The response of single guard and down hair mechanoreceptors to moving air-jet stimulation (original) (raw)
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The Journal of physiology, 1988
1. In chloralose-anaesthetized cats single-unit microelectrode recordings were made from axons in the dorsal columns, at the lumbar level, identified as belonging to the postsynaptic dorsal column (PSDC) system. 2. Excitatory and inhibitory receptive field arrangements of a sample of seventy-five PSDC neurones were examined in detail using natural cutaneous stimuli. 3. The sample was characterized by a high degree of convergent input: 80% of units were activated by both light tactile and noxious mechanical stimuli and more than half of those examined were excited by noxious radiant heat. In addition, three-quarters of the units had inhibitory receptive fields on the ipsilateral limb. 4. Twenty-three units (27%) were influenced by input from areas of both hairy and glabrous skin covering the foot and distal limb. Neurones in this group had complex receptive fields, many of which occupied several discontinuous areas of skin. Background and evoked activity of these units could frequent...
The Journal of physiology, 1989
1. The influence of activity in descending systems on the cutaneous receptive field properties of postsynaptic dorsal column (PSDC) neurones has been investigated in chloralose-anaesthetized cats. The main aim of the study was to determine whether the receptive field boundaries of PSDC neurones are under the control of systems descending from the brain. 2. Single-unit recordings were made from the ascending axons of PSDC units in the dorsal columns. Receptive fields were analysed using light tactile and noxious mechanical and thermal stimuli, both before and during a reversible block of spinal conduction produced by cooling the cord rostral of the recording site. 3. The light tactile excitatory fields of PSDC neurones were largely unaffected by the cold-block procedure. 4. In contrast, both the sensitivity of PSDC neurones to noxious stimuli and the area of skin from which they could be effectively excited by such stimuli were found to be profoundly modified by interruption of desce...
Pyramidal control of skin potential responses in the cat
Experimental Brain Research, 1984
Pyramidal command of Skin Potential Response (SPR) was investigated in 20 cats paralyzed by gallamine and under a halothane anaesthetic. For each animal, a transection of the medulla sparing 9 only the pyramidal tract was carried out. The pyramidal tract and Mesencephalic Reticular Formation (MRF) were stimulated before and after the transection. Results taken before transection show that the SPR can be elicited from stimulation of the pyramidal tract and the MRF. After transection, stereotaxic stimulations of the pyramidal tract still evoked the SPR even after aspiration of the medullary tissue posterior to the section and overlying the pyramids. Control reticular stimulations with higher stimulus intensities failed to evoke the SPR. These results showthat stimulation of the pyramidal tract can elicit the SPR independently of reticulospinal neurons. It is hypothesized that a group of corticospinal fibers could transmit volleys having autonomic activity on preganglionic autonomic neurons of the intermediate zone of the grey matter.
Processing of Vibrotactile Inputs From Hairy Skin by Neurons of the Dorsal Column Nuclei in the Cat
Journal of Neurophysiology, 2006
The capacity of single neurons of the dorsal column nuclei (DCN) for coding vibrotactile information from the hairy skin has been investigated in anesthetized cats to permit quantitative comparison first with the capacities of DCN neurons responding to glabrous skin vibrotactile inputs and second with those of spinocervical tract neurons responding to vibrotactile inputs from hairy skin. Dynamically sensitive tactile neurons of the DCN the input of which came from hairy skin could be divided into two classes, one associated with hair follicle afferent (HFA) input, the other with Pacinian corpuscle (PC) input. The HFA-related class was most sensitive to low-frequency (<50 Hz) vibration and had a graded response output as a function of vibrotactile intensity changes. PC-related neurons had a broader vibrotactile sensitivity, extending to ≥300 Hz and appeared to derive their input from the margins of hairy skin, near the footpads, or from deeper PC sources such as the interosseous m...
