Hypothesis regarding the transformation of the intended direction of movement during the production of graphic trajectories: A study of drawing movements in 8- to 12-year-old children
Differential contribution of superior parietal and dorsal-lateral prefrontal cortices in copying
permalinkCortex - 2009-03-01Averbeck B, Crowe D, Chafee M, Georgopoulos AP10.1016/j.cortex.2008.02.007In this study we examined the differential contribution of superior parietal cortex (SPC) and caudal dorsal-lateral prefrontal cortex (dlPFC) to drawing geometrical shapes. Monkeys were trained to draw triangles, squares, trapezoids and inverted triangles while we recorded the activity of small ensembles of neurons in caudal area 46 and areas 5 and 2 of parietal cortex. We analyzed the drawing factors encoded by individual neurons by fitting a step-wise general-linear model using as our dependent variable the firing rate averaged over segments of the produced trajectories. This analysis demonstrated that both cognitive (shape and segment serial position) and motor (maximum speed, position and direction of segment) factors modulated the activity of individual neurons. Furthermore, SPC had an enriched representation of both shape and motor factors, with the motor enrichment being stronger than the shape enrichment.Following this we used the activity in the simultaneously recorded neural ensembles to predict the hand velocity....
Temporospatial Characterization of Brain Oscillations (TSCBO) Associated with Subprocesses of Verbal Working Memory in Schizophrenia
permalinkClinical EEG and Neuroscience - 2008-10-01Stephane M, Ince NF, Leuthold A, Pellizzer G, Tewfik AH, Surerus C, Kuskowski MA, McClannahan K10.1177/155005940803900409The studies of the neural correlates of verbal working memory in schizophrenia are somewhat inconsistent. This could be related to experimental paradigms that engage differentially working memory components or methodological limitations in terms of characterization of brain activity.Magnetoencephalographic recordings were obtained on 10 schizophrenia patients and 11 healthy controls while performing a modified Sternberg paradigm to investigate subprocesses of verbal working memory. A new method for temporospatial characterization of brain oscillations was applied to whole head recordings and a 1-48 Hz frequency range.Patients differed from controls in event-related synchronization/desynchronization (ERS/ERD) patterns during the encode phase, the mid-maintain phase, and the end of the maintain phase. During the encode phase, patients did not show 1-4 Hz ERS in the left anterior frontal and left parietal lobes. In the mid-maintain phase, the left anterior frontal and left parietal lobes 1-4 Hz ERS, and the bilateral occipital lobes 8-32 Hz ERS were not observed...
Dynamic Sculpting of Directional Tuning in the Primate Motor Cortex during Three-Dimensional Reaching
Selection of spectro-temporal patterns in multichannel Magnetoencephalography with support vector machines for schizophrenia classification
permalink2008 30th Annual International Conference of the IEEE Engineering in Medicine and Biology Society - 2008-08-20Ince NF, Goksu F, Pellizzer G, Tewfik AH, Stephane M10.1109/IEMBS.2008.4649973We present a new framework for the diagnosis of schizophrenia based on the spectro-temporal patterns selected by a support vector machine from multichannel magnetoencephalogram (
Magnetoencephalography) recordings in a verbal working memory task. In the experimental paradigm, five letters appearing sequentially on a screen were memorized by subjects. The letters constituted a word in one condition and a pronounceable nonword in the other. Power changes were extracted as features in frequency subbands of 248 channel
MEGdata to form a rich feature dictionary. A support vector machine has been used to select a small subset of features with recursive feature elimination technique (SVM-RFE) and the reduced subset was used for classification. We note that the discrimination between patients and controls in the word condition was higher than in the non-word condition (91.8% vs 83.8%). Furthermore, in the word condition, the most discriminant patterns were extracted in delta (1-4 Hz), theta (4-8Hz) and...
Chronic vagus nerve stimulation for treatment-resistant depression decreases resting ventromedial prefrontal glucose metabolism
permalinkNeuroImage - 2008-08-15Pardo J, Sheikh SA, Schwindt GC, Lee JT, Kuskowski MA, Surerus C, Lewis S, Abuzzahab FS, Adson DE, Rittberg BR10.1016/j.neuroimage.2008.04.267Vagus nerve stimulation (VNS) is used as an adjunctive therapy for treatment-resistant depression (TRD). Its mechanism of action is not fully understood. Longitudinal measurement of changes in brain metabolism associated with VNS can provide insights into this new treatment modality. Eight severely depressed outpatients who were highly treatment-resistant underwent electrical stimulation of the left vagus nerve for approximately one year. The main outcome measures were resting regional brain glucose uptake measured with positron emission tomography (PET) and the 24-item Hamilton Depression Scale. The most significant and extensive change over one year of chronic VNS localized to the ventromedial prefrontal cortex extending from the subgenual cingulate to the frontal pole. This region continued to decline in metabolism even toward the end of the study. Clinically, this cohort showed a trend for improvement. No correlations surfaced between change in glucose uptake and depression scores. However, the sample size was small; none remitted; and...
