Experimental Brain Research

Schmidt, C.; Wist, E.; Dichgans, J.

doi: 10.1007/BF00234954pmid: 5046873

221 15 15 1 1 C. L. Schmidt Prof. E. R. Wist J. Dichgans Neurologische Universitätsklinik mit Abteilung für Neurophysiologie Freiburg i. Br. West-Germany Whitely-Lab. of Psychology Franklin and Marshall College 17604 Lancaster Pa. USA Summary Impulses of single fibres of the vestibular nerve in the goldfish were recorded either from the rostral portion of the left vestibular nerve, or from the left Ramus ampullaris lateralis , or from the proximal stump of the severed nerve. From a total of 420 registered neurons, 44 showed characteristic modulations of the spontaneous activity associated with any rapid eye movement. These neurons were divided into four types : 1. The bidirectionally activated type a was activated with fast phases of nystagmus both to the left and to the right. 2. The bidirectionally inhibited type i was inhibited with fast phases of nystagmus in both directions. 3. The directionally sensitive type d was inhibited during the rapid phase of nystagmus when its direction was ipsilateral and activated when its direction was contralateral to the side of the recording electrode. 4. The position sensitive type p was correlated with the position of the eyes. With deviation of the eye ipsilateral those neurons were tonically activated and with deviation of the eye contralateral to the side of the electrode, their activity was tonically reduced. Activation and inhibition in the type a, i, and d neurons always began before the saccade . In the type p neuron tonic frequency modulation dependent on eye position began up to 100 msec after a position change. Some neurons showed the characteristic behaviour of both type a and p neurons. These, as well as the pure type a, p and i neurons, were found in the intact nerve as well as in the proximal stump of the severed nerve. The rarer type d neurons were found only in the intact nerve. Neurons originating in the macula organs (Utriculus, Sacculus and Lagena) did not show frequency modulation with eye movements. Efferent modulations originating from supranuclear optomotor centers of the mesencephalic and pontine reticular formation were discussed in relation to their functional significance during combined eye and body movements.

Gambarian, L.; Koval, I.; Garibian, A.; Sarkisian, J.

doi: 10.1007/BF00234955pmid: 5046872

221 15 15 1 1 Prof. L. S. Gambarian I. N. Koval A. A. Garibian J. S. Sarkisian Laboratory of Neurobionics Armenian Academy of Sciences Yerevan USSR Summary Hippocampal damage in cats led to: a) A temporary suppression of previously elaborated motor feeding conditioned reflexes (CR); b) A retardation (nearly twice) in the rate of elaboration of a new CR; c) A marked prolongation of latency of CR; d) A disinhibition of negative CR. li)2.|In experiments in which the animals were trained to approach the left-side feeder and press a pedal at one signal and the right-side feeder at another signal, destruction of the hippocampus led to frequent errors in the choice of the proper side of reinforcement. When the choice reactions were elaborated before the operation, the errors were 30% after it. But when the same reactions were elaborated after hippocampal damage, the errors of choice amounted to 60%. li)3.|It is suggested that the hippocampus is one of the structures within the cortical-subcortical integrative system, which achieves simultaneous integration of excitations caused by the conditional signal, the surrounding environment and the mechanism of memory.

Aleksanyan, Z.; Škvařil, J.; Bureš, J.

doi: 10.1007/BF00234956pmid: 5046874

221 15 15 1 1 Z. A. Aleksanyan J. Škvařil J. Bureš Institute of Physiology Czechoslovak Academy of Sciences Prague Czechoslovakia Summary The relationship between mean firing rate and activity pattern was studied in 177 neurons in the ventromedial hypothalamus of rats immobilized by Remyolan. Stationary epochs of spontaneous or stimulated activity containing at least 512 interspike intervals were analyzed with the LINC computer. The most frequently encountered interval histograms (IHs) were of the exponential (35%) or gamma 2 (25%) type. The IH shape remained unchanged even if the average firing rate was varied over a wide range (from 20/sec to 2/sec) by polarization through the recording microelectrode (2–5 nA, 1–10 min) or by intracarotid injection of glucose (0.1 ml, 10–25%). The coefficient of variation (CV = SD/ mean interval) was 1.03 for the spontaneous and 0.90 or 0.95 for the activity influenced by polarization or glucose, respectively. Since according to other studies sensory stimulation decreases CV by reorganization of the synaptic input, it is suggested that polarization and glucose affect predominantly the postsynaptic elements without significantly changing the presynaptic activity pattern.

Hongo, T.; Jankowska, E.; Lundberg, A.

doi: 10.1007/BF00234957pmid: 5046875

221 15 15 1 1 Dr. T. Hongo E. Jankowska A. Lundberg Department of Physiology University of Göteborg Göteborg Sweden Department of Physiology Tokyo Medical and Dental University Tokyo Japan Summary 1. Effects evoked by stimulation of the red nucleus on primary afferent terminals in the lower lumbar segments of cats have been investigated by recording dorsal root potentials (DRPs) and by recording (intracellularly and by excitability measurements) the primary afferent depolarization (PAD) evoked in terminals of different afferent systems. Control experiments suggest that the effects are mediated by the rubrospinal tract. 2. Stimulation of the red nucleus evoked a large DRP and correspondingly there was a pronounced PAD in Ib and low threshold cutaneous afferents. A dual effect was found in Ia afferent terminals; sometimes a weak PAD was detected while in other cases there was dominating primary afferent hyperpolarization (PAH). 3. Rubrospinal volleys are found to facilitate transmission of DRPs evoked from Ia, Ib, cutaneous and high threshold muscle afferents, presumably by exerting an excitatory action on the interneurones mediating the effect from these afferents. Stimulation of the red nucleus may also inhibit transmission in the pathway mediating depolarization of Ia afferent terminals from Ia afferents, probably by activating a segmental pathway from the flexor reflex afferents from which the same effect is evoked. It is postulated that the PAH evoked in Ia afferents from the red nucleus is due to this inhibitory effect and caused by a removal of a tonic PAD in them. 4. The possible role in motor regulation of the rubral effects on primary afferent terminals is discussed in relation to the rubrospinal effects on reflex pathways to motoneurones. This work was supported by the Swedish Medical Research Council (Project No. 14X-94-07C).

