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PubMed1984

Morphological and electrophysiological characteristics of pyramidal tract neurons in the rat.

Responses evoked in neurons of rat sensorimotor cortex upon stimulation of the pyramidal tract and ipsilateral cerebral peduncle were analysed using intracellular recording. Neurons responding antidromically to pyramidal tract stimulation (PT cells) and neurons failing to respond antidromically but exhibiting orthodromic responses were both stained by intracellular injection of horseradish peroxidase (HRP). Layer V pyramidal neurons, including those responding antidromically, exhibited prominent long lasting membrane hyperpolarizations and inhibitions of action potentials following pyramidal tract or cerebral peduncle stimulation. Upon passage of polarizing intracellular current two components were identified within the hyperpolarizing potential. A short duration initial component readily reversed with hyperpolarizing current. Frequently this earlier component overlapped a period of early excitation consisting of action potentials arising from recurrent EPSPs or large slow depolarizing potentials (SDPs). The second, much longer duration hyperpolarizing component did not reverse with passage of hyperpolarizing current and was often followed by a rebound period of depolarization and action potential generation. Both the excitatory and the inhibitory portions of these responses could be demonstrated in animals with acute thalamic transections severing the ascending lemniscal pathway to cortex. Following intracellular staining with HRP, two types of PT cells were identified by their different intracortical axonal arborizations. Most of the injected neurons had local axonal fields extending widely in layers V and VI, but with few or no collaterals extending radially toward the more superficial layers. A second type of PT cell had axon collaterals limited to a narrow zone around the dendritic field but extending radially as far as layer I. Cells of both types were observed to send axon collaterals into neostriatum. Both types of neurons exhibited morphological and physiological characteristics of slow PT cells, and we could find no cells comparable to the fast conducting PT cells observed in other species.

Animals↗
PubMed1982

Formation of functional synapses in the adult cat red nucleus from the cerebrum following cross-innervating of forelimb flexor and extensor nerves. I. Appearance of new synaptic potentials.

We investigated the effects of cross-innervating the peripheral forelimb flexor and extensor nerves of adult cats on the time course of corticorubral EPSPs. Red nucleus neurons were identified by antidromic invasion from C1 or L1 spinal segments as innervating the upper spinal segments (C-cells) or sending axons to the lumbosacral cord (L-cells). In C-cells, a fast-rising component, superimposed on the slow-rising corticorubral EPSPs induced by the cerebral sensorimotor cortex or the cerebral peduncle (CP) stimulation, was noted. The mean time-to-peak of this component in cross-innervated cats operated more than two months earlier was 1.9 +/- 0.9 ms (n = 160), shorter than in normal cats (3.6 +/- 1.4 ms, n = 100). The same value in cats cross-innervated less than two months before was 2.7 +/- 1.0 ms (n = 53). The mean time-to-peak of CP-EPSPs from L-cells was 2.9 +/- 0.9 ms (n = 115). The fast-rising component had a latency of 0.96 +/- 0.19 ms (n = 122), and it was mediated by fibers with conduction velocities of less than 20 m/s. The projective area of the fast-rising component is organized somatotopically. Since it is more sensitive to membrane hyperpolarization than slow rising corticorubral EPSPs, it is mediated by synapses located more proximally than the corticorubral synapses of normal cats. The time course of facilitation by preceding cerebral peduncle stimulation of the nucleus interpositus (IP)-induced RN population responses was measured. It was characterized by a rapid, followed by a slower, rise time in the RN region where C-cells are concentrated. In contrast, the L-cell region was characterized by a slow rise time. In cats subjected to self-union of the peripheral flexor and extensor nerves, the majority of C-cells had CP-EPSPs with a time-to-peak within the normal range. Our results suggest that after cross-innervation sprouting and formation of functional synapses occur on the proximal portion of the soma-dendritic membrane of red nucleus neurons.

Animals↗
PubMed1977

Cerebral evoked responses to skin warming recorded from human scalp.

