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PubMed1993

Imaging of hippocampal and neocortical neural activity following intravenous cocaine administration in freely behaving cats.

We examined spatial-temporal patterns of neural activity, as inferred from 700 nm light reflectance, from the dorsal hippocampus and surrounding neocortex in seven freely behaving cats following 1.5, 2.5, 3.5 and 5.0 mg/kg intravenous cocaine administration. Images were acquired using a new technique which gathered reflected light from cortical and subcortical structures. Cardiac and respiratory patterning, collected simultaneously with optical images, revealed increased rates and diminished variation after intravenous cocaine administration. Cocaine increased reflectance correlates of hippocampal neural activity in a dose-dependent fashion over a 120 min period, with a lengthening time-to-peak effect (22-76 min). The largest dose resulted in an initial decrease, followed by the greatest enhancement in neuronal activity. Correlates of neural activation in the neocortex displayed an inverse dose-response curve to that found in the hippocampus; the time-to-peak effect was shorter (6-43 min) and the maximal change was reduced. Regional patches and bands of activation occurred during the period of the cocaine response, and were more pronounced in the hippocampus than the neocortex. Procaine, administered in a similar dose, slightly increased neural activity for 10 min in both the hippocampus and neocortex, and elicited a small increase in respiration. Cocaine induces a pronounced enhancement of neural activation in the neocortex and dorsal hippocampus; the time course of activation in the hippocampus parallels an increased respiratory pattern and outlasts the neocortical response. We speculate that hippocampal activation may be related to the profound respiratory acceleration found in response to cocaine.

Animals↗

PubMed2003

Fluctuations in neural activity during cocaine self-administration: clues provided by brain thermorecording.

Since metabolic neural activity is accompanied by heat release, measurement of local brain temperature offers a method for assessing alterations in neural activity. This approach, continuous monitoring of local brain (ventral tegmental area, ventral striatum, and hippocampus) and body (temporal muscle) temperature, was used to study intravenous cocaine self-administration in trained rats. The first self-administration of a session was preceded by a strong temperature increase that continued after the drug infusion. After peaking at the time of the second self-administration, temperature plateaued (+0.7 degrees C) with biphasic fluctuations (+/-0.10-0.15 degrees C) around each subsequent self-administration. Temperature gradually increased before and for 30-50 s after the lever-press, but then abruptly decreased to a minimum at 180-240 s, when it began to increase to reach another peak immediately after the next lever-press. Doubling the dose of injected cocaine significantly potentiated the post-cocaine temperature decrease and increased time to the next lever-press. In contrast to drug-reinforced lever-presses, temperatures phasically increased after non-reinforced lever-presses and at the end of a session when the lever was blocked and the rat was hyperactive, trying to reach the inaccessible lever. While temperature changes in each recording location were generally correlative, the initial temperature elevation was stronger in all brain structures than in muscle and ventral striatum was the structure that showed the most pronounced and consistent temperature fluctuations. These data suggest a generalized brain activation associated with cocaine-seeking and cocaine-taking behavior with its phasic fluctuations around individual drug self-injections. While the initial component of brain activation preceding the first lever-press for cocaine is internally determined and closely related to behavioral search, subsequent biphasic fluctuations in neural activity associated with repeated drug intakes appear to be drug-mediated. Cocaine-induced potentiation of monoamine transmission is a possible factor for gradual increases in neural activity that drive cocaine seeking, while a rapid, brain concentration-dependent action on Na(+) transport (local anesthetic action) is the most probable factor determining an abrupt, transient cessation of neural activation associated with cocaine reward.

Animals↗

PubMed1991

Specific monosynaptic sensory-motor connections form in the absence of patterned neural activity and motoneuronal cell death.

