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(Created page with "== Methods== === Data acquisition=== Twenty-eight healthy subjects were recruited from The Brain and Mind Institute at the University of Western Ontario, Canada to participate in this study. Informed written consent was acquired prior to testing from all participants. Ethics approval for this study was granted by the Health Sciences Research Ethics Board and the Non-Medical Research Ethics Board of The University of Western Ontario and all research was performed in acco...")
 
 
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== Methods==
== Métodos==


=== Data acquisition===
=== Adquisición de datos===
Twenty-eight healthy subjects were recruited from The Brain and Mind Institute at the University of Western Ontario, Canada to participate in this study. Informed written consent was acquired prior to testing from all participants. Ethics approval for this study was granted by the Health Sciences Research Ethics Board and the Non-Medical Research Ethics Board of The University of Western Ontario and all research was performed in accordance with the relevant guidelines/regulations and in accordance with the Declaration of Helsinki.
Veintiocho sujetos sanos fueron reclutados del Brain and Mind Institute de la Universidad de Western Ontario, Canadá, para participar en este estudio. El consentimiento informado por escrito se obtuvo antes de la prueba de todos los participantes. La aprobación ética para este estudio fue otorgada por la Junta de Ética de Investigación en Ciencias de la Salud y la Junta de Ética de Investigación No Médica de la Universidad de Western Ontario y toda la investigación se realizó de acuerdo con las pautas/regulaciones relevantes y de acuerdo con la Declaración de Helsinki.


Two suspenseful movie clips were used as the naturalistic stimuli in this study. A video clip from the silent film “Bang! You’re Dead” and an audio excerpt from the movie “Taken” were shown to 13 and 15 subjects respectively in both their original intact and scrambled forms. Prior to the two acquisitions, a section of rest was acquired where the subjects were asked to relax, without any overt stimulation. Stimulus presentation was controlled with the Psychtoolbox plugin for MATLAB <ref>Brainard DH. The psychophysics toolbox. Spat. Vis. 1997;10:433–436. doi: 10.1163/156856897X00357. [PubMed] [CrossRef] [Google Scholar]</ref><ref>Kleiner M, et al. What’s new in psychtoolbox-3. Perception. 2007;36:1–16. [Google Scholar]</ref><ref>Pelli DG. The VideoToolbox software for visual psychophysics: Transforming numbers into movies. Spat. Vis. 1997;10:437–442. doi: 10.1163/156856897X00366. [PubMed] [CrossRef] [Google Scholar]</ref> on a 15″ Apple MacBook Pro. Audio were presented binaurally at a comfortable listening volume through Etymotics ER-1 headphones.
Dos clips de película sospechosos se utilizaron como estímulos naturalistas en este estudio. Un videoclip de la película muda “Bang! You're Dead” y un extracto de audio de la película “Taken” se mostraron a 13 y 15 sujetos respectivamente en su forma original intacta y codificada. Antes de las dos adquisiciones, se adquirió una sección de descanso donde se pidió a los sujetos que se relajaran, sin ningún tipo de estimulación abierta. La presentación de estímulos se controló con el complemento Psychtoolbox para MATLAB<ref>Brainard DH. The psychophysics toolbox. Spat. Vis. 1997;10:433–436. doi: 10.1163/156856897X00357. [PubMed] [CrossRef] [Google Scholar]</ref> <ref>Kleiner M, et al. What’s new in psychtoolbox-3. Perception. 2007;36:1–16. [Google Scholar]</ref><ref>Pelli DG. The VideoToolbox software for visual psychophysics: Transforming numbers into movies. Spat. Vis. 1997;10:437–442. doi: 10.1163/156856897X00366. [PubMed] [CrossRef] [Google Scholar]</ref> en una Apple MacBook Pro de 15″. El audio se presentó de forma binaural a un volumen de escucha cómodo a través de los auriculares Etymotics ER-1.


EEG data were collected using a 129-channel cap (Electrical Geodesics Inc. [EGI], Oregon, USA). Electrode impedances were kept below 50 kΩ with signals sampled at 250 Hz and referenced to the central vertex (Cz). Using the EEGLAB MATLAB toolbox<ref>Makeig, S. & Onton, J. ERP features and EEG dynamics: An ICA perspective. In ''The Oxford Handbook of Event-Related Potential Components'' (Oxford University Press, 2012). 10.1093/oxfordhb/9780195374148.013.0035.</ref>, noisy channels were identified and removed, then interpolated back into the data. A Kolmogorov–Smirnov (KS) test on the data was used to identify regions that were not Gaussian. Independent components analysis (ICA) was then used to visually identify patterns of neural activity characteristic of eye and muscle movements which were subsequently removed from the data. EEG pre-processing was performed individually for each subject and condition.
Los datos de EEG se recopilaron utilizando una tapa de 129 canales (Electrical Geodesics Inc. [EGI], Oregón, EE. UU.). Las impedancias de los electrodos se mantuvieron por debajo de 50 kΩ con señales muestreadas a 250 Hz y referenciadas al vértice central (Cz). Usando la caja de herramientas de EEGLAB MATLAB,<ref>Makeig, S. & Onton, J. ERP features and EEG dynamics: An ICA perspective. In ''The Oxford Handbook of Event-Related Potential Components'' (Oxford University Press, 2012). 10.1093/oxfordhb/9780195374148.013.0035.</ref> se identificaron y eliminaron 00 canales ruidosos, y luego se interpolaron nuevamente en los datos. Se utilizó una prueba de Kolmogorov-Smirnov (KS) sobre los datos para identificar regiones que no eran gaussianas. A continuación, se utilizó el análisis de componentes independientes (ICA) para identificar visualmente patrones de actividad neuronal característicos de los movimientos oculares y musculares que posteriormente se eliminaron de los datos. El preprocesamiento de EEG se realizó individualmente para cada sujeto y condición.