Reponses evoked by warming the glabrous palmar skin were recorded maximally from a contralateral parietal scalp site that approximated the hand projection area of sensorimotor cortex. A smaller and later occurring response was also seen at the corresponding ipsilateral site. The temperature to which the skin was adapted was critical and was maintained at 35 degrees C rather at 30 degrees C as it was in an earlier study where no responses were seen. Peak latencies ranged from 280 msec to 356 msec for stimulus intensities of 8 degree C presented at a rate of 19 degrees C/sec. This warm evoked response appeared to have its origin in the specifically sensitive primary warm afferents. The presence of an evoked response when warming occurred from the 35 degrees C adapting temperature (AT) and its absence at the 30 degrees C AT coincide with the greater sensitivity of warm receptors at the higher AT. Comparison of these results with those for evoked responses to skin cooling and tactile tap suggest that the cortical organization of temperature (both warm and cool stimuli) in human is similar to that of touch.

Adult↗
PubMed1977

Maturation of evoked climbing fiber input to rat cerebellar purkinje cells (I.).

An analysis of evoked responses of Purkinje cells in developing rat cerebellum to climbing fiber input was conducted to determine which identifying properties of this afferent system are established early in development and which specific features mature with age. Rat pups at various ages were anesthetized with 0.5% halothane and unit recordings made with glass micropipettes. By the third postnatal day, electrical stimulation of the sensorimotor cortex and limbs at low stimulation rates (less than 1/sec) could elicit distinct burst responses appearing at long latencies (180 msec), indicating that pathways of both ascending and descending climbing fiber systems are intact early in cerebellar cortical development. A distinctive feature maturing over the first 1-1.5 weeks was the characteristic of the all-or-none burst response since before about day 11 the interspike interval, amount of inactivation, and number of spikes in evoked burst responses all varied from stimulation to stimulation. Mean latencies decreased from 180 msec at dat 3 to 50 msec by day 10, but did not achieve the adult value of 20 msec until the fourth week. Typically, climbing fiber responses could only follow at stimulation rates of less than 0.2/sec at day 3, but by day 12 could follow up to 10/sec, which is the same as in the adult. The data indicate that the climbing fiber system establishes connectivity from diverse sources and exhibits identifying characteristics similar to the adult early in cerebellar development. Most aspects of the maturation of transmission can be explained if there were a decrease in the time scale of function of the synapses involved, mainly those in the inferior olive.

Afferent Pathways↗
PubMed1986

Pyramidal input to the basal ganglia in the cat.

In cats with mesencephalic decerebration sparing the cerebral peduncles and ablation of sensorimotor cortex, changes in firing of single neurons of caudate nucleus (CD), putamen (PU), globus pallidus (GP) and entopeduncular necleus (EN) were studied following stimulation of the ipsilateral medullary pyramidal tract (MPT). Cells in CD and PU were not extensively influenced by impulses backfired from MPT (14.7% and 18.7%, respectively). Conversely, a larger number of GP cells (28.1%) and especially EN cells (46.9%) exhibited pronounced changes in their firing following MPT stimulation. The MPT-induced effects on CD and PU were either inhibition or excitations, the latter appearing at latencies greater than 11 ms. The responses observed in GP and EN cells were most frequently excitations, some of which appeared with latencies below 5 ms.

Afferent Pathways↗
PubMed1982

Stimulus-induced changes in extracellular Na+ and Cl- concentration in relation to changes in the size of the extracellular space.

Extracellular Na+ - and Cl- -concentrations ([Na+]o, [Cl-]o) were recorded with ion-selective microelectrodes during repetitive stimulation and stimulus-induced self-sustained neuronal afterdischarges (SAD) in the sensorimotor cortex of cats. In all cortical layers [Na+]o initially decreased by 4-7 mM. In depths of more than 600 micrometer below the cortical surface such decreases usually turned into increases of 2-6 mM during the course of the SADs, whereas in superficial layers [Na+]o never rose above its resting level. [Cl-]o always showed an increase in the course of the SADs often preceded by an initial small decrease. The average increase at a depth of 1,000 micrometers was about 7 mM. [Cl-]o reached peak values at about the end of the ictal period, whereas [Na+]o reached its maximum shortly after the end of the SAD, at times when [K+]o was still elevated above the baseline concentration. These data indicate that the extracellular osmolarity can increase during SAD by up to 30 mM. Such an increase in osmolarity can be explained by an increase in the number of intracellular particles, caused by cleavage of larger molecules during enhanced metabolism. This could lead to cell-swelling due to passive water influx from the extracellular space (ES). However, the resulting reduction of the size of the ES is calculated to be less than 10% for an increase in intracellular osmolarity by 30 mOsm. This value is too small as compared to previously measured ES-reductions under similar conditions (i.e., 30% reduction at 1,000 micrometers; Dietzel et al. 1980). Reductions of the size of the ES that accompany the observed changes in the ionic environment, are quantitatively explained on the basis of the extended glial buffering mechanism described in the preceding paper.

