The facilitatory influence of anterior cingulate cortex on ON-OFF response of tactile neuron in thalamic ventrobasal nucleus

The structures of limbic system have been found to modulate the auditory, visual and pain afferent signals in the related nuclei of thalamus. One of those structures is anterior cingulate cortex (ACC) that influences nocuous response of the pain-sensitive neurons in the ventropos-tero-lateral nucleus of thalamus. Thus, we inferred that ACC would also modulate tactile information at the thalamic level. To test this assumption, single units were recorded extracellularly from thalamic ventrobasal nucleus (VB). Tactile ON-OFF response and the relationship between different patterns of the responses and the parameters of tactile stimulation were examined. Furthermore, the influence of ACC on the tactile ON-OFF response was studied. ACC stimulation was found to produce a facilitatory effect on the OFF-response of ON-OFF neurons. It lowered the threshold of the off-response of that neuron, and therefore changed the response pattern or enhanced the firing rate of the OFF-response of the neuron. The study on rec     

刺激大鼠杏仁外侧核对皮层AⅠ区ON-OFF神经元反应及调谐曲线的影响

在30只氨基甲酸乙酯麻醉的SD大鼠上记录神经元单位放电,观察短纯音诱发的皮层AI区神经元ON－OFF反应的特性及电刺激杏仁外侧核（lateral amygdaloid nucleus,LA)对ON－OFF反应以及调谐曲线的影响。实验证实,AI区神经元ON－OFF反应的模式与纯音刺激的强度、频率及作用时程有关;刺激LA可以抑制ON－OFF反应的放电频数,使反应的阈值升高,或使反应放电构型发生变化;此外,刺激LA能使ON－OFF神经元的调谐曲线变窄,Q10数值增大。研究结果不仅表明ON－OFF神经元能对纯音刺激的时程、强度和频率等多种信息进行编码,而且还证明杏仁外侧核可以在皮层水平参与听觉信息的调制,削弱或衰减某些听觉信息,导致整个调谐曲线上移变窄,从而提高AI区ON－OFF神经元的频率选择性能,有利于检测外界嘈杂环境中特定的听觉信息。     

Specific Relationship between Excitatory Inputs and Climbing Fiber Receptive Fields in Deep Cerebellar Nuclear Neurons

Many mossy fiber pathways to the neurons of the deep cerebellar nucleus (DCN) originate from the spinal motor circuitry. For cutaneously activated spinal neurons, the receptive field is a tag indicating the specific motor function the spinal neuron has. Similarly, the climbing fiber receptive field of the DCN neuron reflects the specific motor output function of the DCN neuron. To explore the relationship between the motor information the DCN neuron receives and the output it issues, we made patch clamp recordings of DCN cell responses to tactile skin stimulation in the forelimb region of the anterior interposed nucleus in vivo. The excitatory responses were organized according to a general principle, in which the DCN cell responses became stronger the closer the skin site was located to its climbing fiber receptive field. The findings represent a novel functional principle of cerebellar connectivity, with crucial importance for our understanding of the function of the cerebellum in movement coordination.     

Spontaneous Activity and Responses to Sensory Stimulation in Ventrobasal Thalamic Neurons in the Rat: An In Vivo Intracellular Recording and Staining Study

