Widespread Fields Research Articles

Neuromuscular Organization in the Swimming System of the Pteropod Mollusc Clione Limacina

Swim motor neurons of the pteropod mollusc Clione limacina were identified by a combination of electrophysiological and morphological characteristics. Two types of motor neurons were found, including small motor neurons which are active during both slow and fast swimming and which innervated restricted fields of the ipsilateral wing. General excitor motor neurons have large cell bodies, innervate widespread fields and are recruited into activity for fast swimming. Small motor neurons monosynaptically innervate slow-twitch muscle cells, whereas general excitors monosynaptically innervate both slow-twitch and fast-twitch muscle cells. Activity in general excitors can centrally enhance that in small motor neurons because the neurons are electrically coupled. Neuromuscular recordings and lesion experiments indicate that a peripheral nerve network does not appear to play an important role in the spread of excitation throughout the muscle fields.

Mobile acoustic reproduction apparatus

A center loudspeaker is disposed near the middle between the left channel loudspeaker arranged at the front left side of the compartment and the right channel loudspeaker at the front right side, and this center loudspeaker transforms into a sound by the level-controlled signal of the sum of the acoustic signals of the right and left channels, and phase- and level-controlled signals of the acoustic signals of the right and left channels. As a result, the sound field is localized in the front of the listener, and right and left symmetrical wide-spread sound fields may be composed. Additionally, tweeters are disposed outside the right and left channel loudspeakers, and the mounting angles of the tweeters are adjusted so that the sounds released from the tweeters may be at an equal sound pressure level between the listener at the driver's seat and the listener at the front side seat. As a result, the drift of the sound field in the medium and high sound ranges may be eliminated in a simple structure, and right and left symmetrical wide-spread sound field are composed. Furthermore, corresponding to the opening or closing state of the window glass or seated position, by controlling the phase and level of the sounds released from the loudspeakers and the tweeters, sound fields always symmetrical to the listening position and spread widely may be composed.

Paschen-line Stark-broadening as an electric field diagnostic in erupting prominences

We analyse the Stark broadening of the Balmer and Paschen lines emitted in two bright eruptive prominences, to determine the total electric field in these structures. We show that the Paschen lines provide a significantly more sensitive and accurate electric field indicator than the Balmer lines used previously in such studies. In the two eruptive events analysed here, the total electric fields agree to within 5–10 V cm-1 with the pressure-broadening fields expected from local densities of the cool plasma, measured simultaneously and co-spatially by a line-ratio diagnostic. We conclude that in such structures the upper limit to any widespread macroscopic fields is roughly 10 V cm-1 or less. This is in agreement with the motional electric field that might be associated with reconnection at the observed rate of the prominences' outward motion of about 135 km s-1.

Properties of deep spinothalamic tract cells in the rat, with special reference to ventromedial zone of lumbar dorsal horn.

Spinothalamic tract cells lying at the base of the dorsal horn or in deeper areas were identified in the rat at the lumbar spinal cord level by injecting horseradish peroxidase or stimulating posterior thalamic areas. Two groups of neurons were delineated; each constituted a homogeneous population of cells in terms of electrophysiological properties. Ventromedial dorsal horn cells lay at the base of the dorsal horn in its most medial aspect. They constitute a densely packed formation, which in the rat's ascending pathway system is restricted to the spinothalamic tract. Their main characteristics were a) ongoing activity, which consisted of small groups of spikes occurring at regular intervals, with a maximal discharge during ankle extension; b) unilateral receptive fields, which were restricted to the distal parts of the limb and involved both proprioceptive (ankle, joint digits) and exteroceptive (foot skin) structures; c) input of innocuous origin (midrange articular movement, touch, pressure) that was excitatory and input of noxious cutaneous origin (radiant heat) that was inhibitory; the same areas of foot skin were thus potentially either excitatory or inhibitory, depending on the nature of the stimulus applied; d) ankle flexion could differentially modulate both ongoing activity and excitatory responses from distal parts of the limb, inhibiting the former and potentiating the latter. In consequence, the ability of these cells to be driven by both proprioceptive and cutaneous inputs from limb extremities as well as by interactions of these inputs would appear to be very favorable for informing the central nervous system about limb position in both passive postural changes and the step cycle. It is suggested that they supply the thalamus with integrated information about locomotion. Lamina VII cells also constituted a subpopulation of neurons with very homogeneous electrophysiological properties. They were characterized by widespread inhibitory receptive fields, possibly spanning both hindlimbs and the ipsilateral forelimb. Inhibition was most effective when the stimulus (pressure, pinch) was intense and applied to proximal parts of the hindlimb. Ongoing activity consisted of spikes set at regular intervals and sometimes related to midrange movements of the knee. Although the significance of the widespread inhibitory receptive fields remains unclear, it has been suggested that these neurons are involved in the transmission of proprioceptive information.(ABSTRACT TRUNCATED AT 400 WORDS)

