Nonbursting Neurons Research Articles

Operant conditioning of motor cortex neurons reveals neuron-subtype-specific responses in a brain-machine interface task

Operant conditioning is implemented in brain-machine interfaces (BMI) to induce rapid volitional modulation of single neuron activity to control arbitrary mappings with an external actuator. However, intrinsic factors of the volitional controller (i.e. the brain) or the output stage (i.e. individual neurons) might hinder performance of BMIs with more complex mappings between hundreds of neurons and actuators with multiple degrees of freedom. Improved performance might be achieved by studying these intrinsic factors in the context of BMI control. In this study, we investigated how neuron subtypes respond and adapt to a given BMI task. We conditioned single cortical neurons in a BMI task. Recorded neurons were classified into bursting and non-bursting subtypes based on their spike-train autocorrelation. Both neuron subtypes had similar improvement in performance and change in average firing rate. However, in bursting neurons, the activity leading up to a reward increased progressively throughout conditioning, while the response of non-bursting neurons did not change during conditioning. These results highlight the need to characterize neuron-subtype-specific responses in a variety of tasks, which might ultimately inform the design and implementation of BMIs.

Dopamine/Tyrosine Hydroxylase Neurons of the Hypothalamic Arcuate Nucleus Release GABA, Communicate with Dopaminergic and Other Arcuate Neurons, and Respond to Dynorphin, Met-Enkephalin, and Oxytocin.

Here, we show that the great majority of mouse hypothalamic arcuate nucleus (ARC) neurons that synthesize TH in the dorsomedial ARC also contain immunoreactive dopamine, and show either bursting or nonbursting electrical activity. Unlike rats, the mechanism underlying bursting was not dependent on gap junctions but required T-type calcium and A-type potassium channel activation. Neuropeptides dynorphin and met-enkephalin inhibited dopamine neurons, whereas oxytocin excited them. Most ventrolateral ARC TH cells did not contain dopamine and did not show bursting electrical activity. TH-containing neurons appeared to release synaptic GABA within the ARC onto dopamine neurons and unidentified neurons, suggesting that the cells not only control pituitary hormones but also may modulate nearby neurons.

Participation of a persistent sodium current and calcium-activated nonspecific cationic current to burst generation in trigeminal principal sensory neurons

The properties of neurons participating in masticatory rhythmogenesis are not clearly understood. Neurons within the dorsal trigeminal principal sensory nucleus (dPrV) are potential candidates as components of the masticatory central pattern generator (CPG). The present study examines in detail the ionic mechanisms controlling burst generation in dPrV neurons in rat (postnatal day 8-12) brain stem slices using whole cell and perforated patch-clamp methods. Nominal extracellular Ca(2+) concentration transformed tonic discharge in response to a maintained step pulse of current into rhythmical bursting in 38% of nonbursting neurons. This change in discharge mode was suppressed by riluzole, a persistent Na(+) current (INaP) antagonist. Veratridine, which suppresses the Na(+) channel inactivation mechanism, induced rhythmical bursting in nonbursting neurons in normal artificial cerebrospinal fluid, suggesting that INaP contributes to burst generation. Nominal extracellular Ca(2+) exposed a prominent afterdepolarizing potential (ADP) following a single spike induced by a 3-ms current pulse, which was suppressed, but not completely blocked, by riluzole. Application of BAPTA, a Ca(2+) chelator, intracellularly, or flufenamic acid, a Ca(2+)-activated nonspecific cationic channel (ICAN) antagonist, extracellularly to the bath, suppressed rhythmical bursting and the postspike ADP. Application of drugs to alter Ca(2+) release from endoplasmic reticulum also suppressed bursting. Finally, voltage-clamp methods demonstrated that nominal Ca(2+) facilitated INaP and induced ICAN. These data demonstrate for the first time that the previously observed induction in dPrV neurons of rhythmical bursting in nominal Ca(2+) is mediated by enhancement of INaP and onset of ICAN, which are dependent on intracellular Ca(2+).

