Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Neural activity”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 55 records · Page 3Linked to original sources
PubMed1998

The effects of glucose, mannose, fructose and lactate on the preservation of neural activity in the hippocampal slices from the guinea pig.

Using hippocampal slices from guinea pigs, we investigated the effect of different concentrations of glucose and replacement of glucose with mannose, fructose and lactate on neural activity. As an index of neural activity, the population spikes (PS) were recorded in the granule cell layer of the dentate gyrus (DG) and the pyramidal cell layer of the CA3 area in the hippocampal slices. Lowering the concentration of glucose from 10 mM to 5, 3, 2, 1 and 0 mM caused a reduction in the PS amplitude. There were differences in the decay times of the PS evoked in these two regions. PS evoked in CA3 region decayed faster even at a concentration of 3 mM glucose at which PS in granule cell layer was well maintained. The decay time of the PS in the CA3 region in the presence of glucose up to a concentration of 3 mM was shorter than that evoked in the DG. After the replacement of glucose with mannose, fructose or lactate, the PS disappeared within 35 min and there were no significant differences between the decay times in the two regions of slices incubated in the same medium. ATP, creatine phosphate (CrP) and lactate levels in each slice were determined. To investigate whether mannose and fructose could be metabolized or not in the tissue slice, anaerobic production of lactate from glucose, mannose and fructose were measured during oxygen and glucose deprivation. Under anaerobic conditions for 60 min, the levels of high-energy phosphates decreased to 50% of the initial level and lactate was produced from glucose, mannose or fructose. However, there were significant differences in the rate of lactate production between the DG and CA3 areas during application of 3 mM glucose, 10 mM mannose and 10 mM fructose. These results indicate that mannose, fructose and lactate can be metabolized and are available for maintaining the levels of high-energy phosphates but not for neural activity in the tissue slices and that the presence of glucose is indispensable for the maintenance of neural activity.

Adenosine Triphosphate↗
PubMed1998

Neural activity of the subthalamic nucleus in Parkinson's disease patients.

The neural activity pattern of the subthalmic nucleus (STN) was investigated in five patients with Parkinson's disease who were scheduled for electrode implantation for chronic stimulation of the STN. The initial target was placed 8 mm or 10 mm lateral to the midline, 3 mm to 4 mm posterior to the midcommissural point, and 5 mm to 6 mm below the intercommissural (AC-PC) line. The STN was identified by semi-microelectrode recordings with a trajectory moving laterally in 2-mm steps. The amplitudes of multi-unit activities were relatively low at depths from 8 mm to 5 mm above and from 1 mm to 4 mm below the target, while those 4 mm to 0 mm above the target were significantly higher than at the other sites (ANOVA, Fisher's test, p < 0.05), with the highest amplitude at 2 mm above the target (91.0 +/- 23.3 mu v, n = 15). In the mediolateral direction, amplitudes were relatively higher in the lateral portion, and amplitudes at 14 mm lateral to the midline were significantly higher than at the other sites (ANOVA, Fisher's test, p < 0.05). The target for chronic electrical stimulation was determined to be at the midpoint of the hyperactive STN, i.e., 12 mm lateral to the midline in three patients and 13 mm lateral in two patients. Movement-related neural activity was observed at 5 sites, i.e., 3 sites responded to passive movement of the contralateral wrist and 2 sites to passive knee and/or ankle movement. In conclusion, our data show that the lateral part of the STN is hyperactive in PD, and recordings of neural activities contributed greatly to identifying the STN and determining the target for chronic stimulation within it.

Aged↗
PubMed1993

Neural activity in the monkey anterior ventrolateral thalamus during trained, ballistic movements.

