Biomedical subjects

Elena Dominguez-Marin

Publications and source records attributed to Elena Dominguez-Marin.

4 recordsLinked to original sources

PubMed2003

Effects of temporal encoding on auditory object formation: a mismatch negativity study.

Analysis of auditory scene relies on the appropriate division of the sensory input into meaningful events. The auditory system uses a sequential grouping strategy to segregate different acoustic events in the time domain. As a result of grouping, the organization of sound is expected to include acoustic events spanning different scales of time. It is unclear, however, at which moment the central auditory system begins to introduce changes in the neural representation of the auditory scene as a result of grouping different information units into a larger acoustic event. The present set of experiments examines this issue by using the mismatch negativity (MMN) component of event-related potentials. The MMN is elicited in response to changes in the previously registered auditory regularity whether or not the subject's attention is focused on the auditory stimuli. By presenting three consecutive pairs of alternating tones in serial stimulus trains, we found that across-train repetitions of the tone elicited the MMN with inter-train intervals up to 240 ms. Beyond this interval, only within-train repetitions of the tone elicited the MMN, suggesting that pairs of tones were bound together into a single acoustic event (i.e., train of six tones) within a temporal window not much longer than 240 ms. Furthermore, a different pattern of responses was seen depending on the position of the deviant event within the train and the frequency distance between the alternating tones. These results suggest that grouping discrete auditory inputs may introduce changes in the neural representation of the auditory scene by applying rules to sounds spanning larger temporal scales.

Acoustic Stimulation↗

PubMed2002

Effects of prolonged waking-auditory stimulation on electroencephalogram synchronization and cortical coherence during subsequent slow-wave sleep.

Evidence suggests that sleep homeostasis is not only dependent on duration of previous wakefulness but also on experience- and/or use-dependent processes. Such homeostatic mechanisms are reflected by selective increases in the duration of a sleep stage, modifications to electrophysiological-metabolic brain patterns in specific sleep states, and/or reactivation to neuronal ensembles in subsequent sleep periods. Use-dependent sleep changes, apparently different from those changes caused by memory consolidation processes, are thought to reflect neuronal restoration processes after the sustained exposure to stimulation during the preceding wakefulness. In the present study, we investigated changes in the brain electrical activity pattern during human sleep after 6 hr of continuous auditory stimulation during previous wakefulness. Poststimulation nights showed a widespread increase of spectral power within the alpha (8-12 Hz) and sleep spindle (12-15 Hz) frequency range during slow-wave sleep (SWS) compared with the baseline night. This effect was mainly attributable to an enhanced EEG amplitude rather than an increase of oscillations, except for temporal (within alpha and sleep spindles) and parietal regions (within sleep spindles) in which both parameters contributed equally to the increase of spectral energy. Power increments were accompanied by a strengthening of the coherence between fronto-temporal cortical regions within a broad frequency range during SWS but to the detriment of the coherence between temporal and parieto-occipital areas, suggesting underlying compensatory mechanisms between temporal and other cortical regions. In both cases, coherence was built up progressively across the night, although no changes were observed within each SWS period. No electrophysiological changes were found in rapid eye movement sleep. These results point to SWS as a critical brain period for correcting the cortical synaptic imbalance produced by the predominant use of specific neuronal populations during the preceding wakefulness, as well as for synaptic reorganization after prolonged exposure to a novel sensory experience.

Acoustic Stimulation↗

PubMed2002

Mismatch negativity (MMN): an objective measure of sensory memory and long-lasting memories during sleep.

Sleep, unlike wakefulness, facilitates the internal stimulus generation and hinders the processing of external stimulation. Nevertheless, evidence yielded by physiological studies in animals and event-related potential (ERP) studies in humans suggest that basic functions of the central auditory system are still preserved during sleep. This review is focused on the automatic change-detection function of the auditory system as revealed by a negative ERP component called mismatch negativity (MMN). MMN mainly originates in the auditory cortex, although it also receives an important contribution from subcortical areas (especially at thalamic level), as well as frontal areas. We discuss recent experiments supporting the use of MMN as an objective measure of sensory memory and long-lasting memories not only during wakefulness, but also during sleep. The outcome of the activation of MMN generating system during sleep highly differs from that in waking, especially when there is no previous information about the stimulus sequence in the neuronal network as a result of learning. We discuss these differences in MMN generation in terms of a dynamicist view of the brain that emphasizes the importance of the integration between bottom-up and top-down influences on sensory processing, independently of the processing level in the auditory hierarchy.

Acoustic Stimulation↗

PubMedDate not supplied

The time course of neural changes underlying auditory perceptual learning.

Improvement in perception takes place within the training session and from one session to the next. The present study aims at determining the time course of perceptual learning as revealed by changes in auditory event-related potentials (ERPs) reflecting preattentive processes. Subjects were trained to discriminate two complex auditory patterns in a single session. ERPs were recorded just before and after training, while subjects read a book and ignored stimulation. ERPs showed a negative wave called mismatch negativity (MMN)-which indexes automatic detection of a change in a homogeneous auditory sequence-just after subjects learned to consciously discriminate the two patterns. ERPs were recorded again 12, 24, 36, and 48 h later, just before testing performance on the discrimination task. Additional behavioral and neurophysiological changes were found several hours after the training session: an enhanced P2 at 24 h followed by shorter reaction times, and an enhanced MMN at 36 h. These results indicate that gains in performance on the discrimination of two complex auditory patterns are accompanied by different learning-dependent neurophysiological events evolving within different time frames, supporting the hypothesis that fast and slow neural changes underlie the acquisition of improved perception.

Adolescent↗