Principalis, oralis and interpolaris responses to whisker movements provoked by air jets in rats
NeuroReport, 2005
The present study was designed to compare the electrophysiological characteristics of the principalis, oralis and interpolaris nuclei of the trigeminal sensory complex under stimulation of the vibrissae by air puffs. This stimulus generates deflection profiles resembling those induced by contact with real objects in natural conditions. Three populations of neurons were identified in each nucleus according to their mean spiking frequency at rest. The three nuclei differed in terms of their mean spiking frequencies, the response latencies of their neurons and the proportions of each neuron population observed in single and multi-unit recordings. Findings suggest different information processing tasks for each nucleus.
Nuclei in the Cat Processing of Vibrotactile Inputs From Hairy Skin by Neurons of the Dorsal Column
2000
The response characteristics and tactile coding capacities of individual dorsal horn neurons, in particular, those of the spinocervical tract (SCT), have been examined in the anesthetized cat. Twenty one of 38 neurons studied were confirmed SCT neurons based on antidromic activation procedures. All had tactile receptive fields on the hairy skin of the hindlimb. Most (29/38) could also be activated transynaptically by electrical stimulation of the cervical dorsal columns, suggesting that a common set of tactile primary afferent fibers may provide the input for both the dorsal column-lemniscal pathway and for parallel ascending pathways, such as the SCT. All but 3 of the 38 neurons studied displayed a pure dynamic sensitivity to controlled tactile stimuli but were unable to sustain their responsiveness throughout 1s trains of vibration at vibration frequencies exceeding 5-10 Hz. Stimulus-response relations revealed a very limited capacity of individual SCT neurons to signal, in a graded way, the intensity parameter of the vibrotactile stimulus. Furthermore, because of their inability to respond on a cycle-by-cycle pattern at vibration frequencies Ͼ5-10 Hz, these neurons were unable to provide any useful signal of vibration frequency beyond the very narrow bandwidth of ϳ5-10 Hz. Similar limitations were observed in the responsiveness of these neurons to repetitive forms of antidromic and transynaptic inputs generated by electrical stimulation of the spinal cord. In summary, the observed limitations on the vibrotactile bandwidth of SCT neurons and on the precision and fidelity of their temporal signaling, suggest that SCT neurons could serve as little more than coarse event detectors in tactile sensibility, in contrast to DCN neurons the bandwidth of vibrotactile responsiveness of which may extend beyond 400 Hz and is therefore broader by ϳ40 -50 times than that of SCT neurons.
Brain Research, 1989
Premotor neurones mediating skin reflex actions onto cat forelimb motoneurones at T~ were identified by observing their monosynaptic effects on motoneurones by means of spike-triggered averaging. Both excitatory and inhibitory premotor neurones, with mono-or polysynaptic inputs from skin afferents, were identified at C7 to rostrai Ca, and were found mostly in laminae V-VI. They received excitatory inputs from corticospinal and rubrospinal tract fibres.
The Journal of Physiology, 1984
1. Previous studies of input on to spinocervical tract neurones have been extended by investigating the post-synaptic actions of non-cutaneous afferent fibres and of descending tracts on to these neurones, using intracellular recording. In particular, actions of group II muscle, joint and Pacinian afferent fibres and rubro-and corticospinal tract fibres were investigated. 2. Group II muscle afferent fibres evoked excitation and inhibition at a minimal latency compatible with a disynaptic linkage. Increasing the stimulus strength to include group III afferent fibres enhanced these post-synaptic actions only modestly. Inhibition was evoked less frequently and/or required trains of stimuli. 3. Weak stimulation of the interosseous nerve evoked short latency (disynaptic) inhibition or excitation, the latter less frequently. Post-synaptic potentials evoked below threshold for group III afferent fibres of the interosseous nerve are attributed to the actions of Pacinian corpuscles. 4. Low threshold joint afferent fibres evoked excitation at short latency. Higher threshold joint afferent fibres usually evoked inhibition at longer latency, although high threshold excitation was sometimes observed. 5. Stimulation of the pyramidal tract evoked constant latency, unitary e.p.s.p.s which followed high frequencies. The evidence suggests that such e.p.s.p.s are evoked monosynaptically. Polysynaptic excitation and inhibition were also observed. 6. No convincing evidence could be found of actions evoked directly by the rubrospinal tract, although actions mediated via other descending systems could be induced from the red nucleus. 7. A large degree of convergence was seen from different peripheral and descending systems on to individual neurones.