Of the two movie clips tested, the first was an 8-min segment from Alfred Hitchcock’s TV silent movie “Bang! You’re Dead”. This scene portrays a 5-year-old boy who picks up his uncle’s revolver. The boy loads a bullet into the gun and plays with it as if it were a toy. The boy (and viewer) rarely knows whether the gun has a bullet in its chamber and suspense builds as the boy spins the chamber, points it at others, and pulls the trigger. As an alternative to visual stimulation, a 5-min audio excerpt from the movie “Taken” was also used. This clip portrays a phone conversation in which a father overhears his daughters’ kidnapping.
De los dos clips de película probados, el primero era un segmento de 8 minutos de la película muda para televisión de Alfred Hitchcock “Bang! Estas muerto". Esta escena retrata a un niño de 5 años que toma el revólver de su tío. El niño carga una bala en el arma y juega con ella como si fuera un juguete. El niño (y el espectador) rara vez sabe si el arma tiene una bala en su recámara y el suspenso aumenta a medida que el niño hace girar la recámara, apunta a los demás y aprieta el gatillo. Como alternativa a la estimulación visual, también se utilizó un extracto de audio de 5 minutos de la película “Taken”. Este clip retrata una conversación telefónica en la que un padre escucha el secuestro de sus hijas.


Furthermore, two “scrambled” control stimuli were used—one for each movie. This separates the neural responses elicited by the sensory properties of watching or listening to the movies from those involved in following the plot. The scrambled version of “Bang! You’re Dead” was generated by isolating 1 s segments and pseudorandomly shuffling the segments, thereby eliminating the temporal coherence of the narrative<ref name=":0" /> <ref name=":6">Laforge G, Gonzalez-Lara LE, Owen AM, Stojanoski B. Individualized assessment of residual cognition in patients with disorders of consciousness. NeuroImage Clin. 2020;28:102472. doi: 10.1016/j.nicl.2020.102472. [PMC free article] [PubMed] [CrossRef] [Google Scholar]</ref>. The scrambled version of “Taken” was created by spectrally rotating the audio, thus rendering the speech indecipherable<ref name=":6" /><ref>Naci L, Sinai L, Owen AM. Detecting and interpreting conscious experiences in behaviorally non-responsive patients. Neuroimage. 2017;145:304–313. doi: 10.1016/j.neuroimage.2015.11.059.[PubMed] [CrossRef] [Google Scholar]</ref>. The scrambled movie clips were presented before the intact versions to prevent potential carry-over effects of the narrative. Prior to subjects watching/listening to the scrambled stimulus a short segment of resting EEG was acquired.
Además, se utilizaron dos estímulos de control "codificados", uno para cada película. Esto separa las respuestas neuronales provocadas por las propiedades sensoriales de ver o escuchar películas de aquellas involucradas en seguir la trama. La versión codificada de “Bang! Estás muerto” se generó aislando segmentos de 1 s y barajando pseudoaleatoriamente los segmentos, eliminando así la coherencia temporal de la narrativa .<ref name=":0" /><ref name=":6">Laforge G, Gonzalez-Lara LE, Owen AM, Stojanoski B. Individualized assessment of residual cognition in patients with disorders of consciousness. NeuroImage Clin. 2020;28:102472. doi: 10.1016/j.nicl.2020.102472. [PMC free article] [PubMed] [CrossRef] [Google Scholar]</ref>
 
La versión codificada de “Taken” se creó girando espectralmente el audio, lo que hace que el discurso sea indescifrable.<ref name=":6" /><ref>Naci L, Sinai L, Owen AM. Detecting and interpreting conscious experiences in behaviorally non-responsive patients. Neuroimage. 2017;145:304–313. doi: 10.1016/j.neuroimage.2015.11.059.[PubMed] [CrossRef] [Google Scholar]</ref>
 
Los clips de película codificados se presentaron antes que las versiones intactas para evitar posibles efectos de arrastre de la narrativa. Antes de que los sujetos observaran/escucharan el estímulo codificado, se adquirió un breve segmento de EEG en reposo.
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