Voltage-gated membrane currents in neurons involved in odor information processing in snail procerebrum

The procerebrum (PC) of the snail brain is a critical region for odor discrimination and odor learning. The morphological organization and physiological function of the PC has been intensively investigated in several gastropod species; however, the presence and distribution of ion channels in bursting and non-bursting cells has not yet been described. Therefore, the aim of our study was to identify the different ion channels present in PC neurons. Based on whole cell patch-clamp and immunohistochemical experiments, we show that Na(+)-, Ca(2+)-, and K(+)-dependent voltage-gated channels are differentially localized and expressed in the cells of the PC. Different Na-channel subtypes are present in large (10-15μm) and small (5-8μm) diameter neurons, which are thought to correspond to the bursting and non-bursting cells, respectively. Here, we show that the bursting neurons possess fast sodium current (I NaT) and NaV1.9-like channels and the non-bursting neurons possess slow sodium current (I NaT) and NaV1.8-like channels in addition to the L-type Ca(-), KV4.3 (A-type K-channel) and KV2.1 channels. We suggest that the bursting and/or non-bursting character of the PC neurons is at least partly determined by the battery of ion-channels present and their cellular and subcellular compartmentalization.

Inward-Rectifying Potassium (Kir) Channels Regulate Pacemaker Activity in Spinal Nociceptive Circuits during Early Life

Pacemaker neurons in neonatal spinal nociceptive circuits generate intrinsic burst firing and are distinguished by a lower "leak" membrane conductance compared with adjacent nonbursting neurons. However, little is known about which subtypes of leak channels regulate the level of pacemaker activity within the developing rat superficial dorsal horn (SDH). Here we demonstrate that a hallmark feature of lamina I pacemaker neurons is a reduced conductance through inward-rectifying potassium (K(ir)) channels at physiological membrane potentials. Differences in the strength of inward rectification between pacemakers and nonpacemakers indicate the presence of functionally distinct K(ir) currents in these two populations at room temperature. However, K(ir) currents in both groups showed high sensitivity to block by extracellular Ba²⁺ (IC₅₀ ~ 10 μm), which suggests the presence of "classical" K(ir) (K(ir)2.x) channels in the neonatal SDH. The reduced K(ir) conductance within pacemakers is unlikely to be explained by an absence of particular K(ir)2.x isoforms, as immunohistochemical analysis revealed the expression of K(ir)2.1, K(ir)2.2, and K(ir)2.3 within spontaneously bursting neurons. Importantly, Ba²⁺ application unmasked rhythmic burst firing in ∼42% of nonbursting lamina I neurons, suggesting that pacemaker activity is a latent property of a sizeable population of SDH cells during early life. In addition, the prevalence of spontaneous burst firing within lamina I was enhanced in the presence of high internal concentrations of free Mg²⁺, consistent with its documented ability to block K(ir) channels from the intracellular side. Collectively, the results indicate that K(ir) channels are key modulators of pacemaker activity in newborn central pain networks.

Excitatory effects of GABA on procerebrum neurons in a slug

Classical neurotransmitters, such as glutamate and γ-aminobutyric acid (GABA), often have different actions on invertebrate neurons from those reported for vertebrate neurons. In the terrestrial mollusk Limax, glutamate was found to function as an inhibitory transmitter in the procerebrum (PC), but it has not yet been clarified how GABA acts in the PC. We thus examined what effects GABA exerts on PC neurons in the present study. For this purpose, we first applied GABA to isolated PC preparations and recorded postsynaptic currents and potentials in PC neurons. The GABA application reduced the amplitude of inhibitory postsynaptic currents and depolarization-induced outward currents recorded in nonbursting neurons and increased the number of spontaneous spikes of nonbursting neurons. However, direct GABA-induced currents were not observed in either bursting or nonbursting neurons. These results suggest a potential direct effect of GABA on outward currents resulting in enhanced excitability of PC neurons. Next, we measured the change in [Ca(2+)](i) in cultured PC neurons by application of GABA. The GABA application increased spontaneous Ca(2+) events in cultured neurons. These Ca(2+) events were ascribable to the influx of extracellular Ca(2+). We then confirmed the presence of GABA and GABA receptors in the PC. The GABA-like immunoreactivity was observed in the neuropil layers of the PC, and the mRNAs for both GABA(A) and GABA(B) receptors were expressed in the PC. In particular, GABA(B) receptor mRNA, rather than GABA(A), was found to be more abundantly expressed in the PC. These results suggest that GABA functions as an excitatory modulator for PC neurons via mainly GABA(B) receptors.

