Neuromagnetic evidence of impaired cortical auditory processing in pediatric intractable epilepsy.
ABSTRACT We aimed to determine the changes in neural correlates of auditory information processing such as auditory detection, encoding, and sensory discrimination in pediatric patients with intractable epilepsy.
In this magnetoencephalography (MEG) study, 10 patients and 10 age- and gender-matched healthy controls were investigated with the multi-feature mismatch negativity (MMN) paradigm. Latencies and amplitudes of M100, M150, M200, and MMN event-related fields were evaluated.
All event-related fields in response to standard stimuli (M100, M150 and M200) and responses to occasional five deviant sounds, deviating from the standard stimuli either in duration, frequency, intensity, location, or by including a silent gap were reduced in amplitude in epilepsy patients compared with healthy controls.
Our study suggests that auditory information processing is impaired in patients with drug-resistant epilepsy, being evident both in stimulus feature encoding (as reflected by changes of early event-related components, e.g., M100) and in cortical sound discrimination (as reflected by MMNm). The neural changes involving diminished M100 as well as MMNms for all five deviant sound types suggest wide-spread auditory information processing impairments in these patients.
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ABSTRACT: Cognition is often affected in a variety of neuropsychiatric, neurological, and neurodevelopmental disorders. The neural discriminative response, reflected in mismatch negativity (MMN) and its magnetoencephalographic equivalent (MMNm), has been used as a tool to study a variety of disorders involving auditory cognition. MMN/MMNm is an involuntary brain response to auditory change or, more generally, to pattern regularity violation. For a number of disorders, MMN/MMNm amplitude to sound deviance has been shown to be attenuated or the peak-latency of the component prolonged compared to controls. This general finding suggests that while not serving as a specific marker to any particular disorder, MMN may be useful for understanding factors of cognition in various disorders, and has potential to serve as an indicator of risk. This review presents a brief history of the MMN, followed by a description of how MMN has been used to index auditory processing capability in a range of neuropsychiatric, neurological, and neurodevelopmental disorders. Finally, we suggest future directions for research to further enhance our understanding of the neural substrate of deviance detection that could lead to improvements in the use of MMN as a clinical tool.Brain Topography 05/2014; DOI:10.1007/s10548-014-0374-6 · 2.52 Impact Factor
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ABSTRACT: Mismatch negativity (MMN) is an event-related potential (ERP) component that reflects preattentive sensory memory functions. Previous research revealed that MMN is generated by distinct sources in the frontal and temporal lobes. Event-related potential abnormalities have been shown in the vicinity of seizure foci in epilepsy. Additionally, no published study has investigated the MMN in response to variations in both frequency and duration deviants in patients with temporal lobe epilepsy (TLE). The aims of this study were to compare MMN changes between the frontocentral sites and the mastoid sites and to compare MMNs related to deviant stimuli with different durations and frequencies in patients with TLE. We recorded MMNs elicited by duration and frequency changes of deviant stimuli from 15 patients with TLE and 15 healthy control subjects. We found that mean MMN amplitudes related to duration deviants were lower in patients with TLE at the mastoid sites relative to controls, whereas the MMN amplitudes at the frontocentral sites did not differ between the two groups. There were no MMN differences related to frequency deviants between TLE subjects and controls at the frontocentral sites or the mastoid sites. Mismatch negativity parameters related to duration deviants did not correlate with those related to deviant frequencies in the group with TLE. The present findings suggest selective impairments among multiple mismatch generators in TLE and suggest that processing of temporal information of auditory stimuli is selectively disturbed in TLE. Changes in MMN amplitudes related to duration deviants at the mastoid sites may represent deficits in time-dependent processing in TLE.Epilepsy & Behavior 01/2014; 31C:136-142. DOI:10.1016/j.yebeh.2013.11.026 · 2.06 Impact Factor
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ABSTRACT: Epilepsy surgery is a potentially curative option for children with intractable epilepsy. In order to avoid postsurgical deficits in language and cognitive functioning, the mapping of these brain functions must be performed. Neurophysiological techniques, such as Electroencephalography (EEG) and Magnetoencephalography (MEG) are non-invasive procedures that can be used to attain this goal. However, they often fail when used to perform functional mapping in uncooperative patients who are unwilling, or unable to communicate or follow the commands. Therefore, there is a need for cognitive function mapping procedures that can be performed without active patient’s participation. The aim of this paper is to integrate and organize currently existing body of knowledge regarding passive testing of information processing and cognitive functioning in pediatric epilepsy patients. It is the first attempt to present a cohesive summary of literature regarding this topic. We will summarize results from currently available passive paradigms for neurophysiological assessment. There are a number of paradigms that could be used for passive evaluation of cognitive function in children with epilepsy. Examples include odd-ball paradigms eliciting Mismatch Negativity (MMN) and P3a responses, continuous word recognition paradigm, and story listening paradigms. In addition, resting state connectivity analysis with correlation to the cognitive testing/behavioral data can be used. Importantly, the majority of these paradigms can be performed during sedation.