-
ELife Mar 2016In humans, listening to speech evokes neural responses in the motor cortex. This has been controversially interpreted as evidence that speech sounds are processed as...
In humans, listening to speech evokes neural responses in the motor cortex. This has been controversially interpreted as evidence that speech sounds are processed as articulatory gestures. However, it is unclear what information is actually encoded by such neural activity. We used high-density direct human cortical recordings while participants spoke and listened to speech sounds. Motor cortex neural patterns during listening were substantially different than during articulation of the same sounds. During listening, we observed neural activity in the superior and inferior regions of ventral motor cortex. During speaking, responses were distributed throughout somatotopic representations of speech articulators in motor cortex. The structure of responses in motor cortex during listening was organized along acoustic features similar to auditory cortex, rather than along articulatory features as during speaking. Motor cortex does not contain articulatory representations of perceived actions in speech, but rather, represents auditory vocal information.
Topics: Acoustic Stimulation; Auditory Cortex; Auditory Perception; Brain Mapping; Humans; Motor Cortex; Phonetics
PubMed: 26943778
DOI: 10.7554/eLife.12577 -
Journal of Cognitive Neuroscience Nov 2023Motor interactions require observing and monitoring a partner's performance as the interaction unfolds. Studies in monkeys suggest that this form of social monitoring...
Motor interactions require observing and monitoring a partner's performance as the interaction unfolds. Studies in monkeys suggest that this form of social monitoring might be mediated by the activity of the ventral premotor cortex (vPMc), a critical brain region in action observation and motor planning. Our previous fMRI studies in humans showed that the left vPMc is indeed recruited during social monitoring, but its causal role is unexplored. In three experiments, we applied online anodal or cathodal transcranial direct current stimulation over the left lateral frontal cortex during a music-like interactive task to test the hypothesis that neuromodulation of the left vPMc affects participants' performance when a partner violates the agent's expectations. Participants played short musical sequences together with a virtual partner by playing one note each in turn-taking. In 50% of the trials, the partner violated the participant's expectations by generating the correct note through an unexpected movement. During sham stimulation, the partner's unexpected behavior led to a slowdown in the participant's performance (observation-induced posterror slowing). A significant interaction with the stimulation type showed that cathodal and anodal transcranial direct current stimulation induced modulation of the observation-induced posterror slowing in opposite directions by reducing or enhancing it, respectively. Cathodal stimulation significantly reduced the effect compared to sham stimulation. No effect of neuromodulation was found when the partner behaved as expected or when the observed violation occurred within a context that was perceptually matched but noninteractive in nature. These results provide evidence for the critical causal role that the left vPMc might play in social monitoring during motor interactions, possibly through the interplay with other brain regions in the posterior medial frontal cortex.
Topics: Humans; Transcranial Direct Current Stimulation; Motor Cortex; Movement; Brain
PubMed: 37677055
DOI: 10.1162/jocn_a_02046 -
International Journal of Molecular... Jan 2023Transcranial focused ultrasound (tFUS) is a novel neuromodulating technique. It has been demonstrated that the neuromodulatory effects can be induced by weak ultrasound...
Transcranial focused ultrasound (tFUS) is a novel neuromodulating technique. It has been demonstrated that the neuromodulatory effects can be induced by weak ultrasound exposure levels (spatial-peak temporal average intensity, I < 10 mW/cm) in vitro. However, fewer studies have examined the use of weak tFUS to potentially induce long-lasting neuromodulatory responses in vivo. The purpose of this study was to determine the lower-bound threshold of tFUS stimulation for inducing neuromodulation in the motor cortex of rats. A total of 94 Sprague-Dawley rats were used. The sonication region aimed at the motor cortex under weak tFUS exposure (I of 0.338-12.15 mW/cm). The neuromodulatory effects of tFUS on the motor cortex were evaluated by the changes in motor-evoked potentials (MEPs) elicited by transcranial magnetic stimulation (TMS). In addition to histology analysis, the in vitro cell culture was used to confirm the neuromodulatory mechanisms following tFUS stimulation. In the results, the dose-dependent inhibitory effects of tFUS were found, showing increased intensities of tFUS suppressed MEPs and lasted for 30 min. Weak tFUS significantly decreased the expression of excitatory neurons and increased the expression of inhibitory GABAergic neurons. The PIEZO-1 proteins of GABAergic neurons were found to involve in the inhibitory neuromodulation. In conclusion, we show the use of weak ultrasound to induce long-lasting neuromodulatory effects and explore the potential use of weak ultrasound for future clinical neuromodulatory applications.
