Emergence of Bursting Activity in Connected Neuronal Sub-Populations

Uniform and modular primary hippocampal cultures from embryonic rats were grown on commercially available micro-electrode arrays to investigate network activity with respect to development and integration of different neuronal populations. Modular networks consisting of two confined active and inter-connected sub-populations of neurons were realized by means of bi-compartmental polydimethylsiloxane structures. Spontaneous activity in both uniform and modular cultures was periodically monitored, from three up to eight weeks after plating. Compared to uniform cultures and despite lower cellular density, modular networks interestingly showed higher firing rates at earlier developmental stages, and network-wide firing and bursting statistics were less variable over time. Although globally less correlated than uniform cultures, modular networks exhibited also higher intra-cluster than inter-cluster correlations, thus demonstrating that segregation and integration of activity coexisted in this simple yet powerful in vitro model. Finally, the peculiar synchronized bursting activity shown by confined modular networks preferentially propagated within one of the two compartments (‘dominant’), even in cases of perfect balance of firing rate between the two sub-populations. This dominance was generally maintained during the entire monitored developmental frame, thus suggesting that the implementation of this hierarchy arose from early network development.     

Motor Activity Improves Temporal Expectancy

Certain brain areas involved in interval timing are also important in motor activity. This raises the possibility that motor activity might influence interval timing. To test this hypothesis, we assessed interval timing in healthy adults following different types of training. The pre- and post-training tasks consisted of a button press in response to the presentation of a rhythmic visual stimulus. Alterations in temporal expectancy were evaluated by measuring response times. Training consisted of responding to the visual presentation of regularly appearing stimuli by either: (1) pointing with a whole-body movement, (2) pointing only with the arm, (3) imagining pointing with a whole-body movement, (4) simply watching the stimulus presentation, (5) pointing with a whole-body movement in response to a target that appeared at irregular intervals (6) reading a newspaper. Participants performing a motor activity in response to the regular target showed significant improvements in judgment times compared to individuals with no associated motor activity. Individuals who only imagined pointing with a whole-body movement also showed significant improvements. No improvements were observed in the group that trained with a motor response to an irregular stimulus, hence eliminating the explanation that the improved temporal expectations of the other motor training groups was purely due to an improved motor capacity to press the response button. All groups performed a secondary task equally well, hence indicating that our results could not simply be attributed to differences in attention between the groups. Our results show that motor activity, even when it does not play a causal or corrective role, can lead to improved interval timing judgments.     

Reduced Motor Cortex Activity during Movement Preparation following a Period of Motor Skill Practice

Experts in a skill produce movement-related cortical potentials (MRCPs) of smaller amplitude and later onset than novices. This may indicate that, following long-term training, experts require less effort to plan motor skill performance. However, no longitudinal evidence exists to support this claim. To address this, EEG was used to study the effect of motor skill training on cortical activity related to motor planning. Ten non-musicians took part in a 5-week training study learning to play guitar. At week 1, the MRCP was recorded from motor areas whilst participants played the G Major scale. Following a period of practice of the scale, the MRCP was recorded again at week 5. Results showed that the amplitude of the later pre-movement components were smaller at week 5 compared to week 1. This may indicate that, following training, less activity at motor cortex sites is involved in motor skill preparation. This supports claims for a more efficient motor preparation following motor skill training.     

Motor Activity of Eyelids as a Functional State Indicator

The authors consider an insufficiently studied indicator, i.e., motor activity of eyelids, recorded with or without miniature contacts in infrared rays for the visual analyzer states eyes open / eyes closed. Eyelid movement characteristics are highly informative in diagnosing the functional state and evaluating operator activity quality under monotonous conditions. The authors discuss possible mechanisms of the influence of such functional states on the motor activity of eyelids.     

Time-Dependent Effects of Trichloroethylene on Motor Activity in Rats

Circadian variations in acute and subacute neurobehavioural effects of trichloroethylene (TRI: 1.2 g/kg i.p.) were investigated in the rat under a light: dark = 12:12 hr cycle. An acute effect of TRI evaluated by decreased muscle tone was maximal during the early dark phase (21:00). A subacute effect of TRI was evaluated by a continuous recording of spontaneous locomotor activity in the rat. The circadian rhythm in spontaneous locomotor activity was extensively impaired by the injection of TRI for three consecutive days. Spectral analysis of spontaneous locomotor activity showed that ultradian periods became more dominant than the circadian period, and the 1//fluctuation of the spectrum disappeared after the injection of TRI. The effect of TRI on the circadian rhythm in spontaneous locomotor activity was circadian-phase dependent, and the treatment of TRI at 09:00 provoked greater circadian rhythm impairment than that at 21:00. The mechanisms of the time-dependent effect of TRI on neurobehaviour are the subject of further investigation.     

