Brain Sciences Center - News

Time robust movement direction decoding in Local Field Potentials using channel ranking

Movement direction for Brain Machine Interface (BMI) can be decoded successfully using Local Field Potentials (LFP) and Single Unit Activity (SUA). A major challenge when dealing with the intra-cortical recordings is to develop decoders that are robust in time. In this paper we present for the first time a technique that uses the qualitative information derived from multiple LFP channels rather than the absolute power of the recorded signals. In this novel method, we use a power based inter-channel ranking system to define the quality of a channel in multi-channel LFP. This representation enables us to bypass the problems associated with the dynamic ranges of absolute power. We also introduce a parameter based ranking system that provides the same rank to channels that have comparable powers. We show that using our algorithms, we can develop models that provide stable decoding of eight movement directions with an average efficiency of above 56%...
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Beta-Band Activity during Motor Planning Reflects Response Uncertainty

It has been known for many years that the power of beta-band oscillatory activity in motor-related brain regions decreases during the preparation and execution of voluntary movements. However, it is not clear yet whether the amplitude of this desynchronization is modulated by any parameter of the motor task. Here, we examined whether the degree of uncertainty about the upcoming movement direction modulated beta-band desynchronization during motor preparation. To this end, we recorded whole-head neuromagnetic signals while human subjects performed an instructed-delay reaching task with one, two, or three possible target directions. We found that the reduction of power of beta-band activity (16-28 Hz) during motor preparation was scaled relative to directional uncertainty. Furthermore, we show that the change of beta-band power correlates with the change of latency of response associated with response uncertainty. Finally, we show that the main source of beta-band desynchronization was located in the peri-Rolandic region. The results...
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Fluorodeoxyglucose positron emission tomography of mild cognitive impairment with clinical follow-up at 3 years

BackgroundAlzheimer's disease (AD) is the most common dementing illness. Development of effective treatments directed at AD requires an early diagnosis. Mild cognitive impairment (MCI) often heralds AD. Thus, characterizing MCI is fundamental to the early diagnosis of AD.Methods19 MCI patients referred from a memory loss clinic and 27 healthy subjects, all followed up for 3 years. Metabolism scans (MCI minus controls) were compared voxel-wise after anatomic normalization and were examined both visually and with a computerized classifier.ResultsAgreement between raters as to whether the individual scans were normal or abnormal was high. Agreement between raters of the eventual clinical diagnosis and baseline metabolic pattern was poor. A computerized classifier was unsuccessful at classifying MCI from normal; however, its performance improved when using only prototypic AD-like MCI scans, indicating the classifier worked well when shared patterns existed in the data. Outcomes on follow-up were nine of 19 AD, five of 19 remained MCI,...
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Cortical processing of facial tactile stimuli in temporomandibular disorder as revealed by magnetoencephalography

We used to investigate the cortical processing of an innocuous facial tactile stimulus in healthy subjects and in a group of subjects suffering from chronic temporomandibular disorder (TMD). Equivalent current dipoles (ECDs) were extracted for a time period of 1 s following stimulus application, and their location, duration and onset time determined. The counts of ECDs extracted did not differ significantly between the two groups. In contrast, we found statistically significant differences in ECD duration and onset time. Specifically, ECD duration was longer in the TMD group in the precentral gyrus, and ECD onset time was earlier in the parietal operculum. In addition, we found differences in the internal organization and clustering of the brain areas involved indicating a less tight association and a less coordinated stimulus information processing in the TMD group. Altogether, these results show that an innocuous facial tactile stimulus is differently processed in the brain...
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Understanding the parietal lobe syndrome from a neurophysiological and evolutionary perspective

In human and nonhuman primates parietal cortex is formed by a multiplicity of areas. For those of the superior parietal lobule (SPL) there exists a certain homology between man and macaques. As a consequence, optic ataxia, a disturbed visual control of hand reaching, has similar features in man and monkeys. Establishing such correspondence has proven difficult for the areas of the inferior parietal lobule (IPL). This difficulty depends on many factors. First, no physiological information is available in man on the dynamic properties of cells in the IPL. Second, the number of IPL areas identified in the monkey is paradoxically higher than that so far described in man, although this issue will probably be reconsidered in future years, thanks to comparative imaging studies. Third, the consequences of parietal lesions in monkeys do not always match those observed in humans. This is another paradox if one considers that, in certain cases, the...
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A magnetoencephalography study of choice bias

