Population response characteristics of neurons in anterior motorsensory cerebral cortex (field 6) of the domestic cat (original) (raw)
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Brain Research, 1991
Long-term enhancement of the evoked potential was induced in the primary somatosensory cortex of anaesthetized raccoons after mechanical stimulation of the skin was paired with electrical stimulation of the nucleus basalis of Meynert (NBM). Sets of 4 pulses, 0.5 ms duration at 300 Hz were delivered at 2-s intervals to the basal forebrain 80 ms before the glabrous skin on the 4th digit of the contralateral forepaw was stimulated mechanically. The average waveform of 30 evoked potentials was separated into an initial positive, a negative and a second positive component. During pairing of the skin and NBM stimuli, the area under the initial positive component was smaller than before or after pairing. The negative and second positive waves were unchanged. One minute after pairing, the initial positive wave returned to control values and continued to increase until the end of the experiment 50 min later, at which time it was 300% above control. The negative and second positive waves increased after the pairing to between 130 and 200% and remained at that level for the duration of the experiment. The effective NBM site for stimulation was the area rich in cholinergic neurons corresponding to the NBM. In control animals, repeated stimulation of the skin or NBM alone, or their random, unpaired stimulation together, did not enhance the somatosensory evoked potential. The results suggest that the NBM input enhances the efficacy of cortical responses to cutaneous input and thus may play a role in cortical neuronal plasticity.
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...
Experimental Brain Research, 1986
Experiments were performed to examine the responses of cortical neurons in the pericruciate cortex to cutaneous afferent input from the distal forepaw. Ninty-nine cortical ncurons responding to electrical stimulation of the forepaw were recorded from four cats. Their response latencies ranged from 6 to 23 ms. The units had cutandous receptive fields which ranged in size from those restricted to one digit to those extending over the whole forelimb. They were recorded from area 4 and area 3. Intracortical microstimulation at the recording sitcs activated either the distal or proximal musculature of the forelimb. When the charactcristics obtained from cach recording site were examined as a group of features, a uniform population emerged which was significantly different from the rest of the sample. These units had 1) the shortest latency responses to distal forepaw electrical stimulation, 2) the shortest duration of evoked discharge, 3) the smallest distal cutaneous receptive fields. Such units were recorded at the border between areas 3 and 4, at sites which on microstimulation resulted in movements of the distal forepaw musculature.
Brain Research, 1980
Three ascending spinal cord pathways conduct somatic sensory inputs towards the cat somatic sensory cortex: (1) the dorsal column medial lemmscal (DCML) system; (2) the ventral tracts which include spinothalamic, spinobulbar and spinotectal components; and (3) the spinocervical tract (reviewed in refs. 18 and 23). No anatomical or well-controlled physiological data are available on whether the dorsal column and ventral tracts can interact on single neurons m the somatic sensory cortex. Physiological approaches have been hampered by the difficulty of restricting electrical stimulation to one of the three pathways due to their mtraspinal connections z,5,6,o,11,13,2z. A technique combining spinal surgical lesions and localized electrical stimuh was devised for studying interactions between spmally disconnected dorsal column and ventral inputs on single postcruclate cortical (SmI) neurons in cats. Experiments were performed on 18 adult cats, 12 of which were m~tlally anesthetized with chloralose (70 mg/kg, 1.p.) and 6 with Nembutal (36 mg/kg, l.p.) Supplementary doses of Nembutal (10 mg/kg, i.v.) were given as required. All animals were subsequently paralyzed with Flaxedil and artificially respired. In some animals, bilateral pneumothorax was performed to reduce brain pulsations due to respiratory movements. Body temperature, end-t~dal CO2 and blood pressure were monitored and maintained within the physiological range. The pencruciate region of one hemisphere and the first 4 cervical segments were exposed. Additional surgery was necessary to expose the ventral tracts on one side. The usual precautions to keep the exposed cerebral and spinal tissues warm were taken. Extracellular unit recordings were made from the forepaw focus of the postcruciate cortex with glass (3 M NaC1 filled) microelectrodes using conventional electrophysiological equipment. At least 10 photographed observahons were made of each stimulus condition. The size, locus, and nature of the receptive field, as well as unit depth within the cortex, were noted. Electrical stimuli from the output of a Grass ($88
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.
Neuroscience Letters, 2002
Simultaneous recordings of cortical evoked potentials in the posterior sigmoid gyrus, and spontaneous negative cord dorsum potentials (CDPs) of the L6 lumbar spinal segment, were made in the anaesthetised cat. The electrodes were positioned in cortical and spinal somatosensory regions where the largest spontaneous and evoked negative potentials were detected. Evoked potentials were produced by electrical stimulation to cutaneous nerves or by mechanical stimulation of the hindpaw skin. We found that both electrically and mechanically cortical evoked potentials were facilitated during the spontaneous negative CDPs. The magnitude of such facilitation was proportional to the amplitude of the 'conditioning' spontaneous negative CDPs. This led to a high positive correlation between amplitude fluctuations of spontaneous negative CDPs and fluctuations of the cortical evoked potentials. This observation suggests that transmission of cutaneous sensory information in ascending pathways could be facilitated when dorsal horn spinal neurones are active. q
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.
NeuroImage: Clinical, 2016
Enlarged cortical components of somatosensory evoked potentials (giant SEPs) recorded by electroencephalography (EEG) and abnormal somatosensory evoked magnetic fields (SEFs) recorded by magnetoencephalography (MEG) are observed in the majority of patients with cortical myoclonus (CM). Studies on simultaneous recordings of SEPs and SEFs showed that generator mechanism of giant SEPs involves both primary sensory and motor cortices. However the generator sources of giant SEPs have not been fully understood as only one report describes clearly giant SEPs following lower limb stimulation. In our study we performed a combined EEG-MEG recording on responses elicited by electric median and tibial nerve stimulation in a patient who developed consequently to methyl bromide intoxication CM with giant SEPs to median and tibial nerve stimuli. SEPs wave shapes were identified on the basis of polarity-latency components (e.g. P15-N20-P25) as defined by earlier studies and guidelines. At EEG recording, the SEP giant component did not appear in the latency range of the first cortical component for median nerve SEP (N20), but appeared instead in the range of the P37 tibial nerve SEP, which is currently identified as the first cortical component elicited by tibial nerve stimuli. Our MEG and EEG SEPs recordings also showed that components in the latency range of P37 were preceded by other cortical components. These findings suggest that lower limb P37 does not correspond to upper limb N20. MEG results confirmed that giant SEFs are the second component from both tibial (N43m-P43m) and median (N27m-P27m) nerve stimulation. MEG dipolar sources of these giant components were located in the primary sensory and motor area.