Burst dynamics enable contrast coding via synchrony

Neurons in various sensory systems respond to stimuli with a variety of action potential patterns including isolated action potentials and bursts (i.e. high frequency groups of action potentials). There is accumulating evidence that, instead of being just a collection of action potentials, bursts are instead a specific pattern that signals stimulus attributes that are distinct than those signaled by isolated action potentials [1]. Specifically, it has been proposed that synchronous bursts can signal the occurrence of certain stimuli [2] and encode higher order stimulus attributes such as contrast [3]. Here we test experimentally whether synchronous activity in a population of neurons can encode a time varying stimulus contrast. To do so, we performed intracellular recordings of the activity of electrosensory pyramidal cells in-vitro. These cells have been well characterized and previous studies have shown that they tonically fire isolated action potentials under control conditions but that application of the neuromodulator serotonin (5-HT) can cause them to transition into a burst firing mode [4]. As such, we tested the information transmission capabilities of these cells about stimulus contrast in both modes. To do so, we provided the cells with a time-varying stimulus and investigated how the number of synchronous spikes correlates with stimulus contrast. We found that synchrony had a larger dependence on stimulus contrast in pyramidal cells after 5-HT injection than under control conditions. These experimental results agree with the predictions of the model presented in [2]. Furthermore, we developed a mathematical theory that supports our experimental results and proposes that the change in coding properties between bursting and non-bursting neurons is solely attributed to the higher baseline response variability as quantified by the coefficient of variation (CV) present in bursting neurons. Our experimental results therefore show that bursting neurons are more apt at coding stimulus contrast through synchronous firing than tonic ones. Moreover, our theoretical results suggest that this occurs because burst dynamics introduce variability in the responses of single neurons. The latter is supported by the fact that bursting neurons with the highest CVs showed the greatest dependency on stimulus contrast in their synchronous activities. Our results thus provide the first experimental evidence that bursting neurons can code for stimulus contrast via their synchronous activity and provide a novel function for burst dynamics.

A mathematical model for Cantor coding in the hippocampus

Recent studies suggest that the hippocampus is crucial for memory of sequentially organized information. Cantor coding in hippocampal CA1 is theoretically hypothesized to provide a scheme for encoding temporal sequences of events. Here, in order to investigate this Cantor coding in detail, we construct a CA1 network model consisting of conductance-based model neurons. It is assumed that CA3 outputs temporal sequences of spatial patterns to CA1. We examine the dependence of output patterns of CA1 neurons on input time series by taking each output and combining it with an input sequence. It is shown that the output patterns of CA1 were hierarchically clustered in a self-similar manner according to the similarity of input temporal sequences. The population dynamics of the network can be well approximated by a set of contractive affine transformations, which forms a Cantor set. Furthermore, it is shown that the performance of the encoding scheme sensitively depends on the interval of input sequences. The bursting neurons with NMDA synapses are effective for encoding sequential input with long (over 150 ms) intervals while the non-bursting neurons with AMPA synapses are effective for encoding input with short (less than 30 ms) intervals.

FMRFamide regulates oscillatory activity of the olfactory center in the slug

In the olfactory center of terrestrial animals, changes in the oscillatory frequency of the local field potential (LFP) are thought to be involved in olfaction-based behavior and olfactory memory. The terrestrial slug Limax has a highly developed olfactory center, the procerebrum, in which the LFP spontaneously oscillates. Although changes in the oscillatory frequency are thought to correspond to the preference for specific odors, our knowledge about the mechanism of this frequency regulation is limited. To clarify the mechanism of the bidirectional frequency changes in the procerebrum, we focused on the neuropeptide Phe-Met-Arg-Phe-NH₂ (FMRFamide), which is known to have neuromodulatory functions in invertebrate nervous systems. Application of FMRFamide decreased the oscillatory frequency via G-protein-mediated cascades. Immunohistochemistry showed that FMRFamide-like-immunoreactive neuronal cell bodies are located in the cell mass layer of the procerebrum, projecting their neurites to the neuropile layers. The procerebrum was shown to also receive innervation from other regions of the cerebral ganglion. Furthermore, according to their morphological and projection characteristics, FMRFamide-containing neurons belong to the subpopulations of both bursting and nonbursting neurons in the procerebrum. The mRNA splice variant encoding multiple copies of canonical FMRFamide was specifically expressed in the procerebrum. Taking into account previous results showing that serotonin increases the oscillatory frequency, our results indicate that FMRFamide and serotonin both regulate the LFP frequency but in exactly the opposite direction in the olfactory center of the terrestrial slug.