1. To examine the role of the anterior ventrolateral thalamic nucleus (VLa) in motor control, extracellular single-cell recordings were made from the VLa nucleus in three conscious monkeys performing visually triggered, rapid movements requiring flexion and extension of the wrist joint. The movement paradigms consisted of three components: an initial hold period, a ballistic movement, and a final hold period. 2. Cerebellar nuclear stimulation was used to physiologically identify thalamic neurons receiving input from the cerebellum. Neurons subsequently confirmed histologically as lying within the VLa nucleus were located anterior to those "driven" by cerebellar stimulation. 3. The activities of 261 VLa neurons displaying movement-related behavior were examined. In the absence of movement, the activity of these neurons ranged from 5 to 80 spikes/s, the majority of cells (222/261; 85%) firing between 10 and 30 spikes/s. Neural activity was not influenced by afferent input from skin, joint, or muscle but altered markedly when the animal engaged in active movement. 4. The relationship between neural activity and movement at a specific joint was determined in 189 of the 261 neurons. The majority of these neurons (161/189; 85%) modulated their activity in response to movement confined to a single joint; the remaining neurons displayed multijoint motor responses, their activity being best related to a motor act, such as grasping, reaching, or feeding. There was no clear segregation in the representation of body parts in the VLa nucleus to suggest the presence of clearly defined somatotopy. 5. The activities of wrist-related neurons (45 of the 261) were examined to determine the motor characteristics of the VLa nucleus. Three distinctive activity patterns were exhibited by these neurons during the performance of the movement paradigms: 1) a phasic burst of < 300 ms in duration (34/45; 76%); 2) a sustained change in neural activity lasting > 300 ms (typically up to 1,000 ms; 4/45; 9%); and 3) both a phasic and a sustained response, the sustained response occurring either prior or subsequent to the phasic response (7/45; 15%). 6. The movement-related activity of the wrist-related neurons occurred late, 52% firing after the onset of the forearm electromyogram (EMG). In 47% of the neurons, discharge rate was related to movement direction and, in a smaller proportion (13%), joint position. No relationship was found between neural activity patterns and amplitude of movement or velocity of movement. (ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed2006

Depressive behavior in mice due to immune stimulation is accompanied by reduced neural activity in brain regions involved in positively motivated behavior.

BACKGROUND: Immune stimulation inhibits positively motivated behavior and induces depressive illness. To help clarify the mechanism of these effects, neural activity in response to a positive stimulus was examined in brain regions associated with positively motivated activity defined on the basis of prior behavioral studies of central alpha1-adrenoceptor action. METHODS: Mice pretreated with either lipopolysaccharide or, for comparison, reserpine were exposed to a motivating stimulus (fresh cage) and subsequently assayed for fos expression and mitogen-activated protein kinase (MAPK) phosphorylation, two measures associated with alpha1-adrenoceptor-dependent neural activity, in several positive-activity-related (motor, piriform, cingulate cortex, nucleus accumbens, locus coeruleus) and stress-related brain regions (paraventricular hypothalamus, bed nucleus stria terminalis). RESULTS: Both lipopolysaccharide and reserpine pretreatment abolished fresh cage-induced fos expression and MAPK activation in the positive activity-related brain regions but enhanced these measures in the stress-related areas. CONCLUSIONS: The results support the hypothesis that immune activation reduces alpha1-adrenoceptor-related signaling and neural activity in brain regions associated with positive activity while it increases these functions in stress-associated areas. It is suggested that neural activities of these two types of brain regions are mutually antagonistic and that a reciprocal shift toward the stress regions is a factor in the loss of positively motivated behaviors in sickness behavior and depressive illness.

Adjuvants, Immunologic↗
PubMed1995

Locally activated neural networks and stable neural controller design for nonlinear dynamic systems.

A stable neural control scheme using a locally activated neural network has been proposed for a class of nonlinear dynamic systems. The locally activated neural network, for a given input, essentially selects a small subset of the network hidden nodes for output computation using the CMAC-like content addressing mechanism. This network aims to maintain local representations of the system dynamics. Thus, the global control performance in the concerned state space is achieved by the cooperation of many local control efforts and furthermore, real-time control can be facilitated because only a small sized network is involved to control and learn at any given time. The proposed control scheme is composed of two stages: (1) prediction error based learning in which the network attempts to learn the nonlinear basis functions of the plant inverse dynamics by a modified backpropagation learning rule; and (2) tracking error based learning in which the network weights are further fine-tuned using the basis set obtained in (1). This basis set spans the locally partitioned vector space of the system inverse dynamics when the prediction error based learning is achieved within a prescribed error tolerance. For uniform stability, the sliding mode control is introduced as a safety mechanism when the network has not sufficiently learned the plant dynamics yet. With suitable assumptions on the controlled plant, global stability and tracking error convergence proof has been given. Finally, the proposed control scheme is verified with computer simulation.