Animals↗
PubMed1981

Corticospinal tract collaterals to the dorsal column nuclei of cats. An anatomical single and double retrograde tracer study.

A double-labelling anatomical strategy employing horseradish peroxidase and tritiated, enzymatically inactive horseradish peroxidase allowed simultaneous visualization of corticospinal neurones and cortical neurones projecting to the dorsal column nuclei in cats. By this approach it is shown that although most cortical fibres to these nuclei are not branches of corticospinal axons, neurones projecting to both targets are present in all areas of the sensorimotor cortex and especially in area 3a. Thus, cortical control upon the dorsal column nuclei is mediated via descending fibres that differ as to their origin and to their branching pattern.

Animals↗
PubMed1981

Spinal, trigeminal, and cortical climbing fibre paths to the lateral vermis of the cerebellar anterior lobe in the cat.

The spinal, trigeminal and cortical climbing fibre projection to the lateral vermis of the cerebellar anterior lobe in the cat has been investigated. The b zone, which occupies a one mm wide band in the lateral vermis, receives a somatotopically arranged input. Successively more rostral segments (tail, hindlimb, thorax, forelimb and trigeminal nerves) project to successively more medial microzones. The b zone receives an input through each of three spino-olivocerebellar paths (SOCPs) ascending in the ventral, dorsal and dorsolateral funiculi (VF, DF and DLF). In the b zone, the hindlimb input is bilateral through the VF-SOCP and ipsilateral through he DF- and DLF-SOCPs. The forelimb input is bilateral through the VF-SOCP, ipsilateral through the DLF-SOCP and lacking from the DF-SOCP. The trigeminal input is bilateral. Medial to the b zone in lobule V is the x zone, which receives an input from the ipsilateral forelimb through the DF- and DLF-SOCPs. The climbing fibres to the x zone are collaterals of the climbing fibres projecting to the c1 zone in the pars intermedia and paramedian lobule. The climbing fibre input from the cerebral sensorimotor cortex to the lateral vermis matches the spinal input. The lateral and medial parts of the b zone receive a bilateral input from hind- and forelimb cortical areas, respectively. The x zone receives an input from the contralateral forelimb area. The functional significance of the converging paths is discussed.

Afferent Pathways↗
PubMed1983

Convergence in the somatosensory pathway between cutaneous afferents from the index and middle fingers in man.

Average short-latency cerebral potentials were recorded from the parietal scalp to mechanical stimulation of the index and middle fingers and to electrical stimulation of the digital nerves in normal subjects. The early components of the cerebral potential, representing the arrival of the afferent volley at the sensorimotor cortex, were studied during stimulation of the fingers separately and together. When strong or moderate stimuli were used there was a suppressive interaction between the afferent input from the two fingers with either electrical or mechanical stimulation. During simultaneous stimulation of both fingers the size of the early component of the cerebral potential was less than predicted by simple addition of the potentials produced by stimulation of the fingers individually. When very weak stimuli, close to the level necessary for detection by the subject, the input from the two fingers produced additive or facilitatory interactions in the early components of the cerebral potential. These results suggest that there is convergence between the afferent inputs from the index and middle fingers along the somatosensory pathway. At levels of stimulation comparable to those which produced facilitation in the electrophysiological studies, simultaneous stimulation to both fingers was detected significantly more frequently than would be expected from the detection of stimulation to individual fingers.

Adult↗
PubMed1994

Electrophysiological evidence for formation of new corticorubral synapses associated with classical conditioning in the cat.

