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Orlando, FL, United States

Griskova-Bulanova I.,Vilnius University | Griksiene R.,Vilnius University | Korostenskaja M.,Functional Brain Mapping and Brain Computer Interface Laboratory | Korostenskaja M.,MEG Laboratory | Ruksenas O.,Vilnius University
Acta Neurobiologiae Experimentalis

Auditory steady-state responses (ASSRs) are widely applied to test brain's ability to follow external stimulation in neuropsychiatric disorders. It is known that ASSRs are related to GABAergic transmission. Female sex steroid homones -both estrogens and progesterone -affect functioning of GABAergic system. However, it is not known how these hormones affect brain's ability to entrain. This study was designed to test the ability to synchronize to 40 Hz stimulation during different phases of the menstrual cycle. Twenty-eight healthy females participated in the research during one of the menstrual cycle phases: (1) early follicular; (2) late follicular; (3) and mid-luteal. Auditory 40 Hz trains of 500 ms were delivered binaurally and EEG was recorded. Time-frequency analysis of the data was performed and phase-locking index, evoked amplitude and total intensity measures were extracted and decomposed by non-negative multi-way factorization. Additionally, alpha power of the baseline period was calculated. Parameters of ASSR were increasing in a linear manner with increasing levels of 17β-estradiol and largest estimates of ASSR parameters were obtained in the late follicular phase, smallest -in the mid-luteal phase. Alpha power values were highest in the late follicular phase and lowest in the mid-luteal phase, pointing to lower arousal level in the late follicular phase. We speculate that increased 40 Hz ASSRs during mid-cycle might be related to the level of general arousal and specific GABA-mediated changes during the menstrual cycle. The results suggest that the ability to entrain to 40 Hz stimulation depends on the phase of menstrual cycle. This should be taken into account, particularly when ASSRs are used in clinical practice, comparing patients and healthy subjects. © 2014 by Polish Neuroscience Society - PTBUN, Nencki Institute of Experimental Biology. Source

Takata Y.,Tohoku University | Kawase T.,Tohoku University | Nakasato N.,Tohoku University | Kanno A.,Tohoku University | And 2 more authors.
Clinical Neurophysiology

Objective: To examine whether auditory evoked fields (AEFs) can be used to objectively evaluate hearing in patients with absent auditory brainstem responses (ABRs) due to auditory neuropathy. Methods: Subjects were 3 patients with auditory neuropathy, 1 male aged 29. years and 2 females aged 18 and 27. years, with absence of click evoked ABRs for bilateral ear stimuli at a level of 105. dB nHL. All patients also had optic atrophy. AEFs were measured with a helmet-shaped magnetoencephalography system for 2.0. kHz tone bursts of 60. ms duration to the unilateral ear. Results: Bihemispherical AEF responses were clearly recorded in all three patients for either left or right ear stimulus. Although the latencies of N100m were severely prolonged and amplitudes were considerably decreased compared to the normal range of N100m responses in our facilities, N100m latency of AEF was shorter in the contralateral hemisphere to the stimulated ear, as usually found in normal subjects, despite the abnormal delay in N100m latency in all conditions. Conclusions: Presence and abnormality of auditory cortical responses can be evaluated by AEFs in patients with auditory neuropathy even under null responses in ABRs. Significance: AEFs are useful to evaluate residual hearing in patients with auditory neuropathy. © 2011 International Federation of Clinical Neurophysiology. Source

Kawase T.,Tohoku University | Kanno A.,Tohoku University | Kanno A.,MEG Laboratory | Takata Y.,Tohoku University | And 3 more authors.
Clinical Neurophysiology

Objective: To compare the detectability of the different auditory evoked responses in patients with retrocochlear lesion. Methods: The 40-Hz auditory steady state response (ASSR) and the N1m auditory cortical response were examined by magnetoencephalography in 4 patients with vestibular schwannoma, in whom the auditory brainstem response (ABR) was absent. Results: Apparent N1m responses were observed despite total absence of the ABR or absence except for small wave I in all patients, although the latency of N1m was delayed in most patients. On the other hand, clear ASSFs could be observed only in one patient. Very small 40-Hz ASSFs could be detected in 2 patients (amplitude less than 1. fT), but no apparent ASSFs were observed in one patient, in whom maximum speech intelligibility was extremely low and the latency of N1m was most prolonged. Conclusion: The N1m response and 40-Hz ASSR could be detected in patients with absent ABR, but the N1m response appeared to be more detectable than the 40-Hz ASSR. Significance: Combined assessment with several different evoked responses may be useful to evaluate the disease conditions of patients with retrocochlear lesions. © 2013 International Federation of Clinical Neurophysiology. Source

Pardos M.,Cincinnati Childrens Hospital Medical Center | Korostenskaja M.,Cincinnati Childrens Hospital Medical Center | Korostenskaja M.,Milenas Functional Brain Mapping and Brain Computer Interface Laboratory | Korostenskaja M.,Comprehensive Pediatric Epilepsy Center | And 13 more authors.
Behavioural Neurology

Objective evaluation of language function is critical for children with intractable epilepsy under consideration for epilepsy surgery. The purpose of this preliminary study was to evaluate word recognition in children with intractable epilepsy by using magnetoencephalography (MEG). Ten children with intractable epilepsy (M/F 6/4, mean ± SD 13.4 ± 2.2 years) were matched on age and sex to healthy controls. Common nouns were presented simultaneously from visual and auditory sensory inputs in "match" and "mismatch" conditions. Neuromagnetic responses M1, M2, M3, M4, and M5 with latencies of 100 ms, 150 ms, 250 ms, 350 ms, and 450 ms, respectively, elicited during the "match" condition were identified. Compared to healthy children, epilepsy patients had both significantly delayed latency of the M1 and reduced amplitudes of M3 and M5 responses. These results provide neurophysiologic evidence of altered word recognition in children with intractable epilepsy. © 2015 Maria Pardos et al. Source

Korostenskaja M.,Center for Pediatric Research and Outcomes | Korostenskaja M.,MEG Laboratory | Chen P.-C.,Center for Pediatric Research and Outcomes | Chen P.-C.,MEG Laboratory | And 8 more authors.
Journal of Neurosurgery: Pediatrics

Accurate language localization expands surgical treatment options for epilepsy patients and reduces the risk of postsurgery language deficits. Electrical cortical stimulation mapping (ESM) is considered to be the clinical gold standard for language localization. While ESM affords clinically valuable results, it can be poorly tolerated by children, requires active participation and compliance, carries a risk of inducing seizures, is highly time consuming, and is labor intensive. Given these limitations, alternative and/or complementary functional localization methods such as analysis of electrocorticographic (ECoG) activity in high gamma frequency band in real time are needed to precisely identify eloquent cortex in children. In this case report, the authors examined 1) the use of real-time functional mapping (RTFM) for language localization in a high gamma frequency band derived from ECoG to guide surgery in an epileptic pediatric patient and 2) the relationship of RTFM mapping results to postsurgical language outcomes. The authors found that RTFM demonstrated relatively high sensitivity (75%) and high specificity (90%) when compared with ESM in a "next-neighbor" analysis. While overlapping with ESM in the superior temporal region, RTFM showed a few other areas of activation related to expressive language function, areas that were eventually resected during the surgery. The authors speculate that this resection may be associated with observed postsurgical expressive language deficits. With additional validation in more subjects, this finding would suggest that surgical planning and associated assessment of the risk/benefit ratio would benefit from information provided by RTFM mapping. ©AANS, 2014. Source

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