Adaptation, Physiological↗
PubMed1995

Role of neural activity during synaptogenesis in Drosophila.

This article reveals a novel aspect in the regulation of synaptic connectivity in Drosophila. Reducing neural activity genetically or pharmacologically disrupts the normally precise embryonic and larval neuromuscular connections. In third instar larvae with mutations that affect sodium channel function or expression such as no action potential, temperature-induced paralysis E, or seizure1, foreign neuromuscular synapses, arising from inappropriate nerve sources, are observed on muscle fibers throughout the abdominal body wall. Their frequencies increase as neural activity is further reduced in double mutant combinations. These foreign connections are first observed during late embryogenesis as filopodial-like contacts, but critical period analysis suggests that neural activity must be reduced during both late embryogenesis and the first larval instar to promote the differentiation of these embryonic contacts into foreign motor synapses. In addition, the loss of electrical activity in the motoneuron, as opposed to the loss of postsynaptic potentials in the muscle fibers, appears to be responsible for these changes in connectivity. Our experiments suggest that neural activity may function during development by preventing inappropriate connections and thereby maintaining the precise connectivity achieved during nerve outgrowth and target selection.

Animals↗
PubMed2004

Persistent neural activity: prevalence and mechanisms.

Persistent neural activity refers to a sustained change in action potential discharge that long outlasts a stimulus. It is found in a diverse set of brain regions and organisms and several in vitro systems, suggesting that it can be considered a universal form of circuit dynamics that can be used as a mechanism for short-term storage and accumulation of sensory or motor information. Both single cell and network mechanisms are likely to co-operate in generating persistent activity in many brain areas.

Action Potentials↗
PubMed1995

Neural activity and the levels of high energy phosphates during deprivation of oxygen and/or glucose in hippocampal slices of immature and adult rats.

To investigate the relationship between neural activity and cerebral energy metabolism during anoxia or ischemia in neural tissue of different ages, hippocampal slices were prepared from four-, seven- and 10-day-old and adult rats. For the index of the neural activity, the population spikes were recorded in the pyramidal cell layer of the CA3 area. ATP and phosphocreatine levels in the slices were measured during oxygen and/or glucose deprivation. After deprivation of both oxygen and glucose, population spikes of the slices from four, seven- and 10-day-old and adult rats ceased completely in 14.2, 11.8, 9.4 and 5.3 min, respectively. The level of ATP at the time of cessation of population spike in four-, seven- and 10-day-old and adult rats was 37.4, 30.2, 28.5 and 56.4% of the original concentrations. After deprivation of glucose only, the decay time of the population spikes of the slices from four-, seven- and 10-day-old and adult rats was 17.8, 14.5, 9.0 and 10.0 min and at the time of population spikes cessation the level of ATP was 99.8, 84.2, 79.3 and 49%, respectively. After deprivation of oxygen only, population spikes of the slices from four, seven- and 10-day old and adult rats ceased completely in 257, 283, 109 and 8.5 min, respectively. The level of ATP at the time of population spikes cessation was 50, 40, 36.6 and 94.4% of the initial values, respectively. These results indicate that the immature rat is extremely resistant to oxygen deprivation from a functional and a metabolic view, whereas in the adult rat, preservation of neural activity depends much on both oxygen and glucose. During glucose deprivation, population spikes of the slices of immature and mature rats ceased rapidly although the level of ATP is preserved at high levels. This suggests that glucose plays an important role in the preservation of neural activity in addition to its major function as an energy substrate especially in immature animals.

Adenosine Triphosphate↗
PubMedDate not supplied

Daily changes in neural activation, force-time and relaxation-time characteristics in athletes during very intense training for one week.

