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1. Practice modulates motor‐related beta oscillations differently in adolescents and adults

   https://doi.org/10.1113/JP277326  

   Gehringer, James E. ; Arpin, David J. ; Heinrichs‐Graham, Elizabeth ; Wilson, Tony W. ; Kurz, Max J. ( May 2019 , The Journal of Physiology)

   Magnetoencephalography data were acquired during a leg force task in pre‐/post‐practice sessions in adolescents and adults.

   Strong peri‐movement alpha and beta oscillations were mapped to the cortex.

   Following practice, performance improved and beta oscillations were altered.

   Beta oscillations decreased in the sensorimotor cortex in adolescents after practice, but increased in adults.

   No pre‐/post‐practice differences were detected for alpha oscillations.

   There is considerable evidence that there are motor performance and practice differences between adolescents and adults. Behavioural studies have suggested that these motor performance differences are simply due to experience. However, the neurophysiological nexus for these motor performance differences remains unknown. The present study investigates the short‐term changes (e.g. fast motor learning) in the alpha and beta event‐related desynchronizations (ERDs) associated with practising an ankle plantarflexion motor action. To this end, we utilized magnetoencephalography to identify changes in the alpha and beta ERDs in healthy adolescents (n = 21; age = 14 ± 2.1 years) and middle‐aged adults (n = 22; age = 36.6 ± 5 years) after practising an isometric ankle plantarflexion target‐matching task. After practice, all of the participants matched more targets and matched the targets faster, and had improved accuracy, faster reaction times and faster force production. However, the motor performance of the adults exceeded what was seen in the adolescents regardless of practice. In conjunction with the behavioural results, the strength of the beta ERDs across the motor planning and execution stages was reduced after practice in the sensorimotor cortices of the adolescents, but was stronger in the adults. No pre‐/post‐practice changes were found in the alpha ERDs. These outcomes suggest that there are age‐dependent changes in the sensorimotor cortical oscillations after practising a motor task. We suspect that these noted differences might be related to familiarity with the motor task, GABA levels and/or maturational differences in the integrity of the white matter fibre tracts that comprise the respective cortical areas.

    

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2. Bihemispheric network dynamics coordinating vocal feedback control

   https://doi.org/10.1002/hbm.23114  

   Kort, Naomi S. ; Cuesta, Pablo ; Houde, John F. ; Nagarajan, Srikantan S. ( February 2016 , Human Brain Mapping)

   Modulation of vocal pitch is a key speech feature that conveys important linguistic and affective information. Auditory feedback is used to monitor and maintain pitch. We examined induced neural high gamma power (HGP) (65–150 Hz) using magnetoencephalography during pitch feedback control. Participants phonated into a microphone while hearing their auditory feedback through headphones. During each phonation, a single real‐time 400 ms pitch shift was applied to the auditory feedback. Participants compensated by rapidly changing their pitch to oppose the pitch shifts. This behavioral change required coordination of the neural speech motor control network, including integration of auditory and somatosensory feedback to initiate change in motor plans. We found increases in HGP across both hemispheres within 200 ms of pitch shifts, covering left sensory and right premotor, parietal, temporal, and frontal regions, involved in sensory detection and processing of the pitch shift. Later responses to pitch shifts (200–300 ms) were right dominant, in parietal, frontal, and temporal regions. Timing of activity in these regions indicates their role in coordinating motor change and detecting and processing of the sensory consequences of this change. Subtracting out cortical responses during passive listening to recordings of the phonations isolated HGP increases specific to speech production, highlighting right parietal and premotor cortex, and left posterior temporal cortex involvement in the motor response. Correlation of HGP with behavioral compensation demonstrated right frontal region involvement in modulating participant's compensatory response. This study highlights the bihemispheric sensorimotor cortical network involvement in auditory feedback‐based control of vocal pitch.Hum Brain Mapp 37:1474‐1485, 2016. © 2016 Wiley Periodicals, Inc.

