Morpho-functional effects of kainic acid injection into the cat's pulvinar-lateralis posterior nucleus complex

The histological, electroencephalographic, behavioral changes as well as the changes in the intensity threshold of stimulation necessary to induce contralateral turning were studied in 16 cats, in which kainic acid (KA) was injected locally into the pulvinar-lateralis posterior nucleus complex (P-LP). In 13 cats a stainless-steel tube with two attached electrodes was implanted in P-LP, and electrodes were also implanted in the ipsilateral dorsal hippocampus, the superior colliculus and the caudate nucleus. KA was injected through the tube using a 10 microliters Hamilton syringe. In other 3 cats, KA was injected stereotaxically through the needle of the Hamilton syringe and two electrodes were implanted in these areas after withdrawal of the syringe. The intensity thresholds of stimulation required to induce turning behavior were controlled before and after KA administration in the 13 cats with an implanted tube and only after KA injections in the three cats without a tube; in these instances the current threshold of the contralateral P-LP served as control. The histological results showed a moderate KA damage of the P-LP, with destruction of neuronal soma and gliosis and additional involvement, in all the experiments, of the dorsal hippocampus; however, passage fibers were spared by the lesions. A dose-dependent epileptic effect of KA was seen, which was slight with the 3 micrograms dose and intense with 6 micrograms. The EEG recording showed a prominent and almost simultaneous epileptic involvement of the hippocampus and the P-LP after KA, with less involvement of the other implanted structures. Turning behavior induced by electrical stimulation of the P-LP was suppressed when the electrode tip was located inside the lesioned area. When the electrode tip was placed inside a slight or moderate damaged tissue, a significative increase in current threshold was found, and finally when the tip of the electrode was outside the lesioned area no change in threshold was observed. These findings do not contradict our previous hypothesis of an intrinsic cholinergic mechanism involved in the turning response evoked by P-LP electrical stimulation, although it cannot be excluded that fibers coming presumably from the superior colliculus or pretectum may contribute to the response.     

Role of the pulvinar-lateralis posterior nucleus complex (P-LP) in the experimental epilepsy of the cat

The ability of the pulvinar-lateralis posterior nucleus complex (P-LP) to evoke epileptic activity when stimulated, was studied in 20 adult cats. Twelve animals were analyzed after they recovered from the surgical procedure (chronic model). In seven of them a cannula with electrodes was implanted in the P-LP and one twisted bipolar electrode was placed ipsilaterally in the following structures: hippocampus, superior colliculus, caudate nucleus and cerebral cortex. Through the cannula Na penicillin was injected. The electrodes allowed both to stimulate and to record the electrical activity. In the remaining five cats, the cannula was implanted in hippocampus in order to compare its sensitivity to generate epileptic activity to that of P-LP. Another group of eight cats were surgically implanted and studied in the same day (acute model). In four of them the cannula was placed in the P-LP through the temporal pathway, to avoid crossing the hippocampus and the ventricle. In another four, penicillin was injected in the P-LP after suctioning the cerebral cortex and the hippocampus overlying the former structure. Epileptic activity could be induced in P-LP and it spread rapidly to hippocampus and after a while to the other implanted structures. This was observed both with penicillin and electrical stimulation. The sensitivity of P-LP to generate epileptic activity was lower than that of the hippocampus. In particular, it was necessary to use two to ten times more penicillin and three times the electrical current intensity in the P-LP as compared to the values needed in the hippocampus. These results are discussed in view of the controversial problem about the ability of the thalamus to generate and spread epileptic activity.     

The head-eye-body turning behavior induced by electrical or cholinergic stimulation of the pulvinar-lateralis posterior nucleus complex is not dependent on the catecholaminergic system

Two experimental designs were developed in cats in order to analyze the role of the catecholaminergic system in the turning response evoked by cholinergic or electrical stimulation of the pulvinar-lateralis posterior nucleus complex (P-LP). Twenty one adult cats were employed. In one series of experiments, nine cats had a cannula implanted in one P-LP, and through it, apomorphine alone or mixed with carbachol were microinjected. The behavior was observed and the EEG was recorded. In the second experimental design, a cannula and bipolar electrodes were implanted unilaterally in the P-LP of nine cats, and a series of electrical stimulations were performed before and after 6-OHDA administration into the P-LP, and apomorphine was injected parenterally in order to induce turning behavior. Finally three cats received 16 micrograms of 6 OHDA into the P-LP, through a Hamilton syringe and no electrodes or cannula were implanted, to study the histological damage. No evidence of involvement of the catecholaminergic system was found in either of these two experimental series. These results contrast with what has been found in the nigrostriatal dopaminergic system, where an imbalance in dopamine concentration induces turning behavior. High doses (16 micrograms) of 6-OHDA induced minimal damage in the P-LP.     

