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Biomedical subjects

N Hirai

Publications and source records attributed to N Hirai.

At least 127 records · Page 7Linked to original sources
PubMed1984

[A biological rhythm in a patient with normal pressure hydrocephalus--comparative studies in pre- and postoperative patients by a polygraphy].

The authors had studies the correlation between the appearance of the pressure waves and the level of the sleep in pre- and postoperative patients with normal pressure hydrocephalus (NPH). The changes from preoperative findings to postoperative ones were discussed in detail with the relation of the pathophysiological state in these patients. Seventeen patients were evaluated for the suspected diagnosis of the disease of NPH. Thirteen patients of them were treated with ventriculo-peritoneal shunts. Four representative cases among them were evaluated by pre- and postoperative polygraphic studies. A polygraphic overnight study includes a monitoring of an intracranial pressure (ICP), electroencephalography (EEG), electrooculography (EOG), respiratory movement and electromyography (EMG). Each data was recorded for the analysis on data recorder using a computer system. A pressure waves (largely B type) appeared accompanied with an apnea at a resting state (so-called sleep) of each patients. An arousal response in EEG was also observed in the raising period of the pressure waves. At the peak respiration was resumed with transient activities in EMG and continued to the disappearance of the pressure wave. Pressure waves were observed frequently and continually in hours in the resting state of these patients. As a result the level of sleep alternated frequently between an awake stage and a stage 1, including extremely rare appearance of stage 2. In short, the level of sleep was frequently interrupted by the appearance of the pressure waves and apneas. Such pathological states of patient's sleep were involved in the entity of the sleep apnea syndrome.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1983

Vestibular afferent inputs to lobules I and II of the cerebellar anterior lobe vermis in the cat.

Vestibular nerve stimulation evoked mossy fiber responses in lobule I and a part of lobule II of the cerebellar cortex in the anesthetized cat. The latencies of the N2 and N3 potentials were in the range of 1.7-2.0 and 3.2-5.0 ms, respectively. The contribution of both primary and secondary vestibular neurons in producing these responses were indicated by electrophysiological methods.

Afferent Pathways↗
PubMed1983

The vestibulo-ocular reflex arc in the newborn kitten. An electrophysiologic investigation.

Field potentials and postsynaptic potentials were recorded in the vestibular and abducens nuclei and neurons following vestibular nerve stimulation in anesthetized newborn kittens (within 72 h after birth). Stimulation of the ipsilateral vestibular nerve evoked an initial P wave and an N1 field potential in the vestibular nuclei. No N2 potential was evoked. Latencies of the peak of the P wave, the onset and the peak of the N1 potential were 0.99 +/- 0.16 ms, 1.66 +/- 0.18 ms, and 2.51 +/- 0.23 ms, respectively. Ipsilateral vestibular nerve stimulation evoked monosynaptic excitatory postsynaptic potentials (EPSPs) and polysynaptic inhibitory postsynaptic potentials (IPSPs) in vestibular nuclear neurons. Stimulation of the contralateral vestibular nerve evoked polysynaptic IPSPs in vestibular nuclear neurons. In abducens motoneurons, ipsilateral vestibular nerve stimulation evoked monosynaptic EPSPs and disynaptic IPSPs; contralateral vestibular nerve stimulation produced disynaptic EPSPs. We conclude that short circuit pathways of the vestibulo-vestibular and vestibulo-ocular reflex arc are present in the kitten already at birth.

Abducens Nerve↗
PubMed1982

Branching pattern and properties of vertical- and horizontal-related excitatory vestibuloocular neurons in the cat.