    

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3. Corticospinal drive is associated with temporal walking adaptation in both healthy young and older adults

   https://doi.org/10.3389/fnagi.2022.920475  

   Sato, Sumire D. ; Choi, Julia T. ( August 2022 , Frontiers in Aging Neuroscience)

   Healthy aging is associated with reduced corticospinal drive to leg muscles during walking. Older adults also exhibit slower or reduced gait adaptation compared to young adults. The objective of this study was to determine age-related changes in the contribution of corticospinal drive to ankle muscles during walking adaptation. Electromyography (EMG) from the tibialis anterior (TA), soleus (SOL), medial, and lateral gastrocnemius (MGAS, LGAS) were recorded from 20 healthy young adults and 19 healthy older adults while they adapted walking on a split-belt treadmill. We quantified EMG-EMG coherence in the beta-gamma (15–45 Hz) and alpha-band (8–15 Hz) frequencies. Young adults demonstrated higher coherence in both the beta-gamma band coherence and alpha band coherence, although effect sizes were greater in the beta-gamma frequency. The results showed that slow leg TA-TA coherence in the beta-gamma band was the strongest predictor of early adaptation in double support time. In contrast, early adaptation in step length symmetry was predicted by age group alone. These findings suggest an important role of corticospinal drive in adapting interlimb timing during walking in both young and older adults. 

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4. Developmental trajectory of MEG resting-state oscillatory activity in children and adolescents: a longitudinal reliability study

   https://doi.org/10.1093/cercor/bhac023  

   Candelaria-Cook, Felicha T. ; Solis, Isabel ; Schendel, Megan E. ; Wang, Yu-Ping ; Wilson, Tony W. ; Calhoun, Vince D. ; Stephen, Julia M. ( February 2022 , Cerebral Cortex)

   Neural oscillations may be sensitive to aspects of brain maturation such as myelination and synaptic density changes. Better characterization of developmental trajectories and reliability is necessary for understanding typical and atypical neurodevelopment. Here, we examined reliability in 110 typically developing children and adolescents (aged 9–17 years) across 2.25 years. From 10 min of magnetoencephalography resting-state data, normalized source spectral power and intraclass correlation coefficients were calculated. We found sex-specific differences in global normalized power, with males showing age-related decreases in delta and theta, along with age-related increases in beta and gamma. Females had fewer significant age-related changes. Structural magnetic resonance imaging revealed that males had more total gray, subcortical gray, and cortical white matter volume. There were significant age-related changes in total gray matter volume with sex-specific and frequency-specific correlations to normalized power. In males, increased total gray matter volume correlated with increased theta and alpha, along with decreased gamma. Split-half reliability was excellent in all frequency bands and source regions. Test–retest reliability ranged from good (alpha) to fair (theta) to poor (remaining bands). While resting-state neural oscillations can have fingerprint-like quality in adults, we show here that neural oscillations continue to evolve in children and adolescents due to brain maturation and neurodevelopmental change.

    

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5. Responses of Cortical Neurons to Intracortical Microstimulation in Awake Primates

   https://doi.org/10.1523/ENEURO.0336-22.2023  

   Yun, Richy ; Mishler, Jonathan H. ; Perlmutter, Steve I. ; Rao, Rajesh P. N. ; Fetz, Eberhard E. ( April 2023 , eneuro)

   Intracortical microstimulation (ICMS) is commonly used in many experimental and clinical paradigms; however, its effects on the activation of neurons are still not completely understood. To document the responses of cortical neurons in awake nonhuman primates to stimulation, we recorded single-unit activity while delivering single-pulse stimulation via Utah arrays implanted in primary motor cortex (M1) of three macaque monkeys. Stimuli between 5 and 50 μA delivered to single channels reliably evoked spikes in neurons recorded throughout the array with delays of up to 12 ms. ICMS pulses also induced a period of inhibition lasting up to 150 ms that typically followed the initial excitatory response. Higher current amplitudes led to a greater probability of evoking a spike and extended the duration of inhibition. The likelihood of evoking a spike in a neuron was dependent on the spontaneous firing rate as well as the delay between its most recent spike time and stimulus onset. Tonic repetitive stimulation between 2 and 20 Hz often modulated both the probability of evoking spikes and the duration of inhibition; high-frequency stimulation was more likely to change both responses. On a trial-by-trial basis, whether a stimulus evoked a spike did not affect the subsequent inhibitory response; however, their changes over time were often positively or negatively correlated. Our results document the complex dynamics of cortical neural responses to electrical stimulation that need to be considered when using ICMS for scientific and clinical applications.

    

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