Many factors can influence, or bias, human decision making. A considerable amount of research has investigated the neural correlates of such biases, mostly correlating hemodynamic responses in brain areas with some aspect of the decision. These studies, typically done using or positron emission tomography, have provided useful information about the location of processing in the brain. However, comparatively little research has examined when these processes occur. The present experiment addressed this question by using to record brain activity while subjects chose preferred options from decision sets. We found that signal deviations for biased decisions occurred as early as 250-750 ms following stimulus onset. Such deviations occurred earliest in sensors over the right anterior cortex. These findings improve our understanding of temporal dynamics of decision biases and suggest ways that existing explanations for this bias could be refined.

Attachment Style Classification and Posttraumatic Stress Disorder in Former Prisoners of War

Adult attachment style and symptomatology were investigated in 107 former prisoner of war veterans. Those with secure attachment styles scored significantly lower on measures of than did those with insecure styles, and attachment style was a stronger predictor of symptom intensity than was trauma severity. The suggested association between attachment style and 's development and persistence are discussed in relation to research and clinical practice.

Study Points at a Clear-Cut Way to Diagnose Post-traumatic Stress DisorderPost-traumatic Stress Disorder (PTSD)A complex psychiatric syndrome that develops in response to trauma exposure. Individuals with PTSD experience intrusive recollections or reexperiencing of the traumatic event, avoidance of trauma reminders, emotional numbing, and hyperarousal. In addition, PTSD is associated with high rates of concomitant physical and mental health problems, increased health care use, and impairment in social and occupational functioning. Almost 7% of the general population and up to 30% of veterans meet lifetime criteria for PTSD. Indeed, PTSD is one of the most common psychiatric disorders, representing a significant and costly public health concern.

From the article:

For all the attention focused on posttraumatic stress disorder (PTSDPost-traumatic Stress Disorder (PTSD)A complex psychiatric syndrome that develops in response to trauma exposure. Individuals with PTSD experience intrusive recollections or reexperiencing of the traumatic event, avoidance of trauma reminders, emotional numbing, and hyperarousal. In addition, PTSD is associated with high rates of concomitant physical and mental health problems, increased health care use, and impairment in social and occupational functioning. Almost 7% of the general population and up to 30% of veterans meet lifetime criteria for PTSD. Indeed, PTSD is one of the most common psychiatric disorders, representing a significant and costly public health concern.) in recent years, doctors have never had a clear-cut way to be certain a patient has it. But Minnesota scientists now believe they have found a long-sought PTSDPost-traumatic Stress Disorder (PTSD)A complex psychiatric syndrome that develops in response to trauma exposure. Individuals with PTSD experience intrusive recollections or reexperiencing of the traumatic event, avoidance of trauma reminders, emotional numbing, and hyperarousal. In addition, PTSD is associated with high rates of concomitant physical and mental health problems, increased health care use, and impairment in social and occupational functioning. Almost 7% of the general population and up to 30% of veterans meet lifetime criteria for PTSD. Indeed, PTSD is one of the most common psychiatric disorders, representing a significant and costly public health concern. fingerprint that confirms the disorder by measuring electromagnetic fields in the brain. The finding, detailed in the latest issue of the Journal of Neural Engineering, could help the 300,000 cases of PTSDPost-traumatic Stress Disorder (PTSD)A complex psychiatric syndrome that develops in response to trauma exposure. Individuals with PTSD experience intrusive recollections or reexperiencing of the traumatic event, avoidance of trauma reminders, emotional numbing, and hyperarousal. In addition, PTSD is associated with high rates of concomitant physical and mental health problems, increased health care use, and impairment in social and occupational functioning. Almost 7% of the general population and up to 30% of veterans meet lifetime criteria for PTSD. Indeed, PTSD is one of the most common psychiatric disorders, representing a significant and costly public health concern. that are anticipated among the 2 million U.S. troops who have gone to war in Afghanistan and Iraq."This shows that PTSDPost-traumatic Stress Disorder (PTSD)A complex psychiatric syndrome that develops in response to trauma exposure. Individuals with PTSD experience intrusive recollections or reexperiencing of the traumatic event, avoidance of trauma reminders, emotional numbing, and hyperarousal. In addition, PTSD is associated with high rates of concomitant physical and mental health problems, increased health care use, and impairment in social and occupational functioning. Almost 7% of the general population and up to 30% of veterans meet lifetime criteria for PTSD. Indeed, PTSD is one of the most common psychiatric disorders, representing a significant and costly public health concern. is a brain disease," says Dr. Apostolos Georgopoulos, who led the research along with Brian Engdahl and a team from the Brain Sciences CenterBrain Sciences Center (BSC) at the Minneapolis VA Medical CenterVA Medical Center (VAMC) and University of Minnesota. "There have been questions that this is a made-up disorder and isn't a true brain disease, but it is." Just as importantly, he says,...
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The Synchronous Neural InteractionsSynchronous 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. test as a functional neuromarker for Post-traumatic Stress DisorderPost-traumatic Stress Disorder (PTSD)A complex psychiatric syndrome that develops in response to trauma exposure. Individuals with PTSD experience intrusive recollections or reexperiencing of the traumatic event, avoidance of trauma reminders, emotional numbing, and hyperarousal. In addition, PTSD is associated with high rates of concomitant physical and mental health problems, increased health care use, and impairment in social and occupational functioning. Almost 7% of the general population and up to 30% of veterans meet lifetime criteria for PTSD. Indeed, PTSD is one of the most common psychiatric disorders, representing a significant and costly public health concern.: a robust classification method based on the bootstrap

