-
Movement Disorders : Official Journal... Jun 2024
Topics: Humans; Motor Cortex; Tremor; Parkinson Disease; Parkinsonian Disorders; Nerve Net
PubMed: 38924141
DOI: 10.1002/mds.29872 -
European Journal of Neurology Jun 2024Human motor planning and control depend highly on optimal feedback control systems, such as the neocortex-cerebellum circuit. Here, diffusion tensor imaging was used to...
BACKGROUND AND PURPOSE
Human motor planning and control depend highly on optimal feedback control systems, such as the neocortex-cerebellum circuit. Here, diffusion tensor imaging was used to verify the disruption of the neocortex-cerebellum circuit in spinocerebellar ataxia type 3 (SCA3), and the circuit's disruption correlation with SCA3 motor dysfunction was investigated.
METHODS
This study included 45 patients with familial SCA3, aged 17-67 years, and 49 age- and sex-matched healthy controls, aged 21-64 years. Tract-based spatial statistics and probabilistic tractography was conducted using magnetic resonance images of the patients and controls. The correlation between the local probability of probabilistic tractography traced from the cerebellum and clinical symptoms measured using specified symptom scales was also calculated.
RESULTS
The cerebellum-originated probabilistic tractography analysis showed that structural connectivity, mainly in the subcortical cerebellar-thalamo-cortical tract, was significantly reduced and the cortico-ponto-cerebellar tract was significantly stronger in the SCA3 group than in the control group. The enhanced tract was extended to the right lateral parietal region and the right primary motor cortex. The enhanced neocortex-cerebellum connections were highly associated with disease progression, including duration and symptomatic deterioration. Tractography probabilities from the cerebellar to parietal and sensorimotor areas were significantly negatively correlated with motor abilities in patients with SCA3.
CONCLUSION
To our knowledge, this study is the first to reveal that disrupting the neocortex-cerebellum loop can cause SCA3-induced motor dysfunctions. The specific interaction between the cerebellar-thalamo-cortical and cortico-ponto-cerebellar pathways in patients with SCA3 and its relationship with ataxia symptoms provides a new direction for future research.
PubMed: 38923784
DOI: 10.1111/ene.16368 -
Cell Reports Jun 2024During behavior, the motor cortex sends copies of motor-related signals to sensory cortices. Here, we combine closed-loop behavior with large-scale physiology,...
During behavior, the motor cortex sends copies of motor-related signals to sensory cortices. Here, we combine closed-loop behavior with large-scale physiology, projection-pattern-specific recordings, and circuit perturbations to show that neurons in mouse secondary motor cortex (M2) encode sensation and are influenced by expectation. When a movement unexpectedly produces a sound, M2 becomes dominated by sound-evoked activity. Sound responses in M2 are inherited partially from the auditory cortex and are routed back to the auditory cortex, providing a path for the reciprocal exchange of sensory-motor information during behavior. When the acoustic consequences of a movement become predictable, M2 responses to self-generated sounds are selectively gated off. These changes in single-cell responses are reflected in population dynamics, which are influenced by both sensation and expectation. Together, these findings reveal the embedding of sensory and expectation signals in motor cortical activity.
PubMed: 38923464
DOI: 10.1016/j.celrep.2024.114396 -
Developmental Psychobiology Sep 2024Repeated exposure to abused drugs leads to reorganizing synaptic connections in the brain, playing a pivotal role in the relapse process. Additionally, recent research...
Repeated exposure to abused drugs leads to reorganizing synaptic connections in the brain, playing a pivotal role in the relapse process. Additionally, recent research has highlighted the impact of parental drug exposure before gestation on subsequent generations. This study aimed to explore the influence of parental morphine exposure 10 days prior to pregnancy on drug-induced locomotor sensitization. Adult male and female Wistar rats were categorized into morphine-exposed and control groups. Ten days after their last treatment, they were mated, and their male offspring underwent morphine, methamphetamine, cocaine, and nicotine-induced locomotor sensitization tests. The results indicated increased locomotor activity in both groups after drug exposure, although the changes were attenuated in morphine and cocaine sensitization among the offspring of morphine-exposed parents (MEPs). Western blotting analysis revealed altered levels of D2 dopamine receptors (D2DRs) in the prefrontal cortex and nucleus accumbens of the offspring from MEPs. Remarkably, despite not having direct in utero drug exposure, these offspring exhibited molecular alterations affecting morphine and cocaine-induced sensitization. The diminished sensitization to morphine and cocaine suggested the development of a tolerance phenotype in these offspring. The changes in D2DR levels in the brain might play a role in these adaptations.
Topics: Animals; Female; Morphine; Male; Cocaine; Pregnancy; Prenatal Exposure Delayed Effects; Rats, Wistar; Rats; Receptors, Dopamine D2; Nucleus Accumbens; Prefrontal Cortex; Locomotion; Behavior, Animal; Narcotics; Paternal Exposure; Dopamine Uptake Inhibitors; Motor Activity
PubMed: 38922890
DOI: 10.1002/dev.22514 -
Journal of Clinical Neurophysiology :... Jul 2024The corpus callosum is crucial for interhemispheric interactions in the motor control of limb functions. Human and animal studies suggested spinal cord pathologies may...
