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PubMed1990

Learning-induced change in neural activity during acquisition and consolidation of a passive avoidance response in the rat.

Time-dependent alterations in neural activity have been established during the acquisition and consolidation of a stepdown passive avoidance paradigm. Change in neural activity was established by administering a glucose analogue, [3H]2-deoxyglucose, 50min prior to sacrifice and estimating perchloric acid soluble counts in nine hand dissected brain regions. Change in [3H]2-deoxyglucose uptake was closely paralleled in both trained and yoked animals for up to 40min following task acquisition however the striatum was the only area to exhibit a task-specific increase in [3H]2-deoxyglucose uptake at 20-30min after training. Longterm changes in neural activity were also apparent as the amygdala and brainstem showed increased [3H]2-deoxyglucose uptake at the 24 h time point. No further paradigm-specific changes were apparent at 48 h. These findings are concluded to suggest that the striatum is involved in the early events of acquiring a passive avoidance response and the amygdala and brainstem during the later events.

Amygdala↗

PubMed1999

The effects of stochastic neural activity in a model predicting intensity perception with cochlear implants: low-rate stimulation.

Most models of auditory nerve response to electrical stimulation are deterministic, despite significant physiological evidence for stochastic activity. Furthermore, psychophysical models and analyses of physiological data using deterministic descriptions do not accurately predict many psychophysical phenomena. In this paper we investigate whether inclusion of stochastic activity in neural models improves such predictions. To avoid the complication of interpulse interactions and to enable the use of a simpler and faster auditory nerve model we restrict our investigation to single pulses and low-rate (< 200 pulses/s) pulse trains. We apply signal detection theory to produce direct predictions of behavioral threshold, dynamic range and intensity difference limen. Specifically, we investigate threshold versus pulse duration (the strength-duration characteristics), threshold and uncomfortable loudness (and the corresponding dynamic range) versus phase duration, the effects of electrode configuration on dynamic range and on strength-duration, threshold versus number of pulses (the temporal-integration characteristics), intensity difference limen as a function of loudness, and the effects of neural survival on these measures. For all psychophysical measures investigated, the inclusion of stochastic activity in the auditory nerve model was found to produce more accurate predictions.

Cochlear Implants↗

PubMed2001

Effect of nucleus pulposus on the neural activity of dorsal root ganglion.

STUDY DESIGN: This study was designed to investigate, using neurophysiologic techniques in an in vivo rat model, the effect of application of nucleus pulposus to the nerve root on the neural activity of the dorsal root ganglion and the corresponding receptive fields. OBJECTIVES: To assess a further role of the dorsal root ganglion in mechanisms of radicular pain in lumbar disc herniation. SUMMARY OF BACKGROUND DATA: It has been suggested that the epidural application of autologous nucleus pulposus without mechanical compression causes nerve root inflammation and related radicular pain in lumbar disc herniation. Concerning the dorsal root ganglion, its mechanical hypersensitivity and potential for generating ectopic discharges have been reported. However, the effect of autologous nucleus pulposus on the dorsal root ganglion is uncertain. METHODS: In adult Sprague-Dawley rats spontaneous neural activity was recorded from the surgically exposed L5 dorsal root using electrophysiologic techniques, and the mechanosensitivity of L5 dorsal root ganglia and corresponding receptive fields on the hind paw were measured using calibrated nylon filaments. Autologous nucleus pulposus from the tail or fat was implanted at the L5 nerve root. Neural activity was monitored for 6 hours. RESULTS: Spontaneous neural activity in the nucleus pulposus group gradually increased and showed significant differences compared with the fat group from 2.5 to 6 hours after exposure. The mechanosensitivity of the dorsal root ganglia showed significant increases compared with the fat group. CONCLUSIONS: After application of nucleus pulposus to the nerve root, the dorsal root ganglion demonstrated increased excitability and mechanical hypersensitivity. These results suggest that nucleus pulposus causes excitatory changes in the dorsal root ganglion.

Animals↗

PubMed2006

Early neural activity and dendritic growth in turtle retinal ganglion cells.

