Clinical Neurophysiology最新文献

Background: Aperiodic resting electroencephalography (EEG) activity is dynamic, reflecting shifting excitatory:inhibitory (E:I) balance with changing environmental conditions. We examined developmental and cognitive correlates of aperiodic and dynamic aperiodic indices in a cross-sequential cohort of early, middle, and late childhood youth with and without attention deficit hyperactivity disorder (ADHD).

Methods: Two-hundred eighty-five children ages 2 - 14 years provided resting EEG during high- and low-visual input conditions. Licensed clinical psychologists determined ADHD diagnosis or likelihood (in young children). Linear regressions were estimated to examine associations between aperiodic features and age, ADHD diagnosis, IQ, and experimental condition.

Results: From early to middle childhood, the aperiodic exponent increased linearly, indicating lower E:I, followed by a decreasing trajectory in late childhood. The aperiodic exponent was greater with high versus low visual input in young children, but this effect reversed with age. The ADHD group had a decreased aperiodic exponent, overall. Dynamic aperiodic activity, i.e. shifts in E:I balance, was associated with IQ.

Conclusions: The aperiodic exponent and aperiodic dynamics are proxies for age-related cortical maturation and E:I balance, and have distinct associations with ADHD symptoms and cognitive ability.

Significance: We provide novel evidence that dynamic aperiodic activity is a candidate marker of cortical efficiency in childhood.

Objective: This study aimed to optimally evaluate the effect of the long-interval intracortical inhibition (LICI) in the dorsolateral prefrontal cortex (DLPFC) through transcranial magnetic stimulation combined with electroencephalography (TMS-EEG) by eliminating the volume conductance with signal source estimation and using a realistic sham coil as a control.

Methods: We compared the LICI effects from the DLPFC between the active and sham stimulation conditions in 27 healthy participants. Evoked responses between the two conditions were evaluated at the sensor and source levels.

Results: At the sensor level, a significant LICI effect was confirmed in the active condition in the global mean field power analysis; however, in the local mean field power analysis focused on the DLPFC, no LICI effect was observed in the active condition. However, in the signal source estimation analysis for the DLPFC, we could reconfirm a significant LICI effect (p = 0.023) in the interval 30-250 ms post-stimulus, compared to the sham condition.

Conclusions: Our results demonstrate that application of realistic sham stimulation condition and source estimation method allows for a robust and optimal identification of the LICI effect in the DLPFC.

Significance: The optimal DLPFC-LICI effect was identified by the use of the sophisticated sham coil.

Objective: Noisy galvanic vestibular stimulation (GVS) using weak random noise waveforms enhances postural stability by modulating vestibular-related neural networks. This study aimed to investigate the neural interference mechanisms of noisy GVS on lateral vestibulospinal tract (LVST) excitability.

Methods: Twenty-six healthy volunteers were randomly divided into two groups: balance training combined with noisy GVS and sham GVS. Participants performed 10-minute balance training while standing on a soft foam surface with their eyes closed while adapting to each electrical stimulus. LVST excitability was assessed by measuring the soleus H-reflex following square-wave pulse GVS. Postural stability was measured by assessing the center of foot pressure sway while standing on a foam surface with eyes closed.

Results: The noisy GVS group showed significantly increased post-intervention H-reflex amplitude. The sham GVS group showed no significant difference in H-reflex amplitude pre- and post-intervention. The average sway velocity in the noisy and sham GVS groups significantly decreased in the medial-lateral direction of the center of foot pressure.

Conclusions: Noisy GVS may enhance LVST excitability and decrease body sway via vestibular system interference during holding upright, which relies heavily on vestibular sensations.

Significance: These findings may help understand the neural mechanisms of noisy GVS in neurorehabilitation.

Objective: Motivated by previous inconsistent findings, this study aims to improve understanding of sensorimotor beta (β; 15-30 Hz) and alpha (α; 8-14 Hz) speech-related power differences between stuttering and non-stuttering adults.

Methods: Electroencephalography was recorded as adults who stutter (AWS) and matched fluent controls answered questions in Quiet and Informational Masked backgrounds. Bilateral sensorimotor β and α power during speech planning and execution were measured from mu (μ) rhythm components.

Results: Compared to controls, AWS exhibited reduced left hemisphere β and α power in both speaking conditions during speech planning and execution. AWS displayed reduced left α power in the Informational Masking compared to Quiet. Within AWS β and α power, which were tightly coupled, oppositely predicted stuttering severity and β-α dissociation (β minus α) was the strongest predictor.

Conclusion: Neither β nor α power are reliable markers of speech motor stability due to their sensitivity to speech task automaticity. However, relationships between these two sensorimotor rhythms warrant further investigation for understanding motor control.

Significance: Data help explain previous mixed findings in reference to extant models of speech motor control in stuttering and may have clinical implications for developing neurostimulation protocols targeting improved speech fluency.

Objective: Direct cortical responses (DCR) and axono-cortical evoked potentials (ACEP) are generated by electrically stimulating the cortex either directly or indirectly through white matter pathways, potentially leading to different electrogenic processes. For ACEP, the slow conduction velocity of axons (median ≈ 4 m.s^-1) is anticipated to induce a delay. For DCR, direct electrical stimulation (DES) of the cortex is expected to elicit additional cortical activity involving smaller and slower non-myelinated axons. We tried to validate these hypotheses.

Methods: DES was administered either directly on the cortex or to white matter fascicles within the resection cavity, while recording DCR or ACEP at the cortical level in nine patients.

Results: Short but significant delays (≈ 2 ms) were measurable for ACEP immediately following the initial component (≈ 7 ms). Subsequent activities (≈ 40 ms) exhibited notable differences between DCR and ACEP, suggesting the presence of additional cortical activities for DCR.

Conclusion: Distinctions between ACEPs and DCRs can be made based on a delay at the onset of early components and the dissimilarity in the shape of the later components (>40 ms after the DES artifact).

Significance: The comparison of different types of evoked potentials allows to better understand the effects of DES.