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Peak Morphology and Scalp Topography of the Pharyngeal Sensory-Evoked Potential
The initiation of the pharyngeal stage of swallowing is dependent upon sensory input to the brainstem and cortex. The event-related evoked potential provides a measure of neuronal electrical activity as it relates to a specific stimulus. Air-puff stimulation to the posterior pharyngeal wall produces a sensory-evoked potential (PSEP) waveform. The goal of this study was to characterize the scalp topography and morphology for the component peaks of the PSEP waveform. Twenty-five healthy men and women served as research participants. PSEPs were measured via a 32-electrode cap (10–20 system) connected to SynAmps2 Neuroscan EEG System. Air puffs were delivered directly to the oropharynx using a thin polyethylene tube connected to a flexible laryngoscope. The PSEP waveform is characterized by four early- and mid-latency component peaks: an early positivity (P1) and negativity (N1), followed by a mid-latency positivity (P2) and negativity (N2). The early positive peak P1 is localized bilaterally to the lateral parietal scalp, the N1 medially in the frontoparietal region, and the P2 and N2 with diffuse scalp locations. Somatosensory and premotor regions are possible anatomical correlates of peak locations. Based on the latencies of the peaks, they are likely analogous to somatosensory- and respiratory-related evoked potential peaks.
from Dysphagia
Age trends in auditory oddball evoked potentials via component scoring and deconvolution
Age trends in component scores can be related to physiological changes in the brain. However, component scores show a high degree of redundancy, which limits their information content, and are often invalid when applied to young children. Deconvolution provides additional information on development not available through other methods.
A Method for Removing Cochlear Implant Artifact
When cortical auditory evoked potentials (CAEPs) are recorded in individuals with a cochlear implant (CI), electrical artifact can make the CAEP difficult or impossible to measure. Since increasing the interstimulus interval (ISI) increases the amplitude of physiological responses without changing the artifact, subtracting CAEPs recorded with a short ISI from those recorded with a longer ISI should show the physiological response without any artifact. In the first experiment, N1-P2 responses were recorded using a speech syllable and tone, paired with ISIs that changed randomly between 0.5 and 4 seconds. In the second experiment, the same stimuli, at ISIs of either 500 or 3000 ms, were presented in blocks that were homogeneous or random with respect to the ISI or stimulus. In the third experiment, N1-P2 responses were recorded using pulse trains with 500 and 3000 ms ISIs in 4 CI listeners. The results demonstrated: 1) N1-P2 response amplitudes generally increased with increasing ISI. 2) Difference waveforms were largest for the homogeneous and random-stimulus blocks than for the random-ISI block. 3) The subtraction technique almost completely eliminated the electrical artifact in individuals with cochlear implants. Therefore, the subtraction technique is a feasible method of removing from the N1-P2 response the electrical artifact generated by the cochlear implant.
from Hearing Research
A Method for Removing Cochlear Implant Artifact
When cortical auditory evoked potentials (CAEPs) are recorded in individuals with a cochlear implant (CI), electrical artifact can make the CAEP difficult or impossible to measure. Since increasing the interstimulus interval (ISI) increases the amplitude of physiological responses without changing the artifact, subtracting CAEPs recorded with a short ISI from those recorded with a longer ISI should show the physiological response without any artifact. In the first experiment, N1-P2 responses were recorded using a speech syllable and tone, paired with ISIs that changed randomly between 0.5 and 4 seconds. In the second experiment, the same stimuli, at ISIs of either 500 or 3000 ms, were presented in blocks that were homogeneous or random with respect to the ISI or stimulus. In the third experiment, N1-P2 responses were recorded using pulse trains with 500 and 3000 ms ISIs in 4 CI listeners. The results demonstrated: 1) N1-P2 response amplitudes generally increased with increasing ISI. 2) Difference waveforms were largest for the homogeneous and random-stimulus blocks than for the random-ISI block. 3) The subtraction technique almost completely eliminated the electrical artifact in individuals with cochlear implants. Therefore, the subtraction technique is a feasible method of removing from the N1-P2 response the electrical artifact generated by the cochlear implant.
from Hearing Research
Characterizing responses from auditory cortex in young people with several years of cochlear implant experience
Objective
To determine if cortical responses evoked by a cochlear implant in children who are deaf differ from normal and to characterize these differences in children who achieve good versus fair speech perception outcomes post-implantation.
Methods
Late latency-evoked potential responses were recorded at 28 scalp locations in 16 children who were deaf from infancy and experienced cochlear implant users. Speech perception measures indicated that 8 had good scores and 8 had fair scores. In each child, responses were evoked by 36 ms electrical pulse trains delivered from a single-implant electrode at the apical and basal ends of the array and by 36 ms tone bursts (0.5, 2, and 6 kHz). Responses to the tone bursts were also recorded in 14 age-matched children with normal hearing.
Results
We found (1) a dominant positive wave in all implant users and (2) a larger than normal negative amplitude peak in users with fair speech perception scores which had similar scalp topography to N1 but did not show the expected changes in amplitude with stimulus frequency.
Conclusions
Late latency-evoked potential responses in children using cochlear implants reflect abnormal and/or immature patterns of cortical activity.
Significance
Limitations in auditory skills with a cochlear implant in children may be due to developmental processes in the cortex which are either slow to mature or which mature abnormally.
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