Differential contribution of superior parietal and dorsal-lateral prefrontal cortices in copying

In 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

Clinical EEG and Neuroscience - 2008-10-01Stephane M, Ince NF, Leuthold A, Pellizzer G, Tewfik AH, Surerus C, Kuskowski MA, McClannahan K10.1177/155005940803900409
The 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

In the present study, we investigated how directional tuning of putative pyramidal cells is sharpened by inhibition from neighboring interneurons. First, different functional and electrophysiological criteria were used to identify putative pyramidal and interneuronal subtypes in a large database of motor cortical cells recorded during performance of the three-dimensional center-out task. Then we analyzed the relationship between the magnitude of inhibition and the tuning width, and a significant decrease of the latter as a function of the former was found in a population of putative pyramidal cells. In fact, the coupling of inhibition with narrow tuning was observed before and during movement execution on a cell-by-cell basis, indicating an important dynamic role of inhibition during movement control. Overall, these results suggest that local inhibition is involved in sculpting the directional specificity of a group of putative pyramidal neurons in the motor cortex.

Selection of spectro-temporal patterns in multichannel
Magnetoencephalography

Magnetoencephalography (MEG)

A noninvasive technique that detects magnetic fields above the surface of the head produced by postsynaptic potentials in the brain.
with support vector machines for schizophrenia classification

2008 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.2008.4649973
We 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

Magnetoencephalography (MEG)

A noninvasive technique that detects magnetic fields above the surface of the head produced by postsynaptic potentials in the brain.
) 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
MEG

Magnetoencephalography (MEG)

A noninvasive technique that detects magnetic fields above the surface of the head produced by postsynaptic potentials in the brain.
data 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

NeuroImage - 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.2008.04.267
Vagus 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

Journal of Neurologic Physical Therapy - 2008-08-01Kimberley TJ, Lewis S, Strand C, Rice BD, Hall S, Slivnik P10.1097/NPT.0b013e318183d716
Purpose: 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

Functional Magnetic Resonance Imaging (fMRI)

A functional neuroimaging procedure using MRI technology that measures brain activity by detecting changes associated with blood flow. This technique relies on the fact that cerebral blood flow and neuronal activation are coupled. When an area of the brain is in use, blood flow to that region also increases.[citation needed] The primary form of fMRI uses the blood-oxygen-level dependent (BOLD) contrast, discovered by Seiji Ogawa. This is a type of specialized brain and body scan used to map neural activity in the brain or spinal cord of humans or other animals by imaging the change in blood flow (hemodynamic response) related to energy use by brain cells. Since the early 1990s, fMRI has come to dominate brain mapping research because it does not require people to undergo shots, surgery, or to ingest substances, or be exposed to ionising radiation, etc.
. 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

We used
MEG

Magnetoencephalography (MEG)

A noninvasive technique that detects magnetic fields above the surface of the head produced by postsynaptic potentials in the brain.
in 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

Synchronous Neural Interactions (SNI)

Zero-lag partial correlations in pairs of MEG time series and denote the strength and polarity (positive or negative) of neuronal interactions. Anomalies in SNIs as assessed by MEG differentiate psychiatric disorders from healthy brain functioning and can discriminate among various brain diseases. From this research, a highly distinctive, unique PTSD SNI signature characterized by miscommunication of temporal and parietal and/or parieto-occipital right hemispheric areas with other brain areas has emerged. These findings, in addition to the growing research applying MEG to other psychiatric disorders, highlight the utility of MEG in identifying biomarkers of disease and underscore the potential for broader clinical applications of MEG.
as revealed by magnetoencephalography: A canonical correlation analysis

Alzheimer's & Dementia - 2008-07-01Karageorgiou E, Lewis S, McCarten JR, Leuthold A, Hemmy LS, McPherson SE, Rottunda SJ, Georgopoulos AP10.1016/j.jalz.2008.05.1108
In a recent study we showed that
Synchronous Neural Interactions

Synchronous Neural Interactions (SNI)

Zero-lag partial correlations in pairs of MEG time series and denote the strength and polarity (positive or negative) of neuronal interactions. Anomalies in SNIs as assessed by MEG differentiate psychiatric disorders from healthy brain functioning and can discriminate among various brain diseases. From this research, a highly distinctive, unique PTSD SNI signature characterized by miscommunication of temporal and parietal and/or parieto-occipital right hemispheric areas with other brain areas has emerged. These findings, in addition to the growing research applying MEG to other psychiatric disorders, highlight the utility of MEG in identifying biomarkers of disease and underscore the potential for broader clinical applications of MEG.
assessed by
MEG

Magnetoencephalography (MEG)

A noninvasive technique that detects magnetic fields above the surface of the head produced by postsynaptic potentials in the brain.
in 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
SNI