Spontaneous activity and responses to sensory stimulation in ventrobasal (VB) thalamic neurons were studied in barbiturate-anesthetized rats through intracellular recordings. The recordings were carried out with micropipettes filled with K acetate, KCl plus horseradish peroxidase (HRP), our KCl plus biocytin. Two types of spontaneous depolarizing events were observed: fast potentials (FPs), characterized by a low amplitude (5.3 ± 1.8 mV [mean and standard deviation]), a fast rising slope (1.15 ± 0.19 msec), and a short duration (8.47 ± 0.89 msec); and slow potentials (SPs), characterized by a larger and more variable amplitude (9.1 ± 5.6 mV) and a longer duration (62.5 ± 27.2 msec), with a slower rising slope (26.2 ± 6.4 msec). The potential changes elicited by sensory stimuli delivered manually were similar to those elicited by electronically gated short air jets to the receptive fields. FPs were evoked by sensory stimulation in 62.7% of the recorded neurons, and SPs in the remaining 37.3%. Both types of events could occur spontaneously in the same neuron, but only one of them was triggered by stimulation of the receptive field. Five neurons that were successfully stained with either HRP or biocytin were studied in detail. AH were medium-sized stellate cells, with spine-like appendages sparsely distributed along slender radiating dendrites. The axons took a rostrolateral course across the VB, and all but one left one or two thin collaterals in the reticular thalamic nucleus. No overt morphological differences were observed between VB neurons that responded with FPS or SPs to sensory stimulation.     

Axonal conduction properties of antidromically identified neurons in rat barrel cortex

Physiological studies of the rodent somatosensory cortex have consistently described considerable heterogeneity in receptive field properties of neurons outside of layer IV, particularly those in layers V and VI. One such approach for distinguishing among different local circuits in these layers may be to identify the projection target of neurons whose axon collaterals contribute to the local network. In vivo, this can be accomplished using antidromic stimulation methods. Using this approach, the axonal conduction properties of cortical efferent neurons are described. Four projection sites were activated using electrical stimulation: (1) vibrissal motor cortex, (2) ventrobasal thalamus (VB), (3) posteromedial thalamic nucleus (POm), and (4) cerebral peduncle. Extracellular recordings were obtained from a total of 169 units in 21 animals. Results demonstrate a close correspondence between the laminar location of the antidromically identified neurons and their anatomically known layer of origin. Axonal properties were most distinct for corticofugal axons projecting through the crus cerebri. Corticothalamic axons projecting to either VB or POm were more similar to each other in terms of laminar location and conduction properties, but could be distinguished using focal electrical stimulation. It is concluded that, once stimulation parameters are adjusted for the small volume of the rat brain, the use of antidromic techniques may be an effective strategy to differentiate among projection neurons comprising different local circuits in supra- and infragranular circuits.     

Axonal conduction properties of antidromically identified neurons in rat barrel cortex

Physiological studies of the rodent somatosensory cortex have consistently described considerable heterogeneity in receptive field properties of neurons outside of layer IV, particularly those in layers V and VI. One such approach for distinguishing among different local circuits in these layers may be to identify the projection target of neurons whose axon collaterals contribute to the local network. In vivo, this can be accomplished using antidromic stimulation methods. Using this approach, the axonal conduction properties of cortical efferent neurons are described. Four projection sites were activated using electrical stimulation: (1) vibrissal motor cortex, (2) ventrobasal thalamus (VB), (3) posteromedial thalamic nucleus (POm), and (4) cerebral peduncle. Extracellular recordings were obtained from a total of 169 units in 21 animals. Results demonstrate a close correspondence between the laminar location of the antidromically identified neurons and their anatomically known layer of origin. Axonal properties were most distinct for corticofugal axons projecting through the crus cerebri. Corticothalamic axons projecting to either VB or POm were more similar to each other in terms of laminar location and conduction properties, but could be distinguished using focal electrical stimulation. It is concluded that, once stimulation parameters are adjusted for the small volume of the rat brain, the use of antidromic techniques may be an effective strategy to differentiate among projection neurons comprising different local circuits in supra- and infragranular circuits.     

