Pyramidal influences on ventral thalamic nuclei in the cat (original) (raw)
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Duality of cortical control on ventrolateral thalamic activity
Experimental Brain Research, 1970
In cats anesthetized with chloralose, a systematic study of the responses evoked by cortical stimulation in the ventrolateral nucleus has been performed with concentric macroelectrodes and with microelectrodes. Two types of cortical areas have been described: those with ipsilateral effect and those with bilateral effect. The areas with ipsilateral effect correspond to the cortical projection areas of the ventrolateral nucleus, i.e. the precruciate motor cortex. Short latency spikes (including antidromic responses) were rarely obtained (5% of the cells), while the inhibitory responses followed by a late burst of spikes were obtained for 36~o of the cells. The areas with bilateral effect correspond roughly to the cortical sensory areas. Two types of responses are induced by their stimulation: a short latency spike discharge and a "rhythmic response" characterized by a prolonged hyperpolarization followed by a ]ate burst of spikes, with some tendancy for this sequence to become rhythmic. When considering the whole population of cells recorded, each cortical area is able to trigger the short latency response, the rhythmic response or both together. For the individual ceils, there is generally some preferential pattern of response, as seen when comparing the effects of peripheral sensory and cortical sensory stimulation. The possible significance of the bilateral and nervertheless topographic influence from the sensory areas onto the ventrolateral nucleus is discussed, as well as the hypothetical role of the short latency response and of the rhythmic response.
Pyramidal excitation in long propriospinal neurones in the cervical segments of the cat
Experimental Brain Research, 1991
1. The effect of stimulating the contralateral pyramid has been investigated with intracellular recording from 128 long propriospinal neurones (long PNs) in the C3-Th1 segments of the cat. Long PNs were identified by the antidromic activation from the Th13 segment. They were located in laminae VII-VIII of Rexed. Single pyramidal stimulation evoked monosynaptic EPSPs in 15/40 of the long PNs in cats with intact pyramid. In 15 other long PNs, a train of three to four pyramidal stimuli evoked EPSPs with latencies indicating a minimal disynaptic linkage. The remaining 25% of the long PNs lacked mono- or disynaptic pyramidal EPSPs. In a few cases longer latency excitation was observed. 2. The location of the intercalated neurones which mediate the disynaptic pyramidal EPSPs was investigated by making four different lesions of the corticofugal fibres: 1) at the border of the C5 and C6 segments, 2) at the border of the C2 and C3 segments, 3) at the caudal part of the pyramid; three mm rostral to the decussation and 4) at the level of the trapezoid body. Stimulation of the corticofugal fibres was made either rostral to lesion 3 (rPyr) in order to activate neurones in a cortico-bulbospinal pathway or caudal to lesion 3 (cPyr) to activate neurones in a corticospinal pathway. In the former case, in one experiment, stimulation was made in the pyramid between lesions 3 and 4 (double pyramidal lesion). In case of cPyr stimulation, lesions 1 and 2 were added sequentially in order to investigate if the corticospinal excitation was mediated via C3-C4 PNs. All lesions were made mechanically, except lesion 2 which in some of the experiments was performed by reversible cooling. 3. Stimulation in the pyramid rostral to lesion 3 and in between lesions 3 and 4 evoked disynaptic EPSPs in the long PNs, which shows that they were mediated via reticulospinal neurones. Stimulation in cPyr after lesion 3 elicited disynaptic EPSPs, which remained after lesion 1 but were abolished after adding lesion 2. It is concluded that the disynaptic cPyr EPSPs were mediated via intercalated neurones in the C3-C4 segments. 4. When the disynaptic cPyr EPSP was conditioned with a single volley in nucleus ruber and/or in tectum, it was markedly facilitated, especially when the conditioned volley was applied simultaneously with the effective cPyr volley. The results show that the intercalated neurones in the C3-C4 segments receive monosynaptic convergence from cortico-, rubro- and tectospinal fibres. Stimulation in the lateral reticular nucleus (LRN) evoked monosynaptic EPSPs.(ABSTRACT TRUNCATED AT 400 WORDS)
Neurons in the lateral sacral cord of the cat project to periaqueductal grey, but not to thalamus