Early neural activity, both prenatal spontaneous bursts and early visual experience, is believed to be important for dendritic proliferation and for the maturation of neural circuitry in the developing retina. In this study, we have investigated the possible role of early neural activity in shaping developing turtle retinal ganglion cell (RGC) dendritic arbors. RGCs were back-labelled from the optic nerve with horseradish peroxidase (HRP). Changes in dendritic growth patterns were examined across development and following chronic blockade or modification of spontaneous activity and/or visual experience. Dendrites reach peak proliferation at embryonic stage 25 (S25, one week before hatching), followed by pruning in large field RGCs around the time of hatching. When spontaneous activity is chronically blocked in vivo from early embryonic stages (S22) with curare, a cholinergic nicotinic antagonist, RGC dendritic growth is inhibited. On the other hand, enhancement of spontaneous activity by dark-rearing (Sernagor & Grzywacz (1996)Curr. Biol., 6, 1503-1508) promotes dendritic proliferation in large-field RGCs, an effect that is counteracted by exposure to curare from hatching. We also recorded spontaneous activity from individual RGCs labelled with lucifer yellow (LY). We found a tendency of RGCs with large dendritic fields to be spontaneously more active than small-field cells. From all these observations, we conclude that immature spontaneous activity promotes dendritic growth in developing RGCs.

Action Potentials↗

PubMed1997

Neural activity affects distribution of glutamate receptors during neuromuscular junction formation in Drosophila embryos.

Changes in the distribution and density of transmitter receptors in the postsynaptic cell are required steps for functional synapse formation. We raised antibodies against Drosophila glutamate receptors (DGluR-II) and visualized the distribution of receptors during neuromuscular junction formation in embryos. In wild-type embryos, embryonic development is complete within 22 hr after egg lying (AEL) and neuromuscular junction (NMJ) formation begins at 13 hr AEL. At the time of initial synapse formation, DGluR-IIs appeared as clusters closely associated with some muscle nuclei. Subsequently, these nonjunctional clusters dispersed while DGluR-IIs accumulated at the junctional region. In a paralytic temperature-sensitive mutant, para(ts1), neural activity decreases drastically at restrictive temperatures. When neural activity was blocked throughout synaptogenesis by rearing embryos at a restrictive temperature prior to the beginning of synaptogenesis, 12 hr AEL, the dispersal of extrajunctional clusters was significantly suppressed and no accumulation of receptors at the junction was observed at 22 hr AEL. However, when neural activity was blocked later, by rearing embryos at a restrictive temperature from 13 hr AEL, DGluR-IIs did not accumulate at the NMJ, although extrajunctional clusters dispersed normally. These findings suggest that the neural activity differentially regulates dissipation of receptor clusters in the nonjunctional region and accumulation of receptors at the junctional region.

Amino Acid Sequence↗

PubMed2005

Neural activity between ovaries and the prevertebral celiac-superior mesenteric ganglia varies during the estrous cycle of the rat.

The ovaries' innervation arrives via the superior ovarian nerve, which originates from the celiac ganglion. Using True Blue as an antidromic marker, the present study analyzed the changes in the anatomical relation between each ovary and the prevertebral celiac-superior mesenteric ganglia during the estrous cycle. The number of labeled neurons increased from the day of diestrus 1 to the day of proestrus. The largest number of labeled cells was observed when tracer was injected into the left ovary on proestrus. The number of labeled cells was significantly higher when the tracer was injected into the left ovary on proestrus than when it was done in the right one. When tracer was injected into the left ovary, the average labeled area of cells increased significantly from diestrus 1 to proestrus, and declined at estrus. In contrast, when True Blue was injected into the right ovary, the average labeled area was similar in diestrus 1 and diestrus 2, and the values increased in proestrus and estrus. The results indicate an apparent asymmetry in the activity of neural connections between ovaries and the prevertebral celiac-superior mesenteric ganglia, and that the number of active neurons of these connections varies during the estrous cycle.

Animals↗

PubMed2003

Effect of acute ethanol administration and acute allopregnanolone administration on spontaneous hippocampal pyramidal cell neural activity.

We investigated the effect of acute ethanol administration and acute allopregnanolone administration on spontaneous hippocampal pyramidal cell neural activity. Both agents produced significant reductions in spontaneous firing rate of hippocampal pyramidal neurons at a medium and high doses. Furthermore, blockade of allopregnanolone biosynthesis by preadministration of finasteride, a 5alpha-reductase blocker, prevented ethanol-induced inhibition on hippocampal pyramidal neural activity. The results further demonstrate similar effects of allopregnanolone and ethanol on hippocampal neurophysiology and that allopregnanolone plays a key role in producing ethanol-induced inhibition of hippocampal neural activity.