The contribution of the principal and spinal trigeminal nuclei to the receptive field properties of thalamic VPM neurons in the rat

Primary sensory information from neurons innervating whisker follicles on one side of a rat's face is relayed primarily through two subnuclei of the brainstem trigeminal complex to the contralateral thalamus. The present experiments were undertaken to separate the contribution of the principal trigeminal nucleus (PrV) from that of the spinal trigeminal nucleus (SpV) to whisker evoked responses in the ventral posterior medial (VPM) nucleus in the adult rat thalamus. Extracellular single-unit responses of VPM neurons to controlled stimulation of the contralateral whiskers under urethane anesthesia were quantified in terms of receptive field size, modal latency, response probability and response magnitude. The SpV contribution to VPM cell responses was isolated by making kainic acid lesions of the PrV. The PrV contribution was ascertained by cutting the trigeminothalamic axons arising from SpV just before they cross the midline. After destruction of the PrV, the SpV pathway alone produced large receptive fields (mean: 9.04 whiskers) and long latency (mean: 11.07 ms) responses from VPM neurons. In contrast, PrV input alone (SpV disconnected) generated small receptive fields (mean: 1.06 whiskers) and shorter latency (mean: 6.74 ms) responses. With both pathways intact the average receptive field size was 2.4 whiskers and peak (modal) response latency was 7.33 ms. The responses with both pathways intact were significantly different from either pathway operating in isolation. Response probability and magnitude followed the same trend. We conclude that normal responses of individual VPM neurons represent the integration of input activity transmitted through both PrV and SpV pathways.     

Corticofugal modulation of initial neural processing of sound information from the ipsilateral ear in the mouse

Background

Cortical neurons implement a high frequency-specific modulation of subcortical nuclei that includes the cochlear nucleus. Anatomical studies show that corticofugal fibers terminating in the auditory thalamus and midbrain are mostly ipsilateral. Differently, corticofugal fibers terminating in the cochlear nucleus are bilateral, which fits to the needs of binaural hearing that improves hearing quality. This leads to our hypothesis that corticofugal modulation of initial neural processing of sound information from the contralateral and ipsilateral ears could be equivalent or coordinated at the first sound processing level.

Methodology/Principal Findings

With the focal electrical stimulation of the auditory cortex and single unit recording, this study examined corticofugal modulation of the ipsilateral cochlear nucleus. The same methods and procedures as described in our previous study of corticofugal modulation of contralateral cochlear nucleus were employed simply for comparison. We found that focal electrical stimulation of cortical neurons induced substantial changes in the response magnitude, response latency and receptive field of ipsilateral cochlear nucleus neurons. Cortical stimulation facilitated auditory response and shortened the response latency of physiologically matched neurons whereas it inhibited auditory response and lengthened the response latency of unmatched neurons. Finally, cortical stimulation shifted the best frequencies of cochlear neurons towards those of stimulated cortical neurons.

Conclusion

Our data suggest that cortical neurons enable a high frequency-specific remodelling of sound information processing in the ipsilateral cochlear nucleus in the same manner as that in the contralateral cochlear nucleus.     

Effects of ES52, an enkephalinase inhibitor, on responses of ventrobasal thalamic neurons in rat

The effects of ES52, a highly potent derivative of Thiorphan, an inhibitor of enkephalinase, at doses of 5 and 10 mg/kg IV were studied on the responses to cutaneous stimuli of 18 “nociceptive” (N), 10 “convergent” (NNn) and 4 “non-nociceptive” (Nn) neurons recorded in the ventrobasal (VB) complex of the rat. The responses of neurons exclusively driven by noxious mechanical and thermal stimuli (N neurons) were depressed by 56% by ES52 15 min after the injection of 5 or 10 mg/kg IV. This depressive effect was reversed by naloxone for half the neurons. For the ten neurons driven by both noxious and non-noxious stimuli (convergent NNn neurons), the responses to noxious heat were decreased by 42% at 15 min. By contrast, there was a marked enlargement of their receptive fields to light tactile stimuli, which was not naloxone-reversible. The receptive fields of neurons exclusively driven by non-noxious stimuli (Nn neurons) were also greatly expanded by ES52. These results show that ES52 can depress the responses of VB thalamic neurons to noxious stimuli; the effects on receptive field size underlines the complexity of the endogenous opiate systems.     