The importance of neural activity and motoneuronal cell death in the formation of specific synaptic connections between muscle afferents and motoneurons was studied in chick embryos. Patterned neural activity was blocked by applying d-tubocurarine (dtc) chronically to embryos during the period when sensory-motor connections are formed [stages (St) 28-42]. Dtc blocks neurogenic muscle contractions, thereby abolishing any temporal correlation between neural activity in motoneurons and stretch-sensitive afferents. The normal pattern of motoneuronal bursting is also blocked (Landmesser and Szente, 1986), as is motoneuronal cell death (Pittman and Oppenheim, 1979). Dtc applications were started more than 1 d before muscle sensory afferent collaterals make anatomical contact with motoneuronal dendrites and continued until St 38-42, when the pattern of synaptic connectivity was examined by recording synaptic potentials intracellularly from identified lumbosacral motoneurons upon stimulation of identified populations of muscle afferents. In both normal and dtc-treated animals, large monosynaptic excitatory potentials were evoked in homonymous motoneurons (those that supply the same muscle as the sensory afferents) and were often observed in motoneurons that supplied synergistic muscles. Monosynaptic potentials were uncommon in motoneurons supplying antagonistic muscles. The overt patterns of sensory-motor connections in normal and dtc-treated embryos were essentially identical. However, the amplitudes of the composite EPSPs recorded in dtc-treated animals were consistently about twice as large as normal. These observations suggest that neither normal patterns of neuronal activity nor motoneuronal cell death play a large role in determining the specificity of connections between the sensory and motor neurons involved in the stretch reflex.

Afferent Pathways↗

PubMed2000

Anaerobic glycolysis is crucial for the maintenance of neural activity in guinea pig hippocampal slices.

To investigate the functional significance of anaerobic and aerobic glycolysis on neural activity and levels of high energy phosphates, we tested the effects of glucose, mannose, fructose lactate, and pyruvate on the maintenance of neural activity and on the levels of ATP and creatine-P (CrP) in hippocampal slices. For an index of neural activity, population spikes (PS) evoked in the granule cell layer were monitored. Immediately after deprivation of glucose, the PS amplitude was gradually reduced and extinguished within 30 mm. Replacement of glucose with either lactate or pyruvate resulted in a decay and loss of PS with a similar time-course as observed during glucose deprivation. However, after the complete loss of neural activity for 10-20 min the PS reappeared and recovered to normal levels. The replacement of glucose with either mannose or fructose resulted in a transient decrease of the PS to 80-70% of the original amplitude in 20 mm, followed by recovery. The time-course of the decrease of PS in the mannose-containing medium was slower than that in the medium containing fructose and the time-course of recovery was faster. ATP and CrP were reduced to 90 and 70% of original level in each slice after glucose deprivation for 30 and 100 mm, respectively. In media containing either lactate, pyruvate, mannose, or fructose, the level of ATP and CrP was maintained at the original level. The anaerobic metabolic rate of glucose, mannose and fructose, determined by the rate of lactate production during complete anoxia, was consistent with the order of the decay and recovery of the PS in mannose and fructose-containing medium. The mode of the transient decay or loss of PS with no apparent reduction in the levels of ATP and CrP in each slice, in the presence of either mannose, fructose or lactate, indicates that anaerobic glycolysis is crucial for the maintenance of PS. The results obtained in this experiment are not in accordance with the reports by Schurr and Fowler in which they showed that lactate can support neural activity, although they did not measure the levels of ATP and CrP in slices. The present experiment disclosed that this discrepancy was due to the difference of slice preparation; namely rapidly prepared slice with shorter period anoxia (1 mm after removal of hippocampal tissue block) gives the results mentioned in the present study whereas slowly prepared slices by vibratome or chopper method with longer period of ischemia (5-20 mm), did not show transient loss of PS after application of lactate. Thus present experiment indicates that glycolytic process is essential for maintaining neural activity for physiological state of slices, if it is admitted to say that rapidly prepared slices is more physiological because they are exposed on shorter period of ischemia, and that more careful attention should be paid for the interpretation of the results of slice experiment according to the method of slice preparation.

Action Potentials↗

PubMed2003

Subjective rating of emotionally salient stimuli modulates neural activity.

Studies using emotionally salient stimuli have demonstrated neural activation in limbic and paralimbic brain regions. In some studies, subjects passively perceive evocative stimuli, while in other studies, they perform specific cognitive tasks. Evidence is emerging that even a simple cognitive task performed on emotionally salient stimuli can affect neural activation in emotion-associated brain regions. We tested the hypothesis that rating the subjective experience of an aversive visual stimulus would decrease limbic/paralimbic activation and increase activity in medial frontal regions. Ten healthy subjects underwent (15)O PET scans while they viewed pictures of aversive (AV) and nonaversive (NA) content, taken from the International Affective Picture System. Subjects appraised pictures on a scale of pleasantness/unpleasantness during one set of scans (RTNG), and they passively viewed pictures during another set (PSVW). After each scan, emotional responses were assessed. RTNG was associated with significantly less intensity of sadness and significantly less activation (AV - NA) of the right insula/amygdala and left insula, relative to PSVW. RTNG also activated the dorsal medial prefrontal cortex and the anterior cingulate sulcus, which were not differentially activated during PSVW. For both RTNG and PSVW, subjects activated the left fusiform gyrus. The results support the proposition that task instructions about how subjects should process evocative stimuli can affect neural activity.