Traumatic experiences can produce which is a debilitating condition and for which no biomarker currently exists (Institute of Medicine (US) 2006 Posttraumatic Stress Disorder: Diagnosis and Assessment (Washington, DC: National Academies)). Here we show that the test which assesses the functional interactions among neural populations derived from magnetoencephalographic () recordings (Georgopoulos A P et al 2007 J. Neural Eng. 4 349-55) can successfully differentiate patients from healthy control subjects. Externally cross-validated, bootstrap-based analyses yielded >90% overall accuracy of classification. In addition, all but one of 18 patients who were not receiving medications for their disease were correctly classified. Altogether, these findings document robust differences in brain function between the and control groups that can be used for differential diagnosis and which possess the potential for assessing and monitoring disease progression and effects of therapy.

Brain scans pinpoint stress disorder in war veterans

From the article:

There's never been a simple test to diagnose post-traumatic stress, but a group of Minnesota scientists say they've found a high-tech way to identify people who have the disorder -- by studying their brain signals. The discovery could have huge implications for the way PTSDPost-traumatic Stress Disorder (PTSD)A complex psychiatric syndrome that develops in response to trauma exposure. Individuals with PTSD experience intrusive recollections or reexperiencing of the traumatic event, avoidance of trauma reminders, emotional numbing, and hyperarousal. In addition, PTSD is associated with high rates of concomitant physical and mental health problems, increased health care use, and impairment in social and occupational functioning. Almost 7% of the general population and up to 30% of veterans meet lifetime criteria for PTSD. Indeed, PTSD is one of the most common psychiatric disorders, representing a significant and costly public health concern. is diagnosed and treated in the future, says Dr. Apostolos Georgopoulos, who led the research as director of the BSCBrain Sciences Center (BSC) at the Minneapolis VAMCVA Medical Center (VAMC).PTSDPost-traumatic Stress Disorder (PTSD)A complex psychiatric syndrome that develops in response to trauma exposure. Individuals with PTSD experience intrusive recollections or reexperiencing of the traumatic event, avoidance of trauma reminders, emotional numbing, and hyperarousal. In addition, PTSD is associated with high rates of concomitant physical and mental health problems, increased health care use, and impairment in social and occupational functioning. Almost 7% of the general population and up to 30% of veterans meet lifetime criteria for PTSD. Indeed, PTSD is one of the most common psychiatric disorders, representing a significant and costly public health concern. is thought to afflict tens of thousands of combat veterans, but it can be hard to diagnose. It's a collection of psychological symptoms that can, in some cases, be caused by other conditions, such as head injuries or depression. That's one reason that exact numbers are hard to pin down; the VA estimates that anywhere from 11 to 20 percent of returning veterans from Afghanistan and Iraq have PTSDPost-traumatic Stress Disorder (PTSD)A complex psychiatric syndrome that develops in response to trauma exposure. Individuals with PTSD experience intrusive recollections or reexperiencing of the traumatic event, avoidance of trauma reminders, emotional numbing, and hyperarousal. In addition, PTSD is associated with high rates of concomitant physical and mental health problems, increased health care use, and impairment in social and occupational functioning. Almost 7% of the general population and up to 30% of veterans meet lifetime criteria for PTSD. Indeed, PTSD is one of the most common psychiatric disorders, representing a significant and costly public health concern.. But in a study released Wednesday, Dr....
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Asymmetric learning transfer between imagined viewer- and object-rotations: Evidence of a hierarchical organization of spatial reference frames