The present study was performed to clarify whether or not structural plasticity of synaptic connections underlies classical conditioning mediated by the red nucleus (RN) in the cat. Conditioned forelimb flexion is established by pairing electrical conditioned stimuli (CS), applied to corticorubral fibers at the cerebral peduncle (CP), with a forelimb skin shock (the unconditioned stimulus, US), but not by applying the CS alone or by pairing the CS and US at random intervals. In our previous study, it was shown that the firing probability of rubrospinal neurons (RN neurons) in response to the CS was well correlated with acquisition of the conditioned forelimb flexion and that the primary site of neural change underlying establishment of the conditioned forelimb flexion was suggested to be at corticorubral synapses. In the present study, we investigated corticorubral excitatory postsynaptic potentials evoked by CP stimulation (CP-EPSPs), in order to identify the neuronal mechanism underlying establishment of classical conditioning. In normal cats, CP-EPSPs had a typical slow-rising phase, which has been attributed to the distal location of corticorubral synapses on the dendrites of RN neurons. In contrast, in animals that received paired conditioning, subsequent CP stimulation evoked potentials with a fast-rising time course. In control groups of cats that received CS alone, CS randomly paired with the US, or only the same surgical operations as the conditioned animals, most of the CP-EPSPs displayed slow-rising EPSPs that similar to those observed in normal cats. The mean time from onset to peak of the potentials in the conditioned animals was significantly shorter than that seen in other groups. Therefore, the appearance of a fast-rising potential correlates well with acquisition of the conditioned forelimb flexion. The amplitude of the fast-rising potential was gradually changed with stimulus intensity. It had a short onset latency following CP stimulation (0.9 ms), which was similar to that of the slow-rising EPSP in normal cats. It followed high-frequency stimulation up to 100 Hz. These results suggest that the newly appearing, fast-rising potential was a monosynaptically evoked EPSP. Fast-rising EPSPs were also induced by stimulation of the sensorimotor cortex (SM). Since the SM-EPSP was occluded by the CP-EPSP, the SM cortex is, at least in part, a likely source of fast-rising EPSPs. Fast-rising SM-EPSPs were also observed at the unitary level. The SM-EPSPs in the conditioned animals exhibited somatotopical representation in their cortical origin, as has been described in normal cats.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1985

Behavioral analysis of the effect of substance P injected into the ventral mesencephalon on investigatory and spontaneous motor behavior in the rat.

In the present experiments the behavioral response to substance P (SP) microinfusion into the ventral tegmental area (VTA), substantia nigra (SN), and sensorimotor cortex (CX) was investigated in detail. The experiments were carried out using an eight-hole box to measure exploratory behavior and a video monitor for the analysis of spontaneous motor behavior. When infused into the VTA, SP (0.125, 0.5, 3.0 micrograms) augmented the frequency and total duration of hole-pokes, and tended to diminish the mean duration of hole-pokes. The strategy and organization of responses, as measured by the order of hole-visits and hole-switching, were unchanged by SP and there was no indication of stereotypy, measured by the number of hole-pokes per hole-visit. The open-field analysis revealed a marked increase in locomotion and rearing, both in the periphery and center of the arena; grooming was decreased by SP. The behavioral profile following SN infusions of SP (3.0 micrograms) was similar to that elicited by VTA infusions, with the exception that center rearing was not enhanced. SP administration into cortex (3 micrograms) had no significant effect on any behavioral measures. It is hypothesized that SP infused into the ventral mesencephalon results in an enhancement of approach response tendencies, suggesting that endogenous SP in this region may regulate spontaneous behavior. The possibility of an interaction between SP and meso-telencephalic dopamine neurons is discussed.

Animals↗
PubMed1993

Effects of GABAmimetics on electrocorticographic spike discharges induced by guanidinoethanesulfonic acid (amidino-taurine) in the rat.

