摘要:

AbstractSets of animals with lesions to either the vertical lobe or median inferior frontal lobe were trained first visually and then by touch. Lesions of the vertical lobe system did not affect the increase produced by food in tendency to attack a moving figure in the visual field. Any lesion that interrupted the circuit through the vertical lobe greatly impaired the capacity to inhibit attacks on crabs when these attacks resulted in shocks. Removal of the median inferior frontal lobe did not impair this capacity to learn not to attack a crab in the octopus's visual field.The Capacity to learn to respond positively to a black disc but to avoid a white one was grossly impaired by an interruption of the vertical lobe circuit. After such operations the animals showed a strong preference for white over black. The capacity to learn to discriminate between black and white was not affected by removal of the median inferior frontal lobe. Animals with interruptions of the vertical lobe circuit could learn to make discrimination between white as a positive figure and black as a negative one, but they made more mistakes than controls. Most mistakes consisted of attacks on the negative (black) figure, but there were also some failures to attack the white.In tactile discrimination between rough and smooth spheres given successively, animals with vertical lobe lesions were, under some circumstances, less accurate than controls. They took more objects than controls. They were less able than controls to reverse the discrimination. After removal of the median inferior frontal lobe tactile discrimination was greatly impaired. The animals showed a strong preference for rough objects and could not learn to take smooth objects. However, they showed improvement in discrimination when trained with smooth negative and are therefore not wholly incapable of long‐term memory storag

ISSN:0360-4012    

DOI:10.1002/jnr.490010302

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1975

数据来源: WILEY

摘要:

AbstractA compartmental hardware model of an alligator Purkinje cell is described, consisting of a branched dendritic tree with four zones of spike generation and electrically excitable soma and initial‐segment regions. Passive properties of the model compartments are represented by a cable analog circuit. Simulated action potentials, generated by a combination of depolarizing and hyperpolarizing conductance changes, are triggered in active compartments when the simulated membrane potential passes through preset thresholds. These were set at values corresponding to 28mV depolarization in the dendrites, 22 mV in the soma, and 7 mV in the initial‐segment compartment. Synaptic inputs consisting of brief (0.35 msec) rectangular conductance changes give rise to exponentially decaying postsynaptic potentials in the input compartment which are electrotonically spread to other compartments. Orthodromic activation of the model neuron by computer‐generated random pulse trains generates a simple discharge in the initial‐segment compartment without evoking complex spikes. Synchronized excitatory input to the same compartments, however, does evoke a complex spike response in the soma and initial segment, coupled with dendritic spikes, Following antidromic activation of the model neuron, dendritic spikes are not generated, demonstrating a tendency in the dendritic tree for preferential conduction of spikes toward the soma. Investigation of some of the factors underlying this tendency suggests that variations in voltage attenuation due to dendritic geometry, convergence of electrotonically spread dendritic spikes, and the relative durations of dendritic and somatic action potentials may contribute to it. The presence of a threshold gradient in the dendritic tree, proposed by Llinás and his coworkers, was not found to be necessary to explain this tendency toward somatopetal conduction, although it cannot be excluded by the model. Examination of the role of the conically shaped initial‐segment region suggests that this zone may provide a low‐pass filter for signals conducted electrotonically from the axon to the soma, blocking repolarization of the soma during the complex spike burst generated

ISSN:0360-4012    

DOI:10.1002/jnr.490010303

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1975

数据来源: WILEY

摘要:

AbstractThe effects of various doses of 6‐hydroxydopamine(6‐OHDA) injected into the hypothalamus on DOCA‐salt‐induced hypertension were studied. The development of hypertension was prevented in the group treated with the highest dose of 6‐OHDA, and the onset of hypertension was delayed in a dose‐dependent fashion in the groups treated with the lower doses of 6‐OHDA. Catecholamine histofluorescence observations showed that the cannula tips placed the drug lateral to the third ventricle. The most prominent change observed was a marked unilateral reduction in the fluorescence of the dopaminergic nerves of the caudate‐putamen and in the number of cell bodies in the substantia nigra. These results suggest possible sites of central aminergic control of

ISSN:0360-4012    

DOI:10.1002/jnr.490010304

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1975

数据来源: WILEY

摘要:

AbstractStudies of the diffuse electroretinogram (ERG) and evoked responses in the optic lobe in the baby chick have shown that epinephrine produces changes in both. Epinephrine produces enhancement of the a‐wave and depression of the b‐ and d‐waves in both intact and isolated eyes. In the optic lobe it produces enhancement of both components of the evoked response. The presence of epinephrine in the vertebrate retina and the optic lobe of chicks suggests that these changes may reflect the involvement of epinephrine in synaptic transmi

ISSN:0360-4012    

DOI:10.1002/jnr.490010305

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1975

数据来源: WILEY

摘要:

AbstractPosttetanic potentiation of monosynaptic reflexes has been used as a paradigm for neuronal plasticity. The explanation for this phenomenon is an increased responsiveness of the synaptic junctions. This would basically required chemical changes of the nervous structures involved. The ventral horn area of the spinal cord was therefore analyzed neurochemically. The determination of the phospholipids revealed an alteration of their composition. Sphingomyelin, phosphatidylcholine and phosphatidylinositide/serine behaved differently, whereas phosphatidylethanolamine and the total phospholipid content remained unchanged.

