Reading in a deep orthography: neuromagnetic evidence for dual-mechanisms
permalinkExperimental Brain Research - 2007-06-01Wilson T, Leuthold A, Moran JE, Pardo P, Lewis S, Georgopoulos AP10.1007/s00221-007-0852-0Despite 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...
Paving the way for cross-site pooling of Magnetoencephalography data
permalinkInternational Congress Series - 2007-06-01Weisend MP, Hanlon FM, Montano R, Ahlfors SP, Leuthold A, Pantazis D, Mosher JC, Georgopoulos AP, Hamalainen MS, Aine CJ10.1016/j.ics.2006.12.095Pooling of
Magnetoencephalographydata across laboratories is non-trivial because of differences in hardware, software, and environmental noise levels. To investigate these issues, we conducted a study with the same five subjects at three sites with different
MEGarrays: Elekta-Neuromag Vectorview (Boston), VSM MedTech Omega 275 (Albuquerque), and 4D Neuroimaging Magnes 3600 WH (Minneapolis). Subjects were run in a simple somatosensory paradigm. Phantom data were also taken at each site. We developed software to allow comparisons of test/retest reliability across subjects, machines, and analysis methods. Preliminary analyses showed excellent test/retest results within subjects across instruments. Analysis of phantom data showed a localization error of less than 2 mm across multiple software packages. Our results show that (1) instruments from different manufacturers yield similar results for somatosensory data, and that (2) multiple software packages produce very accurate results for simple source configurations.
Schizophrenia Classification using Working Memory Magnetoencephalography ERD/ERS Patterns
permalink2007 3rd International IEEE/EMBS Conference on Neural Engineering - 2007-05-02Ince NF, Stephane M, Tewfik AH, Pellizzer G, McClannahan K10.1109/CNE.2007.369708In this paper we investigate the use of event related desynchronization (ERD) and synchronization (ERS) patterns extracted from magnetoencephalogram (
MEG) in a working memory task to discriminate between controls and patients with schizophrenia. In the experimental paradigm, sequential letters appearing on a screen are memorized by subjects. In one of two conditions the letters constituted a word. The ERD and ERS patterns are extracted in the theta, alpha, beta and gamma bands from 248 electrode locations covering the whole head. We noticed that most of the ERD patterns are localized on the left frontotemporal area in both word and nonword conditions in the late memorization stage. The beta band showed the most significant difference in this cortical area between controls and schizophrenia patients. By using a decision tree, 94.7% and 87.5% classification accuracy was obtained for controls and patients individually in both word and nonword conditions. Furthermore, we report that on...
The dynamic architecture of working memory in schizophrenia
Post-Traumatic Stress Disorder and Service Utilization in a Sample of Service Members from Iraq and Afghanistan
permalinkMilitary Medicine - 2007-04-01Erbes CR, Westermeyer JJ, Engdahl B, Johnson E10.7205/MILMED.172.4.359Objective: The purpose of this study was to evaluate levels of post-traumatic stress disorder (
Posttraumatic Stress Disorder), depression, alcohol abuse, quality of life, and mental health service utilization among returnees from Operation Enduring Freedom and
Operation Iraqi Freedom. Methods: One hundred twenty returnees, enrolled for health care at a midwestern Veterans Affairs medical center, completed questionnaires approximately 6 months after their return from deployment. Results:
PTSDlevels (12%) were consistent with previous research while problematic drinking levels were also elevated (33%).
PTSDand, to a lesser degree, alcohol abuse were associated with lower quality of life in multiple domains, even when controlling for the influence of depression. Of those screening positive for
PTSD, 56% reported using mental health services. Only 18% of those screening positive for alcohol abuse reported using such services. Conclusions:
PTSDand alcohol problems are prevalent in Operation Enduring Freedom/
OIFreturnees and associated with lower quality of life....