Electrophysiological projections of pulvinar-lateralis posterior complex (P-LP) upon superior colliculus units in the cat

The effect of Pulvinar-Lateral Posterior (P-LP) electrical stimulation on superior colliculus unitary responses and eye movements is analyzed in 17 encéphale isolé cats. Twelve of them were curarized. Out of a total of 190 recorded units, 117 were localized in the superior colliculus and 73 units in the Mesencephalic Reticular Formation (MRF) below the superior colliculus. Thirty eight per cent (n = 45) of the collicular units modified their discharge frequency when the ipsilateral P-LP was electrically stimulated. The current intensity thresholds of transynaptic activation had a range between 0.5 and 2.0 mA. Most of the orthodromic responses were produced by ipsilateral P-LP stimulation and were localized in the intermediate and deep layers of the superior colliculus. Three types of responses were obtained: short latency responses between 2 and 10 ms (57%); intermediate latency responses between 15 and 40 ms (29%), and long latency responses between 50 and 200 ms (14%). Thirty one per cent (n = 18) of the units recorded in the MRF responded to P-LP stimulation with 10 ms pulse-trains duration. In the MRF 3 types of responses were observed: 1) a decrease or blockade in the resting discharge during 20 to 100 ms after stimulation (20%); simple responses with a latency between 25 and 150 ms (40%), and complex responses with an early response and a latency between 15-40 ms, and a late response with a latency between 150 and 200 ms (40%).(ABSTRACT TRUNCATED AT 250 WORDS)     

Motor effects of electrical and cholinergic stimulation of the cat's dorsal hippocampus

The effect of electrical stimulation of the dorsal hippocampus was studied in 17 adult cats with implanted electrodes and those effects of carbachol and dioxolane in a group of ten adult cats with a cannula and electrodes implanted in the above cited structure. Electrical stimulation induced a contralateral head-eye-body turning response in 3 cats (17.6%), only when it was associated with afterdischarge. On the other hand the cholinergic agonists evoked contralateral head-eye-body turning in nine out of ten cats in whom the injections were administered into the hippocampus. The fact that dioxolane, an exclusive muscarinic agonist evoked this behavior and that atropine sulfate blocked this response, favours the postulation that turning is due to activation of muscarinic receptors inside the dorsal hippocampus. Comparison was done between the hippocampal group with a group similarly studied with electrodes implanted in the pulvinar-lateralis posterior nucleus complex (P-LP), and in the caudate nucleus, in which the electrical stimulation evoked contralateral head-eye-body turning response without any EEG activation.     

Hypoglossal high threshold afferents projecting to the secondary somatosensory area in the cat

Recording with microelectrodes in the anterior ectosylvian area of the cerebral cortex in cats showed responses on stimulation of the hypoglossal nerve. The responses persisted after cutting the hypoglossal rootlets close to the brainstem but disappeared after cutting the glossopharyngeal and vagal roots. The responses were high threshold and probably mediated by "pain fibers".     

The effects of lesioning both the superior colliculus and the substantia nigra of cats on turning behavior

In twenty two adult cats, distributed in four groups, stainless steel electrodes were implanted in the superior colliculus and the substantia nigra of both sides in order: 1) to find the current intensity threshold values necessary to evoke turning behavior, and record their variations after lesion of the cited structures; 2) to study the effects of lesioning two of these structures, specifically related to the direction of turning behavior, and 3) to assess the time-course of recovery from postural asymmetry after damaging two structures involved in rotation behavior, located either in the same or in the opposite side, as well as the importance of performing these lesions simultaneously or at different periods. Three main results were observed: 1) a large proportion of lesioned cats showed an increase in threshold values necessary to evoke rotation of the implanted structures located either in the same or in the opposite side; 2) the lesions induced in a significant number of cats a transient postural asymmetry. After lesioning the superior colliculus, the direction of turning was towards the damaged hemisphere. Apomorphine injected fourteen days later demonstrated the existence of an occult asymmetry, and the direction of turning was maintained. In the substantia nigra lesioned animals, the direction of turning, was towards the non-lesioned side. Apomorphine reversed the direction of turning; 3) the cats showed a remarkable capacity to recover from the postural asymmetry produced by the lesion. This experimental series further support the hypothesis of a close functional relationship between structures of both cerebral hemispheres related to turning behavior.     

