TY - JOUR T1 - ECoG high gamma activity reveals distinct cortical representations of lyrics passages, harmonic and timbre-related changes in a rock song. JF - Front Hum Neurosci Y1 - 2014 A1 - Sturm, Irene A1 - Benjamin Blankertz A1 - Potes, Cristhian A1 - Gerwin Schalk A1 - Curio, Gabriel KW - acoustic features KW - electrocorticography (ECoG) KW - high gamma KW - music processing KW - natural music AB -

Listening to music moves our minds and moods, stirring interest in its neural underpinnings. A multitude of compositional features drives the appeal of natural music. How such original music, where a composer's opus is not manipulated for experimental purposes, engages a listener's brain has not been studied until recently. Here, we report an in-depth analysis of two electrocorticographic (ECoG) data sets obtained over the left hemisphere in ten patients during presentation of either a rock song or a read-out narrative. First, the time courses of five acoustic features (intensity, presence/absence of vocals with lyrics, spectral centroid, harmonic change, and pulse clarity) were extracted from the audio tracks and found to be correlated with each other to varying degrees. In a second step, we uncovered the specific impact of each musical feature on ECoG high-gamma power (70-170 Hz) by calculating partial correlations to remove the influence of the other four features. In the music condition, the onset and offset of vocal lyrics in ongoing instrumental music was consistently identified within the group as the dominant driver for ECoG high-gamma power changes over temporal auditory areas, while concurrently subject-individual activation spots were identified for sound intensity, timbral, and harmonic features. The distinct cortical activations to vocal speech-related content embedded in instrumental music directly demonstrate that song integrated in instrumental music represents a distinct dimension in complex music. In contrast, in the speech condition, the full sound envelope was reflected in the high gamma response rather than the onset or offset of the vocal lyrics. This demonstrates how the contributions of stimulus features that modulate the brain response differ across the two examples of a full-length natural stimulus, which suggests a context-dependent feature selection in the processing of complex auditory stimuli.

VL - 8 UR - http://www.ncbi.nlm.nih.gov/pubmed/25352799 ER - TY - JOUR T1 - Spatial and temporal relationships of electrocorticographic alpha and gamma activity during auditory processing. JF - NeuroImage Y1 - 2014 A1 - Potes, Cristhian A1 - Peter Brunner A1 - Gunduz, Aysegul A1 - Robert T. Knight A1 - Gerwin Schalk KW - alpha and high gamma activity KW - auditory processing KW - electrocorticography (ECoG) KW - functional connectivity KW - granger causality KW - thalamo-cortical interactions AB - Neuroimaging approaches have implicated multiple brain sites in musical perception, including the posterior part of the superior temporal gyrus and adjacent perisylvian areas. However, the detailed spatial and temporal relationship of neural signals that support auditory processing is largely unknown. In this study, we applied a novel inter-subject analysis approach to electrophysiological signals recorded from the surface of the brain (electrocorticography (ECoG)) in ten human subjects. This approach allowed us to reliably identify those ECoG features that were related to the processing of a complex auditory stimulus (i.e., continuous piece of music) and to investigate their spatial, temporal, and causal relationships. Our results identified stimulus-related modulations in the alpha (8-12 Hz) and high gamma (70-110 Hz) bands at neuroanatomical locations implicated in auditory processing. Specifically, we identified stimulus-related ECoG modulations in the alpha band in areas adjacent to primary auditory cortex, which are known to receive afferent auditory projections from the thalamus (80 of a total of 15,107 tested sites). In contrast, we identified stimulus-related ECoG modulations in the high gamma band not only in areas close to primary auditory cortex but also in other perisylvian areas known to be involved in higher-order auditory processing, and in superior premotor cortex (412/15,107 sites). Across all implicated areas, modulations in the high gamma band preceded those in the alpha band by 280 ms, and activity in the high gamma band causally predicted alpha activity, but not vice versa (Granger causality, p<1e(-8)). Additionally, detailed analyses using Granger causality identified causal relationships of high gamma activity between distinct locations in early auditory pathways within superior temporal gyrus (STG) and posterior STG, between posterior STG and inferior frontal cortex, and between STG and premotor cortex. Evidence suggests that these relationships reflect direct cortico-cortical connections rather than common driving input from subcortical structures such as the thalamus. In summary, our inter-subject analyses defined the spatial and temporal relationships between music-related brain activity in the alpha and high gamma bands. They provide experimental evidence supporting current theories about the putative mechanisms of alpha and gamma activity, i.e., reflections of thalamo-cortical interactions and local cortical neural activity, respectively, and the results are also in agreement with existing functional models of auditory processing. VL - 97 UR - http://www.ncbi.nlm.nih.gov/pubmed/24768933 ER - TY - Generic T1 - cortiQ – Clinical Software for Electrocorticographic Real-Time Functional Mapping of the Eloquent Cortex T2 - 35th Annual International IEEE EMBS Conference (EMBC) Y1 - 2013 A1 - Prueckl, R. A1 - Kapeller, C A1 - Potes, Cristhian A1 - Korostenskaja, M A1 - Gerwin Schalk A1 - Lee, K.H. A1 - Guger, C JF - 35th Annual International IEEE EMBS Conference (EMBC) ER - TY - JOUR T1 - CortiQ - clinical software for electrocorticographic real-time functional mapping of the eloquent cortex. JF - Conf Proc IEEE Eng Med Biol Soc Y1 - 2013 A1 - Prueckl, Robert A1 - Kapeller, Christoph A1 - Potes, Cristhian A1 - Korostenskaja, Milena A1 - Gerwin Schalk A1 - Lee, Ki H A1 - Guger, Christoph AB - Planning for epilepsy surgery depends substantially on the localization of brain cortical areas responsible for sensory, motor, or cognitive functions, clinically also known as eloquent cortex. In this paper, we present the novel software package 'cortiQ' that allows clinicians to localize eloquent cortex, thus providing a safe margin for surgical resection with a low incidence of neurological deficits. This software can be easily used in addition to traditional mapping procedures such as the electrical cortical stimulation (ECS) mapping. The software analyses task-related changes in gamma activity recorded from implanted subdural electrocorticography electrodes using extensions to previously published methods. In this manuscript, we describe the system's architecture and workflow required to obtain a map of the eloquent cortex. We validate the system by comparing our mapping results with those acquired using ECS mapping in two subjects. Our results indicate that cortiQ reliably identifies eloquent cortex much faster (several minutes compared to an hour or more) than ECS mapping. Next-neighbour analyses show that there are no false positives and an average of 1.24% false negatives. VL - 2013 UR - http://www.ncbi.nlm.nih.gov/pubmed/24111197 ER - TY - JOUR T1 - Dynamics of electrocorticographic (ECoG) activity in human temporal and frontal cortical areas during music listening. JF - Neuroimage Y1 - 2012 A1 - Potes, Cristhian A1 - Gunduz, Aysegul A1 - Peter Brunner A1 - Gerwin Schalk KW - auditory processing KW - electrocorticography (ECoG) KW - high gamma activity KW - sound intensity AB -