Time-Dependent Effects of Trichloroethylene on Motor Activity in Rats

Circadian variations in acute and subacute neurobehavioural effects of trichloroethylene (TRI: 1.2 g/kg i.p.) were investigated in the rat under a light: dark = 12:12 hr cycle. An acute effect of TRI evaluated by decreased muscle tone was maximal during the early dark phase (21:00). A subacute effect of TRI was evaluated by a continuous recording of spontaneous locomotor activity in the rat. The circadian rhythm in spontaneous locomotor activity was extensively impaired by the injection of TRI for three consecutive days. Spectral analysis of spontaneous locomotor activity showed that ultradian periods became more dominant than the circadian period, and the 1//fluctuation of the spectrum disappeared after the injection of TRI. The effect of TRI on the circadian rhythm in spontaneous locomotor activity was circadian-phase dependent, and the treatment of TRI at 09:00 provoked greater circadian rhythm impairment than that at 21:00. The mechanisms of the time-dependent effect of TRI on neurobehaviour are the subject of further investigation.     

Recording the Motor Activity of Aquatic Animals by Ultrasound

An ultrasonic technique based on the Doppler effect is presented to allow the registration of aquatic animal movements. The method was tested on crucians (Carassius carassius) in an aquarium as part of chronobiological investigations. Comparison with light barrier measurements shows that the Doppler technique is suitable for detecting typical circadian and seasonal changes in the motor activity of the fishes. The features of the ultrasonic method are discussed.     

Suppression of Abdominal Motor Activity during Swallowing in Cats and Humans

Diseases affecting pulmonary mechanics often result in changes to the coordination of swallow and breathing. We hypothesize that during times of increased intrathoracic pressure, swallow suppresses ongoing expiratory drive to ensure bolus transport through the esophagus. To this end, we sought to determine the effects of swallow on abdominal electromyographic (EMG) activity during expiratory threshold loading in anesthetized cats and in awake-healthy adult humans. Expiratory threshold loads were applied to recruit abdominal motor activity during breathing, and swallow was triggered by infusion of water into the mouth. In both anesthetized cats and humans, expiratory cycles which contained swallows had a significant reduction in abdominal EMG activity, and a greater percentage of swallows were produced during inspiration and/or respiratory phase transitions. These results suggest that: a) spinal expiratory motor pathways play an important role in the execution of swallow, and b) a more complex mechanical relationship exists between breathing and swallow than has previously been envisioned.     

Coupled Spike Activity in Micropopulations of Motor Cortex Neurons in Rats

Using eight-channel metal microelectrodes (diameter of a separate channel 12 μm), we extracellularly recorded the impulse activity of 186 single neurons or their small groups (usually, pairs) localized in the motor cortex of rats anesthetized with ketamine. In 60 cases (32.3%), action potentials (APs) of two single neurons were generated in a parallel manner and demonstrated fixed time relations with each other. This is interpreted as being a result of excitation of two neighboring functionally connected (coupled) cells. These AP pairs could be recorded via one and the same or two neighboring microelectrode channels. Second APs in the pair were elicited exclusively in the case where an AP was preliminarily generated by another neuron, while APs of the latter in some cases could arrive independently. Therefore, “leading” and “accompanying” cells could be identified in such neuronal pairs. The coupling coefficient in the generation of APs by an accompanying unit with respect to APs generated by a leading cell was close to 100%, with no dependence on the discharge frequency in the latter. Intervals between APs of two neurons in different coupled pairs varied from about 1.0 to 22-23 msec. In the case of minimum values of these interspike intervals, APs generated by coupled neurons overlapped each other; this resulted in the formation of spikes looking like “complex APs.” Within some time intervals, interspike intervals could increase, and such APs began to be decomposed. The above-described data are considered electrophysiological proof of the existence of tight functional coupling between a significant part of cortical neurons spatially close to each other, i.e., members of a micropopulation, which was obtained in an in vivo experiment.     

BicaudalD Actively Regulates Microtubule Motor Activity in Lipid Droplet Transport

Background

A great deal of sub-cellular organelle positioning, and essentially all minus-ended organelle transport, depends on cytoplasmic dynein, but how dynein''s function is regulated is not well understood. BicD is established to play a critical role in mediating dynein function—loss of BicD results in improperly localized nuclei, mRNA particles, and a dispersed Golgi apparatus—however exactly what BicD''s role is remains unknown. Nonetheless, it is widely believed that BicD may act to tether dynein to cargos. Here we use a combination of biophysical and biochemical studies to investigate BicD''s role in lipid droplet transport during Drosophila embryogenesis.

Methodology/Principal Findings

Functional loss of BicD impairs the embryo''s ability to control the net direction of droplet transport; the developmentally controlled reversal in transport is eliminated. We find that minimal BicD expression (near-BicD^null) decreases the average run length of both plus and minus end directed microtubule (MT) based transport. A point mutation affecting the BicD N-terminus has very similar effects on transport during cellularization (phase II), but in phase III (gastrulation) motion actually appears better than in the wild-type.