Inhibition and excitation of thoracic spinoreticular neurons by electrical stimulation of vagal afferent nerves

Neurons in spinal segments T1–T3 of cats projecting to the region of the nucleus reticularis gigantocellularis were tested for their responses to electrical stimulation of the vagus nerve. The effects of vagal efferent activity were blocked with methylatropine, thereby limiting vagal input to the effects of afferent fibers. Seventeen spinoreticular (SR) neurons were inhibited by vagal stimulation; one was excited; four were both inhibited and excited, and nine were unaffected. Half of the SR neurons were not spontaneously active; they were excited by somatic stimuli for 20- to 30-s periods in order to test for vagal inhibition. Vagal stimuli sometimes were sufficiently potent to completely suppress neuronal discharge during and just after 10-s periods of stimulation. Parameters of stimulus duration and frequency suggest activation of both A delta and C fibers in the vagus nerves. Vagal stimulation could inhibit increased firing from cardiac stimuli, such as coronary artery occlusion and injection of bradykinin into the heart. Two-thirds of the SR neurons so tested responded to bilateral sympathetic stimuli, whereas about one-half had excitatory somatic receptive fields restricted to the left foreleg and upper left side. The other half had bilateral, widespread, and complex somatic fields, including inhibitory responses. Such multiple inputs suggest an integrative role for spinoreticular neurons in sensory processing. Vagal inhibition and excitation of SR neurons probably operates via well known descending inhibitory systems from the nucleus raphe magnus and other medullary centers. The vagi are the only peripheral afferent pathway into this descending system that has been described to date.

The structural organization of the ventral posterolateral nucleus in the rat.

The structural plan of the ventral posterolateral nucleus (VLP) in the rat was analyzed by using a variety of techniques to study the pattern of distribution of the ascending afferent fibers and the synaptology of the neuropil within this somatosensory relay nucleus. Golgi stains, Fink-Heimer methods, HRP labeling methods, and electron microscopy were all used in the analysis. The neurons in VPL are aligned in rostrocaudal and dorsoventral rows that are roughly parallel to the curvature of the external medullary lamina (EML) and curve partially around the rostral pole of the ventral posteromedial nucleus (VPM). Golgi-impregnated sections reveal that the dendritic trees of the VPL neurons conform in general to the laminar pattern of VPL. Thick proximal dendrites extend about 25 mu m from the cell bodies. Most proximal dendrites are aligned with the laminae of VPL but the distal dendrites spread over many laminae within VPL. The inputs from the dorsal column nuclei (DCN) end only on proximal dendrites as large, round-vesicle terminals. About 20--25% of the small round-vesicle terminals originate in the cerebral cortex and synapse only on the distal dendrites. The third type of synapse contains many flattened vesicles and is of unknown origin. No serial synapses or vesicle-containing dendrites were observed. Input from the spinal cord projects to two segregated zones which are transitional between the ventral lateral nucleus (VL) and VPL rostrally and between the posterior thalamic complex (PO) and VPL caudally. Each transition zone contains neurons characteristic of both VPL and the adjacent region. Ascending afferent projections were demonstrated by the antegrade transport of HRP following injections into the ventral mesencephalon and by Fink-Heimer stains of degeneration resulting from small lesions of the DCN. Both methods indicate that large-caliber axons course parallel to each other and give off collaterals that diverge to widespread areas of the VPL. The widespread terminal fields that result do not conform to the laminar pattern of the nucleus. Small punctate lesions of DCN result in sparse degeneration that is also widespread in VPL. Structures which appear to be clusters of terminal arborizations of the ascending afferent input were also observed in VPL. These results suggest that somatotopy and modality separation in VPL may be determined either by intrinsic and/or corticothalamic morphological relationships and not by precise topographical ordering of sensory input.

