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Javier Lopez-Calderon

Bio: Javier Lopez-Calderon is an academic researcher from Autonomous University of Chile. The author has contributed to research in topics: Psychology & Medicine. The author has an hindex of 5, co-authored 9 publications receiving 1386 citations. Previous affiliations of Javier Lopez-Calderon include University of California, Davis & Nathan Kline Institute for Psychiatric Research.

Papers
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Journal ArticleDOI
TL;DR: ERPLAB adds to EEGLAB’s EEG processing functions, providing additional tools for filtering, artifact detection, re-referencing, and sorting of events, among others.
Abstract: ERPLAB Toolbox is a freely available, open-source toolbox for processing and analyzing event-related potential (ERP) data in the MATLAB environment. ERPLAB is closely integrated with EEGLAB, a popular open-source toolbox that provides many EEG preprocessing steps and an excellent user interface design. ERPLAB adds to EEGLAB’s EEG processing functions, providing additional tools for filtering, artifact detection, re-referencing, and sorting of events, among others. ERPLAB also provides robust tools for averaging EEG segments together to create averaged ERPs, for creating difference waves and other recombinations of ERP waveforms through algebraic expressions, for filtering and re-referencing the averaged ERPs, for plotting ERP waveforms and scalp maps, and for quantifying several types of amplitudes and latencies. ERPLAB’s tools can be accessed either from an easy-to-learn graphical user interface or from MATLAB scripts, and a command history function makes it easy for users with no programming experience to write scripts. Consequently, ERPLAB provides both ease of use and virtually unlimited power and flexibility, making it appropriate for the analysis of both simple and complex ERP experiments. Several forms of documentation are available, including a detailed user’s guide, a step-by-step tutorial, a scripting guide, and a set of video-based demonstrations.

1,726 citations

Journal ArticleDOI
TL;DR: Brain activity during the displacement of attention in a modified visuo-spatial orienting paradigm revealed an attention directing anterior negativity contralateral to the shift of attention and P3 and contingent negative variation waveforms that were enhanced in both shift conditions as compared to the no-shift task.
Abstract: We studied brain activity during the displacement of attention in a modified visuo-spatial orienting paradigm. Using a behaviorally relevant no-shift condition as a control, we asked whether ipsi- or contralateral parietal alpha band activity is specifically related to covert shifts of attention. Cue-related event-related potentials revealed an attention directing anterior negativity (ADAN) contralateral to the shift of attention and P3 and contingent negative variation waveforms that were enhanced in both shift conditions as compared to the no-shift task. When attention was shifted away from fixation, alpha band activity over parietal regions ipsilateral to the attended hemifield was enhanced relative to the control condition, albeit with different dynamics in the upper and lower alpha subbands. Contralateral-to-attended parietal alpha band activity was indistinguishable from the no-shift task.

37 citations

Journal ArticleDOI
TL;DR: It is found that people with schizophrenia (PSZ) were actually superior to HCS in focusing attention at the point of gaze and filtering out peripheral distractors when the task required a narrow focusing of attention.
Abstract: A recently proposed hyperfocusing hypothesis of cognitive dysfunction in schizophrenia proposes that people with schizophrenia (PSZ) tend to concentrate processing resources more narrowly but more intensely than healthy control subjects (HCS). The present study tests a key prediction of this hypothesis, namely, that PSZ will hyperfocus on information presented at the center of gaze. This should lead to greater filtering of peripheral stimuli when the task requires focusing centrally but reduced filtering of central stimuli when the task requires attending broadly in the periphery. These predictions were tested in a double oddball paradigm, in which frequent standard stimuli and rare oddball stimuli were presented at central and peripheral locations while event-related potentials were recorded. Participants were instructed to discriminate between the standard and oddball stimuli at either the central location or at the peripheral locations. PSZ and HCS showed opposite patterns of spatial bias at the level of early sensory processing, as assessed with the P1 component: PSZ exhibited stronger sensory suppression of peripheral stimuli when the task required attending narrowly to the central location, whereas HCS exhibited stronger sensory suppression of central stimuli when the task required attending broadly to the peripheral locations. Moreover, PSZ exhibited a stronger stimulus categorization response than HCS, as assessed with the P3b component, for central stimuli when the task required attending to the peripheral region. These results provide strong evidence of hyperfocusing in PSZ, which may provide a unified mechanistic account of multiple aspects of cognitive dysfunction in schizophrenia.SIGNIFICANCE STATEMENT Schizophrenia clearly involves impaired attention, but attention is complex, and delineating the precise nature of attentional dysfunction in schizophrenia has been difficult. The present study tests a new hyperfocusing hypothesis, which proposes that people with schizophrenia (PSZ) tend to concentrate processing resources more intensely but more narrowly than healthy control subjects (HCS). Using electrophysiological measures of sensory and cognitive processing, we found that PSZ were actually superior to HCS in focusing attention at the point of gaze and filtering out peripheral distractors when the task required a narrow focusing of attention. This finding of superior filtering in PSZ supports the hyperfocusing hypothesis, which may provide the mechanism underlying a broad range of cognitive impairments in schizophrenia.