The effect of guanidinoethanesulfonic acid (GES) on rat electrocorticograms (ECoG) and the effects of gamma-aminobutyric acid (GABA) and GABA-agonists on the ECoG changes induced by GES were studied. Sporadic spike discharges began 2-5 min after 1 mumol GES/10 microliters on filter paper was applied to the pia mater of the left sensorimotor cortex; spike discharges extended to the opposite cerebral hemisphere 60 min after the onset of the ipsilateral spike discharges. The spike discharges with a frequency of 5-10 spikes/min lasted until the end of the 4 hour recording. The induced spike discharges were suppressed when the original GES soaked filter paper was replaced by one containing GES (1 mumol) supplement combined with taurine (1 mumol/10 microliters). GABA (1 mumol) and its receptor agonist, muscimol (10 nmol) and (3R)-(-)-4-amino-3-hydroxybutyric acid (1 mumol) also suppressed the GES-induced spike discharges when applied topically. Diazepam (DZP) (10 mg/kg) suppressed the GES-induced spike discharges 10 min after i.p. injection, but phenobarbital (20 mg/kg) increased the frequency and voltage of spike discharges 100 min following subcutaneous administration. Intraperitoneal injection of either valproate (200 mg/kg) or phenytoin (25 mg/kg), after the completion of the spike discharges, showed no effect. These findings suggest that neurotransmission or neuromodulatory effects of taurine participate in GES-induced seizure activity, and that GABAA and DZP receptors may play a role in the mechanism that suppresses GES-induced seizures.

Action Potentials↗
PubMed1982

A double-blind investigation of the relationship between seizure activity and the sleep EEG following EEG biofeedback training.

The sleep EEGs of eight medically refractory epileptic patients were examined as part of a double-blind, ABA crossover study designed to determine the effectiveness of EEG biofeedback for the control of seizures. The patients were initially reinforced for one of three EEG criteria recorded from electrodes placed over sensorimotor cortex: (a) suppression of 3- to 7-Hz activity, (b) enhancement of 12- to 15-Hz activity, or (c) simultaneous suppression of 3- to 7-Hz and enhancement of 11- to 19-Hz activity. Reinforcement contingencies were reversed during the second or B phase, and then reinstated in their original form during the final A' phase. All-night polysomnographic recordings were obtained at the end of each conditioning phase and were subjected to both visual and computer-based power spectral analyses. Four of the patients showed changes in their nocturnal paroxysmal activity that were either partially or totally consistent with the ABA' contingencies of the study. The spectral data proved difficult to interpret, though two trends emerged from the analyses. Decreases in nocturnal 4- to 7-Hz activity were correlated with decreases in seizure activity, and increases in 8- to 11-Hz activity were correlated with decreases in seizure activity. These findings were shown to strengthen the hypothesis that EEG biofeedback may produce changes in the sleep EEG that are related to seizure incidence.

Adolescent↗
PubMed1988

Biochemical composition and dynamics of the axonal cytoskeleton in the corticospinal system of the adult hamster.

The corticospinal system is an important central nervous system (CNS) pathway that is implicated in debilitating diseases such as amyotrophic lateral sclerosis and in traumatic injuries to the spinal cord. This study characterizes some of the fundamental biochemical and kinetic properties of normal corticospinal axons, establishing an important reference for studies that aim to elucidate the cellular modifications that result during pathological conditions of these axons. Slow axonal transport which conveys the axonal cytoskeleton as well as cytomatrix constituents, such as many of the metabolic enzymes and regulatory proteins, has been examined. For these studies, [35S]methionine was injected into the sensorimotor cortex of adult male Golden hamsters, and labeled, transported proteins present in corticospinal axons at 1-42 days after injection were assessed using one- and two-dimensional gel electrophoresis/fluorography. The complex group of slow component b (SCb) proteins (including clathrin, actin, enolase, creatine phosphokinase, and many others) was observed to move at a rate of approximately 2 mm/day in adult corticospinal axons. The slow component a (SCa) proteins (tubulins, neurofilament proteins, and actin) were transported at a substantially slower rate of approximately 0.4 mm/day. The biochemical and kinetic properties of slow transport in corticospinal axons were very similar to those previously described in another CNS pathway, axons of retinal ganglion cells, and substantially different from those documented in large, peripheral sensory or motor axons. These findings suggest that some of the basic properties of axonal transport which determine many of the structural and functional properties of axons may be different in the CNS compared to the peripheral nervous system.

