Automatic Response Assessment in Regions of Language Cortex in Epilepsy Patients Using ECoG-based Functional Mapping and Machine Learning

Accurate localization of brain regions responsible for language and cognitive functions in Epilepsy patients should be carefully determined prior to surgery. Electrocorticography (ECoG)-based Real Time Functional Mapping (RTFM) has been shown to be a safer alternative to the electrical cortical stimulation mapping (ESM), which is currently the clinical/gold standard. Conventional methods for analyzing RTFM signals are based on statistical comparison of signal power at certain frequency bands. Compared to gold standard (ESM), they have limited accuracies when assessing channel responses. In this study, we address the accuracy limitation of the current RTFM signal estimation methods by analyzing the full frequency spectrum of the signal and replacing signal power estimation methods with machine learning algorithms, specifically random forest (RF), as a proof of concept. We train RF with power spectral density of the time-series RTFM signal in supervised learning framework where ground truth labels are obtained from the ESM. Results obtained from RTFM of six adult patients in a strictly controlled experimental setup reveal the state of the art detection accuracy of $\approx 78\%$ for the language comprehension task, an improvement of $23\%$ over the conventional RTFM estimation method. To the best of our knowledge, this is the first study exploring the use of machine learning approaches for determining RTFM signal characteristics, and using the whole-frequency band for better region localization. Our results demonstrate the feasibility of machine learning based RTFM signal analysis method over the full spectrum to be a clinical routine in the near future.Comment: This paper will appear in the Proceedings of IEEE International Conference on Systems, Man and Cybernetics (SMC) 201

A MEG Study on the Processing of Time and Quantity: Parietal Overlap but Functional Divergence

A common magnitude system for the processing of time and numerosity, supported by areas in the posterior parietal cortex, has been proposed by some authors. The present study aims to investigate possible intersections between the neural processing of non-numerical (time) and numerical magnitudes in the posterior parietal lobe. Using Magnetoencephalography for the comparison of brain source activations during the processing of duration and numerosity contrasts, we demonstrate parietal overlap as well as dissociations between these two dimensions. Within the parietal cortex, the main areas of overlap were bilateral precuneus, bilateral intraparietal sulci, and right supramarginal gyrus. Interestingly, however, these regions did not equivalently correlated with the behavior for the two dimensions: left and right precuneus together with the right supramarginal gyrus accounted functionally for durational judgments, whereas numerosity judgments were accounted by the activation pattern in the right intraparietal sulcus. Present results, indeed, demonstrate an overlap between the neural substrates for processing duration and quantity. However, the functional relevance of parietal overlapping areas for each dimension is not the same. In fact, our data indicates that the same parietal sites rule differently non-numerical and numerical dimensions, as parts of broader networks

Emotion-Related Visual Mismatch Responses in Schizophrenia: Impairments and Correlations with Emotion Recognition.

BACKGROUND AND OBJECTIVES:Mismatch negativity (MMN) is an event-related potential (ERP) measure of preattentional sensory processing. While deficits in the auditory MMN are robust electrophysiological findings in schizophrenia, little is known about visual mismatch response and its association with social cognitive functions such as emotion recognition in schizophrenia. Our aim was to study the potential deficit in the visual mismatch response to unexpected facial emotions in schizophrenia and its association with emotion recognition impairments, and to localize the sources of the mismatch signals. EXPERIMENTAL DESIGN:The sample comprised 24 patients with schizophrenia and 24 healthy control subjects. Controls were matched individually to patients by gender, age, and education. ERPs were recorded using a high-density 128-channel BioSemi amplifier. Mismatch responses to happy and fearful faces were determined in 2 time windows over six regions of interest (ROIs). Emotion recognition performance and its association with the mismatch response were also investigated. PRINCIPAL OBSERVATIONS:Mismatch signals to both emotional conditions were significantly attenuated in patients compared to controls in central and temporal ROIs. Controls recognized emotions significantly better than patients. The association between overall emotion recognition performance and mismatch response to the happy condition was significant in the 250-360 ms time window in the central ROI. The estimated sources of the mismatch responses for both emotional conditions were localized in frontal regions, where patients showed significantly lower activity. CONCLUSIONS:Impaired generation of mismatch signals indicate insufficient automatic processing of emotions in patients with schizophrenia, which correlates strongly with decreased emotion recognition

Differentiation of Schizophrenia Patients from Healthy Subjects by Mismatch Negativity and Neuropsychological Tests

BACKGROUND: Schizophrenia is a heterogeneous disorder with diverse presentations. The current and the proposed DSM-V diagnostic system remains phenomenologically based, despite the fact that several neurobiological and neuropsychological markers have been identified. A multivariate approach has better diagnostic utility than a single marker method. In this study, the mismatch negativity (MMN) deficit of schizophrenia was first replicated in a Han Chinese population, and then the MMN was combined with several neuropsychological measurements to differentiate schizophrenia patients from healthy subjects. METHODOLOGY/PRINCIPAL FINDINGS: 120 schizophrenia patients and 76 healthy controls were recruited. Each subject received examinations for duration MMN, Continuous Performance Test, Wisconsin Card Sorting Test, and Wechsler Adult Intelligence Scale Third Edition (WAIS-III). The MMN was compared between cases and controls, and important covariates were investigated. Schizophrenia patients had significantly reduced MMN amplitudes, and MMN decreased with increasing age in both patient and control groups. None of the neuropsychological indices correlated with MMN. Predictive multivariate logistic regression models using the MMN and neuropsychological measurements as predictors were developed. Four predictors, including MMN at electrode FCz and three scores from the WAIS-III (Arithmetic, Block Design, and Performance IQ) were retained in the final predictive model. The model performed well in differentiating patients from healthy subjects (percentage of concordant pairs: 90.5%). CONCLUSIONS/SIGNIFICANCE: MMN deficits were found in Han Chinese schizophrenia patients. The multivariate approach combining biomarkers from different modalities such as electrophysiology and neuropsychology had a better diagnostic utility