A novel nitric oxide synthase expressed specifically in the olfactory center

Nitric oxide (NO) plays important roles in the olfactory center of various animals. In the terrestrial slug, NO is indispensable for field potential oscillation in the higher olfactory center, the procerebrum (PC), and also for odor learning. Here we identify a novel NO synthase (NOS) gene, limNOS2, in the terrestrial slug. The mRNA (∼10kb) of limNOS2 encodes a protein consisting of 1616 amino acids, including a PDZ domain. The protein has 70.0% sequence identity with the previously identified limNOS1 gene. In contrast to limNOS1, however, limNOS2 is expressed specifically in the PC. Moreover, most of the cells in the PC contain limNOS2 mRNA, indicating that the nonbursting neurons, the major constituent of the PC, have this mRNA. The expression pattern of limNOS2 conforms well to the pattern of NOS enzymatic histochemical staining. Our present findings indicate that limNOS2 is responsible for most of the NO generation in the PC.

Determining Burst Firing Time Distributions from Multiple Spike Trains

Recent experimental findings have shown the presence of robust and cell-type-specific intraburst firing patterns in bursting neurons. We address the problem of characterizing these patterns under the assumption that the bursts exhibit well-defined firing time distributions. We propose a method for estimating these distributions based on a burst alignment algorithm that minimizes the overlap among the firing time distributions of the different spikes within the burst. This method provides a good approximation to the burst's intrinsic temporal structure as a set of firing time distributions. In addition, the method allows labeling the spikes in any particular burst, establishing a correspondence between each spike and the distribution that best explains it, and identifying missing spikes. Our results on both simulated and experimental data from the lobster stomatogastric ganglion show that the proposed method provides a reliable characterization of the intraburst firing patterns and avoids the errors derived from missing spikes. This method can also be applied to nonbursting neurons as a general tool for the study and the interpretation of firing time distributions as part of a temporal neural code.

Selective calcium imaging of olfactory interneurons in a land mollusk

The procerebrum (PC) of the land slug Limax is the olfactory center involved in olfactory discrimination and learning. The PC contains two types of neurons, bursting (B) and nonbursting (NB) neurons. B neurons are local interneurons and show spontaneous bursting while NB neurons directly receive input from olfactory nerve fibers, and are possibly involved in odor coding. In order to observe activity of NB neurons, selective calcium imaging was made by retrograde staining of NB neurons with the calcium sensitive dye, rhod-2 AM, from the internal mass (IM) of the PC. The stained cells, presumably NB neurons, appeared to be mostly silent, but showed transient calcium elevation in response to electrical stimulus to the tentacle nerve. Stimulation of the tentacle with an odorant also evoked calcium events in some of the stained cells. These included one or multiple calcium events, and these events were synchronized with each other. These results revealed characteristics of the activity of NB neurons.

Persistent sodium is a better linearizing mechanism than the hyperpolarization-activated current

The hyperpolarization-activated mixed cation and the persistent sodium conductances are compared as linearizing mechanisms for somatodendritic synaptic integration in steady-state systems. In the steady-state model used, the persistent sodium conductance creates a well-defined region of linear synaptic excitation, from - 66 to - 55 mV . This corresponds to a moderate level of synaptic depolarization (total active synaptic conductance ranging from 2 to 5.9 nS). In contrast, a model enhanced with a hyperpolarization-activated mixed cation conductance only linearizes over a short voltage range, from - 68 to - 61 mV . This in turns corresponds to very low levels of synaptic activity (0–3.7 nS). Given in vivo recordings of firing thresholds for nonbursting neurons ranging from around - 60 to - 55 mV , the persistent sodium current emerges as the better linearizing mechanism for these neurons because it operates across the full physiologically relevant voltage range for perisomatic, proximal dendritic synaptic excitation.

Stable propagation of a burst through a one-dimensional homogeneous excitatory chain model of songbird nucleus HVC

We demonstrate numerically that a brief burst consisting of two to six spikes can propagate in a stable manner through a one-dimensional homogeneous feedforward chain of nonbursting neurons with excitatory synaptic connections. Our results are obtained for two kinds of neuronal models: leaky integrate-and-fire neurons and Hodgkin-Huxley neurons with five conductances. Over a range of parameters such as the maximum synaptic conductance, both kinds of chains are found to have multiple attractors of propagating bursts, with each attractor being distinguished by the number of spikes and total duration of the propagating burst. These results make plausible the hypothesis that sparse, precisely timed sequential bursts observed in projection neurons of nucleus HVC of a singing zebra finch are intrinsic and causally related.

