Our study describes the effects of sensory tetanization on neurophysiological and behavioral measures in humans linking cellular studies of long-term potentiation with high-level brain processes. Rapid (every 75ms) presentation of pure tone (1020 Hz, 50ms) for 2 minutes was preceded and followed by oddball blocks that contained the same stimulus presented as deviant (probability of 5–10%) interspersed with standard (80–90%) and deviant tones (5–10%) of adjacent frequencies (1000 and 980Hz, respectively). Mismatch negativity (MMN) component in response to tetanized tone (1020Hz), while being similar to MMN for non-tetanized tone before tetanization, became larger than that after tetanization, pointing to the increase in cortical differentiation of these tones. However, this differentiation was partially due to the MMN decrease after tetanization for tones adjacent to tetanized frequency, suggesting the influence of lateral inhibition to this effect. Although MMN correlated with tone discriminability in a psychophysical task, the behavioral improvement after tetanization was not statistically detectable. To conclude, short-term auditory tetanization affects cortical representation of tones that are not limited to the tetanized stimuli.
Major depressive disorder (MDD) is characterized by dramatic and persistent worsening of mood, as well as a subjective feeling of time slowing. However, experimental data on time perception are inconsistent. As serotonergic dysfunction implicated in MDD etiology, we aim to examine time perception in MDD through the framework of lossy temporal integration model, previously also related to serotonergic transmission. Thirty-one patients with recurrent depressive disorder in partial remission and thirty control participants, without a history of psychiatric and neurological disorders, performed duration discrimination of visual stimuli (duration ranges from 3.2 to 6.4 s) and subjective minute production tasks. To infer about central serotonergic transmission, an electroencephalogram in response to the 1000 Hz tone of different intensity (50, 60, 70 and 80 dB SPL) was recorded. Patients with MDD shorten the past durations in the duration discrimination task significantly less than controls, thus being more objective. No difference in the subjective minute production was recorded. Patients with MDD have also exhibited larger auditory evoked potentials in response to the tones of high intensity (70 and 80 dB SPL) when compared with the controls. This resulted in a steeper slope of auditory evoked potentials by intensity function. These converging findings suggest a lower loss rate of neuronal temporal accumulator modulated by serotonergic transmission in patients with MDD.
Studying mu-rhythm in developmental disorders is crucial for identifying the origin of motor and social malfunctioning. However, the commonly used mu-rhythm experimental protocol, that requires following instructions, is challenging for children with motor and cognitive deficits. Here we present an inclusive experimental procedure that contains passive hand movement, closed and open eyes and hand movement observation and examine properties of EEG mu-rhythm obtained in this paradigm in 51 typically developing children and adults aged from 4 to 31 years. The independent component analysis (ICA) was used to separate occipital alpha- and mu-rhythm components and showed better performance than the channel-wise analysis. The identified mu-rhythm ICA components were localized above the left and right sensorimotor cortex, demonstrating suppression both to passive hand movement and hand movement observation and no difference in power between closed- and open-eye conditions. No interhemispheric differences were observed. The alpha-rhythm ICA components were localized in occipital regions and demonstrate characteristic suppression to open-eye conditions. The mu-rhythm frequency of peak suppression to passive hand movement as well as the amount of suppression increased with age. The beta-band mu-rhythm activity, while being less pronounced, was also suppressed both during passive hand movement and hand movement observation, while to a lesser degree than alpha-band mu during passive hand movement. Thus, we confirmed the classical properties of mu-rhythm and for the first time showed the developmental trajectory of mu-rhythm properties obtained during passive hand movement. The proposed experimental protocol and pipeline can be used further in studies of the mu-rhythm in challenging populations.
Spontaneous EEG contains important information about neuronal network properties that is valuable for understanding different neurological and psychiatric conditions. Rett syndrome (RTT) is a rare neurodevelopmental disorder, caused by mutation in the MECP2 gene. RTT is characterized by severe motor impairments that prevent adequate assessment of cognitive functions. Here we probe EEG parameters obtained in no visual input condition from a 28-channels system in 23 patients with Rett Syndrome and 38 their typically developing peers aged 3–17 years old. Confirming previous results, RTT showed a fronto-central theta power (4–6.25 Hz) increase that correlates with a progression of the disease. Alpha power (6.75–11.75 Hz) across multiple regions was, on the contrary, decreased in RTT, also corresponding to general background slowing reported previously. Among novel results we found an increase in gamma power (31–39.5 Hz) across frontal, central and temporal electrodes, suggesting elevated excitation/inhibition ratio. Long-range temporal correlation measured by detrended fluctuation analysis within 6–13 Hz was also increased, pointing to a more predictable oscillation pattern in RTT. Overall measured EEG parameters allow to differentiate groups with high accuracy, ROC AUC value of 0.92 ± 0.08, indicating clinical relevance.