European Journal of Neuroscience, 2005
Previous work of our laboratory has shown that neurons in the lateral sacral cord in cat project heavily to the periaqueductal grey (PAG), in all likelihood conveying information from bladder and genital organs. In humans this information usually does not reach consciousness, which raises the question of whether the lateral sacral cell group projects to the thalamus. After wheatgerm agglutinin-horseradish peroxidase (WGA-HRP) injections into the sacral cord, anterogradely labelled fibers were found in the thalamus, specifically in the ventral anterior and ventral lateral nuclei, the medial and intralaminar nuclei, the lateral ventrobasal complex ⁄ ventroposterior lateral nucleus, and the nucleus centre mé dian, lateral to the fasciculus retroflexus. Much denser projections were found to the central parts of the PAG, mainly to its dorsolateral and ventrolateral parts at caudal levels and lateral parts at intermediate levels. In a subsequent retrograde tracing study, injections were made in those parts of the thalamus that received sacral fibers, as found in the anterograde study. Labelled neurons were observed in the sacral cord, but not in the lateral sacral cell group. In contrast, a small control injection in the caudal PAG resulted in many labelled neurons in the lateral sacral cord. These results suggest that afferent information regarding micturition and sexual behaviour is relayed to the PAG, rather than to the thalamus.
Pyramidal tract control over cutaneous and kinesthetic sensory transmission in the cat thalamus
Experimental Brain Research, 1975
In the thalamic ventrobasa] complex (VB) of the cat, effects of electrical stimulation of the pyramidal tract (PT) upon activities of 112 relay cells and 18 internuncial cells were examined. Single PT shocks to the cerebral peduncle elicited short-latency discharges in 31 relay cells (mean latency, 1.4+ 0.5 msec). When weak PT stimuli were employed as conditioning shocks, facilitatory effects upon responses to medial lemniseal (ML) stimulation were observed. It was revealed that VB relay cells were excited monosynaptically via collaterals of the fast PT fibers. Among 31 PT-excited cells 22 were fired by movements of joints (joint-movement units) and they made up 88% of all the joint-movement units. A majority of the relay cells responding to stimulation of hairs (hair units) did not receive excitatory effects from PT, except some special ones which represented long hairs at the distal or proximal end of the forearm-forepaw.
Brain Research, 1995
There are substantial differences in the incidence of inhibitory neurons in the ventrobasal complex of rat and cat thalamus. This marked dissimilarity in neuronal composition suggests that there should be corresponding differences in the orchestration of neural activity in these regions during cutaneous stimulation. To explore this possibility, we conducted a cross-correlation analysis of neuronal activity in the ventroposterolateral (VPL) nucleus of anesthetized rats and cats. Pairs of neurons representing hairy skin were recorded simultaneously with one or two electrodes during air jet stimulation of multiple sites throughout the receptive fields. Cross-correlation histograms indicated that correlated activity among adjacent neurons occurred in three distinct patterns. In one pattern, classified as narrow-unimodal, the discharge of one neuron preceded a discharge in the partner neuron over a narrow interval of time (< 5 ms). Narrow-bimodal patterns were characterized by responses in which the temporal order of discharges from the two neurons was variable, but the interspike intervals were always < 5 ms. In wide-unimodal patterns, the discharge of one neuron was correlated with subsequent discharges in the partner neuron over a wide interval of time (> 5 ms). In rat VPL, two-thirds of the 58 neuron pairs showing correlated responses were characterized by narrow-unimodal responses and nearly one-third of the neuron pairs displayed narrow-bimodal patterns. Only one pair of rat VPL neurons were characterized by a wide-unimodal pattern of coordination. By comparison, half of the 61 adjacent neuron pairs with coordinated responses in cat VPL were characterized by narrow-unimodal patterns. Slightly more than one-third of the correlated neuron pairs had narrow-bimodal patterns, while the remainder (13%) were classified as wide-unimodal responses. Pairs of neurons separated by 340-405 microns discharged synchronously in a pattern that was similar to the temporal relationship expressed in the narrow-bimodal patterns found among adjacent neurons. In both species, the