques. Furthermore, activation increased and decreased with a time course that was highly consistent with the Task manipulations. These findings corroborate the results of positron emission tomography studies, which suggest that the prefrontal cortex is engaged by Tasks that rely on Working Memory. Furthermore, they demonstrate the applicability of newly developed fMRI techniques using conventional scanners to study the associative cortex in individual subjects. © 1994 Wiley-Liss, Inc.
-
Activation of the prefrontal cortex in a nonspatial Working Memory Task with functional MRI
Human brain mapping, 1994Co-Authors: Jonathan D. Cohen, B. J. Casey, Steven D Forman, Todd S Braver, David Servan-schreiber, Douglas C. NollAbstract:Functional magnetic resonance imaging (fMRI) was used to examine the pattern of activity of the prefrontal cortex during performance of subjects in a nonspatial Working Memory Task. Subjects observed sequences of letters and responded whenever a letter repeated with exactly one nonidentical letter intervening. In a comparison Task, subjects monitored similar sequences of letters for any occurrence of a single, prespecified target letter. Functional scanning was performed using a newly developed spiral scan image acquisition technique that provides high-resolution, multislice scanning at approximately five times the rate usually possible on conventional equipment (an average of one image per second). Using these methods, activation of the middle and inferior frontal gyri was reliably observed within individual subjects during performance of the Working Memory Task relative to the comparison Task. Effect sizes (2-4%) closely approximated those that have been observed within primary sensory and motor cortices using similar fMRI techniques. Furthermore, activation increased and decreased with a time course that was highly consistent with the Task manipulations. These findings corroborate the results of positron emission tomography studies, which suggest that the prefrontal cortex is engaged by Tasks that rely on Working Memory. Furthermore, they demonstrate the applicability of newly developed fMRI techniques using conventional scanners to study the associative cortex in individual subjects. © 1994 Wiley-Liss, Inc.
Jonathan D. Cohen - One of the best experts on this subject based on the ideXlab platform.
-
Reproducibility of fMRI Results across Four Institutions Using a Spatial Working Memory Task
NeuroImage, 1998Co-Authors: B. J. Casey, Jonathan D. Cohen, Kathy O'craven, Richard J. Davidson, William Irwin, Charles A. Nelson, Douglas C. Noll, Mark J. Lowe, Bruce R. RosenAbstract:Four U.S. sites formed a consortium to conduct a multisite study of fMRI methods. The primary purpose of this consortium was to examine the reliability and reproducibility of fMRI results. FMRI data were collected on healthy adults during performance of a spatial Working Memory Task at four different institutions. Two sets of data from each institution were made available. First, data from two subjects were made available from each site and were processed and analyzed as a pooled data set. Second, statistical maps from five to eight subjects per site were made available. These images were aligned in stereotactic space and common regions of activation were examined to address the reproducibility of fMRI results when both image acquisition and analysis vary as a function of site. Our grouped and individual data analyses showed reliable patterns of activation in dorsolateral prefrontal cortex and posterior parietal cortex during performance of the Working Memory Task across all four sites. This multisite study, the first of its kind using fMRI data, demonstrates highly consistent findings across sites.
-
temporal dynamics of brain activation during a Working Memory Task
Nature, 1997Co-Authors: Jonathan D. Cohen, Douglas C. Noll, Todd S Braver, William M Perlstein, Leigh E Nystrom, John Jonides, Edward E SmithAbstract:Working Memory is responsible for the short-term storage and online manipulation of information necessary for higher cognitive functions, such as language, planning and problem-solving. Traditionally, Working Memory has been divided into two types of processes: executive control (governing the encoding manipulation and retrieval of information in Working Memory) and active maintenance (keeping information available 'online'). It has also been proposed that these two types of processes may be subserved by distinct cortical structures, with the prefrontal cortex housing the executive control processes, and more posterior regions housing the content-specific buffers (for example verbal versus visuospatial) responsible for active maintenance. However, studies in non-human primates suggest that dorsolateral regions of the prefrontal cortex may also be involved in active maintenance. We have used functional magnetic resonance imaging to examine brain activation in human subjects during performance of a Working Memory Task. We used the temporal resolution of this technique to examine the dynamics of regional activation, and to show that prefrontal cortex along with parietal cortex appears to play a role in active maintenance.
