"...and were instructed to read a self-selected book while ignoring the auditory stiimuli": The effects of task demands on the mismatch negativity
ABSTRACT The Mismatch Negativity (MMN) is commonly recorded while the subject is reading, and instructed to ignore the auditory stimuli. It is generally assumed that the demands of the diversion task will have no effect on the MMN. Several studies, however, have reported that a diversion task presumably requiring strong attentional focus is associated with a smaller MMN than that elicited during a less demanding task. This study examines the effect of variations in the classical reading paradigm on the MMN.
In Experiment 1, event-related potentials (ERP) were recorded while subjects were presented with standard (80 dB SPL 1000 Hz) and frequency deviant (1050 Hz) stimuli. Subjects were instructed to ignore the tone pips and, in separate conditions, engage in different tasks. They were asked to read a text or to sit passively. Subjects were informed that they would subsequently be queried or not about the content of the reading. In Experiment 2, the auditory sequence included the same standard (80 dB SPL 1000 Hz) but the deviant was changed to an intensity decrement (70 dB SPL). A different sample of subjects was again asked to ignore the auditory stimuli and engage in different reading tasks that would or not be followed by query.
In all task conditions, MMN was elicited by the frequency and intensity change. The intensity MMN did not significantly vary with task. A significant effect of task was, however, found for the frequency MMN. Its amplitude was largest when subjects were later queried about their reading.
This finding is counter-intuitive in light of previous research on the attentional modulation of the MMN. The pattern of frequency MMN results may relate to the differences in cortical excitability across tasks.
The present results indicate that the nature of the diversion task may affect the MMN. The choice of diversion task during MMN recording should thus be carefully considered.
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ABSTRACT: Sounds emitted by different sources arrive at our ears as a mixture that must be disentangled before meaningful information can be retrieved. It is still a matter of debate whether this decomposition happens automatically or requires the listener's attention. These opposite positions partly stem from different methodological approaches to the problem. We propose an integrative approach that combines the logic of previous measurements targeting either auditory stream segregation (interpreting a mixture as coming from two separate sources) or integration (interpreting a mixture as originating from only one source). By means of combined behavioral and event-related potential (ERP) measures, our paradigm has the potential to measure stream segregation and integration at the same time, providing the opportunity to obtain positive evidence of either one. This reduces the reliance on zero findings (i.e., the occurrence of stream integration in a given condition can be demonstrated directly, rather than indirectly based on the absence of empirical evidence for stream segregation, and vice versa). With this two-way approach, we systematically manipulate attention devoted to the auditory stimuli (by varying their task relevance) and to their underlying structure (by delivering perceptual tasks that require segregated or integrated percepts). ERP results based on the mismatch negativity (MMN) show no evidence for a modulation of stream integration by attention, while stream segregation results were less clear due to overlapping attention-related components in the MMN latency range. We suggest future studies combining the proposed two-way approach with some improvements in the ERP measurement of sequential stream segregation.Psychological Research 02/2014; 78(3). DOI:10.1007/s00426-014-0547-7 · 2.47 Impact Factor
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ABSTRACT: Despite the recognition that the surface Laplacian may counteract adverse effects of volume conduction and recording reference for surface potential data, electrophysiology as a discipline has been reluctant to embrace this approach for data analysis. The reasons for such hesitation are manifold but often involve unfamiliarity with the nature of the underlying transformation, as well as intimidation by a perceived mathematical complexity, and concerns of signal loss, dense electrode array requirements, or susceptibility to noise. We revisit the pitfalls arising from volume conduction and the mandated arbitrary choice of EEG reference, describe the basic principle of the surface Laplacian transform in an intuitive fashion, and exemplify the differences between common reference schemes (nose, linked mastoids, average) and the surface Laplacian for frequently-measured EEG spectra (theta, alpha) and standard event-related potential (ERP) components, such as N1 or P3. We specifically review common reservations against the universal use of the surface Laplacian, which can be effectively addressed by employing spherical spline interpolations with an appropriate selection of the spline flexibility parameter and regularization constant. We argue from a pragmatic perspective that not only are these reservations unfounded but that the continued predominant use of surface potentials poses a considerable impediment on the progress of EEG and ERP research. Copyright © 2015 Elsevier B.V. All rights reserved.International journal of psychophysiology: official journal of the International Organization of Psychophysiology 04/2015; DOI:10.1016/j.ijpsycho.2015.04.012 · 2.65 Impact Factor
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ABSTRACT: Event-related potentials (ERPs) have been proven to be a useful tool to complement clinical assessment and to detect residual cognitive functions in patients with disorders of consciousness. These ERPs are often recorded using passive or unspecific instructions. Patient data obtained this way are then compared to data from healthy participants, which are usually recorded using active instructions. The present study investigates the effect of attentive modulations and particularly the effect of active vs. passive instruction on the ERP components mismatch negativity (MMN) and N400. A sample of 18 healthy participants listened to three auditory paradigms: an oddball, a word priming, and a sentence paradigm. Each paradigm was presented three times with different instructions: ignoring auditory stimuli, passive listening, and focused attention on the auditory stimuli. After each task, the participants indicated their subjective effort. The N400 decreased from the focused task to the passive task, and was extinct in the ignore task. The MMN exhibited higher amplitudes in the focused and passive task compared to the ignore task. The data indicate an effect of attention on the supratemporal component of the MMN. Subjective effort was equally high in the passive and focused tasks but reduced in the ignore task. We conclude that passive listening during EEG recording is stressful and attenuates ERPs, which renders the interpretation of the results obtained in such conditions difficult.Frontiers in Human Neuroscience 08/2014; 8:654. DOI:10.3389/fnhum.2014.00654 · 2.90 Impact Factor