Search results for "ECoG"
showing 10 items of 3774 documents
Surrogate data approaches to assess the significance of directed coherence: Application to EEG activity propagation
2009
This paper addresses the topic of evaluating the significance of frequency domain measures of causal coupling in multivariate time series through generation of surrogate data. The considered approaches are the traditional Fourier Transform (FT) algorithm and a new causal FT (CFT) algorithm for surrogate data generation. Both algorithms preserve the FT modulus of the original series; differences are in the phase relationships, that are completely destroyed for FT surrogates and imposed after switching off the link over the considered causal direction for CFT surrogates. The ability of the algorithms to assess causality in the frequency domain was tested using the directed coherence as discri…
Context, remember–know recognition judgements, and ROC parameters
2007
Recent work (e.g., Dunn, 2004; Heathcote, 2003) has questioned the necessity of postulating two processes to explain recognition memory. As part of this trend, strength theories of the remember-know methodology have gained in support. We present three experiments with pictorial material in which we force participants to use differential contextual information at test. Participants were required to give remember-know judgements and confidence ratings for each test stimulus. Hits, false alarms, remember-know data, and discrimination indices indicated systematic variations as a function of the availability and use of contextual information. Moreover, when we normalised the receiver operating c…
Blocking by word frequency and neighborhood density in visual word recognition: A task-specific response criteria account
2004
International audience; Effects of blocking words by frequency class (high vs. low) and neighborhood density (high vs. low) were examined in two experiments using progressive demasking and lexical decision tasks. The aim was to examine the predictions of a task-specific response criteria account of list-blocking effects. Distinct patterns of blocking effects were obtained in the two tasks. In the progressive demasking task, a pure-list disadvantage was obtained to low frequency-high density words, whereas high frequency-low density produced a trend toward a pure-list advantage. In lexical decision, high-frequency words showed a pure-list advantage that was strongest in high-density words, w…
Phase information of time-frequency transforms as a key feature for classification of atrial fibrillation episodes
2015
[EN] Patients suffering from atrial fibrillation can be classified into different subtypes, according to the temporal pattern of the arrhythmia and its recurrence. Nowadays, clinicians cannot differentiate a priori between the different subtypes, and patient classification is done afterwards, when its clinical course is available. In this paper we present a comparison of classification performances when differentiating paroxysmal and persistent atrial fibrillation episodes by means of support vector machines. We analyze short surface electrocardiogram recordings by extracting modulus and phase features from several time-frequency transforms: short-time Fourier transform, Wigner-Ville, Choi-…
Does Bold Emphasis Facilitate the Process of Visual-Word Recognition?
2014
AbstractThe study of the effects of typographical factors on lexical access has been rather neglected in the literature on visual-word recognition. Indeed, current computational models of visual-word recognition employ an unrefined letter feature level in their coding schemes. In a letter recognition experiment, Pelli, Burns, Farell, and Moore-Page (2006), letters in Bookman boldface produced more efficiency (i.e., a higher ratio of thresholds of an ideal observer versus a human observer) than the letters in Bookman regular under visual noise. Here we examined whether the effect of bold emphasis can be generalized to a common visual-word recognition task (lexical decision: “is the item a wo…
Simulating Images Seen by Patients with Inhomogeneous Sensitivity Losses
2012
PURPOSE We aim to simulate how colored images are perceived by subjects with local achromatic and chromatic contrast sensitivity losses in the visual field (VF). METHODS The spatiochromatic corresponding pair algorithm, introduced in a previous article (J Opt Soc Am (A) 2004;21:176-186), has been implemented with a linear model of the visual system. Spatial information is processed separately by the chromatic and achromatic mechanisms by means of a multiscale model, with sensors selective to frequency, orientation, and spatial position, whose mechanism-dependent relative weights change with the spatial location of the image. These weights have been obtained from perimetric data from a patie…
Neural specialization to human faces at the age of 7 months.
2021
AbstractSensitivity to human faces has been suggested to be an early emerging capacity that promotes social interaction. However, the developmental processes that lead to cortical specialization to faces has remained unclear. The current study investigated both cortical sensitivity and categorical specificity through event-related potentials (ERPs) previously implicated in face processing in 7-month-old infants (N290) and adults (N170). Using a category-specific repetition/adaptation paradigm, cortical specificity to human faces, or control stimuli (cat faces), was operationalized as changes in ERP amplitude between conditions where a face probe was alternated with categorically similar or …
Alexithymia and facial emotion recognition in patients with eating disorders
2006
Objective: Patients with anorexia or bulimia nervosa are reported to show high levels of alexithymia and to have difficulties recognizing facially displayed emotions. The current study tested whether it could be that facial emotion recognition is a basic skill that is independent from alexithymia. Method: We assessed emotion recognition skills and alexithymia in a group of 79 female inpatients with eating disorders and compared them with a group of 78 healthy female controls. Instruments used were the Toronto Alexithymia Scale, the Facially Expressed Emotion Labeling (FEEL) test, and the revised Symptom Check List (SCL-90-R). Results: There were no significant differences between patients a…
Attributional style in a case of Cotard delusion.
2007
Young and colleagues (e.g. Young, A. W., & Leafhead, K. M. (1996). Betwixt life and death: case studies of the Cotard delusion. In P. W. Halligan & J. C. Marshall (Eds.), Method in madness: Case studies in cognitive neuropsychiatry. Mahway, NJ: Lawrence Erlbaum Associates.) have suggested that cases of the Cotard delusion (the belief that one is dead) result when a particular perceptual anomaly (caused by a disruption to the affective component of visual recognition) occurs in the context of an internalising attributional style. This hypothesis has not previously been tested directly. We report here an investigation of attributional style in a 24-year-old woman with Cotard delusion ("LU"). …
Effects of panel experience on olfactory memory performance: influence of stimuly familiarity and labeling ability of subjects
1996
This work attempted to define the impact of panel experience on olfactory memory performance by comparing scores in an odor recognition task obtained from a highly trained descriptive panel (17 subjects) and a naive one (33 subjects with no experience in sensory analysis). During the inspection phase, 16 odorants were presented monadically to subjects for familiarity rating and a written description. The recognition session was planned 7 days later with 32 odorants (including the 16 of the target set). Subjects also described the odor of the stimuli. The memory performance of each panel was estimated by the mean value of individual d' (index of detectability). Training of the descriptive pa…