Amygdala↗

PubMed2005

Tissue and electrode capacitance reduce neural activation volumes during deep brain stimulation.

OBJECTIVE: The growing clinical acceptance of neurostimulation technology has highlighted the need to accurately predict neural activation as a function of stimulation parameters and electrode design. In this study we evaluate the effects of the tissue and electrode capacitance on the volume of tissue activated (VTA) during deep brain stimulation (DBS). METHODS: We use a Fourier finite element method (Fourier FEM) to calculate the potential distribution in the tissue medium as a function of time and space simultaneously for a range of stimulus waveforms. The extracellular voltages are then applied to detailed multi-compartment cable models of myelinated axons to determine neural activation. Neural activation volumes are calculated as a function of the stimulation parameters and magnitude of the capacitive components of the electrode-tissue interface. RESULTS: Inclusion of either electrode or tissue capacitance reduces the VTA compared to electrostatic simulations in a manner dependent on the capacitance magnitude and the stimulation parameters (amplitude and pulse width). Electrostatic simulations with typical DBS parameter settings (-3 V or -3 mA, 90 micros, 130 Hz) overestimate the VTA by approximately 20% for voltage- or current-controlled stimulation. In addition, strength-duration time constants decrease and more closely match clinical measurements when explicitly accounting for the effects of voltage-controlled stimulation. CONCLUSIONS: Attempts to quantify the VTA from clinical neurostimulation devices should account for the effects of electrode and tissue capacitance. SIGNIFICANCE: DBS has rapidly emerged as an effective treatment for movement disorders; however, little is known about the VTA during therapeutic stimulation. In addition, the influence of tissue and electrode capacitance has been largely ignored in previous models of neural stimulation. The results and methodology of this study provide the foundation for the quantitative analysis of the VTA during clinical neurostimulation.

Algorithms↗

PubMed1997

Neuritin: a gene induced by neural activity and neurotrophins that promotes neuritogenesis.

Neural activity and neurotrophins induce synaptic remodeling in part by altering gene expression. A cDNA encoding a glycosylphoshatidylinositol-anchored protein was identified by screening for hippocampal genes that are induced by neural activity. This molecule, named neuritin, is expressed in postmitotic-differentiating neurons of the developing nervous system and neuronal structures associated with plasticity in the adult. Neuritin message is induced by neuronal activity and by the activity-regulated neurotrophins BDNF and NT-3. Purified recombinant neuritin promotes neurite outgrowth and arborization in primary embryonic hippocampal and cortical cultures. These data implicate neuritin as a downstream effector of activity-induced neurite outgrowth.

Amino Acid Sequence↗

PubMed2006

Periodic neural activity induced by network complexity.

We study a model for neural activity on the small-world topology of Watts and Strogatz and on the scale-free topology of Barabási and Albert. We find that the topology of the network connections may spontaneously induce periodic neural activity, contrasting with nonperiodic neural activities exhibited by regular topologies. Periodic activity exists only for relatively small networks and occurs with higher probability when the rewiring probability is larger. The average length of the periods increases with the square root of the network size.

Journal Article↗

PubMed1997

The effects of lactate and beta-hydroxybutyrate on the energy metabolism and neural activity of hippocampal slices from adult and immature rat.

We investigated the correlation between energy metabolism and neural activity during glucose deprivation and during replacement of glucose with lactate and beta-hydroxybutyrate (OHBA) in neural tissue from rats of different ages. Hippocampal slices were prepared from 4-, 7-, 10-, 13- and 16-day-old and adult rats. The population spikes (PS) were recorded in the pyramidal cell layer of the CA3 area as the index of neural activity. ATP and creatine-phosphate (CrP) levels in each slice were determined during glucose deprivation and during replacement of glucose with lactate or OHBA. After deprivation of glucose, the PS of the slices from 4-, 7- and 10-day-old and adult rats decayed and extinguished in 30 min and the decay time was shortened according to the age of the rat. The levels of ATP and CrP in the slices also decreased, but to a lesser extent than the amplitudes of PS. After substitution of lactate or beta-hydroxybutyrate (OHBA) for glucose, PS of the adult rat disappeared as was the case with glucose deprivation, although the levels of high energy phosphates were well maintained. In the case of the immature rat, however, PS decayed more slowly. Especially in the case of 4-day-old rat, ATP and CrP in the slices were maintained as high as those under the initial concentrations and PS amplitude showed no decay even after 60 min. These results indicate that the presence of glucose is essential for neural activity in the adult rat, and lactate or OHBA cannot replace it for the maintenance of neural activity. In the immature rat, glucose metabolites such as lactate and OHBA are available for both neural activity as well as maintaining the levels of high-energy phosphates in the tissue slice.