Neural Substrates of Cognitive Load Changes During a Motor Task in Subjects with Stroke
permalinkJournal of Neurologic Physical Therapy - 2008-08-01Kimberley TJ, Lewis S, Strand C, Rice BD, Hall S, Slivnik P10.1097/NPT.0b013e318183d716Purpose: A critical component to rehabilitation is the degree to which we challenge patients to facilitate learning without providing excessive competition for cognitive resources. The purpose of this study was to examine brain activation and motor performance during changes in cognitive load in a continuous motor task in subjects with stroke (n = 7) and healthy subjects (n = 17).Methods: Subjects participated in a joystick drawing task during
Functional Magnetic Resonance Imaging. Subjects attempted to continuously draw a square under three conditions of varying cognitive demands.Results: In subjects with stroke, results showed significantly less activation in contralateral primary motor area when the task did not require working memory demands and no change when the condition required online visual feedback processing. Bilaterally, the premotor cortex also demonstrated a significant decrease in activation when the task did not require working memory and then an increase in activation when online visual feedback processing was...
Cortical processing of tactile stimuli applied in quick succession across the fingertips: temporal evolution of dipole sources revealed by magnetoencephalography
permalinkExperimental Brain Research - 2008-08-01Karageorgiou E, Koutlas I, Alonso A, Leuthold A, Lewis S, Georgopoulos AP10.1007/s00221-008-1425-6We used
MEGin 10 healthy human subjects to study cortical responses to tactile stimuli applied to the fingertips of digits 2-5 of the right hand. Each stimulus lasted 50 ms and was produced by air-driven elastic membranes. Four-hundred stimuli were delivered on each finger in three temporal patterns (conditions). In the "Discrete" condition, stimuli were applied to each finger repetitively with an interstimulus interval (ISI) of 1-2 s. In the "Continuous" condition, stimuli were applied to the fingers sequentially as four-stimulus trains with zero ISI and 1-2 s intervening between trains. Finally, in the "Gap" condition, stimuli were applied as in the Continuous condition but with an ISI of 50 ms. A sensation of tactile motion across fingers (digit 2 → digit 5) was reported by all subjects in the Continuous and Gap conditions. Cortical responses were extracted as single equivalent current dipoles over a period of 1 s...
P2-027: Association of cognitive deficits with Synchronous Neural Interactions as revealed by magnetoencephalography: A canonical correlation analysis
permalinkAlzheimer's & Dementia - 2008-07-01Karageorgiou E, Lewis S, McCarten JR, Leuthold A, Hemmy LS, McPherson SE, Rottunda SJ, Georgopoulos AP10.1016/j.jalz.2008.05.1108In a recent study we showed that
Synchronous Neural Interactionsassessed by
MEGin a simple fixation test can be used as a functional biomarker for brain disorders (Georgopoulos et al., J. Neural Engineer. 4:349-355, 2007). The
SNIvariables consist of partial zero-lag cross-correlations estimated between pairs of 248 axial gradiometer sensors after prewhitening of the
MEGtime series. In this study we evaluated the relations between cognitive deficits and
A voxel-by-voxel parametric Functional Magnetic Resonance Imaging study of motor mental rotation: hemispheric specialization and gender differences in neural processing efficiency
permalinkExperimental Brain Research - 2008-07-01Christova P, Lewis S, Tagaris GA, Ugurbil K, Georgopoulos AP10.1007/s00221-008-1405-xDifferences between men and women in brain size, cognitive performance and lateralization of brain activation have been perennial and controversial issues. Here we show that in a motor mental rotation task where women and men performed equally well, the slope of the
fMRIblood oxygenation level dependent (BOLD) signal per degree of mental rotation was overall 2.4x higher in men than in women. This was attributed to the much more inefficient engagement (i.e. higher slopes) of the right hemisphere by men (mainly the frontal lobe). These findings indicate that women process information much more efficiently than men, which could offset smaller brain size.
Ultra-high field parallel imaging of the superior parietal lobule during mental maze solving
permalinkExperimental Brain Research - 2008-06-01Jerde T, Lewis S, Goerke Ute, Gourtzelidis P, Tzagarakis C, Lynch J, Moeller S, Van de Moortele PF, Adriany G, Trangle J, Ugurbil K, Georgopoulos AP10.1007/s00221-008-1318-8We used ultra-high field (7 T)
fMRIand parallel imaging to scan the superior parietal lobule (SPL) of human subjects as they mentally traversed a maze path in one of four directions (up, down, left, right). A counterbalanced design for maze presentation and a quasi-isotropic voxel (1.46 x 1.46 x 2 mm thick) collection were implemented. Fifty-one percent of single voxels in the SPL were tuned to the direction of the maze path. Tuned voxels were distributed throughout the SPL, bilaterally. A nearest neighbor analysis revealed a "honeycomb" arrangement such that voxels tuned to a particular direction tended to occur in clusters. Three-dimensional (3D) directional clusters were identified in SPL as oriented centroids traversing the cortical depth. There were 13 same-direction clusters per hemisphere containing 22 voxels per cluster, on the average; the mean nearest-neighbor, same-direction intercluster distance was 9.4 mm. These results provide a much finer detail of the directional...