Cutaneous receptive fields of cerebellar Purkynĕ cells of unanesthetized cats.

1. In cats with local anaesthesia the cutaneous receptive fields of individual Purkyně cells of the vermis and pars intermedia of the anterior lobe were assessed by recording the simple spike discharges and climbing fiber responses following controlled mechanical stimulation of the foot pads of all four limbs (taps and pressure stimuli) and of the hairy skin (air jets) of the limbs and the body. 2. Exploring the receptive fields with taps and air jets revealed for the mossy fiber transmitted activity that in a population of 93 cells 37 had small receptive fields from the distal areas of one limb only; 28 had discontinuous receptive fields in two limbs and the others had their receptive fields on three or four limbs (multiple discontinuous fields) or over all or almost all of the body surface (widespread fields). 3. Testing with pressure stimuli to the toe pads inside and outside the receptive fields outlined with taps and air jets led to modifications of the simple spike discharges in 86 of 90 cells investigated in this way. Inclusion of these pressure fields increases the percentage of cells with discontinuous multiple mossy fiber transmitted receptive fields on three or four limbs to nearly 70% of our sample of Purkyně cells. 4. Approximately 50% of the cells with mossy fiber transmitted receptive fields also had climbing fiber transmitted fields. With the climbing fiber input the receptive fields were comparable with those for mossy fiber inputs when exploring with taps or air jets. Some additional climbing fiber transmitted cutaneous receptive fields were found with pressure stimuli. These pressure fields were usually restricted to one or two limbs. 5. These findings imply that the mossy fiber transmitted receptive fields of a given Purkyně cell usually extended over a wider area than the climbing fiber transmitted fields. As a rule the (small) climbing fiber fields were overlapped more or less completely by the (large) mossy fiber fields. 6. The receptive fields were either purely excitatory or partly excitatory and partly inhibitory. Pure inhibitory fields were rare. Within a mixed field no dominant pattern has been detected in regard to the arrangement of the excitatory and inhibitory areas. With the multiple fields from three or four limbs, receptive fields of complex composition seem to be the rule rather than the exception. It appears that in samples of cells like the present, each one has its own individuality in regard to shape and extent and in the intermingling of the excitatory and inhibitory field areas from mossy and climbing fiber inputs.

The immediate shift of afferent drive of dorsal column nucleus cells following deafferentation: A comparison of acute and chronic deafferentation in gracile nucleus and spinal cord

The somatotopic map of the gracile nucleus was determined using tungsten electrodes in anesthetized adult cats. Following deafferentation of the hind leg by cutting all dorsal roots caudal to L3, the nucleus was remapped. The total number of points in the map where abdomen responses were recorded doubled immediately following deafferentation. The latency of responses of cells responding to brush of the abdomen was not different after deafferentation. Some of the cells which began responding to abdominal stimulation had one or more of the following characteristics: (i) a rapid flick of the hair was required to fire the cell, (ii) habituation, and (iii) widespread inhibitory fields. To confirm that individual cells had switched the afferents which excite them, we examined the respone of single cells before, during, and after a reversible cold block of all the afferents from the hind leg. Of 40 single cells examined, 11 which had receptive fields on the leg switched their receptive fields to the abdomen as soon as the block of leg afferents was complete. Mapping the gracile nucleus 8 months following deafferentation still showed an increase in abdominal representation. Examination of the dorsal horn in the L6–7 segment of these chronically deafferented cats showed that abdominal afferents excited cells in a region normally responding to leg afferents. These results suggest that deafferentation results in the unmasking of normally ineffective connections. Unmasking could be a mechanism which explains many of the observed changes in the responses of central nervous system neurons following lesions.