3-Hydroxybutyric Acid↗

PubMed2005

Classification of the extracellular fields produced by activated neural structures.

BACKGROUND: Classifying the types of extracellular potentials recorded when neural structures are activated is an important component in understanding nerve pathophysiology. Varying definitions and approaches to understanding the factors that influence the potentials recorded during neural activity have made this issue complex. METHODS: In this article, many of the factors which influence the distribution of electric potential produced by a traveling action potential are discussed from a theoretical standpoint with illustrative simulations. RESULTS: For an axon of arbitrary shape, it is shown that a quadrupolar potential is generated by action potentials traveling along a straight axon. However, a dipole moment is generated at any point where an axon bends or its diameter changes. Next, it is shown how asymmetric disturbances in the conductivity of the medium surrounding an axon produce dipolar potentials, even during propagation along a straight axon. Next, by studying the electric fields generated by a dipole source in an insulating cylinder, it is shown that in finite volume conductors, the extracellular potentials can be very different from those in infinite volume conductors. Finally, the effects of impulses propagating along axons with inhomogeneous cable properties are analyzed. CONCLUSION: Because of the well-defined factors affecting extracellular potentials, the vague terms far-field and near-field potentials should be abandoned in favor of more accurate descriptions of the potentials.

Action Potentials↗

PubMed1981

Effects of fusaric (5-butylpicolinic) acid on the monosynaptic reflex neural activity of cat spinal cord.

It has been demonstrated that most hypertensive drugs which cause increases in levels of norepinephrine influence the stimulation of monosynaptic reflex (MSR) neural activity. However this report discusses the effects of a hypotensive drug, which causes decreases in levels of norepinephrine, on the MSR amplitude of acute spinal cats. This drug is 5-butylpicolinic acid (fusaric acid: FA) which is an effective hypotensive agent and a potent inhibitor of dopamine beta-hydroxylase (approximately 10 times more potent than disurfiram). Intravenous injections of FA increased MSR neural activity in a dose-dependent manner. The FA-induced neural activity was gradually depressed by treatment with haloperidol, a dopamine and/or a alpha receptor blocker and methysergide, a serotonin receptor blocker, respectively. In addition, this neural activity was potentiated by the sequential administration of L-dopa. FA did not cause increases in the blood pressure but inhibit the synthesis of norepinephrine from dopamine. These results suggest that not only hypertensive but also hypotensive drugs can affect the increase of MSR neural activity, and dopamine plays an important role in FA-induced neural activity.

Animals↗

PubMed1994

Hypoglossal neural activity during ingestion and rejection in the awake rat.