-
Activation of prefrontal cortex in children during a nonspatial Working Memory Task with functional MRI.
NeuroImage, 1995Co-Authors: B. J. Casey, Jonathan D. Cohen, Douglas C. Noll, Peter Jezzard, Robert Turner, Rolf J. Trainor, Jay N. Giedd, Debra Kaysen, Lucy Hertz-pannier, Judith L. RapoportAbstract:Functional magnetic resonance imaging (fMRI) was used to examine the pattern of activity of prefrontal cortex in prepubertal children during performance of a nonspatial Working Memory Task. The children observed sequences of letters and responded whenever a letter repeated with exactly one nonidentical letter intervening. In a comparison Task, subjects monitored similar sequences of letters for any occurrence of a single, prespecified target letter. Location of activation closely approximated that observed in a recent fMRI study with adults using exactly the same Task. Activation of the inferior and middle frontal gyri was reliably observed within individual subjects during performance of the Working Memory Task relative to the comparison Task. Activation increased and decreased with a time course that was highly consistent with the Task manipulations and correlated with behavioral performance. To our knowledge, this study is one of the first to demonstrate the applicability of fMRI to a normative developmental population. Issues of age dependence of the hemodynamic responses of fMRI are discussed.
-
activation of the prefrontal cortex in a nonspatial Working Memory Task with functional mri
Human Brain Mapping, 1994Co-Authors: Jonathan D. Cohen, B. J. Casey, Douglas C. Noll, Steven D Forman, Todd S Braver, David ServanschreiberAbstract:Functional magnetic resonance imaging (fMRI) was used to examine the pattern of activity of the prefrontal cortex during performance of subjects in a nonspatial Working Memory Task. Subjects observed sequences of letters and responded whenever a letter repeated with exactly one nonidentical letter intervening. In a comparison Task, subjects monitored similar sequences of letters for any occurrence of a single, prespecified target letter. Functional scanning was performed using a newly developed spiral scan image acquisition technique that provides high-resolution, multislice scanning at approximately five times the rate usually possible on conventional equipment (an average of one image per second). Using these methods, activation of the middle and inferior frontal gyri was reliably observed within individual subjects during performance of the Working Memory Task relative to the comparison Task. Effect sizes (2–4%) closely approximated those that have been observed within primary sensory and motor cortices using similar fMRI techniques. Furthermore, activation increased and decreased with a time course that was highly consistent with the Task manipulations. These findings corroborate the results of positron emission tomography studies, which suggest that the prefrontal cortex is engaged by Tasks that rely on Working Memory. Furthermore, they demonstrate the applicability of newly developed fMRI techniques using conventional scanners to study the associative cortex in individual subjects. © 1994 Wiley-Liss, Inc.
-
Activation of the prefrontal cortex in a nonspatial Working Memory Task with functional MRI
Human brain mapping, 1994Co-Authors: Jonathan D. Cohen, B. J. Casey, Steven D Forman, Todd S Braver, David Servan-schreiber, Douglas C. NollAbstract:Functional magnetic resonance imaging (fMRI) was used to examine the pattern of activity of the prefrontal cortex during performance of subjects in a nonspatial Working Memory Task. Subjects observed sequences of letters and responded whenever a letter repeated with exactly one nonidentical letter intervening. In a comparison Task, subjects monitored similar sequences of letters for any occurrence of a single, prespecified target letter. Functional scanning was performed using a newly developed spiral scan image acquisition technique that provides high-resolution, multislice scanning at approximately five times the rate usually possible on conventional equipment (an average of one image per second). Using these methods, activation of the middle and inferior frontal gyri was reliably observed within individual subjects during performance of the Working Memory Task relative to the comparison Task. Effect sizes (2-4%) closely approximated those that have been observed within primary sensory and motor cortices using similar fMRI techniques. Furthermore, activation increased and decreased with a time course that was highly consistent with the Task manipulations. These findings corroborate the results of positron emission tomography studies, which suggest that the prefrontal cortex is engaged by Tasks that rely on Working Memory. Furthermore, they demonstrate the applicability of newly developed fMRI techniques using conventional scanners to study the associative cortex in individual subjects. © 1994 Wiley-Liss, Inc.