Action Potentials↗

PubMed1997

Neural activation during selective attention to subjective emotional responses.

We examined neural activity associated with selectively attending to subjective emotional responses in a study where subjects viewed emotional picture sets. During picture viewing when subjects attended to their subjective emotional responses, highly significant increased neural activity was elicited in rostral anterior cingulate (BA 32) (Z = 6.87, p < 0.001, corrected). By contrast, under the same stimulus conditions when subjects attended to spatial aspects of identical picture sets activation was observed in the parieto-occipital cortex bilaterally (Z = 5.71, p < 0.001, corrected). The findings indicated a specific role for the anterior cingulate cortex in representing subjective emotional responses and are consistent with a suggested role for associated medial prefrontal structures in representing states of mind.

Adult↗

PubMed2002

Layer-specific thalamocortical innervation in organotypic cultures is prevented by substances that alter neural activity.

Cortical layer IV is the major target of thalamocortical axons and many previous studies have shown that the development of this layer-specific innervation can be modelled in vitro by organotypic cocultures of thalamus and cortex. The mechanisms causing thalamic axons to terminate in layer IV are unknown. We used these in vitro models to test the possibility that neural activity plays a part in this termination process by adding substances that raise or lower levels of neural activity to the cocultures. We found that addition of tetrodotoxin or 2-amino-5-phosphonovalerate, to block activity, or potassium, to raise it, all interfered with termination in layer IV. These findings suggest that termination in layer IV requires neural activity at an appropriate level in the thalamocortical system. They also add support to recent findings that show that the importance of neural activity in development may extend to an earlier period than thought previously, to include the correct targeting of axons as well as the later refinement of connections.

2-Amino-5-phosphonovalerate↗

PubMed1988

Identification and characterization of neurons initiating patterned neural activity in the buccal ganglia of Aplysia.

Two patterns of neural activity were identified in excised buccal ganglia of Aplysia californica. Both are expressed in many cells, and each can be expressed independently. Using cells B4 and B5 as monitors of the activity patterns, we searched the buccal ganglia for cells initiating the patterns. Two electrically coupled cells, B31 and B32, can initiate what we termed pattern 2. The cells are active before pattern 2 is expressed. Stimuli initiating pattern 2 excite B31/B32. Depolarizing B31/B32 induces the pattern, while hyperpolarizing them can prevent its expression. The cells have unusual features. Their somata do not sustain conventional action potentials, and depolarization causes a regenerative response. B33 differs from B31/B32 in that its soma sustains conventional action potentials but otherwise has similar features. B34 also seems to be inexcitable but has weaker synaptic input than B31/B32 and appears unable to induce pattern 2. B35 and B36 have prominent regenerative capabilities. B35 is also able to initiate pattern 2. B37 is presynaptic to B31/B32 and can initiate pattern 2 via its effects on them. The newly identified cells provide a starting point for investigating factors that initiate and control different patterns of neural activity in the buccal ganglia. Since the buccal ganglia are involved in generating feeding behavior, further studies on the newly identified cells may provide insights into the neural control of feeding behavior, and provide a neural substrate for studying modulation of the feeding patterns by associative learning.

Animals↗

PubMed1995

Effects of deprivation of oxygen or glucose on the neural activity in the guinea pig hippocampal slice--intracellular recording study of pyramidal neurons.

The block of synaptic transmission and neural activity during deprivation of oxygen or glucose has been simply attributed to the lack of energy due to the disorder of energy production. To clarify the interrelation between neural activity and energy metabolism during hypoxia or glucose deprivation, we studied the changes in ATP levels and electrical events of pyramidal neurons in the CA3 region and [Ca2+]i mobilization of the dendritic and cellular region of CA3 area, using guinea pig hippocampal slices. The studies of field potentials and intracellular recording from the pyramidal cell of CA3 area during hypoxia or glucose deprivation revealed that the cessation of synaptic activity and the depolarization of resting potential occurred earlier than during glucose deprivation while the increase of [Ca2+]i was slow during hypoxia but rapid during glucose deprivation although the ATP level of CA3 area was maintained at its original level for 20 min during both conditions. When glucose was replaced by lactate, ATP concentration was not reduced but the electrical activity decayed and [Ca2+]i increased with the similar time course as observed during lack of glucose, only. These results suggest that different mechanisms underlie the block of synaptic transmission in the CA3 pyramidal neurons during hypoxia and glucose deprivation and that lactate cannot substitute for glucose in the maintenance of neural activity.

