@article {3406, title = {ECoG high gamma activity reveals distinct cortical representations of lyrics passages, harmonic and timbre-related changes in a rock song.}, journal = {Front Hum Neurosci}, volume = {8}, year = {2014}, month = {10/2014}, pages = {798}, abstract = {

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{\textquoteright}s opus is not manipulated for experimental purposes, engages a listener{\textquoteright}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.

}, keywords = {acoustic features, electrocorticography (ECoG), high gamma, music processing, natural music}, issn = {1662-5161}, doi = {10.3389/fnhum.2014.00798}, url = {http://www.ncbi.nlm.nih.gov/pubmed/25352799}, author = {Sturm, Irene and Benjamin Blankertz and Potes, Cristhian and Gerwin Schalk and Curio, Gabriel} } @article {2950, title = {Spatial and temporal relationships of electrocorticographic alpha and gamma activity during auditory processing.}, journal = {NeuroImage}, volume = {97}, year = {2014}, month = {08/2014}, pages = {188-95}, abstract = {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.}, keywords = {alpha and high gamma activity, auditory processing, electrocorticography (ECoG), functional connectivity, granger causality, thalamo-cortical interactions}, doi = {10.1016/j.neuroimage.2014.04.045}, url = {http://www.ncbi.nlm.nih.gov/pubmed/24768933}, author = {Potes, Cristhian and Peter Brunner and Gunduz, Aysegul and Robert T. Knight and Gerwin Schalk} } @article {3408, title = {CortiQ - clinical software for electrocorticographic real-time functional mapping of the eloquent cortex.}, journal = {Conf Proc IEEE Eng Med Biol Soc}, volume = {2013}, year = {2013}, month = {07/2013}, pages = {6365-8}, abstract = {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 {\textquoteright}cortiQ{\textquoteright} 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{\textquoteright}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.}, issn = {1557-170X}, doi = {10.1109/EMBC.2013.6611010}, url = {http://www.ncbi.nlm.nih.gov/pubmed/24111197}, author = {Prueckl, Robert and Kapeller, Christoph and Potes, Cristhian and Korostenskaja, Milena and Gerwin Schalk and Lee, Ki H and Guger, Christoph} } @proceedings {2955, title = {cortiQ {\textendash} Clinical Software for Electrocorticographic Real-Time Functional Mapping of the Eloquent Cortex}, year = {2013}, author = {Prueckl, R. and Kapeller, C and Potes, Cristhian and Korostenskaja, M and Gerwin Schalk and Lee, K.H. and Guger, C} } @article {2103, title = {Dynamics of electrocorticographic (ECoG) activity in human temporal and frontal cortical areas during music listening.}, journal = {Neuroimage}, volume = {61}, year = {2012}, month = {07/2012}, pages = {841-8}, abstract = {

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.

}, keywords = {auditory processing, electrocorticography (ECoG), high gamma activity, sound intensity}, issn = {1095-9572}, doi = {10.1016/j.neuroimage.2012.04.022}, url = {http://www.ncbi.nlm.nih.gov/pubmed/22537600}, author = {Potes, Cristhian and Gunduz, Aysegul and Peter Brunner and Gerwin Schalk} } @proceedings {2951, title = {Assessment of Human Muscle Fatigue from Surface EMG Signals Recorded during Isometric Voluntary Contractions}, year = {2009}, author = {Potes, Cristhian} } @article {2949, title = {Compressive Sensing Reconstruction with Prior Information by Iteratively reweighted Least-Squares.}, journal = {Signal Processing, IEEE Transactions on}, volume = {57}, year = {2009}, month = {03/2009}, chapter = {2424-31}, abstract = {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.}, doi = {10.1109/TSP.2009.2016889}, url = {http://ieeexplore.ieee.org/xpl/freeabs_all.jsp?arnumber=4799125\&abstractAccess=no\&userType=inst}, author = {Miosso C. J. and von Borries R. and Argaez M. and Velazquez L. and Quintero C. and Potes, Cristhian} } @proceedings {2952, title = {Assessment of Muscle Fatigue from TF Distributions of SEMG Signals}, year = {2008}, author = {Potes, Cristhian and von Borries R. and Miosso C. J. and Pierluissi J. H.} } @proceedings {2954, title = {Compressed Sensing Using Prior Information}, year = {2007}, author = {von Borries R. and Miosso C. J. and Potes, Cristhian} } @proceedings {2953, title = {Directional Filter Banks for Wavelet Decomposition of Images Based on the Radon Transform}, year = {2007}, author = {von Borries R. and Miosso C. J. and Potes, Cristhian} }