1. The axonal trajectories of excitatory vestibuloocular neurons and their synaptic contacts with extraocular motoneurons were studied by means of spike-triggered signal averaging and microstimulation techniques. A majority of the excitatory neurons related to the vertical semicircular canals were located in the border of the descending and medial nuclei and the rostral half of the descending nucleus. 2. Individual vestibuloocular neurons activated by stimulation of the ampullary nerve of the anterior semicircular canal excited motoneurons within both the contralateral inferior oblique and contralateral superior rectus motoneuron pools. 3. Individual vestibuloocular neurons receiving input from the ampullary nerve of the posterior semicircular canal excited motoneurons in both the contralateral trochlear nucleus and contralateral inferior rectus motoneuron pools. The branching pattern of single vestibuloocular neurons activated by the anterior and posterior canals probably underlies conjugate eye movement during vertical head rotation. 4. Time to peak and shape indices of unitary excitatory postsynaptic potentials (EPSPs) suggested that the location of the synaptic contact of vestibuloocular neurons was on the soma or proximal dendrites of the target extraocular motoneurons. 5. In contrast, we did not find conclusive evidence that single vestibuloocular neurons receiving input from the horizontal semicircular canal give off axon collaterals to motoneurons innervating both the contralateral lateral rectus and the ipsilateral medial rectus muscles. Projection of horizontal vestibuloocular neurons to motoneurons supplying individual muscles might be useful for convergence during horizontal head movement.

Abducens Nerve↗
PubMed1981

Properties of secondary vestibular neurons fired by stimulation of ampullary nerve of the vertical, anterior or posterior, semicircular canals in the cat.

Experiments on cats were performed to study the pathway and location of the secondary vestibulo-ocular neurons in response to stimulation of the ampullary nerves of the vertical, anterior or posterior, semicircular canals. Experiments on the medial longitudinal fasciculus transection disclosed that vertical canal-evoked, disynaptic excitation and inhibition were transmitted to the extraocular motoneurons through the contra- and ipsilateral medial longitudinal fasciculus respectively. Secondary vestibular neurons, which receive input from the ampullary nerve of the vertical semicircular canals and send their axons to contralateral medial longitudinal fasciculus, were intermingled in the rostral half of the descending and lateral part of the medial vestibular nuclei. A direct excitatory connection of some of these neurons to the target extraocular motoneurons was confirmed by means of a spike-triggered signal averaging technique. It was also found that neurons activated by antidromic stimulation of ipsilateral medial longitudinal fasciculus were located in the superior vestibular nucleus, some of which made direct inhibitory connections to the target extraocular motoneurons. Both excitatory and inhibitory vestibuloocular neurons made synaptic contact in about half of the impaled target motoneurons.

Animals↗
PubMed1981

Cervical input to vestibulocollic neurons.

Extracellular responses of vestibulospinal neurons projecting to neck segments (vestibulocollic neurons) to stimulation of cervical afferents were studied in decerebellate cats anesthetized with chloralose or decerebrated intercollicularly. These neurons were antidromically activated by microstimulation in the C2 ventral horn ipsilateral or contralateral to the vestibular nuclei. Contralateral neck afferents produce in vestibulocollic neurons the same responses they produce in other vestibulo-spinal neurons, although the response (early excitation, inhibition) which predominates varies with type of preparation. In intercollicular decerebrate cats, the main effect of stimulating the contralateral C2 ganglion was inhibition (latency greater than or equal to 6 msec), often followed by late excitation. Early excitation, at a latency less than 6 msec, was rarely seen, although it occurred in half the vestibulospinal neurons projecting to the cervical enlargement. In contrast to the results in decerebrate cats, stimulation of the contralateral C2 ganglion produced early excitation in over one-third of the vestibulocollic neurons studied in chloralose-anesthetized cats. Results on vestibulocollic neurons were similar whether the cells projected ipsilaterally or contralaterally, or whether or not the cells also projected to the cervical enlargement (branching neurons). The influence of cervical afferents on vestibulocollic neurons demonstrates supraspinal paths by which cervical afferents may act upon the neck and might modify vestibular reflexes of the neck.

Afferent Pathways↗
PubMed1980

Axonal branching in the trochlear and oculomotor nuclei of single vestibular neurons activated from the posterior semicircular canal nerve in the cat.

