The aim of this study was to develop a paradigm for obtaining a multi-feature profile for central auditory processing of different magnitudes of prosodic and phonetic changes in speech sounds. We recorded the MMNs to three vowel identity changes, three magnitudes of changes in intensity, and vowel duration as well as to two magnitudes of pitch changes from semi-synthetic vowels in 34min. Furthermore, we examined how the type and magnitude of deviation affect the size and timing of the MMN. All sound changes elicited statistically significant MMN responses, with the MMNamplitudes increasing with an increase in sound deviance. Importantly, the MMN amplitudes for the vowel changes reflected the differences between the phonemes, as did the MMNs to vowel-duration changes reflect the categorization of these sounds to short and long vowel categories, which are meaningful in the Finnish language. This new multi-feature MMN paradigm is suitable for investigating the central auditory processing of different magnitudes of speech-sound changes and can be used, for instance, in the investigation of pre-attentive phoneme categorization. The paradigm is especially useful for studying speech and language disorders in general, language development, and evolution of phoneme categories early in life, as well as brain plasticity during native or second language learning
How do human brain networks react to dynamic changes in the sensory environment? We measured rapid changes in brain network organization in response to brief, discrete, salient auditory stimuli. We estimated network topology and distance parameters in the immediate central response period, <1 s following auditory presentation of standard tones interspersed with occasional deviant tones in a mismatch-negativity (MMN) paradigm, using magnetoencephalography (MEG) to measure synchronization of high-frequency (gamma band; 33-64 Hz) oscillations in healthy volunteers. We found that global small-world parameters of the networks were conserved between the standard and deviant stimuli. However, surprising or unexpected auditory changes were associated with local changes in clustering of connections between temporal and frontal cortical areas and with increased interlobar, long-distance synchronization during the 120- to 250-ms epoch (coinciding with the MMN-evoked response). Network analysis of human MEG data can resolve fast local topological reconfiguration and more long-range synchronization of high-frequency networks as a systems-level representation of the brain's immediate response to salient stimuli in the dynamically changing sensory environment.
Feedback processing is an important aspect of learning. In the human brain, feedback processing is often examined by measuring an event-related potential, the feedback-related negativity component. Typically, the feedback-related negativity component is investigated by directly comparing gain with loss feedback randomized across trials; however, this method does not control for confounds associated with unexpected feedback. For this study we used a blocked design gambling task to investigate the sensitivity of feedback-related negativity to positive and negative feedback separately for gains and losses. While there appeared to be no significant feedback-related negativity in the loss domain, results revealed an enlarged feedback-related negativity during the omission of gains compared to the reception of gains. These findings further support the reward positivity hypothesis which declares that the feedback-related negativity is associated with the processing of outcomes in the context of gains as opposed to losses, irrespective of unexpectedness.
In Parkinson's disease (PD) levodopa-associated changes in the power and long-range temporal correlations of beta oscillations have been demonstrated, yet the presence and modulation of genuine connectivity in local field potentials (LFP) recorded from the subthalamic nucleus (STN) remains an open question. The present study investigated LFP recorded bilaterally from the STN at wakeful rest in ten patients with PD after overnight withdrawal of levodopa (OFF) and after a single dose levodopa administration (ON). We utilized connectivity measures being insensitive to volume conduction (functional connectivity: non-zero imaginary part of coherency; effective connectivity: phase-slope index). We demonstrated the presence of neuronal interactions in the frequency range of 10-30 Hz in STN-LFP without a preferential directionality of interactions between different contacts along the electrode tracks. While the direction of neuronal interactions per se was preserved after levodopa administration, functional connectivity and the ventral-dorsal information flow were modulated by medication. The OFF-ON differences in functional connectivity were correlated with the levodopa-induced improvement in clinical Unified Parkinson's Disease Rating Scale scores. We hypothesize that regional neuronal interactions, as reflected in STN-LFP connectivity, might represent a basis for the intra-nuclear spatial specificity of deep brain stimulation. Moreover, our results suggest the potential use of volume conduction-insensitive measures of connectivity in STN-LFP as a marker of clinical motor symptoms in PD.
Для неизотермической квазинейтральной плазмы с развитой ионно-акустической турбулентностью проведен вывод обобщённого закона Вильдемана-Франца, определяющего зависимость между электрической и тепловой проводимостями плазмы с хорошо развитой ионно-акустической турбулентностью. На основании этого закона объяснена аномально низкая теплопроводность, и рассмотрена возможность формирования большого температурного градиента и связанного с ним скачка температуры. Полученные результаты использованы для объяснения некоторых свойств переходной области между хромосферой и солнечной короной.