Intelligence in action
A tribute to Tau
Large-Scale Organization of Preferred Directions in the Motor Cortex. II. Analysis of Local Distributions
permalinkJournal of Neurophysiology - 2006-12-01Naselaris T, Merchant H, Amirikian B, Georgopoulos AP10.1152/jn.00488.2006The spatial arrangement of preferred directions (PDs) in the primary motor cortex has revealed evidence for columnar organization and short-range order. We investigated the large-scale properties of this arrangement. We recorded neural activity at sites on a grid covering a large region of the arm area of the motor cortex while monkeys performed a 3D reaching task. Sites were projected to the cortical surface along anatomically defined cortical columns and a PD was extracted from each site with directionally tuned activity. We analyzed the resulting 2D surface map of PDs. Consistent with previous studies, we found that any particular reaching direction was rerepresented at many points across the recorded area. In particular, we determined that the median radius of a cortical region required to represent the full complement of reaching directions is at most 1 mm. We also found that for the majority of regions of this size, the distribution of...
Large-Scale Organization of Preferred Directions in the Motor Cortex. I. Motor Cortical Hyperacuity for Forward Reaching
Computerized binary scale of auditory speech hallucinations (cbSASH)
permalinkSchizophrenia Research - 2006-12-01Stephane M, Pellizzer G, Roberts S, McClannahan K10.1016/j.schres.2006.05.020BackgroundEvidence indicates that the neuropathology of auditory verbal hallucinations (AVH) varies according to their phenomenological characteristics. Therefore, AVH should be subgrouped accordingly in hallucinations research. As evaluation of these characteristics depends entirely on the patient report, obtaining measurement of the reliability of these reports is crucial.MethodA computerized binary scale of auditory speech hallucinations (cbSASH) was developed to evaluate the phenomenology of AVH. It includes two subscales (inconsistency and malingering) to assess the reliability of the patient report. The cbSASH was administered along with MMPI-2, a general psychopathology scale, which includes similar validity subscales. Thirty-four psychotic patients with history of AVH were enrolled in this study.ResultsThe scores on the inconsistency and malingering subscales of the cbSASH were correlated with the scores on the corresponding validity subscales in the MMPI-2. The combination of the malingering and inconsistency subscales provided robust measures of the reliability and ability of the patients' descriptions of their hallucinations.ConclusionThe...
Translational and developmental perspective on N-methyl-D-aspartate synaptic deficits in schizophrenia
permalinkDevelopment and Psychopathology - 2006-09-01MacDonald III AW, Chafee M10.1017/S0954579406060421Schizophrenia has long been approached from a translational perspective; however, new findings from the past decade have radically affected the dominant accounts of this illness. It is now possible to derive a consistent account of one contributing cause of schizophrenia across multiple levels of analysis, from genes to receptors, functional neuroanatomy, cognition, and symptoms. To this end, we summarize the data attributing the disorganization symptoms of schizophrenia to a failure of executive, prefrontal cortical processes. We describe the hypothesis that this failure reflects an impairment in N-methyl-D-aspartate (NMDA) glutamatergic neurotransmission, that is likely to involve both the dysregulated function of NMDA synapses, as well as the physical loss of NMDA synapses, particularly in prefrontal cortex. Dysregulation in NMDA synaptic function can be in turn attributed to polymorphisms in a variety of genes (regulator of G-protein signaling 4, dystrobrevin binding protein 1, neuregulin-1, d-amino acid oxidase activator, and others) that have been...
Time-dependent effects of discrete spatial cues on the planning of directed movements
permalinkExperimental Brain Research - 2006-06-01Pellizzer G, Hedges J, Villanueva RR10.1007/s00221-005-0317-2The degree of preparation of a motor response varies with the information available regarding the response that will need to be executed and with the time provided to process that information. In experiment 1 we investigated the time-course of processing the information specified by discrete spatial cues regarding the upcoming target of directed movements. For this purpose we varied the number of cues that indicated the possible locations of the target and the duration of the cue period preceding the target. The results showed that the effects of processing the information provided by the cues developed progressively and stabilized after 0.2 s. In addition, the level of motor preparation reached was a function of number of cues. However, the effect of number of cues occurred even in the no cue period condition, i.e. when subjects could not have benefited from the information provided by the cues to prepare the response. Further...