Adenosine Triphosphate↗

PubMed1999

Transient neural activity in the medial superior frontal gyrus and precuneus time locked with attention shift between object features.

To investigate the contribution of the superior frontal gyrus and precuneus to the cognitive process of attention set shift, we examined the correlation between change in neural activity in these areas and the timing of attention set shift using event-related functional magnetic resonance imaging. Seven subjects underwent a card-sorting task in which they matched a test card to one of two target cards according to color or shape. The subjects had to determine the correct category based only on feedback and shift the sorting principle when the feedback changed from "correct" to "incorrect." Transient increase of neural activity time locked with attention shift phases was detected in the medial superior frontal gyrus (the rostral part of the supplementary motor area) and precuneus. During the control task, in which the feedback and the motor responses were preserved without any attention shift, this type of change in neural activity was not observed. Our findings indicate that increase in neural activity in these brain areas may be closely related to attention set shift between object features and suggest that these areas may play a role in the shifting of cognitive sets.

Adult↗

PubMed2001

Electroacupuncture-induced neural activation detected by use of manganese-enhanced functional magnetic resonance imaging in rabbits.

OBJECTIVE: To investigate the effects of acupuncture on neural activity detected by use of manganese-enhanced functional magnetic resonance imaging (fMRI) and elucidate the relationship between somatic acupoint stimulation and brain activation. ANIMALS: 40 New Zealand White rabbits. PROCEDURE: Manganese-enhanced fMRI was performed in anesthetized rabbits manipulated with electroacupuncture (EA) on Zusanli (ST-36) and Yanglingquan (GB-34) acupoints. Image acquisition was performed on a 1.5T superconductive clinical scanner with a circular polarized extremity coil. T1-weighted images were acquired sequentially as follows: baseline, after mannitol injection, after manganese infusion, and 5 and 20 minutes after initiation of EA. RESULTS: Changes in focal neural activity were detected by use of manganese-enhanced fMRI. Stimulation on Zusanli (ST-36) for 5 minutes resulted in activation of the hippocampus, whereas stimulation on Yanglingquan (GB-34) resulted in activation of the hypothalamus, insula, and motor cortex. Activation became less specific after 20 minutes of EA. Furthermore, stimulation on ipsilateral acupoints led to bilateral brain activation. CONCLUSIONS AND CLINICAL RELEVANCE: Each acupoint has a corresponding cerebral linkage, and stimulation on these points resulted in time-dependent neural activation. Understanding the linkage between peripheral acupoint stimulation and central neural pathways may provide a useful guide for clinical applications of acupuncture.

Animals↗

PubMed2005

Dynamics of parietal neural activity during spatial cognitive processing.

Dynamic neural processing unrelated to changes in sensory input or motor output is likely to be a hallmark of cognitive operations. Here we show that neural representations of space in parietal cortex are dynamic while monkeys perform a spatial cognitive operation on a static visual stimulus. We recorded neural activity in area 7a during a visual maze task in which monkeys mentally followed a path without moving their eyes. We found that the direction of the followed path could be recovered from neuronal population activity. When the monkeys covertly processed a path that turned, the population representation of path direction shifted in the direction of the turn. This neural population dynamic took place during a period of unchanging visual input and showed characteristics of both serial and parallel processing. The data suggest that the dynamic evolution of parietal neuronal activity is associated with the progression of spatial cognitive operations.

Action Potentials↗

PubMed1994

GABAA receptor agonist muscimol can reset the phase of neural activity rhythm in the rat suprachiasmatic nucleus in vitro.

We investigated the phase-resetting effect of muscimol, gamma-amino butyric acid (GABA)A receptor agonist, on the circadian neural activity rhythm of the rat suprachiasmatic nucleus (SCN), which contains a circadian pacemaker. Acute application of muscimol inhibited the neural activity of the SCN in a dose-dependent manner. Under the tissue culture condition, the treatment with 10 microM muscimol during the early- to mid-subjective day on the first day (day 1) in vitro produced the largest phase advance in neural activity rhythm of the SCN on day 2. By contrast, the administration of muscimol during the subjective night produced no change. These phase changes were similar to those reported for dark pulses in constant light. These findings indicate that muscimol can directly affect SCN neurons and reset the circadian pacemaker in the SCN. The GABA neural function through the activation of GABAA receptors may play a role in modulating the phase of the SCN clock, especially during the subjective day.

