Visual Stimuli Modulate Local Field Potentials But Drive No High-Frequency Activity in Human Auditory Cortex.

Neuroimaging studies suggest cross-sensory visual influences in human auditory cortices (ACs). Whether these influences reflect active visual processing in human ACs, which drives neuronal firing and concurrent broadband high-frequency activity (BHFA; >70 Hz), or whether they merely modulate sound processing is still debatable. Here, we presented auditory, visual, and audiovisual stimuli to 16 participants (7 women, 9 men) with stereo-EEG depth electrodes implanted near ACs for presurgical monitoring. Anatomically normalized group analyses were facilitated by inverse modeling of intracranial source currents. Analyses of intracranial event-related potentials (iERPs) suggested cross-sensory responses to visual stimuli in ACs, which lagged the earliest auditory responses by several tens of milliseconds. Visual stimuli also modulated the phase of intrinsic low-frequency oscillations and triggered 15-30 Hz event-related desynchronization in ACs. However, BHFA, a putative correlate of neuronal firing, was not significantly increased in ACs after visual stimuli, not even when they coincided with auditory stimuli. Intracranial recordings demonstrate cross-sensory modulations, but no indication of active visual processing in human ACs.

Distributed source modeling of intracranial stereoelectro-encephalographic measurements.

Intracranial stereoelectroencephalography (sEEG) provides unsurpassed sensitivity and specificity for human neurophysiology. However, functional mapping of brain functions has been limited because the implantations have sparse coverage and differ greatly across individuals. Here, we developed a distributed, anatomically realistic sEEG source-modeling approach for within- and between-subject analyses. In addition to intracranial event-related potentials (iERP), we estimated the sources of high broadband gamma activity (HBBG), a putative correlate of local neural firing. Our novel approach accounted for a significant portion of the variance of the sEEG measurements in leave-one-out cross-validation. After logarithmic transformations, the sensitivity and signal-to-noise ratio were linearly inversely related to the minimal distance between the brain location and electrode contacts (slope≈-3.6). The signa-to-noise ratio and sensitivity in the thalamus and brain stem were comparable to those locations at the vicinity of electrode contact implantation. The HGGB source estimates were remarkably consistent with analyses of intracranial-contact data. In conclusion, distributed sEEG source modeling provides a powerful neuroimaging tool, which facilitates anatomically-normalized functional mapping of human brain using both iERP and HBBG data.

Treatment-seeking behavior of people with epilepsy in Taiwan: a preliminary study.

To understand the treatment-seeking behavior of people with epilepsy (PWE), 403 PWE were surveyed using structured face-to-face interviews. Nearly half (49.1%) of them had previously tried complementary and alternative medicine (CAM); traditional Chinese medicine (51.5%) and temple worship (48.0%) were the most frequently used forms of CAM. In the 155 patients with adult-onset epilepsy, seeking CAM was substantially more common among females (OR=2.11, 95% CI=1.05-4.24, P=0.036), patients with frequent seizures (OR=2.68, 95% CI=1.30-5.53, P=0.008), patients with less educated parents (OR=2.16, 95% CI=1.06-4.41, P=0.034), and patients with religious beliefs (OR=2.84, 95% CI=1.23-6.56, P=0.015). In the 248 patients with childhood-onset epilepsy, frequent seizures (OR=2.23, 95% CI=1.32-3.77, P=0.003) and lower level of parental education (OR=2.71, 95% CI=1.45-5.06, P=0.002) were significantly associated with CAM use. The patients who seek CAM before receiving conventional medical treatment decreased after implementation of the National Health Insurance (NHI) (34/188 before NHI vs 22/215 after NHI, P=0.023). This study showed that the prevalence of CAM use by PWE in Taiwan is high and that a convenient NHI program can affect treatment-seeking behavior.

Side of the stimulated ear influences the hemispheric balance in coding tonal stimuli.

OBJECTIVE: To evaluate whether the side of stimulated ear affects the hemispheric asymmetry of auditory evoked cortical activations. METHODS: Using a whole-head neuromagnetometer, we recorded neuromagnetic approximately 100 ms responses (N100m) in 21 healthy right-handers to 100 ms 1 kHz tones delivered alternatively to left and right ear. RESULTS: Although the peak latencies of N100m were shorter in contralateral than in ipsilateral hemisphere, the difference was significant only for the left ear stimulation. Based on the relative N100m amplitudes across hemispheres, the laterality evaluation showed a rightward predominance of N100m activation to tone stimuli, but the lateralization toward the right hemisphere was more apparent by the left than by the right ear stimulation (laterality index: -0.27 versus -0.10, p=0.008). Within the right hemisphere, the N100m was 2-4 mm more posterior for left ear than for right ear stimulation. CONCLUSIONS: The hemispheric asymmetry in auditory processing depends on the side of the stimulated ear. The more anterior localization of right N100m responses to ipsilateral than to contralateral ear stimulation suggests that there might be differential neuronal populations in the right hemisphere for processing spatially different auditory inputs.