Reply to Kurtzer and Herter
A comparative study of Posttraumatic Stress Disorder assessment under standard conditions and in the field
permalinkInternational Journal of Methods in Psychiatric Research - 2006-05-19Erbes CR, Dikel TN, Eberly RE, Page WF, Engdahl B10.1002/mpr.185Little is known about the performance of clinician-administered structured diagnostic interviews when given under variable levels of examiner training and monitoring. We sought to explore this question. We examined the performance of a self-report questionnaire and a structured clinical interview in the assessment of post-traumatic stress disorder (
PTSD) in two community samples of war veterans. One sample was interviewed under standard conditions (N = 372) and the other under unknown and less standardized conditions (N = 420), more closely approximating 'field conditions'. Interview results were used to predict questionnaire-based
PTSDstatus. Kappas, sensitivities, specificities, and positive predictive powers were moderate and of similar magnitude in both samples. Our results suggest that even under uncertain ('field') conditions, clinician-administered structured interviews can produce results comparable to those produced under more tightly controlled conditions.
Dipole analysis of magnetoencephalographic data during continuous shape copying
permalinkExperimental Brain Research - 2006-04-01Langheim F, Merkle AN, Leuthold A, Lewis S, Georgopoulos AP10.1007/s00221-005-0234-4High density, whole head
MEGwas used to study ten healthy human subjects (five females and five males) participating in a continuous shape-copying task. The task was performed with eyes open and fixated. The three-part task began with 45 s of fixation on a blue dot, after which the dot turned red, and a pentagon was presented around it. Subjects continued to fixate on the red dot for 45 s, after which it turned green. The green dot instructed subjects to begin copying the shape continuously for 45 s, without visual feedback, using a joystick mounted at arm's length. Data were collected at 1,017.25 Hz with a 248 sensor axial-gradiometer system. After cardiac artifact subtraction (Leuthold 2003), each corner was identified, and 1 s epochs (centered on each corner) were averaged and filtered from 1 to 44 Hz. Grand average flux maps demonstrated dipolar distributions identifying the most relevant sensors....
Synchronous dynamic brain networks revealed by magnetoencephalography
Neurophysiology of Perceptual and Motor Aspects of Interception
Classification of adolescent psychotic disorders using linear discriminant analysis
permalinkSchizophrenia Research - 2006-01-01Pardo P, Georgopoulos AP, Kenny JT, Stuve TA, Findling RL, Schulz SC10.1016/j.schres.2006.05.007BackgroundThe differential diagnosis between schizophrenia and bipolar disorder during adolescence presents a major clinical problem. Can these two diagnoses be differentiated objectively early in the courses of illness?MethodsWe used linear discrimination analysis (LDA) to classify 28 adolescent subjects into one of three diagnostic categories (healthy, N = 8; schizophrenia, N = 10; bipolar, N = 10) using subsets from a pool of 45 variables as potential predictors (22 neuropsychological test scores and 23 quantitative structural brain measurements). The predictor variables were adjusted for age, gender, race, and psychotropic medication. All possible subsets composed of k = 2-12 variables, from the set of 45 variables available, were evaluated using the robust leaving-one-subject-out method.ResultsThe highest correct classification (96%) of the 3 diagnostic categories was yielded by 9 sets of k = 12 predictors, comprising both neuropsychological and brain structural measures. Although each one of these sets misclassified one case, each set correctly classified...
Dynamics of Parietal Neural Activity during Spatial Cognitive Processing
On the relations between single cell activity in the motor cortex and the direction and magnitude of three-dimensional dynamic isometric force