Topics: Rats; Animals; Rats, Sprague-Dawley; Motor Cortex; Ultrasonography; Transcranial Magnetic Stimulation; GABAergic Neurons; Evoked Potentials, Motor
PubMed: 36768901
DOI: 10.3390/ijms24032578 -
Behavioral Neuroscience Oct 2010Although there are many studies investigating the effects of early cortical injury on brain and behavioral development in laboratory animals, there are virtually no...
Although there are many studies investigating the effects of early cortical injury on brain and behavioral development in laboratory animals, there are virtually no studies examining the effects of cortical injury in adolescence. The purpose of present study was to investigate the effects of unilateral motor cortex lesion received in early and late adolescence periods (Postnatal days 35 and 55 [P35, P55]) on spontaneous neural reorganization and behavioral recovery in adulthood. Rats were given unilateral motor cortex lesions at P35 or P55 and their motor behaviors were compared to sham controls in adulthood. The results of behavioral tests (skilled reaching, postural asymmetry, sunflower seed manipulation, forepaw inhibition in swimming) revealed that rats with P35 lesions had significant functional deficits whereas the rats with P55 lesions showed nearly complete recovery. Golgi-Cox analysis of pyramidal neurons showed bilateral hypertrophy of dendritic fields in the remaining sensorimotor cortex in P55 but not P35 rat brains. Thus, there appears to be an age-related pattern of morphological and behavioral changes in response to cortical injury in the early and late adolescent periods leading to better functional recovery from later injuries, much as is seen in human children.
Topics: Age Factors; Animals; Behavior, Animal; Disease Models, Animal; Female; Motor Cortex; Parietal Lobe; Pyramidal Cells; Rats; Rats, Long-Evans; Recovery of Function
PubMed: 20939661
DOI: 10.1037/a0020911 -
Current Opinion in Neurobiology Dec 1996Recent studies have provided new insights into the visuomotor functions of the dorsal and ventral regions of the lateral pre-motor cortex. Anatomical and physiological... (Review)
Review
Recent studies have provided new insights into the visuomotor functions of the dorsal and ventral regions of the lateral pre-motor cortex. Anatomical and physiological investigations in non-human primates have demonstrated that these regions have differing patterns of cortical connectivity and distinctive neuronal responses. Brain-imaging techniques and lesion studies have begun to probe the functions of homologous regions in humans.
Topics: Animals; Eye Movements; Humans; Motor Cortex; Neural Pathways; Primates
PubMed: 9000029
DOI: 10.1016/s0959-4388(96)80029-8 -
Current Opinion in Neurobiology Feb 2014The brain's cortical maps serve as a macroscopic framework upon which additional levels of detail can be overlaid. Unlike sensory maps generated by measuring the brain's... (Review)
Review
The brain's cortical maps serve as a macroscopic framework upon which additional levels of detail can be overlaid. Unlike sensory maps generated by measuring the brain's responses to incoming stimuli, motor maps are made by directly stimulating the brain itself. To understand the significance of motor maps and the functions they represent, it is necessary to consider the relationship between the natural operation of the motor system and the pattern of activity evoked in it by artificial stimulation. We review recent findings from the study of the cortical motor system and new insights into the control of movement based on its mapping within cortical space.
Topics: Animals; Brain Mapping; Humans; Motor Cortex; Movement; Nerve Net
PubMed: 24492084
DOI: 10.1016/j.conb.2013.08.018 -
The Journal of Neuroscience : the... Aug 2021Primary motor cortex (M1) undergoes protracted development in mammals, functioning initially as a sensory structure. Throughout the first postnatal week in rats, M1 is...