Daily changes in neural activation, force-time and relaxation characteristics of the leg extensor muscles were examined in 8 elite strength athletes during a very intense strength training period with two daily sessions for one week. The maximal neural activation (integrated EMG) of the muscles and their maximal isometric extension force remained statistically unaltered during the entire experimental period. Average integrated EMG of the muscles during the rapid relaxation phase of the isometric contraction and the relaxation-time curve remained statistically unaltered as well. However, considerable decreases (p less than 0.05-0.001) occurred both in the neural activation and in the force production in the early phases of the rapid isometric contraction during the course of the one-week period. After one full day of rest only slight and statistically nonsignificant changes took place in the mean values of the neuromuscular performance variables examined. The present findings indicate that the high overall daily volume of heavy resistance strength training stimuli may have a considerable role in leading to temporary worsening specifically in the rapid neural activation and correspondingly in rapid force production of the neuromuscular performance capacity even during a very short training period. In athletic training the volume of these types of training stimuli should therefore be carefully considered and matched with the specific purpose of the training season and with the specific requirements of various athletic activities.

Adult↗
PubMed1987

Thermal dependence of neural activity in the hamster hippocampal slice preparation.

1. Neural activity was recorded in an in vitro hamster hippocampal slice preparation while the temperature of the Ringer's solution bathing in the slice was controlled at selected levels. 2. The amplitude of the population spike (action potentials from a group of pyramidal cells) was measured as bath temperature was lowered from 35 degrees C to temperatures where a response could not be evoked. 3. Plots of population spike amplitude versus temperature have bell-shaped curves. The population spikes increased in amplitude as temperature was lowered from 35 degrees C, reached a peak amplitude between 25 and 20 degrees C, and then decreased until a response could not be evoked when temperature was further lowered. 4. These in vitro results obtained in the slice preparation are related to in vivo hippocampal studies. Results are interpreted as consistent with the proposal reviewed here that neural activity in the hippocampus plays a role at specific stages of entrance into and arousal from hibernation.

Acclimatization↗
PubMed1983

Theoretical analysis on relationship between the neural activity and the EEG.

Firstly, a collective oscillation mode of the neural activity is derived from the neural network system by using the multicompartment equation and the projection operator technique. This technique takes into account higher order interactions among neurons. The solution of the equation gives a chain structure with an infinite number of circuit loops in which each of them is only composed of four neurons. The obtained eigenvalues are quite similar to the spectrum of frequencies of the EEG. Secondly, the time-dependent behavior of the observed EEG is simulated by starting from the elementary process of action potential trains of neurons, which includes the effect of the collective oscillation mode mentioned above. This gives a comprehensive derivation of the EEG from the neural activity of action potentials. The simulation assumes that information of the action potential trains can be transmitted to the EEG through the intermediate states of the postsynaptic potential trains and the slow waves. The paper reports that a slightly modulated activity of a relatively small amount of neurons can cause a strong influence on the shape of the global EEG and that the calculated results reproduce the characteristic features of the EEG in a rat such as the theta rhythm, the spindle wave and the arousal wave.

Action Potentials↗
PubMed2004

Nonlinear coupling of neural activity and CBF in rodent barrel cortex.

The relationship between neural activity and accompanying changes in cerebral blood flow (CBF) and oxygenation must be fully understood before data from brain imaging techniques can be correctly interpreted. Whether signals in fMRI reflect the neural input or output of an activated region is still unclear. Similarly, quantitative relationships between neural activity and changes in CBF are not well understood. The present study addresses these issues by using simultaneous laser Doppler flowmetry (LDF) to measure CBF and multichannel electrophysiology to record neural activity in the form of field potentials and multiunit spiking. We demonstrate that CBF-activation coupling is a nonlinear inverse sigmoid function. Comparing the data with previous work suggests that within a cortical model, CBF shows greatest spatial correlation with a current sink 500 microm below the surface corresponding to sensory input. These results show that care must be exercised when interpreting imaging data elicited by particularly strong or weak stimuli and that hemodynamic changes may better reflect the input to a region rather than its spiking output.