Previous studies demonstrated that brain signals encode information about specific features of simple auditory stimuli or of general aspects of natural auditory stimuli. How brain signals represent the time course of specific features in natural auditory stimuli is not well understood. In this study, we show in eight human subjects that signals recorded from the surface of the brain (electrocorticography (ECoG)) encode information about the sound intensity of music. ECoG activity in the high gamma band recorded from the posterior part of the superior temporal gyrus as well as from an isolated area in the precentral gyrus was observed to be highly correlated with the sound intensity of music. These results not only confirm the role of auditory cortices in auditory processing but also point to an important role of premotor and motor cortices. They also encourage the use of ECoG activity to study more complex acoustic features of simple or natural auditory stimuli.

VL - 61 UR - http://www.ncbi.nlm.nih.gov/pubmed/22537600 IS - 4 ER - TY - Generic T1 - Assessment of Human Muscle Fatigue from Surface EMG Signals Recorded during Isometric Voluntary Contractions T2 - Twenty-Fifth Southern Biomedical Engineering Conference Y1 - 2009 A1 - Potes, Cristhian JF - Twenty-Fifth Southern Biomedical Engineering Conference ER - TY - JOUR T1 - Compressive Sensing Reconstruction with Prior Information by Iteratively reweighted Least-Squares. JF - Signal Processing, IEEE Transactions on Y1 - 2009 A1 - Miosso C. J. A1 - von Borries R. A1 - Argaez M. A1 - Velazquez L. A1 - Quintero C. A1 - Potes, Cristhian AB - Iteratively reweighted least-squares (IRLS) algorithms have been successfully used in compressive sensing to reconstruct sparse signals from incomplete linear measurements taken in nonsparse domains. The underlying optimization problem corresponds to finding the vector that solves the lp minimization while explaining the measurements, and IRLS allows to easily control the used value of p, with effect on the number of required measurements. In this paper, we propose a weighting strategy in the reconstruction method based on IRLS in order to add prior information on the support of the sparse domain. Our simulation results show that the use of prior knowledge about positions of at least some of the nonzero coefficients in the sparse domain leads to a reduction in the number of linear measurements required for unambiguous reconstruction. This reduction occurs for all values of p , so that a further reduction can be achieved by decreasing p and using prior information. The proposed weighting scheme also reduces the computational complexity with respect to the IRLS with no prior information, both in terms of number of iterations and computation time. VL - 57 UR - http://ieeexplore.ieee.org/xpl/freeabs_all.jsp?arnumber=4799125&abstractAccess=no&userType=inst IS - 6 ER - TY - Generic T1 - Assessment of Muscle Fatigue from TF Distributions of SEMG Signals T2 - Twenty-Fourth Southern Biomedical Engineering Conference Y1 - 2008 A1 - Potes, Cristhian A1 - von Borries R. A1 - Miosso C. J. A1 - Pierluissi J. H. JF - Twenty-Fourth Southern Biomedical Engineering Conference ER - TY - Generic T1 - Compressed Sensing Using Prior Information T2 - The Second International Workshop on Computational Advances in MultiSensor Adaptive Processing Y1 - 2007 A1 - von Borries R. A1 - Miosso C. J. A1 - Potes, Cristhian JF - The Second International Workshop on Computational Advances in MultiSensor Adaptive Processing ER - TY - Generic T1 - Directional Filter Banks for Wavelet Decomposition of Images Based on the Radon Transform T2 - Forty-First Asilomar Conference on Signals, Systems and Computers Y1 - 2007 A1 - von Borries R. A1 - Miosso C. J. A1 - Potes, Cristhian JF - Forty-First Asilomar Conference on Signals, Systems and Computers ER -