Hongo, T.; Jankowska, E.; Lundberg, A.

doi: 10.1007/BF00234958pmid: 5046876

221 15 15 1 1 Dr. T. Hongo E. Jankowska A. Lundberg Department of Physiology University of Göteborg Göteborg Sweden Department of Physiology Tokyo Medical and Dental University Tokyo Japan Summary 1. The effect of stimulation of the red nucleus on interneurones in the dorsal horn and intermediate region in the lower lumbar spinal cord has been investigated in cats. It has been ascertained that the effects are mediated by the rubrospinal tract. 2. Extracellular monosynaptic focal potentials evoked by single volleys in the rubrospinal tract were recorded in Rexed's layer VI and VII from a region partly overlapping with that in which focal potentials from group I muscle afferents are evoked, but extending more ventrally. 3. Monosynaptic excitatory action from the rubrospinal tract (recorded in 60 of 340 interneurones) was found in two main categories of interneurones: a) cells monosynaptically activated or disynaptically inhibited from group I muscle afferents and b) cells di- or polysynaptically activated from the flexor reflex afferents or exclusively from cutaneous afferents. The cells under a) are located more dorsally than those under b) but both within the region in which rubral focal monosynaptic potentials are recorded. There was no evidence suggesting that rubrospinal fibres have monosynaptic connexions with interneurones not influenced from primary afferents. 4. Many of the group I interneurones in the intermediate region are without monosynaptic connexions from the rubrospinal tract as are the dorsal horn cells monosynaptically activated from cutaneous afferents and dorsally located cells which do not receive monosynaptic connexions from primary afferents but are polysynaptically activated from the FRA. 5. Late (di- or polysynaptic) excitatory, inhibitory or mixed postsynaptic rubral effects are common and were found in interneurones with or without monosynaptic connexions from primary afferents but receiving similar effects from the FRA. The occurrence of spatial facilitation between peripheral nerves and the rubrospinal tract in evoking late PSPs suggests that the late rubral PSPs are evoked by activation of interneurones transmitting actions from primary afferents. 6. Some consequences of the conjoint control of interneurones from primary afferents and the rubrospinal tract are discussed. The monosynaptic effects from the rubrospinal tract are considered in relation to the rubral control of Ib reflex pathways and to the disynaptic rubromotoneuronal PSPs evoked by monosynaptic activation of last order interneurones of polysynaptic reflex pathways from primary afferents. The late rubral effects on interneurones are discussed in relation to interactive mechanisms between segmental interneuronal pathways. Rubrospinal and corticospinal effects are compared. This work was supported by the Swedish Medical Research Council (Project No. 14X-9407C).

Goldberger, Michael

doi: 10.1007/BF00234959pmid: 4625805

221 15 15 1 1 Dr. Michael E. Goldberger Department of Anatomy The University of Chicago Chicago USA Summary The pathologic grasp reflex (“forced grasping”) was used to study restitution of function in monkeys conditioned to grasp and release a stick for food. Cortical lesions (area 6) made it impossible for the animals to relinquish the stick or to avoid grasping an unconditioned (tactile) stimulus. Normal tactile evasion was abolished but returned during recovery, i.e. as forced grasping waned. Pyramidal lesions alone provoked no forced grasping but abolished all tactile reflexes. Seriatim cortical and pyramidal (1 year later) lesions brought back pathological grasping after “total” restitution of normal grasping had occurred, whereas ventrolateral spinal lesions hastened restitution and enhanced tactile evasion. The possible mechanisms underlying restitution are discussed; it is suggested that the abnormal grasp is compensated by enhancement of its opposing reflex, tactile evasion, which is subserved by the pyramid. The fundamental physiological change due to area 6 lesion is a reflex imbalance which endures covertly in spite of behavioral restitution and is exposed once again when tactile evasion is abolished by pyramidotomy. Therefore, during “recovery”, pyramidal function vis a vis tactile evasion was enhanced in response to loss of inhibitory control over tactile and proprioceptive grasp reflex activity. This model is offered as an alternative to “functional reorganization” and “vicarious function”.

Appelberg, B.; Jeneskog, T.

doi: 10.1007/BF00234960pmid: 4261655

221 15 15 1 1 B. Appelberg T. Jeneskog Department of Physiology University of Umeå Umeå Sweden Summary In halothane anesthetized cats changes in the afferent activity from muscle spindles in the flexor digitorum longus muscle caused by electrical stimulation in the mesencephalon were studied. From a dorsal stimulating area the dynamic sensitivity of the spindles could be selectively increased. This area was partly situated within the red nucleus, but its efferent pathway, though proceeding dorso-laterally in the cord, could be shown not to be identical to the rubro-spinal tract. From a ventral stimulating area dynamic and/or static properties of the spindles were influenced. The efferent pathway for the static effects was shown to be located laterally and ventro-laterally in the cord and is suggested to be reticulospinal. Differential effects on different spindles from one and the same electrode position was frequently observed and this phenomenon is discussed.