PURPOSE
The corpus callosum is crucial for interhemispheric interactions in the motor control of limb functions. Human and animal studies suggested spinal cord pathologies may induce cortical reorganization in sensorimotor areas. We investigate participation of the corpus callosum in executions of a simple motor task in patients with cervical spondylotic myelopathy (CSM) using transcranial magnetic stimulation.
METHODS
Twenty patients with CSM with various MRI grades of severity of cord compression were compared with 19 normal controls. Ipsilateral silent period, contralateral silent period, central motor conduction time, and transcallosal conduction time (TCT) were determined.
RESULTS
In both upper and lower limbs, TCTs were significantly increased for patients with CSM than normal controls ( p < 0.001 for all), without side-to-side differences. Ipsilateral silent period and contralateral silent period durations were significantly increased bilaterally for upper limbs in comparison to controls ( p < 0.01 for all), without side-to-side differences. There were no significant correlations of TCT with central motor conduction time nor severity of CSM for both upper and lower limbs ( p > 0.05 for all) bilaterally.
CONCLUSIONS
Previous transcranial magnetic stimulation studies show increased motor cortex excitability in CSM; hence, increased TCTs observed bilaterally may be a compensatory mechanism for effective unidirectional and uniplanar execution of muscle activation in the distal limb muscles. Lack of correlation of TCTs with severity of CSM or central motor conduction time may be in keeping with a preexistent role of the corpus callosum as a predominantly inhibitory pathway for counteracting redundant movements resulting from increased motor cortex excitability occurring after spinal cord lesions.
Topics: Humans; Corpus Callosum; Male; Transcranial Magnetic Stimulation; Female; Middle Aged; Spondylosis; Evoked Potentials, Motor; Adult; Aged; Cervical Vertebrae; Neural Conduction; Spinal Cord Diseases; Spinal Cord Compression
PubMed: 38922289
DOI: 10.1097/WNP.0000000000000979 -
Einstein (Sao Paulo, Brazil) 2024This study aimed at assessing the alterations in upper limb motor impairment and connectivity between motor areas following the post-stroke delivery of cathodal... (Randomized Controlled Trial)
Randomized Controlled Trial
OBJECTIVE
This study aimed at assessing the alterations in upper limb motor impairment and connectivity between motor areas following the post-stroke delivery of cathodal transcranial direct current stimulation sessions.
METHODS
Modifications in the Fugl-Meyer Assessment scores, connectivity between the primary motor cortex of the unaffected and affected hemispheres, and between the primary motor and premotor cortices of the unaffected hemisphere were compared prior to and following six sessions of cathodal transcranial direct current stimulation application in 13 patients (active = 6; sham = 7); this modality targets the primary motor cortex of the unaffected hemisphere early after a stroke.
RESULTS
Clinically relevant distinctions in Fugl-Meyer Assessment scores (≥9 points) were observed more frequently in the Sham Group than in the Active Group. Between-group differences in the alterations in Fugl-Meyer Assessment scores were not statistically significant (Mann-Whitney test, p=0.133). ROI-to-ROI correlations between the primary motor cortices of the affected and unaffected hemispheres post-therapeutically increased in 5/6 and 2/7 participants in the Active and Sham Groups, respectively. Between-group differences in modifications in connectivity between the aforementioned areas were not statistically significant. Motor performance enhancements were more frequent in the Sham Group compared to the Active Group.
CONCLUSION
The results of this hypothesis-generating investigation suggest that heightened connectivity may not translate into early clinical benefits following a stroke and will be crucial in designing larger cohort studies to explore mechanisms underlying the impacts of this intervention. ClinicalTrials.gov Identifier: NCT02455427.
Topics: Humans; Transcranial Direct Current Stimulation; Pilot Projects; Male; Female; Motor Cortex; Middle Aged; Stroke Rehabilitation; Aged; Stroke; Treatment Outcome; Recovery of Function; Upper Extremity; Time Factors
PubMed: 38922218
DOI: 10.31744/einstein_journal/2024AO0450 -
Audiology Research Jun 2024Bipedalism is unique among mammals. Until modern times, a fall and resulting leg fracture could be fatal. Balance maintenance after a destabilizing event requires...
A New Perspective to Interpret How the Vestibular Efferent System Correlates the Complexity of Routine Balance Maintenance with Management of Emergency Fall Prevention Strategies.
Bipedalism is unique among mammals. Until modern times, a fall and resulting leg fracture could be fatal. Balance maintenance after a destabilizing event requires instantaneous decision making. The vestibular system plays an essential role in this process, initiating an emergency response. The afferent otolithic neural response is the first directionally oriented information to reach the cortex, and it can then be used to initiate an appropriate protective response. Some vestibular efferent axons feed directly into type I vestibular hair cells. This allows for rapid vestibular feedback via the striated organelle (STO), which has been largely ignored in most texts. We propose that this structure is essential in emergency fall prevention, and also that the system of sensory detection and resultant motor response works by having efferent movement information simultaneously transmitted to the maculae with the movement commands. This results in the otolithic membrane positioning itself precisely for the planned movement, and any error is due to an unexpected external cause. Error is fed back via the vestibular afferent system. The efferent system causes macular otolithic membrane movement through the STO, which occurs simultaneously with the initiating motor command. As a result, no vestibular afferent activity occurs unless an error must be dealt with.