Animals↗
PubMed1980

Long-term effects of axotomy on neural activity during cat locomotion.

1. Neural activity was recorded from cats during locomotion on a treadmill using electrodes in Silastic cuffs placed around the sciatic nerve and the lateral gastrocnemius-soleus, medial gastrocnemius, common peroneal and tibial nerve branches. Each branch gave characteristic patterns of activity which were studied before and after it was cut distal to the recording cuffs. Sensory and motor components were separated and measured using cross-correlation techniques. The amplitude of the cross-correlation peaks was compared with the amplitude of compound action potentials evoked by electrical stimulation and recorded from the same sites in the anaesthetized animal. 2. Sensory activity declined rapidly following axotomy and did not recover unless reinnervation occurred. Sensory activity even 5 months after nerve section and resuture had recovered to only a fraction of the control values. This reduction is attributed to a decline in the evoked compound potentials and to many fibres being unsuccessful in regenerating to appropriate sensory organs. 3. Motor activity declined more than could be accounted for by a decline in evoked potentials over the first month after axotomy. The extra reduction represents a decline in the number of impulses generated by alpha-motoneurones after axotomy. If regeneration was permitted, motor activity recovered to higher levels than did the evoked potentials for the whole nerve. Even if regeneration was prevented by nerve ligation, motoneurones continued to generate activity at a stable level over a period of months during which whole nerve compound potentials continued to decline. 4. The modulation of motor activity in ligated nerves during the step cycle was still appropriate to the required movement. Thus, activity recorded from severed nerves in human amputees may be useful in controlling powered artificial limbs. The persistence of motor activity may be responsible for the lesser degree of atrophy found in motor fibres than in sensory fibres following ligation (Hoffer, Stein & Gordon, 1979b).

Action Potentials↗
PubMed2006

Neural activation after maximal isometric contractions at different muscle lengths.

PURPOSE: To investigate i) whether neural activation dependence on muscle length is preserved with neuromuscular fatigue and ii) whether fatigue induced by a maximal isometric exercise is muscle length dependent. METHODS: Twelve male subjects performed two fatiguing quadriceps muscle exercises: FS is the fatigue carried out at short muscle length (S) (S = 40 degrees of knee flexion) and FL is the fatigue at long muscle length (L) (L = 100 degrees). Before and after each fatiguing exercise (i.e., three maximal isometric contractions maintained until 80, 60, and 40% of the initial maximal torque, respectively), activation level (AL, assessed by means of twitch interpolation technique), EMG activity (RMS), and peak doublet torque (Pd) were measured at the two lengths (S and L). RESULTS: First, AL was greater (P < 0.05) at L compared with S before and after both exercises. Second, despite a similar decrease in maximal voluntary torque (approximately 21% of the initial value) after the two exercises, AL and RMS were significantly reduced after FS (P < 0.05) but remained unchanged after FL, whereas the Pd decrease was more pronounced after FL than FS (P < 0.05). Nevertheless, after a given fatiguing exercise (i.e., FS or FL), AL, RMS, and Pd changes were similar at both postexercise test lengths (S and L). CONCLUSION: These results clearly demonstrate that i) the neural activation dependence on quadriceps muscle length is maintained with fatigue, and ii) neuromuscular fatigue after maximal isometric contractions is dependent on the muscle length at which the exercise is performed: short length preferentially induces neural activation impairment, whereas long length leads to higher contractile failure.

Adult↗
PubMed2003

Biphasic changes in tissue partial pressure of oxygen closely related to localized neural activity in guinea pig auditory cortex.