Changes in electrical thresholds for evoking movements from the cat cerebral cortex following lesions of the sensori-motor area

We evaluated motor maps in the cerebral cortex and motor performance in cats before and after lesions of the forelimb representation in the primary motor area. After the lesion there was a reduction in the use of the affected forelimb and loss of accuracy in prehension tasks using the forelimb; some recovery occurred during the mapping study. Electrode tracts and lesion sites were located in cytoarchitectonically identified cortical areas 4γ, 4δ, 6aα, 6aγ, 3a. The lesions were mainly in area 4γ. In the lesioned hemisphere there were many points around the lesion site (in areas 4γ and 3a) from which movements could not be evoked. In some areas distant from the lesion site (e.g. area 6aγ) the mean thresholds for evoking forelimb movements were significantly elevated. Mean thresholds for evoking hindlimb and facial movements were not different from before. In the contralateral hemisphere mean thresholds for evoking forelimb, but not hindlimb or facial movements, were significantly elevated in several sensorimotor areas (area 4γ, 6aγ and 3a). Mean thresholds for evoking forelimb movements appeared to progressively increase during the time of study. Minimal currents required to evoke forelimb movements from the cerebral cortex increase (possibly progressively) following a lesion of the forelimb representation in the primary motor area, affecting many interconnected motor areas in the hemispheres ipsilateral and contralateral to the lesioned site. This increase in thresholds may play a role in the changes in cortical control of the affected and contralateral limbs following brain lesions and explain the increased sense of effort required to produce movements.     

Changes in electrical thresholds for evoking movements from the cat cerebral cortex following lesions of the sensori-motor area

We evaluated motor maps in the cerebral cortex and motor performance in cats before and after lesions of the forelimb representation in the primary motor area. After the lesion there was a reduction in the use of the affected forelimb and loss of accuracy in prehension tasks using the forelimb; some recovery occurred during the mapping study. Electrode tracts and lesion sites were located in cytoarchitectonically identified cortical areas 4gamma, 4delta, 6aalpha, 6agamma, 3a. The lesions were mainly in area 4gamma. In the lesioned hemisphere there were many points around the lesion site (in areas 4gamma and 3a) from which movements could not be evoked. In some areas distant from the lesion site (e.g. area 6agamma) the mean thresholds for evoking forelimb movements were significantly elevated. Mean thresholds for evoking hindlimb and facial movements were not different from before. In the contralateral hemisphere mean thresholds for evoking forelimb, but not hindlimb or facial movements, were significantly elevated in several sensorimotor areas (area 4gamma, 6agamma and 3a). Mean thresholds for evoking forelimb movements appeared to progressively increase during the time of study. Minimal currents required to evoke forelimb movements from the cerebral cortex increase (possibly progressively) following a lesion of the forelimb representation in the primary motor area, affecting many interconnected motor areas in the hemispheres ipsilateral and contralateral to the lesioned site. This increase in thresholds may play a role in the changes in cortical control of the affected and contralateral limbs following brain lesions and explain the increased sense of effort required to produce movements.     

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。     

Changes in pain sensitivity after the ablation of the somatosensory areas of the cerebral cortex in cats

The effects of ablation of the first and second somatosensory cortex on pain sensitivity were studied in the behavioural experiments on adult cats. The ablation of the first somatosensory cortex (SI) was shown to cause an increase of the response thresholds at all the levels of a conventional scale, while the destruction of the second somatosensory cortex (S2) decreased the response thresholds. The role of SI and S2 in the evaluation of nociceptive information is discussed.     

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.     

Comparison of electrical thresholds for evoking movements from sensori-motor areas of the cat cerebral cortex and its relation to motor training

Motor maps and electrical thresholds for evoking movements from motor areas of the cerebral cortex were evaluated in normal cats by using intracortical microstimulation techniques. Stainless steel chambers were implanted over craniotomies in adult cats trained to perform reaching and retrieval movements with their forelimbs. Prehensile motor training was continued and movement performance monitored for about 6-10 weeks during which the cortex was progressively explored with sharp tungsten electrodes inserted into cortical gyri (anterior and posterior sigmoid, and coronal) and the banks of sulci (cruciate, presylvian and coronal). Twice weekly, under light general anaesthesia, 3-4 tracks were made in either hemisphere till about 50 tracks were made in each hemisphere. Mean thresholds for evoking forelimb movements from different cytoarchitectonic areas (4gamma, 4delta, 6agamma and 3a) were compared and no consistent or significant differences were observed between the different areas. In the animals (4/6) which used either forelimb to perform the tasks, there were no consistent differences in the mean thresholds for evoking forelimb movements from the two hemispheres. However, in 2 animals, which used their right forelimbs predominantly or exclusively to perform all the tasks, mean thresholds for evoking forelimb movements was significantly higher in areas 4gamma and 6agamma of the left hemisphere (compared to the right); no consistent differences in the mean thresholds for evoking hindlimb or facial movements were observed between the two hemispheres. These findings suggest that ICMS thresholds for evoking forelimb movements may be similar in different sensorimotor areas of the cat cerebral cortex, and these thresholds could be influenced by motor training.     