Synchronous Neural Interactions (SNI)

Zero-lag partial correlations in pairs of MEG time series and denote the strength and polarity (positive or negative) of neuronal interactions. Anomalies in SNIs as assessed by MEG differentiate psychiatric disorders from healthy brain functioning and can discriminate among various brain diseases. From this research, a highly distinctive, unique PTSD SNI signature characterized by miscommunication of temporal and parietal and/or parieto-occipital right hemispheric areas with other brain areas has emerged. These findings, in addition to the growing research applying MEG to other psychiatric disorders, highlight the utility of MEG in identifying biomarkers of disease and underscore the potential for broader clinical applications of MEG.
variables consist of partial zero-lag cross-correlations estimated between pairs of 248 axial gradiometer sensors after prewhitening of the
MEG

Magnetoencephalography (MEG)

A noninvasive technique that detects magnetic fields above the surface of the head produced by postsynaptic potentials in the brain.
time series. In this study we evaluated the relations between cognitive deficits and
SNI

Synchronous Neural Interactions (SNI)

Zero-lag partial correlations in pairs of MEG time series and denote the strength and polarity (positive or negative) of neuronal interactions. Anomalies in SNIs as assessed by MEG differentiate psychiatric disorders from healthy brain functioning and can discriminate among various brain diseases. From this research, a highly distinctive, unique PTSD SNI signature characterized by miscommunication of temporal and parietal and/or parieto-occipital right hemispheric areas with other brain areas has emerged. These findings, in addition to the growing research applying MEG to other psychiatric disorders, highlight the utility of MEG in identifying biomarkers of disease and underscore the potential for broader clinical applications of MEG.
.

A voxel-by-voxel parametric
Functional Magnetic Resonance Imaging

Functional Magnetic Resonance Imaging (fMRI)

A functional neuroimaging procedure using MRI technology that measures brain activity by detecting changes associated with blood flow. This technique relies on the fact that cerebral blood flow and neuronal activation are coupled. When an area of the brain is in use, blood flow to that region also increases.[citation needed] The primary form of fMRI uses the blood-oxygen-level dependent (BOLD) contrast, discovered by Seiji Ogawa. This is a type of specialized brain and body scan used to map neural activity in the brain or spinal cord of humans or other animals by imaging the change in blood flow (hemodynamic response) related to energy use by brain cells. Since the early 1990s, fMRI has come to dominate brain mapping research because it does not require people to undergo shots, surgery, or to ingest substances, or be exposed to ionising radiation, etc.
study of motor mental rotation: hemispheric specialization and gender differences in neural processing efficiency

Experimental Brain Research - 2008-07-01Christova P, Lewis S, Tagaris GA, Ugurbil K, Georgopoulos AP10.1007/s00221-008-1405-x
Differences 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
fMRI

Functional Magnetic Resonance Imaging (fMRI)

A functional neuroimaging procedure using MRI technology that measures brain activity by detecting changes associated with blood flow. This technique relies on the fact that cerebral blood flow and neuronal activation are coupled. When an area of the brain is in use, blood flow to that region also increases.[citation needed] The primary form of fMRI uses the blood-oxygen-level dependent (BOLD) contrast, discovered by Seiji Ogawa. This is a type of specialized brain and body scan used to map neural activity in the brain or spinal cord of humans or other animals by imaging the change in blood flow (hemodynamic response) related to energy use by brain cells. Since the early 1990s, fMRI has come to dominate brain mapping research because it does not require people to undergo shots, surgery, or to ingest substances, or be exposed to ionising radiation, etc.
blood 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

Experimental 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/s00221-008-1318-8
We used ultra-high field (7 T)
fMRI

Functional Magnetic Resonance Imaging (fMRI)

A functional neuroimaging procedure using MRI technology that measures brain activity by detecting changes associated with blood flow. This technique relies on the fact that cerebral blood flow and neuronal activation are coupled. When an area of the brain is in use, blood flow to that region also increases.[citation needed] The primary form of fMRI uses the blood-oxygen-level dependent (BOLD) contrast, discovered by Seiji Ogawa. This is a type of specialized brain and body scan used to map neural activity in the brain or spinal cord of humans or other animals by imaging the change in blood flow (hemodynamic response) related to energy use by brain cells. Since the early 1990s, fMRI has come to dominate brain mapping research because it does not require people to undergo shots, surgery, or to ingest substances, or be exposed to ionising radiation, etc.
and 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

The 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

Statistics in Medicine - 2008-02-10Georgopoulos AP, Karageorgiou E10.1002/sim.3137
Brain function and its relations to cognition and behavior can be elucidated only by the use of various complementary methods. Over the past 20 years, we have been studying the brain mechanisms underlying spatial processes using different methods, including the recording of single cell activity in behaving monkeys,
fMRI

