Monkey prefrontal neurons during Sternberg task performance: full contents of working memory or most recent item?
To explore the brain mechanisms underlying multi-item working memory, we monitored the activity of neurons in the dorsolateral prefrontal cortex while macaque monkeys performed spatial and chromatic versions of a Sternberg working-memory task. Each trial required holding three sequentially presented samples in working memory so as to identify a subsequent probe matching one of them. The monkeys were able to recall all three samples at levels well above chance, exhibiting modest load and recency effects. Prefrontal neurons signaled the identity of each sample during the delay period immediately following its presentation. H...
Source: Journal of Neurophysiology - June 6, 2017 Category: Neurology Authors: Konecky, R. O., Smith, M. A., Olson, C. R. Tags: Research Articles Source Type: research
Reach-relevant somatosensory signals modulate tactile suppression
Tactile stimuli on moving limbs are typically attenuated during reach planning and execution. This phenomenon has been related to internal forward models that predict the sensory consequences of a movement. Tactile suppression is considered to occur due to a match between the actual and predicted sensory consequences of a movement, which might free capacities to process novel or task-relevant sensory signals. Here, we examined whether and how tactile suppression depends on the relevance of somatosensory information for reaching. Participants reached with their left or right index finger to the unseen index finger of their ...
Source: Journal of Neurophysiology - June 6, 2017 Category: Neurology Authors: Gertz, H., Voudouris, D., Fiehler, K. Tags: Research Articles Source Type: research
Decisions in motion: passive body acceleration modulates hand choice
In everyday life, we frequently have to decide which hand to use for a certain action. It has been suggested that for this decision the brain calculates expected costs based on action values, such as expected biomechanical costs, expected success rate, handedness, and skillfulness. Although these conclusions were based on experiments in stationary subjects, we often act while the body is in motion. We investigated how hand choice is affected by passive body motion, which directly affects the biomechanical costs of the arm movement due to its inertia. With the use of a linear motion platform, 12 right-handed subjects were s...
Source: Journal of Neurophysiology - June 6, 2017 Category: Neurology Authors: Bakker, R. S., Weijer, R. H. A., van Beers, R. J., Selen, L. P. J., Medendorp, W. P. Tags: Research Articles Source Type: research
Network-wide oscillations in the parkinsonian state: alterations in neuronal activities occur in the premotor cortex in parkinsonian nonhuman primates
This study further supports the concept that PD is a network disorder that induces abnormal spontaneous neural activities across the basal-ganglia-thalamocortical circuit including the premotor cortex and provides foundational knowledge for future studies regarding the relationship between changes in neuronal activity in this region and the development of motor deficits in PD.
NEW & NOTEWORTHY This study begins to fill a gap in knowledge regarding how Parkinson’s disease (PD) may cause abnormal functioning of the premotor cortex. It is novel as the premotor activity is examined in both the naïve and parki...
Source: Journal of Neurophysiology - June 6, 2017 Category: Neurology Authors: Wang, J., Johnson, L. A., Jensen, A. L., Baker, K. B., Molnar, G. F., Johnson, M. D., Vitek, J. L. Tags: Research Articles Source Type: research
The neural control of interlimb coordination during mammalian locomotion
Neuronal networks within the spinal cord directly control rhythmic movements of the arms/forelimbs and legs/hindlimbs during locomotion in mammals. For an effective locomotion, these networks must be flexibly coordinated to allow for various gait patterns and independent use of the arms/forelimbs. This coordination can be accomplished by mechanisms intrinsic to the spinal cord, somatosensory feedback from the limbs, and various supraspinal pathways. Incomplete spinal cord injury disrupts some of the pathways and structures involved in interlimb coordination, often leading to a disruption in the coordination between the arm...