Sensory properties of single neurons of cat's claustrum

A previous gross evoked potential study revealed that although multisensory convergence characterizes the entire claustrum, it is a complex, regionally differentiated formation that receives sensory afferents via primary and non-specific pathways. In the present study the responses of individual claustral neurons to somatic stimulation, clicks and flashes were investigated in immobilized cats with and without chloralose anesthesia. Of 397 neurons, 31% were unresponsive to any of the sensory stimuli that were used. The 275 responsive neurons formed a heterogeneous population and were distributed throughout the structure with no apparent order. Ninety percent were activated by somatic stimulation, 48% by click and 5% by flash. Among somatic cells 18% had ‘restricted’ or ‘highly restricted’ fields, 38% had widespread fields and 44% responded to more than one sensory modality. All somatic cell types were driven by mechanical stimulation of the skin or of deep tissues, and no correlation as found between the cell type and a given stimulus type. Latency distribution studies of somatic cells confirmed the macrophysiological subdivision of the structure into anterior, intermediate and posterior regions. Among auditory neurons, 17% responded only to a click and 83% were multisensory. In contrast to the somatic response, click-evoked response properties were determined by the cell type irrespective of the recording site. Though flash was not tested for in all convergent units, only two units were encountered which were activated by flash alone. In total, 75% of the responsive cells showed heterotopic or heterosensory convergence properties, while 25% were specific. Interaction between pairs of different stimuli varied from neuron to neuron and complex interaction patterns were observed. These data confirm the functional non-homogeneity of the claustrum and indicate that sensory afferents from various origins are distributed differently inside the structure and terminate in different combinations upon individual neurons. Comparison of animals with and without chloralose showed that the neuronal populations were similar in regard to overall responsiveness and the respective proportions of convergent and specific neurons. Response types, however, were markedly different in the two preparations. Under chloralose excitatory responses were rather stereotypical and inhibitory effects were difficult to assess due to the silence of the majority of cells. Without chloralose, excitatory responses were long and complex and inhibitory responses (either initially or following excitation) were predominant. In both preparations, spontaneous firing rates were low and rhythmic responses, as well as the driving up of unresponsive neurons by repetitive stimulation, were observed. The data presented are discussed with regard to the functional significance of the claustrum in sensory perception and in regulating non-sensory functions.

Cutaneous convergence on to the climbing fibre input to cerebellar Purkynĕ cells.

1. In cats anaesthetized with Nembutal, the cutaneous receptive fields of individual cerebellar climbing fibres were assessed by recording the climbing fibre responses of single Purkyne cells following controlled mechanical stimulation (air jets, vibration, taps, pressure) of the foot pads of all four limbs and of the hairy skin of the limbs and the body.2. Three major types of cutaneous receptive fields of individual climbing fibres were recognized: (a) restricted fields generally confined to the distal areas of one limb only; (b) circumscribed fields on the distal areas of two to four limbs (discontinuous fields); and (c) widespread continuous fields extending over all or almost all of the body surface. A fourth group appears to receive cutaneous inputs from one limb and sensory input from deeper structures in other limbs.3. Thresholds for tapping of the foot pads were often quite low (< 100 mum indentation), and there was no noticeable difference in the distribution of thresholds between the climbing fibres having restricted or more widespread cutaneous receptive fields. Similarly, the latencies of climbing fibre responses evoked by vibration and tapping were in the same ranges for climbing fibres with receptive fields restricted to one limb only and for those having more widespread fields.4. In regard to location in the anterior lobe of the cerebellum it was found that those climbing fibres receiving inputs only from the ipsilateral forelimb projected to Purkyne cells located almost entirely in lobule V, whereas all other climbing fibres with restricted or more widespread receptive fields projected to Purkyne cells distributed widely within lobules II to V.