Regional cerebral blood flow in cats with cross-linked hemoglobin transfusion during focal cerebral ischemia

The beneficial effect of hemodilution on cerebral blood flow (CBF) during focal cerebral ischemia is mitigated by reduced arterial oxygen content (CaO2). In anesthetized cats subjected to permanent middle cerebral artery occlusion, the time course of regional CBF was evaluated after isovolemic exchange transfusion with either albumin or a tetrameric hemoglobin-based oxygen carrier. The transfusion started 30 min after arterial occlusion. We tested the hypothesis that bulk oxygen transport (CBF x CaO2) to ischemic tissue is increased by hemoglobin transfusion at a hematocrit of 18% compared with albumin-transfused cats at a hematocrit of 18% or control cats at a hematocrit of 30% and equivalent arterial pressure. In the nonischemic hemisphere, CBF increased selectively after albumin transfusion, and oxygen transport was similar among groups. In the ischemic cortex, albumin transfusion increased CBF, but oxygen transport was not increased above that of the control group. Hemoglobin transfusion increased both CBF and oxygen transport in the ischemic cortex above values in the control group, but the increase was delayed until 4 h of ischemia. Consequently, acute injury volume measured at 6 h of ischemia was not significantly attenuated. In contrast to the cortex, CBF in the ischemic caudate nucleus was not substantially increased by either albumin or hemoglobin transfusion. Therefore, in a large animal model of permanent focal ischemia in which transfusion starts 30 min after ischemia, tetrameric cross-linked hemoglobin transfusion can augment oxygen transport to the ischemic cortex, but the increase can be delayed and not necessarily provide protection. Moreover, an end-artery region such as the caudate nucleus is less likely to benefit from hemodilution.     

Comparison of electrical thresholds for evoking movements from sensori-motor areas of the cat cerebral cortex and its relation to motor training

Motor maps and electrical thresholds for evoking movements from motor areas of the cerebral cortex were evaluated in normal cats by using intracortical microstimulation techniques. Stainless steel chambers were implanted over craniotomies in adult cats trained to perform reaching and retrieval movements with their forelimbs. Prehensile motor training was continued and movement performance monitored for about 6–10 weeks during which the cortex was progressively explored with sharp tungsten electrodes inserted into cortical gyri (anterior and posterior sigmoid, and coronal) and the banks of sulci (cruciate, presylvian and coronal). Twice weekly, under light general anaesthesia, 3–4 tracks were made in either hemisphere till about 50 tracks were made in each hemisphere. Mean thresholds for evoking forelimb movements from different cytoarchitectonic areas (4γ, 4δ, 6aγ and 3a) were compared and no consistent or significant differences were observed between the different areas. In the animals (4/6) which used either forelimb to perform the tasks, there were no consistent differences in the mean thresholds for evoking forelimb movements from the two hemispheres. However, in 2 animals, which used their right forelimbs predominantly or exclusively to perform all the tasks, mean thresholds for evoking forelimb movements was significantly higher in areas 4γ and 6aγ of the left hemisphere (compared to the right); no consistent differences in the mean thresholds for evoking hindlimb or facial movements were observed between the two hemispheres. These findings suggest that ICMS thresholds for evoking forelimb movements may be similar in different sensorimotor areas of the cat cerebral cortex, and these thresholds could be influenced by motor training.     

Functional characteristics of visual cortical neurons of the cat

The characteristics of neurons in Area 17 of the visual cortex in cats were investigated by extracellular recording of their activity. Unit responses to flashes modulated by intensity and duration (100 µsec-1 sec) were recorded. Of 80 neurons tested, 67.6% were spontaneously active and 32.4% were silent. The threshold responses of the neurons to flashes varied by 7 logarithmic units. The distribution curve of the cells by response thresholds had one maximum corresponding to an energy of the order of 1–10 lm·sec. The time during which the cells could summate excitation did not exceed a mean value of 34 msec. Depending on the latent periods of the visual cortical neurons they can be divided into three groups. The first group includes neurons responding 20–40 msec after stimulation, the second and third neurons responding after 100–120 and 160–180 msec, respectively. Photic stimulation considerably altered the ratio between the numbers of cells generating spikes with high and low frequency. No correlation was found between the sensitivity of the visual cortical cells to light, the latent period of their response, and the critical time of summation. This shows that the cortex contains many duplicate units which are grouped together on the basis of only one of the functional characteristics of their spike response.Institute of Higher Nervous Activity and Neurophysiology, Academy of Sciences of the USSR, Moscow. Translated from Neirofiziologiya, Vol. 2, No. 2, pp. 173–179, March–April, 1970.     