Animals↗

PubMed1993

Study of neural activities of the primary auditory cortex and middle latency auditory evoked potentials.

This study was undertaken to clarify the relationship between the neural activities of the auditory cortex and components of middle latency auditory evoked potentials (ML-AEPs) (NI and PI) in the cat. Extracellular single-unit activities in the auditory cortex AI (AC-AI) were recorded simultaneously with ML-AEPs. In addition, the effects of removal of the AC-AI and AII and the cerebral hemisphere on ML-AEPs were also studied. ML-AEPs of humans consist of Na, Pa, and Nb components with preceding VI and VII, and those of the cat consist of NI, PI and NII with preceding P6 and P7. Among the 21 unit activities obtained from the AC-AI, 14 showed time-locked responses to click stimuli. The positive and negative waves of these unit activities have a phase reversal relation to N7 and P7, respectively. They are not related in latencies to NI and PI. Recording of ML-AEPs from the surface of the AC-AI showed large negative potentials (No), which also had a phase reversal relation to P7. The amplitude of P7 and No decreased after the unilateral and the bilateral removal of the AC-AI and AII. NI and PI decreased in amplitude after the unilateral removal of the cerebral hemisphere and further decreased after the bilateral removal. The above mentioned findings indicate that the neural activities of the primary AC are the ones mostly related to P7 and that NI and PI reflect neural activities of the cerebral hemispheres.

Acoustic Stimulation↗

PubMed1996

Neural activity in the VMH associated with suppression of the circulatory system in rats.

Spontaneous neural activity within the ventromedial nucleus of the hypothalamus (VMH) was monitored in rats to search for neurons regulating the autonomic nervous system. By means of multiple unit activity (MUA) recording method, unique explosive rises in neural activity (MUA volleys), 1 to 4 min in duration, were recorded in conscious freely moving animals. Heart rate was monitored as an autonomic parameter and found to decrease when MUA volleys appeared. These MUA volleys also occurred under urethane anesthesia, and blood pressure and heart rate decreased simultaneously with the volleys, but body temperature remained constant. This fall in blood pressure (but not heart rate) was replicated by electrical stimulation through the electrodes that recorded MUA volleys, suggesting that the neurons responsible for MUA volleys can suppress the circulatory system. The frequency of MUA volleys exhibited a clear diurnal variation: they appeared every 15 or 30 min in the light phase but only seldom in the dark. This diurnal variation seems to be an endogenous circadian rhythm because it was indicated to freerun after blinding the animals. These results suggest that there is a discrete population of neurons in the VMH that fires predominantly during the light phase in an episodic manner and suppresses the circulatory system.

Animals↗

PubMed1993

Remapping of neural activity in the motor colliculus: a neural network study.

Neurophysiological studies have shown that the deeper layers of the superior colliculus (SC) contain a topographical neural map representing the ocular vectorial displacement required for foveation of the target (motor error). It is known that the location of the active area in this neural map can be updated, not only following changes in retinal error, but also by efference-copy signals representing a change in eye position. Since it can be shown that a two-layer feedforward network cannot perform this task, we have simulated this system by training a three-layered neural network with access to retinal error and efference copy information about eye position. The network was taught to code motor error topographically (as in the collicular motor map) by generating population activity at the appropriate location in its output layer for different combinations of visual and efference copy signals. After the network had learned the required remapping transformation with sufficient precision (error of one deg over an 80 x 80 deg working range), the properties of the trained network were analyzed. From an investigation of the activity patterns of the hidden units in the trained network it appeared that information about target location relative to the head, implicitly present at the level of input signals, is no longer available at the level of the hidden layer. More detailed inspection of the properties of these units revealed that they code motor error. Their movement field is a monotonic function of motor error amplitude, and shows broad direction tuning specific for each unit. Finally, simulations were made with a four layered network with an architecture and access to input signals closely mimicking Robinson's model of the saccadic system. Again, the network was trained to represent motor error topographically in its output layer. The model shows, for the first time, how the computation of the topographical motor error map in the SC from retinal and eye position signals may proceed in two steps, involving a stage where target location is coded in a distributed fashion in craniotopic coordinates and a subsequent supracollicular stage, where radial motor error is represented in a firing-rate code in units with broad tuning characteristics. These two stages in the model show interesting similarities with the characteristics of neuron populations shown neurophysiologically in area 7a and parietal region LIP, respectively.

Brain Mapping↗