Source: Journal of Neurophysiology - June 1, 2017 Category: Neurology Authors: Frigon, A. Tags: Reviews Source Type: research
In vivo optogenetic activation of Nav1.8+ cutaneous nociceptors and their responses to natural stimuli
Optogenetic methods that utilize expression of the light-sensitive protein channelrhodopsin-2 (ChR2) in neurons have enabled selective activation of specific subtypes or groups of neurons to determine their functions. Using a transgenic mouse model in which neurons natively expressing Nav1.8 (a tetrodotoxin-resistant voltage-gated sodium channel) also express the light-gated channel ChR2, we have been able to determine the functional properties of Nav1.8-expressing cutaneous nociceptors of the glabrous skin in vivo. Most (44 of 53) of the C-fiber nociceptors isolated from Nav1.8-ChR2+ mice were found to be responsive to bl...
Source: Journal of Neurophysiology - June 1, 2017 Category: Neurology Authors: Uhelski, M. L., Bruce, D. J., Seguela, P., Wilcox, G. L., Simone, D. A. Tags: Rapid Reports Source Type: research
Differential processing of the direction and focus of expansion of optic flow stimuli in areas MST and V3A of the human visual cortex
Human neuropsychological and neuroimaging studies have raised the possibility that different attributes of optic flow stimuli, namely radial direction and the position of the focus of expansion (FOE), are processed within separate cortical areas. In the human brain, visual areas V5/MT+ and V3A have been proposed as integral to the analysis of these different attributes of optic flow stimuli. To establish direct causal relationships between neural activity in human (h)V5/MT+ and V3A and the perception of radial motion direction and FOE position, we used transcranial magnetic stimulation (TMS) to disrupt cortical activity in...
Source: Journal of Neurophysiology - June 1, 2017 Category: Neurology Authors: Strong, S. L., Silson, E. H., Gouws, A. D., Morland, A. B., McKeefry, D. J. Tags: Research Articles Source Type: research
Systems-based analysis of dendritic nonlinearities reveals temporal feature extraction in mouse L5 cortical neurons
What do dendritic nonlinearities tell a neuron about signals injected into the dendrite? Linear and nonlinear dendritic components affect how time-varying inputs are transformed into action potentials (APs), but the relative contribution of each component is unclear. We developed a novel systems-identification approach to isolate the nonlinear response of layer 5 pyramidal neuron dendrites in mouse prefrontal cortex in response to dendritic current injections. We then quantified the nonlinear component and its effect on the soma, using functional models composed of linear filters and static nonlinearities. Both noise and w...
Source: Journal of Neurophysiology - June 1, 2017 Category: Neurology Authors: Kalmbach, B. E., Gray, R., Johnston, D., Cook, E. P. Tags: Research Articles Source Type: research
Microinjection of kynurenic acid in the rostral nucleus of the tractus solitarius disrupts spatiotemporal aspects of mechanically induced tracheobronchial cough
The importance of neurons in the nucleus of the solitary tract (NTS) in the production of coughing was tested by microinjections of the nonspecific glutamate receptor antagonist kynurenic acid (kyn; 100 mM in artificial cerebrospinal fluid) in 15 adult spontaneously breathing anesthetized cats. Repetitive coughing was elicited by mechanical stimulation of the intrathoracic airway. Electromyograms (EMG) were recorded from inspiratory parasternal and expiratory transversus abdominis (ABD) muscles. Bilateral microinjections of kyn into the NTS rostral to obex [55 ± 4 nl total in 2 locations (n = 6) or 110 ± 4 nl...
Source: Journal of Neurophysiology - June 1, 2017 Category: Neurology Authors: Poliacek, I., Pitts, T., Rose, M. J., Davenport, P. W., Simera, M., Veternik, M., Kotmanova, Z., Bolser, D. C. Tags: Research Articles Source Type: research
Spaceflight-induced synaptic modifications within hair cells of the mammalian utricle
Exposure to the microgravity conditions of spaceflight alleviates the load normally imposed by the Earth’s gravitational field on the inner ear utricular epithelia. Previous ultrastructural investigations have shown that spaceflight induces an increase in synapse density within hair cells of the rat utricle. However, the utricle exhibits broad physiological heterogeneity across different epithelial regions, and it is unknown whether capabilities for synaptic plasticity generalize to hair cells across its topography. To achieve systematic and broader sampling of the epithelium than was previously conducted, we used im...