Conclusions/Significance

In contrast to a simple static tethering model of BicD function, or a role only in initial dynein recruitment to the cargo, our data uncovers a new dynamic role for BicD in actively regulating transport. Lipid droplets move bi-directionally, and our investigations demonstrate that BicD plays a critical—and temporally changing—role in balancing the relative contributions of plus-end and minus-end motors to control the net direction of transport. Our results suggest that while BicD might contribute to recruitment of dynein to the cargo it is not absolutely required for such dynein localization, and it clearly contributes to regulation, helping activation/inactivation of the motors.     

Altered Regional and Circuit Resting-State Activity Associated with Unilateral Hearing Loss

The deprivation of sensory input after hearing damage results in functional reorganization of the brain including cross-modal plasticity in the sensory cortex and changes in cognitive processing. However, it remains unclear whether partial deprivation from unilateral auditory loss (UHL) would similarly affect the neural circuitry of cognitive processes in addition to the functional organization of sensory cortex. Here, we used resting-state functional magnetic resonance imaging to investigate intrinsic activity in 34 participants with UHL from acoustic neuroma in comparison with 22 matched normal controls. In sensory regions, we found decreased regional homogeneity (ReHo) in the bilateral calcarine cortices in UHL. However, there was an increase of ReHo in the right anterior insular cortex (rAI), the key node of cognitive control network (CCN) and multimodal sensory integration, as well as in the left parahippocampal cortex (lPHC), a key node in the default mode network (DMN). Moreover, seed-based resting–state functional connectivity analysis showed an enhanced relationship between rAI and several key regions of the DMN. Meanwhile, lPHC showed more negative relationship with components in the CCN and greater positive relationship in the DMN. Such reorganizations of functional connectivity within the DMN and between the DMN and CCN were confirmed by a graph theory analysis. These results suggest that unilateral sensory input damage not only alters the activity of the sensory areas but also reshapes the regional and circuit functional organization of the cognitive control network.     

On the Interrelationship of Speech Functioning and Manual Motor Activity in Aphasia

Clinicians, physiologists, and psychologists are familiar with cases of simultaneous disturbance of various functions in localized cerebral lesions. These phenomena have been studied and described repeatedly, but continue to be of substantial interest, as analysis of them may make a contribution to the study of localization of functions in the cerebral cortex, substitution and restoration of functions, and the nature of their interrelationships. Our attention was attracted by a case of simultaneous disturbance of motor function and the power of speech in a lesion of the left (dominant) hemisphere. We began by investigating motor functions in aphasia and in the normal state, with a view to subsequent comparison of the motor and verbal functions in the normal state and in aphasia.     

Heart Rate Variability in Subjects with Increased Motor Activity and Athletes

Heart rate variability (HRV) was assessed with a NeiroSoft hardware and software complex in 303 subjects, including subjects with increased motor activity and athletes. Factor analysis was used to reveal the most informative HRV indices, which accounted for two-thirds of the generalized variance of the indices under study, evidencing a balanced and orderly state of the body in subjects with increased motor activity and athletes and the improvement of neurohumoral and autonomic control of motor functions.     

Self-Initiated Motor Behavioral Act-Related Neuronal Activity in the Cat Locus Coeruleus

In experiments on awake cats, we recorded the activity of 61 putative noradrenergic neurons localized within the region of the locus coeruleus (LC) of the brainstem. The animals were trained to perform a self-initiated (voluntary) motor act aimed at obtaining a food reward by pushing a pedal by the forelimb. The intervals between pushings (stay of the limb on a platform before initiation of the movement) should not be shorter than 4 sec, and the duration of the movement itself should not exceed 1 sec. The following impulse reactions were most clearly manifested (i) related to the pre-starting events and performance of the voluntary movement, (ii) related to the presentations of the conditioning stimuli, which predicted giving out the food reward (a positive signal) or the absence of the latter (a negative signal) and (iii) related to the reward presentation. About 50% of the LC units under study had changed their activities before the movement was initiated. These reactions can be related to a cognitive component (determination of the movement initiation(, which is present in the experimental task. Most neurons responded by phasic activation to presentation of the conditioning signals, and this activation was more pronounced in the case of negative signals. Responses of the studied nerve cells are probably indicative of the involvement of the LC neuronal systems in the perception of the emotiogenic stimuli, as well as in the processes providing the maintenance of selective attention within different stages of targeted behavioral acts.     

A Method for Recording the Motor Activity of the Reticulum in Cattle

A method for recording the motility of the reticulum in normal cattle has been devised. The method is based on measurement of the pressure variations occurring in connection with the reticular contractions. The pressure is transferred through open, water-filled catheters via a pressure transducer to an electromanometer, from which it is recorded with the aid of a mingograf. Mean values for the interval, duration and amplitude of the reticular contractions in 10 normal cows are given. The method permits recording in intact animals without any preliminary measures, and can therefore be used in clinical cases.