Veiksmažodžio iškėlimo parametro nustatymas lietuvių kalboje

The present article is concerned with the verb raising parameter in Lithuanian. As is known, Pollock (1989) postulates the verb raising parameter and examines the differences betweena verb raising language like French and a verb non-raising language like English. The verb raising parameter has become an essential part of analysis within the generative syntactic framework. However, due to its rich morphological system and free word order, Lithuanian has remained virtually unexplored. The present article explores the behaviour of the Lithuanian verb in light of the test environments proposed by Pollock: the position of the verb in negative sentences, yes/no questions, relative to the so-called low adverbs, and floating quantifiers. The preliminary conclusions are further verified in agrammaticality preferencetest, with a particular focus on the placement of manner adverbs, which are regarded to stand the closest to the verb. It is shown that the verb does not raise from its base position in the affirmative sentences and may optionally raise in yes/no questions.The adverb placement relative to the verb is further specified in light of the negative particle "ne-"

Kuuloinformaation käsittelyn neurokemiallinen säätely terveillä ja skitsofreniapotilailla : MEG/EEG tutkimus

Cognitive impairments of attention, memory and executive functions are a fundamental feature of the pathophysiology of schizophrenia. The neurophysiological and neurochemical changes in the auditory cortex are shown to underlie cognitive impairmentsin schizophrenia patients. Functional state of the neural substrate of auditory information processing could be objectively and non-invasively probed with auditory event-related potentials (ERPs) and event- related fields (ERFs). In the current work, we explored the neurochemical effect on the neural origins of auditory information processing in relation to schizophrenia. By means of ERPs/ERFs we aimed to determine how neural substrates of auditory information processing are modulated by antipsychotic medication in schizophrenia spectrum patients (Studies I, II) and by neuropharmacological challenges in healthy human subjects (Studies III, IV). First, with auditory ERPs we investigated the effects of olanzapine (Study I) and risperidone (Study II) in a group of patients with schizophrenia spectrum disorders. After 2 and 4 weeks of treatment, olanzapine has no significant effects on mismatch negativity(MMN) and P300, which, as it has been suggested, respectively reflect preattentive and attention-dependent information processing. After 2 weeks of treatment, risperidone has no significant effect on P300, however risperidone reduces P200 amplitude. This latter effect of risperidone on neural resources responsible for P200 generation could be partly explained through the action of dopamine. Subsequently, we used simultaneous EEG/MEG to investigate the effects of memantine (Study III) and methylphenidate (Study IV) in healthy subjects. We found that memantine modulates MMN response without changing other ERP components. This could be interpreted as being due to the possible influence of memantine through the NMDA receptors on auditory change- detection mechanism, with processing of auditory stimuli remaining otherwise unchanged. Further, we found that methylphenidate does not modulate the MMN response. This finding could indicate no association between catecholaminergic activities and electrophysiological measures of preattentive auditory discrimination processes reflected in the MMN. However, methylphenidate decreases the P200 amplitudes. This could be interpreted as a modulation of auditory information processing reflected in P200 by dopaminergic and noradrenergic systems. Taken together, our set of studies indicates a complex pattern of neurochemical influences produced by the antipsychotic drugs in the neural substrate of auditory information processing in patients with schizophrenia spectrum disorders and by the pharmacological challenges in healthy subjects studied with ERPs and ERFs.Skitsofreniapotilailla on usein psykoottisten oireiden ohella kognitiivisia ongelmia esimerkiksi muistissa ja tarkkavaisuudessa, joihin vanhemmilla psykoosilääkkeillä ei ole vaikutusta. Viime vuosina on kehitetty uusia psykoosilääkkeitä, joiden on arveltu parantavan kognitiivisia oireita. Tässä työssä haluttiin selvittää uusien psykoosilääkkeiden vaikutuksia aivosähköisiin kognitiivisiin mittareihin elektroenkefalografia (EEG)-menetelmällä skitsofreniaspektrin potilailla. 4-viikon mittaisilla risperidoni- ja olantsapiinihoidoilla ei ollut vaikutusta mismatch negatiivisuus - eli MMN - ja P3-vasteisiin, jotka heijastavat tarkkaavaisuusprosessien eri vaiheita. Kuitenkin risperidoni pienensi P2-vastetta, mikä voi heijastaa muutosta potilaiden kognitiivisissa toiminnoissa. Yhdistetyllä MEG/EEG-menetelmällä tutkittiin terveillä koehenkilöillä metyylifenidaatin ja memantiinin vaikutuksia MMN-vasteeseen, jotta saataisiin selvyyttä tarkkaavaisuuden neurokemiallisesta säätelystä. Kerta-annos metyylifenitaaattia ei vaikuttanut MMN-vasteeseen, mutta se pienensi P2-vastetta. Kerta-annos memantiinia suurensi MMN-vastetta EEG:ssä, muttei magnetoenkefalografiassa. Kiihdyttävä glutamaattivälittäjäaine saattaa osallistua tarkkaavaisuuden säätelyyn etuaivokuorella. Risperidonilla, muttei olantsapiinillä oli vaikutuksia aivosähköisiin kognitiivisiin mittareihin lyhyen hoidon jälkeen, mikä voi välittyä dopamiinin kautta