1. The activity of 34 hypoglossal (mXII) neurons was characterized during the ingestion and rejection of gustatory stimuli in the awake rat. Intraoral infusions of water, sucrose, sodium chloride, or hydrochloric acid initiated ingestion responses; infusions of quinine monohydrochloride initiated rejection responses. Electromyographic (EMG) activity from three oropharyngeal muscles monitored the occurrence of lick cycles and swallows (ingestion) and gape cycles (rejection). In addition, the orofacial region was videotaped to provide an independent assessment of lingual and jaw movements in relation to neural activity. 2. EMG activity during lick and gape cycles was quantified by calculating the duration, magnitude, and peak time of muscle contractions. Lick and gape cycles produced highly differentiated patterns of activity from jaw-opener (anterior digastric, AD), lingual protrudor (geniohyoid, GEN), and lingual retractor (styloglossus, STY) muscles. Lick cycles were characterized by an alternating two-phase sequence of protrusion-retraction; gape cycles by an initial coactivation of both lingual muscles (phase I), followed by a sequence of protrusion (phase II) and retraction (phase III). Contraction durations were significantly longer during gape cycles compared with lick cycles for the AD (Xlick +/- 59 ms; Xgape +/- 134 ms, means +/- SD), GEN (Xlick +/- 77 ms; Xgape +/- 200 ms), and STY (Xlick +/- 93 ms; Xgape +/- 220 ms) muscles. 3. Thirty-one out of 34 mXII neurons were functionally classified as protrudor- or retractor-related by cross-correlating anterior digastric EMG activity with neural activity during licking. Fourteen out of 34 neurons were protrudor-related, 17/34 were retractor-related. These classifications were largely consistent with the results from an analysis of a subset of cells (n = 14) that directly compared neural activity with videotaped records of visible tongue movements. 4. The magnitude of mXII activity during ingestion and rejection was compared by determining the mean number of spikes per lick, gape, and swallow for each neuron. Five out of 14 (36%) protrudor-related and 10/17 (59%) retractor-related cells had significant increases in activity during gape responses compared with the number of spikes per lick cycle. This increased activity of mXII neurons was consistent with the more robust lingual motor activity during the gape response. Two protrudor-related and three retractor-related neurons showed significant decreases in activity during gape responses. Although a similar proportion of mXII neurons exhibited decreases in activity during swallows compared with licks (3 protrudor- and 1 retractor-related), fewer mXII neurons (1 protrudor- and 1 retractor-related) showed increased activity during swallows.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗

PubMedDate not supplied

Slow transmission of neural activity in hippocampal area CA1 in absence of active chemical synapses.

Transmission of neural activity in the mammalian cortex involves the operation of chemical synapses. Here we report that activity of hippocampal pyramidal cells (HPC) in vitro can spread through the neural aggregate even when chemical synaptic transmission is blocked by lowering the external Ca2+ concentration ( [Ca2+]0). In these conditions focal stimulation of the HPC body layer (stratum pyramidale) at area CA1 evokes a localized repetitive neural response which, when large enough, spreads along this layer in both transverse directions. It was recently reported for similar conditions that the activated HPC often discharge in synchrony. However, the spread of the neural response does not depend upon the occurrence of synchronized HPC activity, and therefore represents a distinct phenomenon.

Animals↗

PubMed2005

Recording of neural activity from goat cervical facet joint capsule using custom-designed miniature electrodes.

STUDY DESIGN: To establish a methodology for the neurophysiologic study of mechanoreceptors in the cervical facet joint capsule. OBJECTIVES: To test a custom designed miniature dual bipolar electrode for recording the neural activity in cervical dorsal roots. To determine if the neural activity from different receptors in the capsule can be differentiated using this methodology. SUMMARY OF BACKGROUND DATA: Injury to cervical facet joint capsules has been regarded as an important source of whiplash pain, but no neurophysiologic study has been performed to demonstrate or characterize sensory nerve function in the capsule. METHODS: Nineteen goats weighing 34 to 55 kg were used under general anesthesia. A C4-C6 laminectomy was performed to expose the C6 nerve root. Custom designed miniature dual bipolar electrodes were used to record neural activity in the left C6 branches. Electrical and mechanical stimuli were used to evoke receptor activity in the dorsal aspect of the C5/6 capsule. Conduction velocities (CVs) of evoked units were determined by electrical stimulation and dual-bipolar-electrode recording methods. The units were classified based on their CVs. The waveform of each classified unit was saved as a template for later single unit discharge search among multiunit discharges during the stretch of the capsule. The C5/6 facet joint with capsule was pulled by a computer-controlled actuator instrumented with a load cell at a rate of 0.5 mm per second. The evoked neural activity and load were recorded, digitized, and analyzed to determine CV, discharge rate, and response to the stretch. RESULTS: Miniature bipolar electrodes recorded the neural activity in both channels, with single unit CVs being measured. There was no discernible motion between the electrode and dorsal root when the capsule was pulled. Both local compression and stretch on capsule evoked multiunit discharges. A-beta, A-delta, and C-fiber units were found among these multiunit discharges. The rate of single unit and multiunit discharges increased during capsule stretch in the physiologic range and afterdischarges occurred beyond the physiologic range. CONCLUSIONS: The novel miniature electrodes not requiring a micromanipulator made it feasible and reliable to record neural activity from short cervical spinal roots. Waveforms of different units could be identified, making it possible to study sensory functions of the facet joint capsule. A-beta, A-delta, and C-fiber units were found responding to mechanical stimuli, indicating that facet joint capsule has functional proprioceptors and nociceptors.

