Animal models indicate that serotonin (5-HT) release onto motoneurons facilitates motor output, particularly during strong motor activities. However, evidence for 5-HT effects during human movement are limited. This study examined how antagonism of the 5-HT2 receptor, which is a 5-HT receptor that promotes motoneuron excitability, affects human movement. Ten healthy participants (24.2 ± 1.9 yr) ingested

Traumatic musculoskeletal injury (MSI) may involve changes in corticomotor structure and function but direct evidence is needed. To determine the corticomotor basis of MSI, we examined interactions among skeletomotor function, corticospinal excitability, corticomotor structure (cortical thickness and white matter microstructure), and intermittent theta burst stimulation (iTBS)-induced plasticity. Nine

Accumulating evidence indicates that the brain natriuretic peptide(BNP) and its receptor (natriuretic peptide receptor, NPR) are widely distributed in a variety of tissues including trigeminal ganglion (TG). Furthermore, recent studies support the involvement of the BNP-NPRA pathway in acute and chronic pain. To investigate the role of this pathway in chronic pain, an infraorbital nerve-chronic constriction

Recent work has shown that human auditory cortex contains neural populations anterior and posterior to primary auditory cortex that respond selectively to music. However, it is unknown how this selectivity for music arises. To test whether musical training is necessary, we measured fMRI responses to 192 natural sounds in 10 people with almost no musical training. When voxel responses were decomposed

Viewing the faces of familiar people selectively activates a distributed network of brain regions implicated in both the perceptual and non-perceptual processing of conspecifics. In this fMRI study, we investigate the influence of depth of famous-face processing on this network, comparing a passive incidental face-processing to a task that required the extraction of identity and biographic information

Neuroactive substances released by activated microglia contribute to hyperexcitability of spinal dorsal horn neurons in many animal models of chronic pain. An important feedback loop mechanism is via release of fractalkine (CX3CL1) from primary afferent terminals and dorsal horn neurons and binding to CX3CR1 receptors on microglial cells. We studied the involvement of fractalkine signaling in latent

How humans visually select where to grasp an object depends on many factors, including grasp stability and preferred grasp configuration. We examined how endpoints are selected when these two factors are brought into conflict: Do people favor stable grasps or do they prefer their natural grasp configurations? Participants reached to grasp one of three cuboids oriented so that its two corners were either

Ventilatory deficits are common in old age and may result from neuromuscular dysfunction. Signaling via the tropomyosin-related kinase receptor B (TrkB) regulates neuromuscular transmission and in young mice is important for the generation of transdiaphragmatic pressure (Pdi). Loss of TrkB signaling worsened neuromuscular transmission failure and reduced maximal Pdi, and these effects are similar to

The sympathetic nervous system is important for the beat-by-beat regulation of arterial blood pressure and the control of blood flow to various organs. Microneurographic recordings of pulse-synchronous muscle sympathetic nerve activity (MSNA) are used by numerous laboratories worldwide. The transduction of hemodynamic and vascular responses elicited by spontaneous bursts of MSNA provides novel, mechanistic

Four recent articles were examined for their use of resting-state functional magnetic resonance imaging on participants with posttraumatic symptoms. Theory-driven computations were complemented by the novel use of network metrics which revealed reduced global centrality and higher efficiency within the default mode network for participants with posttraumatic symptoms. Data-driven methods from other

Moderate acute intermittent hypoxia (mAIH; 35-55 mmHg PaO2) elicits phrenic long-term facilitation (pLTF) by a mechanism that requires activation of Gq protein-coupled serotonin type 2 receptors, MEK/ERK MAP kinase and NADPH oxidase activity, and is constrained by cAMP-PKA signaling. In contrast, severe AIH (sAIH; 25-35 mmHg PaO2) elicits Gs protein-coupled adenosine type 2A receptor-dependent pLTF

Precise control of upper limb movements in response to external stimuli is vital to effectively interact with the environment. Accurate execution of bimanual movement is known to rely on finely orchestrated interhemispheric communication between the primary motor cortices (M1s). However, relatively little is known about the role of interhemispheric communication during sudden cancellation of prepared

The brainstem noradrenergic locus coeruleus (LC) is reciprocally connected with the prefrontal cortex (PFC). Coupling between LC spiking and the depolarizing phase of slow (1 - 2 Hz) waves in PFC field potentials during sleep and anesthesia suggests that LC drives cortical state transition. Reciprocal LC-PFC connectivity should also allow interactions in the opposing (top-down) direction, but prior

Sense of agency is the experience of control over one's own action and its consequent outcomes. The perceived time between a motor action and its consequent sensory outcomes (e.g., a flash of light) is shorter for a voluntary than involuntary action, a phenomenon known as intentional binding which has been used extensively as an implicit measure of sense of agency. We developed a novel task in which