Source: Journal of Neurophysiology - June 1, 2017 Category: Neurology Authors: Sultemeier, D. R., Choy, K. R., Schweizer, F. E., Hoffman, L. F. Tags: Research Articles Source Type: research
Fixation target representation in prefrontal cortex during the antisaccade task
We examined the properties of prefrontal fixation neurons in the context of an antisaccade task, which requires an eye movement directed away from a prepotent visual stimulus. We tested monkeys with variants of the task, allowing us to dissociate activity synchronized on the fixation offset, presentation of the visual stimulus, and saccadic onset. Fixation neuron activity latency was most strongly tied to the offset of the fixation point across task variants. It was not well predicted by the appearance of the visual stimulus, which is essential for planning of the correct eye movement and inhibiting inappropriate ones. Act...
Source: Journal of Neurophysiology - June 1, 2017 Category: Neurology Authors: Zhou, X., Constantinidis, C. Tags: Research Articles Source Type: research
Local vs. volume conductance activity of field potentials in the human subthalamic nucleus
This study aimed at understanding of the physiological origin of subthalamic field potentials and determining the most accurate method for recording them. We compared different methods of recordings in the human subthalamic nucleus: spikes (300–9,000 Hz) and field potentials (3–100 Hz) recorded by monopolar micro- and macroelectrodes, as well as by differential-bipolar macroelectrodes. The recordings were done outside and inside the subthalamic nucleus during electrophysiological navigation for deep brain stimulation procedures (150 electrode trajectories) in 41 Parkinson’s disease patients. We modeled th...
Source: Journal of Neurophysiology - June 1, 2017 Category: Neurology Authors: Marmor, O., Valsky, D., Joshua, M., Bick, A. S., Arkadir, D., Tamir, I., Bergman, H., Israel, Z., Eitan, R. Tags: Research Articles Source Type: research
Developmental role of DSCAM in spinal locomotor circuits
Studying the development of spinal circuitry is essential in understanding the motor behaviors that arise from them. In their study, Thiry et al. (J Neurophysiol 115: 1338–1354, 2016) show that loss of Down syndrome cell adhesion molecule (DSCAM) leads to locomotor impairments that may stem from specific changes in spinal connectivity altering the balance of central and peripheral excitatory drive onto spinal motoneurons. These findings as well as additional insights and future directions are discussed in the context of the recent literature. (Source: Journal of Neurophysiology)
Source: Journal of Neurophysiology - June 1, 2017 Category: Neurology Authors: Farah, C. Tags: Neuro Forum Source Type: research
Nonreciprocal homeostatic compensation in Drosophila potassium channel mutants
In this study, we report a mechanism by which Drosophila melanogaster larval motor neurons stabilize hyperactivity induced by the loss of the delayed rectifying K+ channel Shaker cognate B (Shab), by upregulating the Ca2+-dependent K+ channel encoded by the slowpoke (slo) gene. We also show that loss of SLO does not trigger a reciprocal compensatory upregulation of SHAB, implying that homeostatic signaling pathways utilize compensatory pathways unique to the channel that was mutated. SLO upregulation due to loss of SHAB involves nuclear Ca2+ signaling and dCREB, suggesting that the slo homeostatic response is transcription...
Source: Journal of Neurophysiology - June 1, 2017 Category: Neurology Authors: Kim, E. Z., Vienne, J., Rosbash, M., Griffith, L. C. Tags: Research Articles Source Type: research
Echo-acoustic flow shapes object representation in spatially complex acoustic scenes
Echolocating bats use echoes of their sonar emissions to determine the position and distance of objects or prey. Target distance is represented as a map of echo delay in the auditory cortex (AC) of bats. During a bat’s flight through a natural complex environment, echo streams are reflected from multiple objects along its flight path. Separating such complex streams of echoes or other sounds is a challenge for the auditory system of bats as well as other animals. We investigated the representation of multiple echo streams in the AC of anesthetized bats (Phyllostomus discolor) and tested the hypothesis that neurons ca...
Source: Journal of Neurophysiology - June 1, 2017 Category: Neurology Authors: Greiter, W., Firzlaff, U. Tags: Research Articles Source Type: research