Neural resources subserving spatial processing in either egocentric or allocentric reference frames are, at least partly, dissociated. However, it is unclear whether these two types of representations are independent or whether they interact. We investigated this question using a learning transfer paradigm. The experiment and material were designed so that they could be used in a clinical setting. Here, we tested healthy subjects in an imagined viewer-rotation task and an imagined object-rotation task. The order of the tasks was counterbalanced across subjects. The results showed that subjects who did the viewer-rotation task first had fewer errors and shorter latencies of response in the object-rotation task, whereas subjects who did the object-rotation task first had little if any advantage in the viewer-rotation task. In other words, the results revealed an asymmetric learning transfer between tasks, which suggests that spatial representations are hierarchically organized. Specifically, the results indicate that the viewer-rotation task engaged...
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What pre-whitened music can tell us about multi-instrument compositions

We have discovered remarkable temporal associations between instruments in multi-instrument musical pieces after elimination of melody. This indicates the presence of a compositional 'structural' framework among instruments based on dynamic, temporal interactions. We hypothesize that such a framework is at the heart of the process of musical composition. Since similar melodies can be arranged in different ways, resulting in unique compositions, the instrument framework above may be a fundamental aspect of the musical arrangement in the composer's palette.

Spatial proximity based subspace decomposition for movement direction decoding of Local Field Potentials

Local Field Potentials (LFP) provides higher spatial resolution and SNR than EEG data and can be used to construct a Brain Computer Interface. In, we have shown that movement direction decoding can be done with about 90 % classification accuracy using spatial patterns (CSP) and Error Correction Output Codes (ECOC). However, a major challenge in this study is to make this method more robust to inter-session variability of the LFP data, where state-of-the-art results are in the high 70 percent. In, we have demonstrated that LFP features that are recurrent across sessions can be extracted using a subspace learning method and used to improve the CSP +ECOC classifier. In this work, we propose an extension of the subspace learning method that exploits the spatial topology of the channels. This allows us to learn spatially diverse features, while previously the subspaces were being learned independently of the channel layout. We proposed a...
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Overcoming measurement time variability in brain machine interface

We introduce a subspace learning approach for multi-channel Local Field Potentials (LFP), and demonstrate its application in movement direction decoding for 8 directions movement. We show that the subspace learning method can effectively address the issue of signal instability across recording sessions by extracting recurrent features from the data. We present results for movement direction decoding, where we trained on two recording sessions, and evaluated decoding performance on a third session. We combine our method with a classifier based on Error-Correcting Output Codes (ECOC) and Common Spatial Patterns (CSP) and found improvement in Decoding Power (DP) from 76% to 88% for a subject known to have strong inter-session variability. Furthermore, we saw an increase from 86% to 90% DP with another subject which exhibited significantly less variability.