Swallow is a primitive behavior regulated by medullary networks, responsible for movement of food/liquid from the oral cavity to the esophagus. To investigate how functionally heterogeneous networks along the medullary intermediate reticular formation (IRt) and ventral respiratory column (VRC) control swallow, we electrically stimulated the nucleus tractus solitarius to induce fictive swallow between

A number of notions in the fields of motor control and kinesthetic perception have been used without clear definitions. In this review, we consider definitions for efference copy, percept, and sense of effort based on recent studies within the physical approach, which assumes that the neural control of movement is based on principles of parametric control and involves defining time-varying profiles

Magnetoencephalography (MEG) is a technique used to measure the magnetic fields generated from neuronal activity in the brain. MEG has a high temporal resolution on the order of milliseconds and provides a more direct measure of brain activity compared to hemodynamic-based neuroimaging methods such as magnetic resonance imaging and positron emission tomography. The current review focuses on basic features

The primate superior colliculus (SC) has recently been shown to possess both a large foveal representation as well as a varied visual processing repertoire. This structure is also known to contribute to eye movement generation. Here we describe our current understanding of how SC visual and movement-related signals interact within the realm of small eye movements associated with the foveal scale of

Smooth pursuit eye movements and visual motion perception rely on the integration of current sensory signals with past experience. Experience shapes our expectation of current visual events and can drive eye movement responses made in anticipation of a target, such as anticipatory pursuit. Previous research revealed consistent effects of expectation on anticipatory pursuit-eye movements follow the

Covert spatial attention is thought to facilitate the maintenance of locations in working memory, and EEG alpha-band activity (8 - 12 Hz) is proposed to track the focus of covert attention. Recent work has shown that multivariate patterns of alpha-band activity track the polar angle of remembered locations relative to fixation. However, a defining feature of covert spatial attention is that it facilitates

The configuration of lizard ears, where sound can reach both surfaces of the eardrums, produces a strongly directional ear, but the subsequent processing of sound direction by the auditory pathway is unknown. We report here on directional responses from the first stage, the auditory nerve. We used laser vibrometry to measure eardrum responses in Tokay geckos, and in the same animals recorded 117 auditory

After menopause, women experience declines in ovarian sex hormones, an event that has recently been associated with increased amyloid-β peptides, a main feature of Alzheimer's Disease. Diet-induced insulin resistance also increases amyloid-β peptides; however, whether this process is exacerbated with ovarian sex hormone loss remains unknown. Female C57BL6/J mice received either bilateral ovariectomy

Arm cycling is a bi-manual motor task used in medical rehabilitation and in sports training. Understanding how muscle coordination changes across different biomechanical constraints in arm cycling is a step towards improved rehabilitation approaches. This exploratory study aims to get new insights on motor control during arm cycling. To achieve our main goal, we used the muscle synergies analysis to

Remarkable trial-by-trial variability is apparent in cortical responses to repeating stimulus presentations. This neural variability across trials is relatively high before stimulus presentation, and then reduced (i.e., quenched) ~0.2s after stimulus presentation. Individual subjects exhibit different magnitudes of variability quenching, and previous work from our lab has revealed that individuals

We recently demonstrated in decerebrate and conscious cat preparations that hindlimb somatosensory inputs converge with vestibular afferent input onto neurons in multiple CNS locations that participate in balance control. While it is known that head position and limb state modulate postural reflexes, presumably through vestibulospinal and reticulospinal pathways, the combined influence of the two inputs

Studies of reach control with the body stationary have shown that proprioceptive and visual feedback signals contributing to rapid corrections during reaching are processed by neural circuits that incorporate knowledge about the physical properties of the limb (an "internal model"). However, among the most common spatial and mechanical perturbations to the limb are those caused by our body's own motion

The preBötzinger complex (preBötC), located within the ventral respiratory column, produces inspiratory bursts in varying degrees of synchronization/amplitude. This wide range of population burst patterns reflects the flexibility of the preBötC neurons, which is expressed in variations in the onset/offset times of their activations and their activity during the population bursts, with respiratory neurons

Activity of parafacial neurons that control active expiration are heavily dependent on tonic and CO2/H+-dependent excitatory and inhibitory inputs from yet poorly defined sources. Contrary to the idea that CO2/H+disinhibits parafacial expiratory neurons, the recent work of J.D. Silva et al., 2020, suggests GABAergic raphe neurons preforentially limit expiratory activity during high CO2. Here I discuss