Action Potentials↗

PubMed2001

When more means less: neural activity related to unsuccessful memory encoding.

The neural correlates of memory encoding have been studied by contrasting neural activity elicited by items at the time of learning according to whether they were later remembered or forgotten [1]. Previous studies have focused on regions where neural activity is greater for subsequently remembered items [2-8]. Here, we describe regions where activity is greater for subsequently forgotten items. In two experiments that employed the same incidental learning task, activity in an overlapping set of cortical regions (posterior cingulate, inferior and medial parietal, and dorsolateral prefrontal) was associated with failure on a subsequent memory test.

Adult↗

PubMed1998

Neural activation of the brain with hemodynamic insufficiency.

Little is known about how ischemia affects hemodynamic responses to neural activation in the brain. We compare the effects of a motor activation task and a cerebral vasodilating agent, acetazolamide (ACZ), on regional cerebral blood flow (rCBF) in primary sensorimotor cortex (PSM) in six patients with major cerebral artery steno-occlusive lesions without paresis of the upper extremities. Quantitative rCBF was measured in all patients using H2(15)O autoradiographic method and positron emission tomography. The CBF was determined at rest, during a bimanual motor activation task, and 10 minutes after ACZ administration. With bimanual motor activation, rCBF increased significantly in both PSM compared with at rest (P < 0.01 on lesion side, and P < 0.02 on contralateral side). However, rCBF did not increase after ACZ injection in the PSM on the lesion side, whereas rCBF increased significantly in the contralateral PSM after ACZ injection compared with the level at rest. This result suggests that despite a decreased hemodynamic reserve, there is a nearly normal flow response to neural activation, indicating that the mechanism of vasodilation responsible for perfusion change is different for acetazolamide and neural activation. The relations among neural activation, hemodynamic status, and cerebral metabolism in the ischemic stroke patients are discussed.

Acetazolamide↗

PubMed2002

In vivo blockade of neural activity alters dendritic development of neonatal CA1 pyramidal cells.

During development, neural activity has been proposed to promote neuronal growth. During the first postnatal week, the hippocampus is characterized by an oscillating neural network activity and a rapid neuronal growth. In the present study we tested in vivo, by injecting tetanus toxin into the hippocampus of P1 rats, whether this neural activity indeed promotes growth of pyramidal cells. We have previously shown that tetanus toxin injection leads to a strong reduction in the frequency of spontaneous GABA and glutamatergic synaptic currents, and to a complete blockade of the early neural network activity during the first postnatal week. Morphology of neurobiotin-filled CA1 pyramidal cells was analyzed at the end of the first postnatal week (P6-10). In activity-reduced neurons, the total length of basal dendritic tree was three times less than control. The number, but not the length, of basal dendritic branches was affected. The growth impairment was restricted to the basal dendrites. The apical dendrite, the axons, or the soma grew normally during activity deprivation. Thus, the in vivo neural activity in the neonate hippocampus seems to promote neuronal growth by initiating novel branches.

Animals↗

PubMed2000

Spatio-temporal analyses of stimulus-evoked and spontaneous stochastic neural activity observed by optical imaging in guinea pig auditory cortex.

Stimulus-evoked response in the cortex involves random neural activity besides the deterministic responses reproducible to the stimulus. Recently, we have developed a new bright optical system that enables us to investigate the spatio-temporal patterns of such stochastic activity in the guinea pig auditory cortex without averaging. We show that (1) the stochastic neural activity is evoked by a tone-stimulus in addition to the deterministic response, and spontaneous stochastic activity is also observed in a similar manner; (2) our statistical estimation of optical responses such as variance showed that the evoked stochastic activity was increased by the sound stimulus compared to the spontaneous activity; (3) both types of stochastic activity mainly display oscillatory behavior, in the frequency range of 5-11 Hz; (4) there are no significant differences between the stimulus-induced and spontaneous stochastic neural activity in our statistical analyses using the PSD (power-spectrum density) and the spatial correlation function; (5) the spatial area of the evoked stochastic activity is not strongly correlated with the tonotopical area of the deterministic response that is mainly localized in the caudal area of field A of the guinea pig auditory cortex. Thus, the stochastic neural activity existing in the stimulus response and the spontaneous activity in the auditory cortex are possibly generated by a common neural mechanism. These results were confirmed statistically using 27 animals.

Acoustic Stimulation↗