Primary motor cortex (M1) undergoes protracted development in mammals, functioning initially as a sensory structure. Throughout the first postnatal week in rats, M1 is strongly activated by self-generated forelimb movements-especially by the twitches that occur during active sleep. Here, we quantify the kinematic features of forelimb movements to reveal receptive-field properties of individual units within the forelimb region of M1. At postnatal day 8 (P8), nearly all units were strongly modulated by movement amplitude, especially during active sleep. By P12, only a minority of units continued to exhibit amplitude tuning, regardless of behavioral state. At both ages, movement direction also modulated M1 activity, though to a lesser extent. Finally, at P12, M1 population-level activity became more sparse and decorrelated, along with a substantial alteration in the statistical distribution of M1 responses to limb movements. These findings reveal a transition toward a more complex and informationally rich representation of movement long before M1 develops its motor functionality. Primary motor cortex (M1) plays a fundamental role in the generation of voluntary movements and motor learning in adults. In early development, however, M1 functions as a prototypical sensory structure. Here, we demonstrate in infant rats that M1 codes for the kinematics of self-generated limb movements long before M1 develops its capacity to drive movements themselves. Moreover, we identify a key transition during the second postnatal week in which M1 activity becomes more informationally complex. Together, these findings further delineate the complex developmental path by which M1 develops its sensory functions in support of its later-emerging motor capacities.
Topics: Animals; Animals, Newborn; Biomechanical Phenomena; Forelimb; Motor Cortex; Movement; Rats; Rats, Sprague-Dawley
PubMed: 34281990
DOI: 10.1523/JNEUROSCI.0921-21.2021 -
Neural Plasticity 2022Temporal interference (TI) could stimulate deep motor cortex and induce movement without affecting the overlying cortex in previous mouse studies. However, there is... (Randomized Controlled Trial)
Randomized Controlled Trial
Temporal interference (TI) could stimulate deep motor cortex and induce movement without affecting the overlying cortex in previous mouse studies. However, there is still lack of evidence on potential TI effects in human studies. To fill this gap, we collected resting-state functional magnetic resonance imaging data on 40 healthy young participants both before and during TI stimulation on the left primary motor cortex (M1). We also chose a widely used simulation approach (tDCS) as a baseline condition. In the stimulation session, participants were randomly allocated to 2 mA TI or tDCS for 20 minutes. We used a seed-based whole brain correlation analysis method to quantify the strength of functional connectivity among different brain regions. Our results showed that both TI and tDCS significantly boosted functional connection strength between M1 and secondary motor cortex (premotor cortex and supplementary motor cortex). This is the first time to demonstrate substantial stimulation effect of TI in the human brain.
Topics: Animals; Brain; Evoked Potentials, Motor; Humans; Magnetic Resonance Imaging; Mice; Motor Cortex; Movement; Transcranial Direct Current Stimulation
PubMed: 35140781
DOI: 10.1155/2022/7605046 -
Progress in Brain Research 2001
Review
Topics: Action Potentials; Animals; Cell Communication; Cortical Synchronization; Motor Cortex; Neurons
PubMed: 11480278
DOI: 10.1016/s0079-6123(01)30016-x -
Biological Psychiatry Mar 2001Using transcranial magnetic stimulation (TMS), a handheld electrified copper coil against the scalp produces a powerful and rapidly oscillating magnetic field, which in...
The transcranial magnetic stimulation motor threshold depends on the distance from coil to underlying cortex: a replication in healthy adults comparing two methods of assessing the distance to cortex.
Using transcranial magnetic stimulation (TMS), a handheld electrified copper coil against the scalp produces a powerful and rapidly oscillating magnetic field, which in turn induces electrical currents in the brain. The amount of electrical energy needed for TMS to induce motor movement (called the motor threshold [MT]), varies widely across individuals. The intensity of TMS is dosed relative to the MT. Kozel et al observed in a depressed cohort that MT increases as a function of distance from coil to cortex. This article examines this relationship in a healthy cohort and compares the two methods of assessing distance to cortex. Seventeen healthy adults had their TMS MT determined and marked with a fiducial. Magnetic resonance images showed the fiducials marking motor cortex, allowing researchers to measure distance from scalp to motor and prefontal cortex using two methods: 1) measuring a line from scalp to the nearest cortex and 2) sampling the distance from scalp to cortex of two 18-mm-square areas. Confirming Kozel's previous finding, we observe that motor threshold increases as distance to motor cortex increased for both methods of measuring distance and that no significant correlation exists between MT and prefontal cortex distance. Distance from TMS coil to motor cortex is an important determinant of MT in healthy and depressed adults. Distance to prefontal cortex is not correlated with MT, raising questions about the common practice of dosing prefontal stimulation using MT determined over motor cortex.
Topics: Adult; Aged; Cerebral Cortex; Electromagnetic Phenomena; Female; Humans; Magnetic Resonance Imaging; Male; Middle Aged; Motor Cortex
PubMed: 11274657
DOI: 10.1016/s0006-3223(00)01039-8