Modulatory actions of inputs from the visual system to cervical interneurons (IN) for arm muscle control are poorly understood in humans. In the present study, we examined whether visual stimulation modulates the excitation of cervical IN systems mediating corticospinal tract (CST) inputs to biceps brachii (BB). Twenty-eight healthy volunteers were seated and electromyogram recordings from the BB were

The accurate processing of temporal information is of critical importance in everyday life. Yet, psychophysical studies in humans have shown that the perception of time is distorted around saccadic eye movements. The neural correlates of this misperception are still poorly understood. Behavioral and neural evidence suggest that it is tightly linked to other known perisaccadic modulations of visual

Modern neurophysiology research requires the interrogation of high-dimensionality datasets. ML/AI workflows have permeated into nearly all aspects of daily life in the developed world, but have not been implemented routinely in neurophysiological analyses. The power of these workflows includes the speed at which they can be deployed, their availability of open-source programming languages, and the

Many studies have compared active and passive touch to understand how motor action shapes touch perception. Current views emphasize the difficulties in making such a comparison and promote investigating how motor strategies enable the filtering out of sensory inputs to reshape touch perception. Cybulska-Klosowicz et al. (2020) suggest that primary somatosensory (S1) cortical remodeling of digit representation

Perception of limb position and motion combines sensory information from spindles in muscles that span one joint (monoarticulars) and two joints (biarticulars). This anatomical organization should create interactions in estimating limb position. We developed two models, one with only monoarticulars (MO Model) and one with monoarticulars and biarticulars (MB Model), to explore how biarticulars influence

Controlling posture requires continuous sensory feedback about body motion and orientation, including from the vestibular organs. Little is known about the role of tilt vs. translation vs. rotation vestibular cues. We examined whether inter-subject differences in vestibular function were correlated with inter-subject differences in postural control. Vestibular function was assayed using vestibular

The mammalian motor cortex is topographically organized into representations of discrete body parts (motor maps). Studies in adult rats using long-duration intracortical microstimulation (LD-ICMS) reveal that forelimb motor cortex is functionally organized into several spatially distinct areas encoding complex, multi-joint movement sequences: elevate, advance, grasp, retract. The topographical arrangement

Observation of object lifting allows updating of internal object representations for object weight, in turn enabling accurate scaling of fingertip forces when lifting the same object. Here, we investigated whether lift observation also enables updating of internal representations for an object's weight distribution. We asked participants to lift an inverted T-shaped manipulandum, of which the weight

Spherical bushy cells (SBCs) in the the anteroventral cochlear nucleus receive a single or very few powerful axosomatic inputs from the auditory nerve. However, SBCs are also contacted by small regular bouton synapses of the auditory nerve, located in their dendritic tree. The function of these small inputs is unknown. It was speculated that the interaction of axosomatic inputs with small dendritic

The planning and execution of sequential saccades can overlap in time, and abrupt changes in neural activity in the oculomotor system can alter the normal trajectory of saccades. In this study, we analyzed saccade trajectories to assess the combined programming of sequential saccades. In two separate psychophysical experiments, subjects were instructed to make a sequence of two saccades. The results

To maintain metabolic homeostasis, motivated behaviors are driven by neuronal circuits that process information encoding the animal's energy state. Such circuits likely include ventromedial hypothalamus (VMH) glutamatergic neurons that project throughout the brain to drive food intake and energy expenditure. Targets of VMH glutamatergic neurons include proopiomelanocortin (POMC) neurons in the arcuate

Perceived frequency of vibrotactile stimuli can be divided into two distinctive cutaneous sensations - flutter (<60 Hz) and vibratory hum (>60 Hz), mediated by two different tactile afferent types (FA1 and FA2, respectively). We recently demonstrated a novel form of neural coding in the human tactile system, where frequency perception of stimulus pulses grouped into periodic bursts in the flutter range

By stopping actions even after their initiation, humans can flexibly adapt ongoing behavior to changing circumstances. The neural processes underlying the inhibition of movement during action-stopping are still controversial. In the 1990s, a fronto-central event-related potential (ERP) was discovered in the human EEG response to stop-signals in the classic stop-signal task, alongside a proposal that

Perception of the frictional properties of a surface contributes to the multidimensional experience of exploring various materials - we slide our fingers over a surface to feel it. In contrast, during object manipulation we grip objects without such intended exploratory movements. Given that we are aware of the slipperiness of objects or tools that are held in the hand, we investigated whether the

Journal of Neurophysiology, Ahead of Print.