Calendar of Documents in the Santa Barbara Mission Archives by Maynard J. Geiger (review)

BOOK REVIEWS Calendar of Documents in the Santa Barbara Mission Archives. By Maynard J. Geiger, O.F.M., Ph.D. (Publications of the Academy of American Franciscan History. Bibliographical Series, Vol. 1). Washington, D. C: Academy of American Franciscan History, 1947. Pp. xiv, 291. Cloth bound, $5.00. Paper bound, $3.50. If there is one field of endeavor where it can truthfully be said the Franciscan Order has always particularly excelled, it is that of missionary work. And one of the most successful and widespread Franciscan mission fields was that of Spanish America, from the sixteenth to the nineteenth century. But when it comes to a detailed and coherent historical record of those glorious missioners, modern Friars are forced to admit the truth of those sad words of Fr. Heribert Holzapfel, one of the Order's chief modern historians, who says: "The Franciscan Order, though surpassed by none in missionary labors, has been surpassed by almost all other Orders in writing the history of those labors". It was to help wipe away that indictment that the Academy of American Franciscan History was founded in 1944. This Academy, formed of Friar members of all the American Franciscan provinces, has for one of its purposes "the discovery, editing and publishing of documents, bibliographies and original historical works pertaining to the history of the Franciscan Order in the Americas". This is indeed a worthy and long-delayed purpose, but a difficult, time-consuming one. For instance, the volume under review, published by the Academy, was the work of many years and many hands. Fr. Francisco Palou scrutinized and marked many of the documents listed, as did Fr. Estevan Tapis, Fr. José Señan, Fr. Joseph O'Keefe, Fr. Theodore Arentz and Fr. Zephyrin Engelhardt. Fr. Maynard Geiger, the author and editor of the Calendar, who is Archivist of the Old Mission, Santa Barbara, and an Academy member, states in the introduction that he himself devoted seven years to examining and arranging the documents and writing the explanatory texts for each one. It was a labor of love, I am sure, but it was nonetheless a difficult task, for which Father Geiger deserves much credit. That is why the Academy is proud to present this, the first volume of its Bibliographical Series. Fr. Maynard has divided the documents, transcripts and photostats of the Santa Barbara Mission Archives into six sections and lists them 205 206BOOK REVIEWS chronologically according to this division, with appropriate explanations for each item. Section One lists the documents (404 of them) of the "Junípero Serra Collection, 1713 to the Present Time". The original archive was in the hands of Fr. Junípero Serra until his death in 1784. With the gradual secularization and confiscation of the California missions in the early nineteenth century, more and more documents came to Santa Barbara, the only California mission to remain permanently under Franciscan control to the present day. These official papers, mostly letters, form the Junípero Serra Collection. The second Section is called "California Mission Documents, 16401853 ". It forms by far the largest part of the Calendar, listing 1,682 items, which are concerned with mission history of California in general, as distinguished from Serra documents. Because of the chronological listing, it is possible to follow the progressive steps of disintegration which the California missions were made to suffer. From 1853 to 1885 Aiission Santa Barbara was an Apostolic College for training missionaries. Section Three, "Documents of the College of Our Lady of Sorrows at Santa Barbara" treats of this college. The items listed (756) are mostly private or quasi-private ecclesiastical documents, of interest mainly to Franciscans and church authorities. Section Four is entitled "Reports, Statistical Tables, Lists, Etc." and covers the period from the beginning to 1934, during which years the Santa Barbara friary was successively an Indian mission, an Apostolic College, a convent belonging to the Sacred Heart Franciscan Province (1885-1916) of Saint Louis, Missouri, and finally one of the principal convents of the Franciscan Province of Santa Barbara (1916- ). Included in this section are 27 valuable lists of missionaries who worked in California during the years 1796 to 1821. General and special reports (informes) on...

Obituaries

THE news of Vice-Chancellor Adami's death came as a great shock to his personal friends, and no man had more: for so great was his passion for pleasant intercourse, and his enjoyment of human fellowship, that he sought and made firm friendships where other men would have only multiplied acquaintances. To meet him was a pleasure which he always actively developed, striking sparks from stones, and even finding entertainment in dullards. Doubtless it was partly this side of his character which found satisfaction in the very onerous post of vice-chancellor in the midst of this busily employed provincial city: a post which he filled with distinction, and with a grace which few could imitate. Not very different was that other interest which could leave no medical problem untouched, and carried him, enthusiastically always, through the wide-spread fields of knowledge in the subject of which he was a master, ever curious to meet new developments and always with the firm hand which grasped what others were satisfied with merely touching.