32 citations

Journal ArticleDOI
TL;DR: The present work used an event-related potential (ERP) approach to reveal that the early neural signature of the spotlight of spatial attention is not sensitive to the validity of secondary feature-based expectancies.
Abstract: A well-replicated finding is that visual stimuli presented at an attended location are afforded a processing benefit in the form of speeded reaction times and increased accuracy (Mangun, ; Posner,). This effect has been described using a spotlight metaphor, in which all stimuli within the focus of spatial attention receive facilitated processing, irrespective of other stimulus parameters. However, the spotlight metaphor has been brought into question by a series of combined expectancy studies that demonstrated that the behavioral benefits of spatial attention are contingent on secondary feature-based expectancies (Kingstone,). The present work used an event-related potential (ERP) approach to reveal that the early neural signature of the spotlight of spatial attention is not sensitive to the validity of secondary feature-based expectancies.

12 citations

Journal ArticleDOI
TL;DR: Overall, these findings demonstrate objective physiological effects of tDCS at the network level that result in effective behavioral modulation when tDCS parameters are matched to network-level requirements of the underlying task.

11 citations


Cited by
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01 Jan 2016
TL;DR: This is an introduction to the event related potential technique, which can help people facing with some malicious bugs inside their laptop to read a good book with a cup of tea in the afternoon.
Abstract: Thank you for downloading an introduction to the event related potential technique. Maybe you have knowledge that, people have look hundreds times for their favorite readings like this an introduction to the event related potential technique, but end up in malicious downloads. Rather than reading a good book with a cup of tea in the afternoon, instead they are facing with some malicious bugs inside their laptop.

2,445 citations

Journal Article
TL;DR: In this article, the authors propose that the brain produces an internal representation of the world, and the activation of this internal representation is assumed to give rise to the experience of seeing, but it leaves unexplained how the existence of such a detailed internal representation might produce visual consciousness.
Abstract: Many current neurophysiological, psychophysical, and psychological approaches to vision rest on the idea that when we see, the brain produces an internal representation of the world. The activation of this internal representation is assumed to give rise to the experience of seeing. The problem with this kind of approach is that it leaves unexplained how the existence of such a detailed internal representation might produce visual consciousness. An alternative proposal is made here. We propose that seeing is a way of acting. It is a particular way of exploring the environment. Activity in internal representations does not generate the experience of seeing. The outside world serves as its own, external, representation. The experience of seeing occurs when the organism masters what we call the governing laws of sensorimotor contingency. The advantage of this approach is that it provides a natural and principled way of accounting for visual consciousness, and for the differences in the perceived quality of sensory experience in the different sensory modalities. Several lines of empirical evidence are brought forward in support of the theory, in particular: evidence from experiments in sensorimotor adaptation, visual \"filling in,\" visual stability despite eye movements, change blindness, sensory substitution, and color perception.

2,271 citations

Journal ArticleDOI
TL;DR: ERPLAB adds to EEGLAB’s EEG processing functions, providing additional tools for filtering, artifact detection, re-referencing, and sorting of events, among others.
Abstract: ERPLAB Toolbox is a freely available, open-source toolbox for processing and analyzing event-related potential (ERP) data in the MATLAB environment. ERPLAB is closely integrated with EEGLAB, a popular open-source toolbox that provides many EEG preprocessing steps and an excellent user interface design. ERPLAB adds to EEGLAB’s EEG processing functions, providing additional tools for filtering, artifact detection, re-referencing, and sorting of events, among others. ERPLAB also provides robust tools for averaging EEG segments together to create averaged ERPs, for creating difference waves and other recombinations of ERP waveforms through algebraic expressions, for filtering and re-referencing the averaged ERPs, for plotting ERP waveforms and scalp maps, and for quantifying several types of amplitudes and latencies. ERPLAB’s tools can be accessed either from an easy-to-learn graphical user interface or from MATLAB scripts, and a command history function makes it easy for users with no programming experience to write scripts. Consequently, ERPLAB provides both ease of use and virtually unlimited power and flexibility, making it appropriate for the analysis of both simple and complex ERP experiments. Several forms of documentation are available, including a detailed user’s guide, a step-by-step tutorial, a scripting guide, and a set of video-based demonstrations.

1,726 citations

01 Jan 2016
TL;DR: As you may know, people have search numerous times for their chosen novels like this statistical parametric mapping the analysis of functional brain images, but end up in malicious downloads.
Abstract: Thank you very much for reading statistical parametric mapping the analysis of functional brain images. As you may know, people have search numerous times for their chosen novels like this statistical parametric mapping the analysis of functional brain images, but end up in malicious downloads. Rather than enjoying a good book with a cup of coffee in the afternoon, instead they cope with some infectious bugs inside their desktop computer.

1,719 citations