A quantitative comparison of the hominoid thalamus: II. Limbic nuclei anterior principalis and lateralis dorsalis

Structures in the limbic system are commonly thought to be similar in form and function in all mammalian brains. In the study reported here, two thalamic limbic nuclei, N. anterior principles and N. lateralis dorsalis, were compared among a group of extant of extant hominoids. The nuclear volumes, neuronal densities, number of neurons per nucleus, and volumes of neuronal perikarya were measured. Humans have much larger nuclei but the nuclei constitute a similar proportion of the whole thalamus as found in the other hominoids. Whereas the human limbic nuclei were observed to have a decrease in the densities of nerve cells compared with those of the other hominoids, this difference is less than that found in most other thalamic nuclei. Consequently the estimated number of neurons is much higher for humans. The total number of neurons best separates the human limbic nuclei from those of the other hominoids. This preliminary study suggests that during hominid evolution neurons were preferentially added to the limbic nuclei of the thalamus.     

Activation of thalamic ventroposteriolateral neurons by phrenic nerve afferents in cats and rats.

It has been demonstrated that phrenic nerve afferents project to somatosensory cortex, yet the sensory pathways are still poorly understood. This study investigated the neural responses in the thalamic ventroposteriolateral (VPL) nucleus after phrenic afferent stimulation in cats and rats. Activation of VPL neurons was observed after electrical stimulation of the contralateral phrenic nerve. Direct mechanical stimulation of the diaphragm also elicited increased activity in the same VPL neurons that were activated by electrical stimulation of the phrenic nerve. Some VPL neurons responded to both phrenic afferent stimulation and shoulder probing. In rats, VPL neurons activated by inspiratory occlusion also responded to stimulation on phrenic afferents. These results demonstrate that phrenic afferents can reach the VPL thalamus under physiological conditions and support the hypothesis that the thalamic VPL nucleus functions as a relay for the conduction of proprioceptive information from the diaphragm to the contralateral somatosensory cortex.     

Unit responses of the thalamic and ventral anterior thalamic nuclei to electrical stimulation of thalamic relay nuclei in cats

Responses of 92 neurons of the reticular (R) and 105 neurons of the ventral anterior (VA) thalamic nuclei to stimulation of the ventrobasal complex (VB) and the lateral (GL) and medial (GM) geniculate bodies were investigated in cats immobilized with D-tobocurarine. Altogether 72.2% of R neurons and 76.2% of VA neurons responded to stimulation of VB whereas only 15.0% of R neurons and 27.1% of VA neurons responded to stimulation of GM and 10.2% of R neurons and 19.6% of VA neurons responded to stimulation of GL. The response of the R and VA neurons to stimulation of the relay nuclei as a rule was expressed as excitation. A primary inhibitory response was observed for only two R and three VA neurons. Two types of excitable neurons were distinguished: The first respond to afferent stimulation by a discharge consisting of 5–15 spikes with a frequency of 250–300/sec; the second respond by single action potentials. Neurons of the first type closely resemble inhibitory interneurons in the character of the response. Antidromic responses were recorded from 2.2% of R neurons and 7.8% of VA neurons during stimulation of the relay nuclei. Among the R and VA neurons there are some which respond to stimulation not only of one, but of two or even three relay nuclei. If stimulation of one relay nucleus is accompanied by a response of a R or VA neuron, preceding stimulation of another nucleus leads to inhibition of the response to the testing stimulus if the interval between conditioning and testing stimuli is less than 30–50 msec.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 8, No. 6, pp. 597–605, November–December, 1976.     