Axonal branches of single vestibular neurons activated by stimulation of the ampullary nerve of the posterior semicircular canal in the cat were studied by means of local antidromic stimulation in the trochlear and the oculomotor nucleus. These vestibulo-ocular neurons were located in the rostral half of the descending vestibular nucleus and the lateral part of the medial vestibular nucleus. The majority of vestibulo-ocular neurons projecting to the inferior rectus motoneuron pool in the contralateral oculomotor nucleus was activated antidromically from the contralateral trochlear nucleus as well. This suggests that axonal branches of a single vestibular neuron project to both nuclei.

Action Potentials↗
PubMed1980

Circadian locomotor rhythms of the night monkey (Aotus trivirgatus) under constant light conditions.

Three quantities, circadian period, amount of activity, and ratio of activity time to rest time of circadian locomotor rhythms in the night monkey (Aotus trivirgatus), were measured under the influence of two constant light intensities. When light intensity was increased from < 0.1 to 100 lx, the circadian period increased, showing that Aschoff's rule can be valid for this dark active primate species. The ratio of activity time to rest time was shorter under 100 lx than under < 0.1 lx of continuous light, but a consistent change in the amount of activity did not occur between both light intensities.

Animals↗
PubMed1979

Comparison of dynamic properties of canal-evoked vestibulospinal reflexes of the neck and forelimb in the decerebrate cat.

The responses of neck and forelimb muscles to sinusoidal polarization of the horizontal canal nerve were compared by recording from these muscles simultaneously. Contrary to results on the vestibulocollic reflex, the central phase lag in the vestibulo-forelimb reflex increases with increasing frequencies up to 3 Hz. This demonstrates a difference in the organization of vestibular-driven pathways to neck and forelimb muscles.

Animals↗
PubMed1979

Analysis of vestibulocollic reflexes by sinusoidal polarization of vestibular afferent fibers.

1. Canal vestibular-neck (vestibulocollic) reflexes have been studied in decerebrate cats by applying modulated polarizing current to individual ampullary nerves, usually the horizontal nerve. 2. Computer-generated stimuli sometimes consisted of sine or square waves at frequencies of 0.01--5 Hz. More often we used a compound wave form of nine superimposed sinusoids within an available frequency range of 0.009--6.11 Hz. The frequencies used were odd, relatively prime multiples of a base frequency selected to minimize distortion or interaction of responses. The response to each of the nine stimulating frequencies could be obtained in subsequent data analysis. 3. Responses to these stimuli were studied by recording the EMG of contralateral neck muscles and extracellular activity of second-order neurons. These neurons were identified by their monosynaptic responses to single-shock stimulation of ampullary nerves. 4. EMG was modulated sinusoidally. Below 0.1 Hz the response was variable, most likely due to differences in the preparations. In the frequency range of 0.1--0.4 Hz there was usually a phase lag, which decreased with incresing frequency and often reversed to a lead at 3 and 6 Hz. Gain decreased from the lowest frequencies, occasionally with an upturn at 3 or 6 Hz. 5. Second-order neuron firing was approximately in phase with the stimulus at the lowest frequencies. Phase advanced with increasing frequency to a lead of 30--50 degrees at 6 Hz. Gain generally increased with frequency. 6. By recording simultaneously from muscle and from second-order neurons, or by comparing the mean behavior of the two, it was possible to determine the central phase lag and gain of the vestibulocollic reflex. The lag was variable at low frequencies, had an average of 50 degrees at 0.18 Hz, and decreased to 20 degrees at 6 Hz. These results are comparable to those obtained by others using natural stimulation at frequencies of 1.0 Hz and below, and provide new information about the behavior of the central processer at higher frequencies. 7. The medial vestibulospinal tract (MVST), which contains the axons of crossed second-order vestibular neurons, was transected in six experiments. In agreement with previous workers there was no effect on phase at frequencies up to 0.4 Hz. There was also no selective effect of phase or gain at the higher frequencies. This shows that the disynaptic pathways in the MVST do not play any role that cannot be taken over by parallel pathways.

Animals↗