Functional Magnetic Resonance Imaging (fMRI)

A functional neuroimaging procedure using MRI technology that measures brain activity by detecting changes associated with blood flow. This technique relies on the fact that cerebral blood flow and neuronal activation are coupled. When an area of the brain is in use, blood flow to that region also increases.[citation needed] The primary form of fMRI uses the blood-oxygen-level dependent (BOLD) contrast, discovered by Seiji Ogawa. This is a type of specialized brain and body scan used to map neural activity in the brain or spinal cord of humans or other animals by imaging the change in blood flow (hemodynamic response) related to energy use by brain cells. Since the early 1990s, fMRI has come to dominate brain mapping research because it does not require people to undergo shots, surgery, or to ingest substances, or be exposed to ionising radiation, etc.
and
MEG

Magnetoencephalography (MEG)

A noninvasive technique that detects magnetic fields above the surface of the head produced by postsynaptic potentials in the brain.
in 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

Functional Magnetic Resonance Imaging (fMRI)

A functional neuroimaging procedure using MRI technology that measures brain activity by detecting changes associated with blood flow. This technique relies on the fact that cerebral blood flow and neuronal activation are coupled. When an area of the brain is in use, blood flow to that region also increases.[citation needed] The primary form of fMRI uses the blood-oxygen-level dependent (BOLD) contrast, discovered by Seiji Ogawa. This is a type of specialized brain and body scan used to map neural activity in the brain or spinal cord of humans or other animals by imaging the change in blood flow (hemodynamic response) related to energy use by brain cells. Since the early 1990s, fMRI has come to dominate brain mapping research because it does not require people to undergo shots, surgery, or to ingest substances, or be exposed to ionising radiation, etc.
, magnetic field strength in
MEG

Magnetoencephalography (MEG)

A noninvasive technique that detects magnetic fields above the surface of the head produced by postsynaptic potentials in the brain.
) 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

Journal of Clinical Psychology - 2007-12-26Harris JI, Erbes CR, Engdahl B, Olson RHA, Winskowski AM, McMahill J10.1002/jclp.20427
While some trauma survivors find their faith helpful in recovery, others find it a source of distress, and still others abandon their faith. More complex conceptualizations of religious functioning are needed to explore its relationship with trauma. This study explores such relationships using measures of religious action and behaviors in a community sample of 327 church-going, self-identified trauma survivors. A principal components analysis of positive and negative religious coping, religious comforts and strains, and prayer functions identified two dimensions: Seeking Spiritual Support, which was positively related to posttraumatic growth, and Religious Strain, which was positively related to posttraumatic symptoms.

Representing Spatial Relationships in Posterior Parietal Cortex: Single Neurons Code Object-Referenced Position

The brain computes spatial relationships as necessary to achieve behavioral goals. Loss of this spatial cognitive ability after damage to posterior parietal cortex may contribute to constructional apraxia, a syndrome in which a patient's ability to reproduce spatial relationships between the parts of an object is disrupted. To explore neural correlates of object-relative spatial representation, we recorded neural activity in parietal area 7a of monkeys performing an object construction task. We found that neurons were activated as a function of the spatial relationship between a task-critical coordinate and a reference object. Individual neurons exhibited an object-relative spatial preference, such that different neural populations were activated when the spatial coordinate was located to the left or right of the reference object. In each case, the representation was robust to translation of the reference object, and neurons maintained their object-relative preference when the position of the object varied relative to the angle of...

Local shaping of function in the motor cortex: motor contrast, directional tuning

Brain Research Reviews - 2007-10-01Georgopoulos AP, Stefanis CN10.1016/j.brainresrev.2007.05.001
In 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

Synchronous Neural Interactions (SNI)

Zero-lag partial correlations in pairs of MEG time series and denote the strength and polarity (positive or negative) of neuronal interactions. Anomalies in SNIs as assessed by MEG differentiate psychiatric disorders from healthy brain functioning and can discriminate among various brain diseases. From this research, a highly distinctive, unique PTSD SNI signature characterized by miscommunication of temporal and parietal and/or parieto-occipital right hemispheric areas with other brain areas has emerged. These findings, in addition to the growing research applying MEG to other psychiatric disorders, highlight the utility of MEG in identifying biomarkers of disease and underscore the potential for broader clinical applications of MEG.
assessed by magnetoencephalography: a functional biomarker for brain disorders

Journal 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 JJ10.1088/1741-2560/4/4/001
We report on a test to assess the dynamic brain function at high temporal resolution using
MEG

Magnetoencephalography (MEG)

A noninvasive technique that detects magnetic fields above the surface of the head produced by postsynaptic potentials in the brain.
. The essence of the test is the measurement of the dynamic
SNI

Synchronous Neural Interactions (SNI)