Responses of cat auditory cortical neurons to tones of different frequencies and electrical stimulation of corresponding regions of the cochlea

Characteristic frequencies of neurons in the cat auditory cortex (area AI) whose receptive fields are located in different parts of the basilar membrane of the cochlea were determined in cats anesthetized with pentobarbital. The higher the characteristic frequency of a neuron in area AI, the nearer its receptive field lies to the base of the cochlea. Receptive fields of neurons with a characteristic frequency higher than 4 kHz lie on the first 10 mm of the basilar membrane. Receptive fields of neurons with a characteristic frequency below 4 kHz lie on the remaining 11–12 mm of the membrane. The effect of electrical stimulation of the center of the receptive field of a neuron corresponds to its response to a tone of characteristic frequency. The more the frequency of the acting tone differs from the characteristic frequency, or the further the point of stimulation from the center of the receptive field of the neuron, the less likely is the neuron to respond with an action potential. Neurons with a low characteristic frequency have wider receptive fields than neurons with a high characteristic frequency. Receptive fields of neurons with close characteristic frequencies on the basilar membrane overlap considerably. It was shown by the method of paired stimulation that excitation evoked in neurons in area AI by the action of a tone of a particular frequency is followed by long-lasting inhibition. This inhibition lasts longest and is most effective if a tone of the characteristic frequency is used.     

研究: 外膝状体神经元的亮度反应与感受野ON-OFF反应的关系

外膝体是视觉信息进入新皮层的主要通路,其编码亮度信息的神经机制还不清楚.我们采用随机呈现的连续快速变化(50 Hz)的均匀亮度刺激,显著地提高了猫外膝体神经元对均匀亮度的反应强度,通过反相关算法抽提出神经元的亮度反应函数.约81%的神经元的亮度反应函数为单调性上升或下降,有19%的神经元亮度反应函数为V型.通过分析这些神经元对亮度上升和下降的反应强度与感受野ON和OFF反应强度的关系,表明83%的神经元对亮度的反应模式是由其感受野ON-OFF反应的相对强度决定的,其余17%则与其感受野ON-OFF区的兴奋和抑制的变化相关.这些结果揭示了外膝体神经元编码亮度变化的机制.     

Unit responses of the first and second somatosensory cortical areas to peripheral,thalamic, and cortical stimulation

Unit responses of the first (SI) somatosensory area of the cortex to stimulation of the second somatosensory area (SII), the ventral posterior thalamic nucleus, and the contralateral forelimb, and also unit responses in SII evoked by stimulation of SI, the ventral posterior thalamic nucleus, and the contralateral forelimb were investigated in experiments on cats immobilized with D-tubocurarine or Myo-Relaxin (succinylcholine). The results showed a substantially higher percentage of neurons in SII than in SI which responded to an afferent stimulus by excitation brought about through two or more synaptic relays in the cortex. In response to cortical stimulation antidromic and orthodromic responses appeared in SI and SII neurons, confirming the presence of two-way cortico-cortical connections. In both SI and SII intracellular recording revealed in most cases PSPs of similar character and intensity, evoked by stimulation of the cortex and nucleus in the same neuron. Latent periods of orthodromic spike responses to stimulation of nucleus and cortex in 50.5% of SI neurons and 37.1% of SII neurons differed by less than 1.0 msec. In 19.6% of SI and 41.4% of SII neurons the latent period of response to cortical stimulation was 1.6–4.7 msec shorter than the latent period of the response evoked in the same neuron by stimulation of the nucleus. It is concluded from these results that impulses from SI play an important role in the afferent activation of SII neurons.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 8, No. 4, pp. 351–357, July–August, 1976.     

Role of sensory signals in the development of cortical influences on hypothalamic structures]

Neuron discharges of the hypothalamic ventro-medial and posterior nuclei were registered in immobilized cats during electrical stimulation of the ipsi- and contralateral nerves of the brachial plexus, the 1st and the 2nd somatosensory regions (SI and SII) and the visual regions of the cortex and the reticular formation (RF) of the mesencephalon. A reversible cold block of the SI and SII failed to change the effect of the nerve stimulation. Stimulation of the postero-ventral thalamic nucleus did not change the initial activity of the hypothalamic neurons and gave rise to no neuron activity that appeared on stimulation of the SII. A conclusion was drawn that cortico-hypothalamic influences that appeared on stimulation of the nerves and the postero-ventral nucleus of the thalamus were pronounced weakly.     

