PubMed Health⌕ Search

Biomedical subjects

R Boyle

Publications and source records attributed to R Boyle.

13 recordsLinked to original sources
PubMed1992

Inputs from regularly and irregularly discharging vestibular nerve afferents to secondary neurons in squirrel monkey vestibular nuclei. III. Correlation with vestibulospinal and vestibuloocular output pathways.

1. A previous study measured the relative contributions made by regularly and irregularly discharging afferents to the monosynaptic vestibular nerve (Vi) input of individual secondary neurons located in and around the superior vestibular nucleus of barbiturate-anesthetized squirrel monkeys. Here, the analysis is extended to more caudal regions of the vestibular nuclei, which are a major source of both vestibuloocular and vestibulospinal pathways. As in the previous study, antidromic stimulation techniques are used to classify secondary neurons as oculomotor or spinal projecting. In addition, spinal-projecting neurons are distinguished by their descending pathways, their termination levels in the spinal cord, and their collateral projections to the IIIrd nucleus. 2. Monosynaptic excitatory postsynaptic potentials (EPSPs) were recorded intracellularly from secondary neurons as shocks of increasing strength were applied to Vi. Shocks were normalized in terms of the threshold (T) required to evoke field potentials in the vestibular nuclei. As shown previously, the relative contribution of irregular afferents to the total monosynaptic Vi input of each secondary neuron can be expressed as a %I index, the ratio (x100) of the relative sizes of the EPSPs evoked by shocks of 4 x T and 16 x T. 3. Antidromic stimulation was used to type secondary neurons as 1) medial vestibulospinal tract (MVST) cells projecting to spinal segments C1 or C6; 2) lateral vestibulospinal tract (LVST) cells projecting to C1, C6; or L1; 3) vestibulooculo-collic (VOC) cells projecting both to the IIIrd nucleus and by way of the MVST to C1 or C6; and 4) vestibuloocular (VOR) neurons projecting to the IIIrd nucleus but not to the spinal cord. Most of the neurons were located in the lateral vestibular nucleus (LV), including its dorsal (dLV) and ventral (vLV) divisions, and adjacent parts of the medial (MV) and descending nuclei (DV). Cells receiving quite different proportions of their direct inputs from regular and irregular afferents were intermingled in all regions explored. 4. LVST neurons are restricted to LV and DV and show a somatotopic organization. Those destined for the cervical and thoracic cord come from vLV, from a transition zone between vLV and DV, and to a lesser extent from dLV. Lumbar-projecting neurons are located more dorsally in dLV and more caudally in DV. MVST neurons reside in MV and in the vLV-DV transition zone.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1991

Morphological correlates of response dynamics and efferent stimulation in horizontal semicircular canal afferents of the toadfish, Opsanus tau.

1. We used the intraaxonal labeling technique to study correlations between the terminal dendritic morphology of horizontal semicircular canal primary afferents and their response dynamics to sinusoidal head rotation and combined electrical stimulation of central efferent vestibular neurons. Thirty-eight canal afferents were identified by their sensitivity and phase of response to rotation between 0.1 and 1.0 Hz (+/- 10 degrees/s) and were subsequently labeled with horseradish peroxidase or biocytin. The afferent's dendritic field and synaptic specializations in the neuroepithelium of the crista were examined under light microscopy. 2. Rate and regularity of background discharge of the afferent were not correlated with its axon diameter or relative location of its dendritic field in the crista. 3. Response sensitivity of the afferent to rotation was correlated both with the relative location of its dendritic field in the crista and with the number of terminal endings it possesses. Afferents having low sensitivities, slow dynamics, and few terminal endings supply the peripheral portions of the crista; afferents with higher sensitivities, faster dynamics, and greater number of terminal endings supply the more central portions. It is suggested that the differences in sensitivity among the afferents reflect principally the variations in both the cupular dynamics along the crista and the number of possible hair cell contact sites in the neuroepithelium. 4. Response phase of the afferent was correlated only with the extent of its dendritic processes along the transverse axis of the crista. Afferents having transversely oriented dendritic fields had less phase lags relative to acceleration than did those having a more longitudinally oriented dendritic field. 5. Efferent stimulation produced a change in both the afferent's discharge rate and its response sensitivity to rotation. Afferents discharge rate and its response sensitivity to rotation. Afferents having a centrally located dendritic field and acceleration afferents, defined by their response to rotation, were the most affected by efferent stimulation. These results suggest that efferent innervation is either directed toward, or most efficacious in, the central regions of the crista and that it may select specific hair cell-afferent complexes.

Animals↗
PubMed1979

[Reciprocal responses to macular stimulation of neurons localized in the region of the forelimb and of the hindlimb of Deiters nucleus].

In decerebrate cats with cerebellum intact the frequency response of 102 neurons located within the lateral vestibular nucleus (NVL) to sinusoidal stimulation of vestibular receptors was analyzed. Positional sensitive units, showing a reciprocal pattern of response to lateral tilting characterized by an excitation during ipsilateral and a depression during contralateral tilt, were equally found in the rostroventral (forelimb) and dorsocaudal (hindlimb) divisions of the NVL. No unit was found to be excited during both ipsilateral and contralateral tilts. A comparison between these findings and those reported in cerebellectomized preparations indicates that the reciprocal pattern of response to tilt of neurons, particularly located in the hindlimb region of the NVL, depends upon the anatomical integrity of the cerebellum.

Acoustic Maculae↗
PubMed1979

Reciprocal responses to tilt of neurones within both fore- and hindlimb regions of Deiters' nucleus.

In decerebrate cats with cerebellum intact the frequency response of 102 neurons located within the lateral vestibular nucleus (LVN) to sinusoidal stimulation of vestibular receptors was analyzed. Positional sensitive units, showing a reciprocal pattern of response to lateral tilting, characterized by an excitation during ipsilateral and a depression during contralateral tilt, were equally found in the rostroventral (forelimb) and dorsocaudal (hindlimb) divisions of the LVN. No unit was found to be excited during both ipsilateral and contralateral tilts. A comparison between these findings and those reported in cerebellectomized preparations indicates that the reciprocal pattern of response to tilt of neurons, particularly located in the hindlimb region of the LVN, depends upon the anatomical integrity of the cerebellum.

Action Potentials↗
PubMed1979

Factors likely to affect the development of multiple sclerosis in patients presenting with optic neuritis in a tropical and subtropical area.

The relationship between optic neuritis (ON) and multiple sclerosis (MS) in a subtropical climate is examined. 105 cases of ON were followed for varying periods over 26 years. The factors studied included place of birth, sex, age at onset, presence of recurrent ON, the interval to the onset of MS, and HLA antigen typing. 55% of cases developed evidence of definite MS. The majority of cases who went on to develop MS had their onset of ON between 21 and 40 years of age. The subtropical climate did not cause any significant variation in incidence. However those case who had HLA Bw4 appear to be protected from developing MS.

Adolescent↗
PubMed1977

Patterns of the use of benzodiazepines in Australia.

In six suburban areas of Sydney, chosen to provide a socioeconomic cross-section of the city, complete records of dispensing of benzodiazepine were collected over a four-week period. These drugs constituted 3.7% of all dispensing, female patients outnumbered males by 2.3:1, and 98% of patients were over 20 years of age. The predominance of females, and higher age groups was found in all the areas studied, but no socioeconomic correlation was detected in the use of the drugs. Analysis of national dispensing figures confirmed the higher consumption in higher age groups, and revealed no heterogeneity in per capita prescribing rates amongst the States.

Adolescent↗