PubMed: 38920965
DOI: 10.3390/audiolres14030044 -
Frontiers in Psychiatry 2024Abuse or misuse of tobacco, e-cigarettes, or antidepressants may have serious clinical consequences during adolescence, a sensitive period during brain development when...
INTRODUCTION
Abuse or misuse of tobacco, e-cigarettes, or antidepressants may have serious clinical consequences during adolescence, a sensitive period during brain development when the distinct neurobiology of adolescent serotonin (5-HT) and dopamine (DA) systems create unique behavioral vulnerabilities to drugs of abuse.
METHODS
Using a pharmacological approach, we modeled the behavioral and neurochemical effects of subchronic (4-day) nicotine (60µg/kg, i.v.) or fluoxetine (1mg/kg, i.v.) exposure in adolescent and adult male rats.
RESULTS
Nicotine and fluoxetine significantly enhance quinpirole-induced locomotor activity and initial cocaine self-administration in adolescents, but not adults. These effects were blocked by serotonin 5-HT receptor antagonists, WAY-100,635 (100 µg/kg, i.v.) or S-15535 (300 µg/kg, i.v.). Neurochemical and anatomical autoradiographic analysis of 8-OH-DPAT-stimulated [S]GTPγS reveal that prior exposure to nicotine and fluoxetine results in both overlapping and distinct effects on regional 5-HT1A receptor activity. Both fluoxetine and nicotine enhance adolescent 5-HT1A receptor activity in the primary motor cortex (M1), whereas fluoxetine alone targets prefrontal cortical neurocircuitry and nicotine alone targets the amygdala.
DISCUSSION
Given their different pharmacological profiles, comparison between WAY-100,635 and S-15535 indicates that postsynaptic 5-HT receptors mediate the behavioral effects of prior nicotine and fluoxetine exposure. In addition, within the adolescent M1, maladaptive changes in 5-HT signaling and 5-HT activity after nicotine or fluoxetine exposure may potentiate hyper-responsiveness to dopaminergic drugs and prime adolescent vulnerability for future substance abuse.
PubMed: 38919632
DOI: 10.3389/fpsyt.2024.1380123 -
Advances in Experimental Medicine and... 2024Timing and motor function share neural circuits and dynamics, which underpin their close and synergistic relationship. For instance, the temporal predictability of a... (Review)
Review
Timing and motor function share neural circuits and dynamics, which underpin their close and synergistic relationship. For instance, the temporal predictability of a sensory event optimizes motor responses to that event. Knowing when an event is likely to occur lowers response thresholds, leading to faster and more efficient motor behavior though in situations of response conflict can induce impulsive and inappropriate responding. In turn, through a process of active sensing, coupling action to temporally predictable sensory input enhances perceptual processing. Action not only hones perception of the event's onset or duration, but also boosts sensory processing of its non-temporal features such as pitch or shape. The effects of temporal predictability on motor behavior and sensory processing involve motor and left parietal cortices and are mediated by changes in delta and beta oscillations in motor areas of the brain.
Topics: Humans; Motor Cortex; Psychomotor Performance; Time Perception; Parietal Lobe; Animals; Motor Activity
PubMed: 38918353
DOI: 10.1007/978-3-031-60183-5_11 -
Advances in Experimental Medicine and... 2024In this chapter, we present recent findings from our group showing that elapsed time, interval timing, and rhythm maintenance might be achieved by the well-known ability... (Review)
Review
In this chapter, we present recent findings from our group showing that elapsed time, interval timing, and rhythm maintenance might be achieved by the well-known ability of the brain to predict the future states of the world. The difference between predictions and actual sensory evidence is used to generate perceptual and behavioral adjustments that help subjects achieve desired behavioral goals. Concretely, we show that (1) accumulating prediction errors is a plausible strategy humans could use to determine whether a train of consecutive stimuli arrives at regular or irregular intervals. By analyzing the behavior of human and non-human primate subjects performing rhythm perception tasks, we demonstrate that (2) the ability to estimate elapsed time and internally maintain rhythms is shared across primates and humans. Neurophysiological recordings show that (3) the medial premotor cortex engages in rhythm entrainment and maintains oscillatory activity that reveals an internal metronome's spatial and temporal characteristics. Finally, we demonstrate that (4) the amplitude of gamma oscillations within this cortex increases proportionally to the total elapsed time. In conjunction with our most recent experiments, our results suggest that timing might be achieved by an internal simulation of the sensory stimuli and the motor commands that define the timing task that needs to be performed.
Topics: Humans; Time Perception; Animals; Motor Cortex; Periodicity
PubMed: 38918351
DOI: 10.1007/978-3-031-60183-5_9