Zero-lag partial correlations in pairs of MEG time series and denote the strength and polarity (positive or negative) of neuronal interactions. Anomalies in SNIs as assessed by MEG differentiate psychiatric disorders from healthy brain functioning and can discriminate among various brain diseases. From this research, a highly distinctive, unique PTSD SNI signature characterized by miscommunication of temporal and parietal and/or parieto-occipital right hemispheric areas with other brain areas has emerged. These findings, in addition to the growing research applying MEG to other psychiatric disorders, highlight the utility of MEG in identifying biomarkers of disease and underscore the potential for broader clinical applications of MEG.
, an essential aspect of the brain function.
MEG

Magnetoencephalography (MEG)

A noninvasive technique that detects magnetic fields above the surface of the head produced by postsynaptic potentials in the brain.
signals 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

Experimental Brain Research - 2007-07-01Pellizzer G, Stephane M10.1007/s00221-007-0892-5
Schizophrenia patients tend to have longer and more variable latencies of response than healthy control subjects. However, the distributions of data from the two groups overlap to a large extent. Therefore, we investigated (1) whether the process of response selection in schizophrenia patients is like that of slow control subjects or has different properties, and (2) whether the intra-individual variability of schizophrenia patients is intrinsically greater than that of control subjects or reflects their longer mean latency. To answer these questions we tested schizophrenia patients and healthy control subjects in a choice reaction time (RT) task with 2-choice and 4-choice conditions. We analyzed how mean RT in the 2-choice condition predicted mean RT in the 4-choice condition and found that the relation was significantly different between the two groups. In contrast, the intra-individual variability of RT was related to mean RT in the same way for schizophrenia patients and control subjects....

Empirical evaluation of language disorder in schizophrenia

Journal of Psychiatry & Neuroscience - 2007-07-01Stephane M, Pellizzer G, Fletcher CR, McClannahan K
ObjectiveStudies of the content of speech and of verbal hallucinations in schizophrenia point to dysfunction at multiple levels of language. In this study, we empirically evaluated language processes.MethodsWe examined the performance of 22 schizophrenia patients and 11 healthy control subjects with procedures designed to explore the sublexical, lexical, semantic, syntactic and discourse levels of language processing.ResultsSchizophrenia patients exhibit impairment in the recognition of incorrect, but not correct, linguistic stimuli at all but the sublexical level of language processing. The patients were not impaired in the recognition of nonlinguistic stimuli.ConclusionThis language-specific differential impairment could explain speech abnormalities in schizophrenia. The nonrecognition of incorrect linguistic information would prevent patients from correcting the abnormal speech they may occasionally produce. A model of decreased power of linguistic computations (reduced number of operations) adequately accounts for this differential impairment.

Mapping of the preferred direction in the motor cortex

Proceedings of the National Academy of Sciences of the United States of America - 2007-06-26Georgopoulos AP, Merchant H, Naselaris T, Amirikian B10.1073/pnas.0611597104
Directional tuning is a basic functional property of cell activity in the motor cortex. Previous work has indicated that cells with similar preferred directions are organized in columns perpendicular to the cortical surface. Here we show that these columns are organized in an orderly fashion in the tangential dimension on the cortical surface. Based on a large number of microelectrode penetrations and systematic exploration of the proximal arm area of the motor cortex while monkeys made free reaching 3D movements, it was estimated that (i) directional minicolumns are ≈30 μm in width, (ii) minicolumns with similar preferred directions tend to occur in doublets or triplets, and (iii) such minicolumns tend to repeat every ≈240 μm (estimated width of a column), with intermediate preferred directions represented in a gradient. These findings provide evidence for an orderly mapping of the preferred direction in the motor cortex.

Reading in a deep orthography: neuromagnetic evidence for dual-mechanisms

Experimental Brain Research - 2007-06-01Wilson T, Leuthold A, Moran JE, Pardo P, Lewis S, Georgopoulos AP10.1007/s00221-007-0852-0
Despite substantial efforts to connect cognitive-linguistic models with appropriate anatomical correlates, the question of which cognitive model best accounts for the neuropsychological and functional neuroimaging evidence remains open. The two most popular models are grounded in conceptually different bases and thus make quasi-distinct predictions in regard to the patterns of activation that should be observed in imaging investigations of linguistic processing. Dual-mechanism models propose that high-frequency regular and irregular words are processed through a lexicon-based word code, which facilitates their processing and pronunciation latencies relative to pseudowords. In contrast, single-mechanism models suggest the same behavioral effects can be explained through semantic mediation without the existence of a lexicon. In most previous studies, words and pronounceable pseudowords were presented in lexical-decision or word reading paradigms, and hemodynamic techniques were utilized to distinguish involved anatomical areas. The results typically indicated that both word classes activated largely congruent tissues, with a magnitude advantage for...

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