Animals↗
PubMedDate not supplied

Involvement of the amygdala in evaluating the biological significance of conditioned stimuli.

The destruction of the amygdala in cats and dogs causes the animals to stop responding adequately to signals of various biological significance; the curves of change in the amplitude and probability of appearance of EPs in the sensorimotor cortex lose the maxima characteristic of intact animals at frequencies of 0.8, 1.6, and in the band from 2.0 to 3.0 kHz, which are the format frequencies of certain communicational signals in cats. The assumption of a signal (food) significance by an indifferent stimulus, earlier without any biological meaning, finds reflection in the neuronal activity of the amygdala, which begins to respond to this signal as if to an unconditioned stimulus. On the basis of the above factors, the role of the amygdala is discussed in the evolution of the biological significance of conditioned stimuli and the differentiation of the afferent influences that reach it.

Amygdala↗
PubMedDate not supplied

The influence of an enkephalin derivative, DAGO, on the behavior and activity of neurons of the neocortex and hippocampus of rabbits during the development of defensive and inhibitory conditioned reflexes.

After the administration of a morphine-like opiate, DAGO (D), in a dose of 250 micrograms/kg, a decrease was observed in the probability of movements of a rabbit in response to light flashes, the signal for a defensive reflex. The level of the background impulse activity of the neurons gradually decreased in the sensorimotor cortex and in the hippocampus, and did not change in the visual cortex. The decrease and the recovery of the responses of the neurons to the reinforcing stimulus (electrodermal stimulation of the limb) proceeded unidirectionally in all of the areas of the cortex studied, while there were substantial differences in the relationship to the cortical area studied and to the biological significance of the stimulus in the dynamics of the responses to the inhibitory and reinforced light flashes. The identification of the features of the systemic organization of the neurons during training with change in the properties of the reinforcement under the influence of the preparation under study is discussed, as well as the similarity of some features in the mechanisms of the development of internal inhibition in the defensive situation and of the properties of positive reinforcement.

Action Potentials↗
PubMedDate not supplied

Significance of the interstimulus time interval in repeating combined presentations of L-glutamate and acetylcholine for change in the reactivity of cortical neurons.

A comparative study of the probability, directionally, and intensity of the changes in the baseline and L-glutamate (Gl)- and acetylcholine(ACh)-induced average frequency of the impulse activity (BIA, GlIA, and AChIA, respectively) of individual neurons of the sensorimotor cortex of unanesthetized rats in the course of repeated isolated and combined presentations of Gl and ACh showed that the process of reduction in reactivity to Gl is slowed in the population of cells which experienced the combined action of Gl and ACh with a 1.5 second postponement of applications of ACh in comparison with the situation of its isolated and combined presentation with a 3 second postponement of ACh. The AChIA decreases to a greater degree in the case of a 3 second postponement of ACh, and the probability of an increase in BIA is less than with the isolated application of ACh. It is concluded that the character of the dynamics of the reactivity of neurons is determine by the temporal relationships of local neurochemical stimuli.

Acetylcholine↗
PubMedDate not supplied

Dynamics of the reactivity of cortical neurons to the repeating isolated action of L-glutamate and acetylcholine.

A comparative analysis of the probability, directionality, and intensity of the changes in the average frequency of the baseline (BIA) and L-glutamate-induced (GlIA) and acetylcholine-induced (AChIA) impulse activity of individual neurons of the sensorimotor cortex of unanesthetized rats showed that the reactions to Gl are most variable; this is expressed in a significantly higher percent of neurons with potentiation of responses to Gl as compared with the proportion of cells which manifested an increase in the AChIA in the course of 20 applications of the mediators. As a result of 100 applications, the GlIA decreases most frequently; also, the degree of decrease in GlIA over the entire duration of the testing exceeds the degree of decrease in AChIA. It is more characteristic of ACh than of Gl to increase the level of BIA in the periods between the reactions to ACh, while in the case of repeated application of Gl, dynamics of decrease in BIA are characteristic. The results are discussed from the perspective of a possibly different functional role of the glutamatergic and cholinergic neuromediator systems in the cerebral cortex in the process of formation of the dynamics of neuronal activity during learning.

Acetylcholine↗