Is the "nonspecific" thalamus still "nonspecific"?

The classical concept of "nonspecific" thalamus, as distinguished from the principal thalamic nuclei (i.e. the primary sensory, motor and limbic relays) is here briefly revisited in the light of anatomical investigations performed in the last decades, and primarily those based on tract tracing techniques. Altogether these data pointed out that the so-called "nonspecific" thalamus is composed by a heterogeneous collection of nuclear masses, which display not only species differences, but also marked internuclear variations in their cytological and neurochemical features, connections, areal and laminar distribution upon the cortex, and functional properties. Thus, the "nonspecific" thalamus exerts a modulatory role on cortical activity, chiefly regulated at the intrathalamic level by the interplay between the thalamic reticular nucleus and the interneurons and projection neurons of the dorsal thalamus. However, each of the components that have been traditionally considered as "nonspecific" also subserves selective roles in the transfer of different kinds of information from the thalamus to the cerebral cortex and basal ganglia.     

Neurons with visual receptive fields independent of eye position in the caudal section of the ventral bank of cat cruciate slucus

Neurons responding to tactile and visual stimulation were found in the caudal section of the cruciate slucus ventral bank in awake cats. Tactile receptive fields were located on the face, mainly around the mouth. Visual stimuli evoked a response when presented close to the tactile receptive field. It was found that the visual responses of these bimodal neurons located in layer VI of the cortex display spatial consistency. The position of these visual receptive fields remained constant through saccadic eye movements, while still linked to the tactile receptive field.Institute for Research into Information Transmission, Academy of Sciences of the USSR, Moscow. Translated from Neifofiziologiya, Vol. 18, No. 6, pp. 800–805, November–December, 1986.     

Meeting Announcement: Barrels XII-1999

(1)Microelectrodes were used to record the extracellular activity of 80 single neurons of the main cuneate nucleus (MCN) of raccoons anesthetized with either methoxyflurane or pentobarbital sodium. All 80 MCN neurons had peripheral receptive fields (RFs) that lay entirely on the glabrous surfaces of the forepaw and were responsive to light mechanical stimulation. Neurons were characterized according to the nature of their response to mechanical stimulation of their RFs, as well as to their response to electrical stimulation of the contralateral thalamic ventrobasal complex (VB). (2) All antidromically activated neurons (64% of sample) were histologically verified as falling within the clusters region of the MCN, while synaptically activated neurons (19% of sample), as well as neurons not responsive to VB stimulation (17% of sample), were located in both the clusters and the polymorphic regions. (3) Antidromically activated neurons typically responded with a single fixed-latency spike, although a few responded with a burst of 3 or more spikes. Others responded with a single antidromic spike followed by a train of synaptically activated spikes. In these latter neurons, it was often possible to block the synaptic spikes selectively. (4) MCN neurons were classed according to their response to controlled mechanical stimuli as rapidly adapting (RA), slowly adapting (SA), or Pacinian (Pc). The proportions of neurons falling into these categories did not vary significantly with the type of response to thalamic stimulation, and the overall percentages were 56% RA, 24% SA, and 20% Pc. These figures are very similar to those previously obtained in a sample of primary afferent fibers of the raccoon cervical cuneate fasciculus (L. M. Pubols and Pubols, 1973). (5) Absolute displacement, displacement velocity, and force thresholds, which ranged between 4 and 326 μm, 0.01 and 16.3 μm/msec, and 120 and 3600 mg, respectively, are comparable to those previously found for primary afferents supplying mechanoreceptors of the glabrous surfaces of the raccoon's forepaw. Neither displacement nor force thresholds differed for RA versus SA neurons; however, displacement velocity thresholds were significantly lower for SA than for RA neurons.