An understanding of the local changes in cerebral oxygen content accompanying functional brain activation is critical for making a valid signal interpretation of hemodynamic-based functional brain imaging. However, spatiotemporal relations between changes in tissue partial pressure of oxygen (Po2) and induced neural activity remain incompletely understood. To characterize the local Po2 response to the given neural activity, the authors simultaneously measured tissue Po2 and neural activity in the identical region of guinea pig auditory cortex with an oxygen microelectrode (tip < 10 microm) and optical recording with voltage-sensitive dye (RH 795). In addition, a laser displacement gauge and a laser-Doppler flowmeter were used to monitor the spatial displacement and regional cerebral blood flow, respectively, in the Po2 measurement region. In the activated region, tissue Po2 initially decreased during the approximately 3-seconds after the onset of acoustic stimuli, and then increased during the next approximately 5 seconds. Such biphasic changes are consistently found in cortical layers I to IV. In addition, amplitude of the biphasic change was closely related to detected peak height of the optical signal changes. The results suggest that the initial decrease in tissue Po2 is coupled to the induced neural activity and depends on response time of local increase in cerebral blood flow.

Acoustic Stimulation↗
PubMed2006

A model of the interaction between autoregulation and neural activation in the brain.

In this paper a model is proposed that predicts the response of the cerebral vasculature to changes in arterial blood pressure, arterial CO2 concentration and neural stimulation. Cerebral blood flow (CBF) is assumed to be controlled through changes in arterial compliance, and hence arterial resistance and volume, through three feedback mechanisms, which act in a linear additive manner, based on CBF, arterial CO2 and neural stimulus. Together with arterial, capillary and venous compartments, a tissue compartment is included, which contributes partly to the initial rise found in the deoxyhaemoglobin response to neural activation. Dynamic simulations of the model under different conditions show that there is significant interaction between the autoregulation and activation processes, and that the level of autoregulation has a strong influence on the CBF and deoxyhaemoglobin responses to neural activation. Overshoot in the deoxyhaemoglobin response is eliminated completely in the absence of this regulation. The feedback mechanism time constants significantly affect the CBF and deoxyhaemoglobin responses. Changes in arterial blood pressure (ABP) are found to have a strong influence on the neural activation response, with the amplitude of the response decreasing significantly at high baseline ABP. Dynamic changes in ABP also have a significant and potentially confounding impact on the measured deoxyhaemoglobin response to neural activation.

Algorithms↗
PubMed2006

Determining the extent of neural activation during maximal effort.

PURPOSE: The purpose of this study was to compare the extent of neural activation assessed by the central activation ratio (CAR) versus activation estimated from T2 magnetic resonance imaging (MRI) and neuromuscular electrical stimulation (NMES). METHODS: Seven college-age individuals volunteered for this study. CAR was determined by manually superimposing a train of NMES (50 Hz, 450-mus biphasic pulses) for 1 s during a maximal voluntary effort. The MRI-NMES method assessed activation by stimulating the knee extensors for 3 min in a 2 s on, 2 s off cycle. T2 MR images were taken at rest and after NMES was administered. Theoretical maximal torque (TMT) of the knee extensors was calculated based on the MRI-NMES activation data. The TMT was then divided by the maximal voluntary isometric contraction (MVIC) of each subject to determine the extent of neural activation during a MVIC. RESULTS: The results for CAR reveal the percent activation (mean +/- SD) of the quadriceps femoris during a MVIC was 92 +/- 7% for the right thigh and 96 +/- 4% for the left thigh. The MRI-NMES method estimated that MVIC could be achieved if 75 +/- 14% of the knee extensors on the right thigh and 74 +/- 14% on the left thigh were activated. These results are similar to findings that showed MVIC could be achieved by stimulating 71% of the knee extensors. CONCLUSIONS: We conclude that CAR overestimates the extent of neural activation during an MVIC because the 3D shape of the thigh is altered. This will change electric current flow to the axonal motor neuron branches and limit the artificially evoked torque, thereby resulting in an overestimation of CAR.

Adult↗
PubMed2006

The role of neural activity in cortical axon branching.

Axonal branching is an important process for establishing the final pattern of connections between a neuron and its target cells. Cortical connections between upper-layer cells in the neocortex have provided insights into the cellular mechanisms by which electrical activity regulates neural connectivity, including branch formation. Recent evidence further indicates that spontaneous firing and synaptic transmission contribute to axonal branching of cortical neurons through postsynaptic activation.

Action Potentials↗