The thalamic medial geniculate body (MGB) is uniquely positioned within the neural tinnitus networks. Deep brain stimulation (DBS) of the MGB has been proposed as a possible novel treatment for tinnitus, yet mechanisms remain elusive. The aim of this study was to characterize neurophysiologic hallmarks in the MGB after noise-exposure and to assess the neurophysiological effects of electrical stimulation

While ethanol consumption leads to an array of neurophysiological alterations involving the neural circuits for reward, the underlying mechanisms remain unclear. Acetic acid is a major metabolite of ethanol with high bioactivity and potentially significant pharmacological importance in regulating brain function. Yet the impact of acetic acid on reward circuit function has not been well explored. Given

In a recent study published in The Journal of Neurophysiology, Ehrardt et al. report that moderate intensity (1 mA/25 cm2) transcranial direct current stimulation (tDCS) is optimal for improving performance on a stimulus-response matching task, as opposed to a lower 0.7 mA/25 cm2 or higher 2 mA/25 cm2 dose. This result suggests that behavioral effects of tDCS do not follow a linear dose-response curve

The spatial processing of color is important for visual perception. Double-opponent (DO) cells likely contribute to this processing by virtue of their spatially opponent and cone-opponent receptive fields (RFs). However, the representation of visual features by DO cells in the primary visual cortex of primates is unclear because the spatial structure of their RFs has not been fully characterized. To

Previous TMS studies have reported a decrease in motor cortical output during pain observation. In contrast, recent behavioural studies have shown that response times are faster after pain observation. This suggests that there is a mismatch between motor activity during vs. after pain observation. We propose that these opposing effects of pain observation on motor activity may be explained by task

Sensitivity to subtle changes in the shape of visual objects has been attributed to the existence of global pooling mechanisms that integrate local form information across space. While global pooling is typically demonstrated under steady fixation, other work suggests prolonged fixation can lead to a collapse of global structure. Here we ask whether small ballistic eye movements that naturally occur

To program a goal-directed response in the presence of acoustic reflections, the audio-motor system should suppress the detection of time-delayed sources. We examined the effects of spatial separation and inter-stimulus delay on the ability of human listeners to localize a pair of broadband sounds in the horizontal plane. Participants indicated how many sounds were heard and where these were perceived

Journal of Neurophysiology, Volume 124, Issue 6, Page 2076-2076, December 2020.

In this tribute to Reggie Edgerton, I briefly review the spinal mechanisms that coordinate locomotion and the interaction between the different sensory mechanisms that help coordinate the locomotor movements and the central locomotor network. The step cycle has four distinct parts, the support phase, the lift off, the flexion phase and the most complex, the touch down, when the limb makes a smooth

Humans are able to generate target-directed visuomotor responses in less than 100ms after stimulus onset. These "express" responses have been termed stimulus-locked responses (SLRs) and are proposed to be modulated by visuomotor transformations performed subcortically via the superior colliculus. Unfortunately, these responses have proven difficult to detect consistently across individuals. The recent

A fundamental problem in motor control is the coordination of complementary movement types to achieve a common goal. As a common example, humans view moving objects through coordinated pursuit and saccadic eye movements. Pursuit is initiated and continuously controlled by retinal image velocity. During pursuit, eye position may lag behind the target. This can be compensated by the discrete execution

When auditory feedback is perturbed in a consistent way, speakers learn to adjust their speech to compensate, a process known as sensorimotor adaptation. While this paradigm has been highly informative for our understanding of the role of sensory feedback in speech motor control, its ability to induce behaviorally-relevant changes in speech that affect communication effectiveness remains unclear. Because

Adaptive behavior in response to adverse experiences facilitates faster recovery and less time spent engaging in maladaptive behaviors that contribute to psychopathology, including anxiety, depression, and post-traumatic stress disorder. Dysregulation of activity in the prefrontal cortex (PFC) has been implicated in these disorders, as well as in diminished cognitive flexibility, with stress further

Action preparation involves widespread modulation of motor system excitability, but the precise mechanisms are unknown. In this study, we investigated whether intracortical inhibition changes in task-irrelevant muscle representations during action preparation. We used transcranial magnetic stimulation (TMS) combined with electromyography in healthy human adults to measure motor evoked potentials (MEPs)

Saccades are stereotypic behaviors whose investigation improves our understanding of how primate brains implement precise motor control. Furthermore, saccades offer an important window into the cognitive and attentional state of the brain. Historically, saccade studies have largely relied on macaque. However, the cortical network giving rise to the saccadic command is difficult to study in macaque

The posteromedial thalamus (POm) has extensive recurrent connectivity with the whisker-related primary somatosensory cortex (wS1) of rodents. However, its functional contribution to somatosensory processing in wS1 remains unclear. This article reviews several recent findings which begin to elucidate the role of POm in sensory evoked plasticity and discusses their implications for somatosensory processing