Neural mechanisms of movement speed and tau as revealed by magnetoencephalography

A fundamental aspect of goal-directed behavior concerns the closure of motion-gaps in a timely fashion. In this context, the critical variable is the time-to-closure, called tau (Lee in Perception 5:437-459, 1976), and is defined as the ratio of the current distance-to-goal gap over the current instantaneous speed towards the goal. In this study, we investigated the neural mechanisms of speed and tau in pointing hand movements by recording activity from the whole brain of 20 right-handed healthy human subjects operating a joystick with their right hand. The relations between neural signals and speed and tau were analyzed using an autoregressive multiple regression model, where the time-varying signal was the dependent variable and the corresponding value of speed and tau were the independent variables. With respect to speed, we found that 81% of sensors showed significant relations over the left frontal-parietal, left parieto-temporal, and, less prominently, the right temporo-occipital sensor...
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Classification of schizophrenia with spectro-temporo-spatial Magnetoencephalography Magnetoencephalography (MEG)A noninvasive technique that detects magnetic fields above the surface of the head produced by postsynaptic potentials in the brain. patterns in working memory

ObjectiveTo investigate whether temporo-spatial patterns of brain oscillations extracted from multichannel magnetoencephalogram () recordings in a working memory task can be used successfully as a biometric marker to discriminate between healthy control subjects and patients with schizophrenia.MethodsFive letters appearing sequentially on a screen had to be memorized. The letters constituted a word in one condition and a pronounceable non-word in the other. Power changes of 248 channel data were extracted in frequency sub-bands and a two-step filter and search algorithm was used to select informative features that discriminated patients and controls.ResultsThe discrimination between patients and controls was greater in the word condition than in the non-word condition. Furthermore, in the word condition, the most discriminant patterns were extracted in delta (1-4 Hz), alpha (12-16 Hz) and beta (16-24 Hz) frequency bands. These features were located in the left dorso-frontal, occipital and left fronto-temporal, respectively.ConclusionThe analysis of the oscillatory patterns of...
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Movement direction decoding with spatial patterns of local field potentials

We show that movement direction can be decoded with high accuracy using the spatial patterns extracted from multichannel local field potentials (LFPs). Two monkeys were trained to execute center-out movement in 8 directions. During the task the LFP activity was recorded with two 64 channel grids from the pre- and primary motor areas. The LFP signals were decomposed into 4 sub-band components in the 0-4 Hz, 4-10 Hz, 14-30 Hz and 48-200 Hz frequency ranges. The sub-band activity was post processed with regularized common spatial patterns algorithm and fed to linear discriminant analysis for final classification. Directions of movement were estimated using a redundant hierarchical classification strategy that tested groups of directions against diametrically opposite groups. The grouping of directions was based on the spatial correlation that we observed between LFP signals corresponding to neighboring movement directions which is similar to the cosine tuning profile of single neurons. We found that...
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Cerebral cortical mechanisms of copying geometrical shapes: a multidimensional scaling analysis of Functional Magnetic Resonance ImagingFunctional 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. patterns of activation

We used multidimensional scaling (MDS) to characterize the integrative neural mechanisms during viewing and subsequently copying nine geometrical shapes. Human subjects initially looked at a central fixation point ("rest" period), then looked at a geometrical shape ("visual" period) which they copied without visual feedback ("copying" period). BOLD signal was recorded from voxels in 28 cortical areas (14 from each hemisphere) using a 4 Tesla magnet. For each voxel, signal ratios of "Visual versus Rest" (VR), and "Copy versus Visual" (CV) were calculated and used to construct two sets of Euclidean distance dissimilarity matrices for the nine shapes, with separate matrices defined for each region of interest (ROI) across subjects. The relations of perceptual and motor aspects of the shapes to MDS dimensions and specific ROIs were assessed using stepwise multiple regressions. The optimal individually scaled (INDSCAL) solutions were 2-dimensional. For the VR condition, MDS dimensions were significantly associated with the presence...
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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

Children from 8 to 12 years of age drew figure-eights and ellipses at a self-chosen tempo on a digitizing tablet. Global aspects (perimeter and average speed) and local aspects (relation between instantaneous speed and curvature) of performance were analyzed across age groups and types of figures. We tested the predictions of the transformation model, which is based on the hypothesis that changing the intended direction of movement is a time-consuming process that affects the evolution in time of the movement trajectory, and compared how well it fitted the data relative to the power law. We found that the relation between speed and curvature was typically better described by the transformation model than by the power law. However, the power law provided a better description when ellipses were drawn at a fast speed. The analyses of the parameters of the transformation model indicate that processing speed increased linearly with age. In addition,...
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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....
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