Physiological characterization, localization and synaptic inputs of bursting and nonbursting neurons in the trigeminal principal sensory nucleus of the rat

A population of neurons in the trigeminal principal sensory nucleus (NVsnpr) fire rhythmically during fictive mastication induced in the in vivo rabbit. To elucidate whether these neurons form part of the central pattern generator (CPG) for mastication, we performed intracellular recordings in brainstem slices taken from young rats. Two cell types were defined, nonbursting (63%) and bursting (37%). In response to membrane depolarization, bursting cells, which dominated in the dorsal part of the NVsnpr, fired an initial burst followed by single spikes or recurring bursts. Non-bursting neurons, scattered throughout the nucleus, fired single action potentials. Microstimulation applied to the trigeminal motor nucleus (NVmt), the reticular border zone surrounding the NVmt, the parvocellular reticular formation or the nucleus reticularis pontis caudalis (NPontc) elicited a postsynaptic potential in 81% of the neurons tested for synaptic inputs. Responses obtained were predominately excitatory and sensitive to glutamatergic antagonists DNQX and/or APV. Some inhibitory and biphasic responses were also evoked. Bicuculline methiodide or strychnine blocked the IPSPs indicating that they were mediated by GABA(A) or glycinergic receptors. About one-third of the stimulations activated both types of neurons antidromically, mostly from the masseteric motoneuron pool of NVmt and dorsal part of NPontc. In conclusion, our new findings show that some neurons in the dorsal NVsnpr display both firing properties and axonal connections which support the hypothesis that they may participate in masticatory pattern generation. Thus, the present data provide an extended basis for further studies on the organization of the masticatory CPG network.

Medial Septal GABAergic Neurons Express the Somatostatin sst2AReceptor: Functional Consequences on Unit Firing and Hippocampal Theta

GABAergic septohippocampal neurons play a major role in the generation of hippocampal theta rhythm, but modulatory factors intervening in this function are poorly documented. The neuropeptide somatostatin (SST) may be one of these factors, because nearly all hippocampal GABAergic neurons projecting to the medial septum/diagonal band of Broca (MS-DB) express SST. In this study, we took advantage of the high and selective expression of the SST receptor sst2A in MS-DB to examine its possible role on theta-related activity. Immunohistochemical experiments demonstrated that sst2A receptors were selectively targeted to the somatodendritic domain of neurons expressing the GABAergic marker GAD67 but were not expressed by cholinergic neurons. In addition, a subpopulation of GABAergic septohippocampal projecting neurons expressing parvalbumin (PV) also displayed sst2A receptors. Using in vivo juxtacellular recording and labeling with neurobiotin, we showed that a number of bursting and nonbursting neurons exhibiting high discharge rates and brief spikes were immunoreactive for PV or GAD67 and expressed the sst2A receptor. Microiontophoresis applications of SST and the sst2A agonist octreotide (OCT) showed that sst2A receptor activation decreased the discharge rate of both nonbursting and bursting MS-DB neurons and lessened the rhythmic activity of the latter. Finally, intraseptal injections of OCT and SST in freely moving rats reduced the power of hippocampal EEG in the theta band. Together, these in vivo experiments suggest that SST action on MS-DB GABAergic neurons, through sst2A receptors, represents an important modulatory mechanism in the control of theta activity.

Nitric oxide synthase and soluble guanylyl cyclase underlying the modulation of electrical oscillations in a central olfactory organ.

We have isolated and characterized the cDNAs for nitric oxide synthase (NOS) and soluble guanylyl cyclase (sGC) from the terrestrial slug Limax marginatus, and examined the presence and distribution of their mRNAs in the central nervous system using histological techniques and a reverse transcription-polymerase chain reaction method. Our results showed that both bursting and nonbursting neurons in the procerebral lobes contain the mRNAs for both NOS and sGC. We further found that the oscillation frequency of electrical activity in the procerebral lobes increases with increasing intracellular concentrations of cyclic GMP (cGMP). Taken together with previous data on the NO-induced cGMP-like immunoreactivity and on the anatomical distribution of neurites and the localization of synapses of bursting and nonbursting neurons, our present results suggest that NO-induced changes in cGMP concentration modulate the oscillation frequency in the procerebral lobes by acting on the olfactory input pathways, but possibly not on the output pathways, in slugs. .