Neural Ensemble Decoding Reveals a Correlate of Viewer- to Object-Centered Spatial Transformation in Monkey Parietal Cortex
permalinkJournal of Neuroscience - 2008-05-14Crowe D, Averbeck B, Chafee M10.1523/JNEUROSCI.5105-07.2008The parietal cortex contains representations of space in multiple coordinate systems including retina-, head-, body-, and world-based systems. Previously, we found that when monkeys are required to perform spatial computations on objects, many neurons in parietal area 7a represent position in an object-centered coordinate system as well. Because visual information enters the brain in a retina-centered reference frame, generation of an object-centered reference requires the brain to perform computation on the visual input. We provide evidence that area 7a contains a correlate of that computation. Specifically, area 7a contains neurons that code information in retina- and object-centered coordinate systems. The information in retina-centered coordinates emerges first, followed by the information in object-centered coordinates. We found that the strength and accuracy of these representations is correlated across trials. Finally, we found that retina-centered information could be used to predict subsequent object-centered signals, but not vice versa. These results are consistent with the...
Neurostatistics: applications, challenges and expectations
MEGin human subjects, all performing the same tasks. These methods provide partially overlapping perspectives, resulting in a gain in knowledge beyond the province of the individual method. A common aspect in this endeavor is the statistical analysis of the data acquired by different methods, especially regarding the encoding of information in unitary elements (single cell activity in neurophysiology, blood oxygenation level-dependent (BOLD) activation of voxels in
fMRI, magnetic field strength in
MEG) and the decoding of information from ensembles. In this paper we illustrate the various approaches, their data analysis and possible applications to medicine...
Christian religious functioning and trauma outcomes
Representing Spatial Relationships in Posterior Parietal Cortex: Single Neurons Code Object-Referenced Position
Local shaping of function in the motor cortex: motor contrast, directional tuning
permalinkBrain Research Reviews - 2007-10-01Georgopoulos AP, Stefanis CN10.1016/j.brainresrev.2007.05.001In this review we bring together three different lines of evidence to bear on the issue of local shaping of function in the motor cortex. The first line of evidence comes from the description by Cajal (1904) of the recurrent collaterals of pyramidal cell axons in the precentral gyrus. The second line of evidence comes from the electrophysiological study of the functional effects of these collaterals [Stefanis, C., Jasper, H. 1964a. Intracellular microelectrode studies of antidromic responses in cortical pyramidal tract neurons. J. Neurophysiol. 27, 828-854.; Stefanis, C., Jasper, H. 1964b. Recurrent collateral inhibition in pyramidal tract neurons. J. Neurophysiol. 27, 855-877.] and associated interneurons [Stefanis, C. 1969. Interneuronal mechanisms in the cortex. In: The Interneuron, Brazier, M.A.B. (ed.), Berkeley, CA: University of California Press, pp. 497-526.] using intracellular recordings. And third came the discovery of directional tuning in the motor cortex [Georgopoulos, A.P., Kalaska, J.F., Caminiti, R., Massey, J.T. 1982....
Synchronous Neural Interactions assessed by magnetoencephalography: a functional biomarker for brain disorders
permalinkJournal of Neural Engineering - 2007-08-27Georgopoulos AP, Karageorgiou E, Leuthold A, Lewis S, Lynch J, Alonso A, Aslam Z, Carpenter A, Georgopoulos A, Hemmy LS, Koutlas I, Langheim F, McCarten JR, McPherson SE, Pardo J, Pardo P, Parry GJ, Rottunda SJ, Segal BM, Sponheim S, Stanwyck JJ, Stephane M, Westermeyer JJ10.1088/1741-2560/4/4/001We report on a test to assess the dynamic brain function at high temporal resolution using
MEG. The essence of the test is the measurement of the dynamic
SNI, an essential aspect of the brain function.
MEGsignals were recorded from 248 axial gradiometers while 142 human subjects fixated a spot of light for 45-60 s. After fitting an autoregressive integrative moving average (ARIMA) model and taking the stationary residuals, all pairwise, zero-lag, partial cross-correlations (PCCij0) and their z-transforms (zij0) between i and j sensors were calculated, providing estimates of the strength and sign (positive, negative) of direct synchronous coupling at 1 ms temporal resolution. We found that subsets of zij0 successfully classified individual subjects to their respective groups (multiple sclerosis, Alzheimer's disease, schizophrenia, Sj"ogren's syndrome, chronic alcoholism, facial pain, healthy controls) and gave excellent external cross-validation results.
Response selection in schizophrenia
Empirical evaluation of language disorder in schizophrenia
Mapping of the preferred direction in the motor cortex