wide-unimodal patterns had the strongest coordinated responses as measured by the correlation coefficient. Although inhibitory relationships did not appear in correlation histograms that had been corrected for stimulus coordination, cross-correlation analysis of the raw spike trains revealed brief (10-40 ms) periods of inhibition that were associated with cat VPL neurons exhibiting wide-unimodal coordination patterns. In rat VPL, most inhibition involved longer (30-60 ms) periods of inhibitory oscillations appearing amidst a much larger rhythmic pattern. These results suggest that correlation patterns transpiring over narrow (< 5 ms) time intervals represent the coordination of activity among neighboring thalamocortical relay neurons.(ABSTRACT TRUNCATED AT 400 WORDS)
Lateral cervical nucleus projections to periaqueductal gray matter in cat
The Journal of Comparative Neurology, 2004
The midbrain periaqueductal gray matter (PAG) integrates the basic responses necessary for survival of individuals and species. Examples are defense behaviors such as fight, flight, and freezing, but also sexual behavior, vocalization, and micturition. To control these behaviors the PAG depends on strong input from more rostrally located limbic structures, as well as from afferent input from the lower brainstem and spinal cord. Mouton and Holstege (2000, J Comp Neurol 428:389 -410) showed that there exist at least five different groups of spino-PAG neurons, each of which is thought to subserve a specific function. The lateral cervical nucleus (LCN) in the upper cervical cord is not among these five groups. The LCN relays information from hair receptors and noxious information and projects strongly to the contralateral ventroposterior and posterior regions of thalamus and to intermediate and deep tectal layers. The question is whether the LCN also projects to the PAG. The present study in cat, using retrograde and anterograde tracing techniques, showed that neurons located in the lateral two-thirds of the LCN send fibers to the lateral part of the PAG, predominantly at rostrocaudal levels A0.6 -P0.2. This part of the PAG is known to be involved in flight behavior. A concept is put forward according to which the LCN-PAG pathway alerts the animal about the presence of cutaneous stimuli that might represent danger, necessitating flight.
2009
(dLGN) were applied iontophoretically in vivo. Application of GABA, or agonists of GABA A and GABA B receptors, markedly decreased responses to low frequency periodic visual stimulation, but, while causing some increases in burst firing, cells continued to produce tonic spikes even when firing was reduced to near zero. Similar actions were seen with compounds manipulating the cholinergic system. Inhibition of local Nitric Oxide production reduced firing rates but did not affect burst firing. Significant levels of tonic firing were found mixed with burst firing throughout the recordings even under conditions most favourable for bursting. We suggest that the local synaptic input to an individual dLGN cell is sufficiently dynamic to prevent the prolonged periods of burst firing which can be evoked in brain slice preparations. ava i l a b l e a t w w w. s c i e n c e d i r e c t . c o m w w w. e l s ev i e r. c o m / l o c a t e / b r a i n r e s ARTICLE IN PRESS Please cite this article as: Grieve, K.L., et al., Mixed burst and tonic firing in the thalamus: A study in the feline lateral geniculate nucleus in vivo, Brain Res. (2009),
2009
(dLGN) were applied iontophoretically in vivo. Application of GABA, or agonists of GABA A and GABA B receptors, markedly decreased responses to low frequency periodic visual stimulation, but, while causing some increases in burst firing, cells continued to produce tonic spikes even when firing was reduced to near zero. Similar actions were seen with compounds manipulating the cholinergic system. Inhibition of local Nitric Oxide production reduced firing rates but did not affect burst firing. Significant levels of tonic firing were found mixed with burst firing throughout the recordings even under conditions most favourable for bursting. We suggest that the local synaptic input to an individual dLGN cell is sufficiently dynamic to prevent the prolonged periods of burst firing which can be evoked in brain slice preparations. ava i l a b l e a t w w w. s c i e n c e d i r e c t . c o m w w w. e l s ev i e r. c o m / l o c a t e / b r a i n r e s ARTICLE IN PRESS Please cite this article as: Grieve, K.L., et al., Mixed burst and tonic firing in the thalamus: A study in the feline lateral geniculate nucleus in vivo, Brain Res. (2009),