Odor-evoked responses in the olfactory center neurons in the terrestrial slug.

The procerebrum (PC) of the terrestrial mollusk Limax is a highly developed second-order olfactory center consisting of two electrophysiologically distinct populations of neurons: nonbursting (NB) and bursting (B). NB neurons are by far the more numerous of the two cell types. They receive direct synaptic inputs from afferent fibers from the tentacle ganglion, the primary olfactory center, and also receive periodic inhibitory postsynaptic potentials (IPSPs) from B neurons. Odor-evoked activity in the NB neurons was examined using perforated patch recordings. Stimulation of the superior tentacle with odorants resulted in inhibitory responses in 45% of NB neurons, while 11% of NB neurons showed an excitatory response. The specific response was reproducible in each neuron to the same odorant, suggesting the possibility that activity of NB neurons may encode odor identity. Analysis of the cycle-averaged membrane potential of NB neurons revealed a correlation between the firing rate and the membrane potential at the plateau phase between IPSPs. Also, the firing rate of NB neurons was affected by the frequency of the IPSPs. These results indicate the existence of two distinct mechanisms for the regulation of NB neuron activity.

Discharge Profiles of Ventral Tegmental Area GABA Neurons during Movement, Anesthesia, and the Sleep–Wake Cycle

Although mesolimbic dopamine (DA) transmission has been implicated in behavioral and cortical arousal, DA neurons in the ventral tegmental area (VTA) and substantia nigra pars compacta (SNc) are not significantly modulated by anesthetics or the sleep-wake cycle. However, VTA and SN non-DA neurons evince increased firing rates during active wakefulness (AW) and rapid eye movement (REM) sleep, relative to quiet wakefulness. Here we describe the effects of movement, select anesthetics, and the sleep-wake cycle on the activity of a homogeneous population of VTA GABA-containing neurons during normal sleep and after 24 hr sleep deprivation. In freely behaving rats, VTA GABA neurons were relatively fast firing (29 +/- 6 Hz during AW), nonbursting neurons that exhibited markedly increased activity during the onset of discrete movements. Adequate anesthesia produced by administration of chloral hydrate, ketamine, or halothane significantly reduced VTA GABA neuron firing rate and converted their activity into phasic 0.5-2.0 sec ON/OFF periods. VTA GABA neuron firing rate decreased 53% during slow-wave sleep (SWS) and increased 79% during REM, relative to AW; however, the discharging was not synchronous with electrocortical alpha wave activity during AW, delta wave activity during SWS, or gamma wave activity during REM. During deprived SWS, there was a direct correlation between increased VTA GABA neuron slowing and increased delta wave power. These findings indicate that the discharging of VTA GABA neurons correlates with psychomotor behavior and that these neurons may be an integral part of the extrathalamic cortical activating system.

Modulation of oscillatory neural activities by cholinergic activation of interneurons in the olfactory center of a terrestrial slug

The neurons in the procerebrum (PC) of the terrestrial slug Limax marginatus show regular oscillation of their membrane potential, and the oscillation has been implicated in olfactory processing. The neural mechanisms for the generation and modulation of the oscillation have been poorly understood. In the present work, we examined the ionic conductances evoked by acetylcholine (ACh) in the PC neurons and the effects of ACh application on the population activities of intrinsic and extrinsic neurons. The PC neurons are categorized into bursting neurons, which are putative local inhibitory neurons, and nonbursting neurons, which likely mediate the input and output of information in the PC. Bath application of ACh augmented the local field potential oscillation in the PC. Perforated patch recording from single PC neurons revealed that ACh has direct excitatory effects on bursting neurons, while it suppresses the activity of nonbursting neurons, possibly via augmented inhibitory synaptic input from bursting neurons. The correlation between the membrane potential of bursting neurons and the frequency of oscillation suggests that bursting neurons are the main determinant of the oscillation frequency. Application of ACh also resulted in a reduction of the oscillation amplitude in the olfactory nerve, suggesting that the frequency modulation in the oscillatory network could change the activities in the follower neurons.