ISSN:0360-4012    

DOI:10.1002/jnr.490010306

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1975

数据来源: WILEY

摘要:

AbstractThe effects of nicotine on the stretch reflex and on electrically induced monosynaptic and cutaneous polysynaptic reflex responses at a lumbosacral level were studied in lightly anesthetized (chloralose‐urethane) cats in which the regional fusimotor‐spindle loops had been interrupted by ventral rhizotomy. Doses of 15–40 μg/kg injected into the superior vena cava or the right atrium produced depression of the reflex responses in extensor and flexor α motoneurons after latent periods of 1–3 sec, while γ activity was initially accelerated. The early phase of this α depression was abolished by bilateral vagotomy. Sebacylcholine (a nicotinic agent) and acetylcholine also caused depression of evoked α activity in the absence of spindle feedback. It is concluded that nicotine activates a viscerosomatic reflex by exciting sensory receptors in the cardiopulmonary region and that α motor depression results independent of the changes in γ activity. However, α depression with delayed onset can still be elicited by nicotine after vagotomy and Renshaw blockade, and this effect is also duplicated by sebacylcholine and aboilshed by hexamethonium. In the doses used, spindle or skin afferents were not excited by nicotine. Thus, two more mechanisms are described by which nicotine can depress α activity. Both are reflex in nature, one implicating vagal, the other nonvagal peri

ISSN:0360-4012    

DOI:10.1002/jnr.490010307

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1975

数据来源: WILEY

摘要:

AbstractUnilateral eye removal results in an increased delivery of blood‐borne glucose, norepinephrine, choline, and tyrosine, but not of proline, to the denervated optic lobes. Administration of reserpine to chicks increases penetrance of norepinephrine into the brain but not of tyrosine, choline, or proline. Selective alterations in the permeability of the blood‐brain barrier may represent a mechanism for the modulation of the delivery of critical nutrients to the br

ISSN:0360-4012    

DOI:10.1002/jnr.490010308

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1975

数据来源: WILEY

摘要:

AbstractA new method for measuring the uptake of materials labeled with radioactive phosphorus (32P) in the brain of a freely moving rat is described. The rat of uptake in the brain of a single animal of32P‐labeled phosphate was compared to the uptake rate in the animal's blood or liver. A comparison was made between the uptake following an intravenous (IV) or an intraperitonel (IP) injection. The effect of convulsions caused by injections of metrazol on the kinetics of32P uptake in the brain is describe

ISSN:0360-4012    

DOI:10.1002/jnr.490010309

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1975

数据来源: WILEY

摘要:

AbstractModels of neural networks with recurrent inhibition are studied, as well as one model which also includes recurrent excitation. The models are intended as possible descriptions of the cerebral cortex.Each network model is composed of neuron models called pyramidal cells and stellate cells in accordance with the names of two types of cells in the cortex. Inputs and outputs of the network are connected to the pyramidal cells while feedback is provided by the stellate cells. Connections within the network are random.During a learning phase the pyramidal cell excitatory synapses become facilitated according to a two‐ conditional facilitation rule. This is the basis of the model's ability for associative learning. The associative retrieval of information can be studied during a subsequent association phase. This has been done by simulation on a digital computer.It was shown that all of the models considered can be designed to perform a so‐called decision‐making function. This means that if the associating input pattern is similar to several patterns which occurred during learning the model can decide which similarity is greatest by responding with the appropriate associated pattern.The model also including recurrent excitation differs from the simpler models in that it can become stabilized in so‐called stable modes of activity which are self‐sustaining and remain even after the input has been turned off. Normally, only one stable mode can be active at a time. However, through careful choice of construction parameters it was possible to obtain a model in which a maximum of two stable modes could be activated independently of each other.Physiological and psychological interpretations are discussed and so are the limitations of the models, which are evident in certain s

ISSN:0360-4012    

DOI:10.1002/jnr.490010310

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1975

数据来源: WILEY

摘要:

AbstractStudies on neuronal control mechanisms of neurotransmitters biosynthesis during the development of peripheral and centralautonomic synapses are reviewed. Particular emphasis is placed on investigations of developing peripheral sympathetic ganglia and brain in chick embryo and chick.Studies on the development of autonomic neurons and synapses under different pharmacological conditions are reported. Principally the effect of (a) the administration of drugs and precursors such L‐dopa,3H‐dopa, 6‐OH dopa; (b) the prenatal administration of reserpine; (c) the blockade of cholinergic receptors; (d) the nerve growth factor (NGF) is analyzed.Results of developmental studies on chick ciliary ganglia are summarized.The review particulary underlines the importance of combining the use of sensitive microchemical methods to pharmacological tools in exploring the development of regulatory mechanisms at the cellular

ISSN:0360-4012    

DOI:10.1002/jnr.490010311

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1975

数据来源: WILEY