Bicuculline and orientation tuning of neurons of the visual cortex

Orientation tuning (OT) of 68 visual cortex neurons (field 17) was studied in cats under conditions of a GABA-ergic inhibition blockade by microiontophoretic bicuculline applications; the neuronal responses were evoked by flashing light strips. All characteristics of orientational detection in most neurons got worse after the applications. The OT became wider in 76.3% of cases: its mean value increased from 52.7±2.8° to 85.2±4.6°. In 63.6% of cases OT selectivity decreased by one-third, and in 68.5% of neurons the detection quality decreased by 60%, on average. The threshold dose of bicuculline causing the OT extension was injected by the phoretic current of 31.0±4.5 nA, and the optimum effect was reached at 67.1±6.0 nA. The background activity and the response magnitude increased under the bicuculline influence 3.0 and 4.4 times, respectively, compared with the control. A few minutes after the iontophoresis termination, the frequency of neuronal discharges and OT characteristics returned to their initial values. We conclude that the local blocking of intracortical inhibition, which causes disinhibition of afferent inputs from the neighboring cells with different (compared with the recorded cell) preferred orientations, considerably worsens orientational specificity of visual cortex neurons, or even results in a complete loss of such specificity. These data are consistent with the concept that intracortical inhibition plays a leading role in the formation and sharpening of OT in the visual cortex neurons.Neirofiziologiya/Neurophysiology, Vol. 27, No. 1, pp. 54–62, January–February, 1995.     

Alteration of shock titration thresholds in the cat following intrathecal substance P administration

Substance P (SP) was injected intrathecally (10 or 100 micrograms) into cats previously implanted with nerve-stimulating electrodes and the effect on shock titration thresholds was evaluated. Elevated shock thresholds were observed in 5 of 8 cats following the 100 micrograms dose of SP. In addition, one cat exhibited a decreased threshold and two cats showed a triphasic (increase, decrease, increase) response. Overt behavioral effects of intrathecal SP were mild, but suggested that injection of the drug was aversive.     

Differences in functional organization of the visual center in frogs and cats

Functional characteristics of responses of tectal neurons in the frog and the primary visual cortex of the cat obtained under indentical experimental conditions during changes in the brightness and duration of flashes within the range of 6 log units were compared. In frogs most units have short summation times and relatively lower thresholds; the response latency is 5–7 times longer than in cats. The overwhelming majority of tectal units can respond only to a narrow range of photic energy that differs for different cells. Most cells in cats respond to changes in brightness of between 4 and 5 log units; they have long summation times, short latent periods, and relatively higher thresholds. The differences found on comparison of the various functional characteristics of the cells in the visual center show that frogs have fixed mechanisms of temporal and spatial interaction responsibile for detection of stimulus brightness. In cats this interaction between individual cell populations and this mutual inhibition between adjacent cells are not prominent. The increased complexity and overlapping of interneuronal connections leads to convergence of day and twilight vision stimuli on the same neuron and to the ability of single units to respond to the whole "working" range of light brightness for the cat visual system.     

Reflection of temporal parameters of an optical stimulus in unitary responses of the sensomotor and visual cortex in cats

Unit activity in the visual (area 17) and sensomotor (areas 4 and 6) cortex in response to an optical stimulus up to 1000 msec in duration was investigated by extracellular recording in acute experiments on cats anesthetized with chloralose (70 mg/kg body weight). Comparative analysis of the types of unitary responses and the durations of the intervals of functional changes showed that: 1) The number of neurons generating on-off responses was about 25% in the visual cortex and 100% in the sensomotor cortex; 2) the intervals of functional changes of the neurons were equal in length to the time intervals of on-off discharges; 3) together with a single time range (200–500 msec), for each area studied specific ranges also exist: from 0 to 200 msec for the visual cortex and from 500 msec and more for the sensomotor cortex; 4) the latent period of after-discharge is equal to the duration of the intervals of functional changes. The results were analyzed from the standpoint of reflection of temporal parameters of optical stimuli by neurons of the sensomotor cortex.A. A. Zhdanov Leningrad State University. Translated from Neirofiziologiya, Vol. 7, No. 4, pp. 365–371, July–August, 1975.