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A A Perachio

Publications and source records attributed to A A Perachio.

At least 19 recordsLinked to original sources
PubMed1992

A model for the characterization of the spatial properties in vestibular neurons.

Quantitative study of the static and dynamic response properties of some otolith-sensitive neurons has been difficult in the past partly because their responses to different linear acceleration vectors exhibited no "null" plane and a dependence of phase on stimulus orientation. The theoretical formulation of the response ellipse provides a quantitative way to estimate the spatio-temporal properties of such neurons. Its semi-major axis gives the direction of the polarization vector (i.e., direction of maximal sensitivity) and it estimates the neuronal response for stimulation along that direction. In addition, the semi-minor axis of the ellipse provides an estimate of the neuron's maximal sensitivity in the "null" plane. In this paper, extracellular recordings from otolith-sensitive vestibular nuclei neurons in decerebrate rats were used to demonstrate the practical application of the method. The experimentally observed gain and phase dependence on the orientation angle of the acceleration vector in a head-horizontal plane was described and satisfactorily fit by the response ellipse model. In addition, the model satisfactorily fits neuronal responses in three-dimensions and unequivocally demonstrates that the response ellipse formulation is the general approach to describe quantitatively the spatial properties of vestibular neurons.

Animals↗
PubMed1992

Changes in monkey horizontal semicircular canal afferent responses after spaceflight.

Extracellular responses from single horizontal semicircular canal afferents in two rhesus monkeys were studied after recovery from a 14-day biosatellite (COSMOS 2044) orbital spaceflight. On the 1st postflight day, the mean gain for 9 different horizontal canal afferents, tested using one or several different passive yaw rotation waveforms, was nearly twice that for 20 horizontal canal afferents similarly tested during preflight and postflight control studies. Adaptation of the afferent response to passive yaw rotation on the 1st postflight day was also greater. These results suggest that at least one component of the vestibular end organ (the semicircular canals) is transiently modified after exposure to 14 days of microgravity. It is unclear whether the changes are secondary to other effects of microgravity, such as calcium loss, or an adaptive response. If the response is adaptive, then this report is the first evidence that the response of the vestibular end organ may be modified (presumably by the central nervous system via efferent connections) after prolonged unusual vestibular stimulation. If this is the case, the sites of plasticity of vestibular responses may not be exclusively within central nervous system vestibular structures, as previously believed.

Adaptation, Physiological↗
PubMed1992

Role of irregular otolith afferents in the steady-state nystagmus during off-vertical axis rotation.

1. During constant velocity off-vertical axis rotations (OVAR) in the dark a compensatory ocular nystagmus is present throughout rotation despite the lack of a maintained signal from the semicircular canals. Lesion experiments and canal plugging have attributed the steady-state ocular nystagmus during OVAR to inputs from the otolith organs and have demonstrated that it depends on an intact velocity storage mechanism. 2. To test whether irregularly discharging otolith afferents play a crucial role in the generation of the steady-state eye nystagmus during OVAR, we have used anodal (inhibitory) currents bilaterally to selectively and reversibly block irregular vestibular afferent discharge. During delivery of DC anodal currents (100 microA) bilaterally to both ears, the slow phase eye velocity of the steady-state nystagmus during OVAR was reduced or completely abolished. The disruption of the steady-state nystagmus was transient and lasted only during the period of galvanic stimulation. 3. To distinguish a possible effect of ablation of the background discharge rates of irregular vestibular afferents on the velocity storage mechanism from specific contributions of the dynamic responses from irregular otolith afferents to the circuit responsible for the generation of the steady-state nystagmus, bilateral DC anodal galvanic stimulation was applied during optokinetic nystagmus (OKN) and optokinetic afternystagmus (OKAN). No change in OKN and OKAN was observed.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1991

Effect of T2 spinal transection on compensation of horizontal canal related activity in the medial vestibular nucleus following unilateral labyrinth ablation in the decerebrate gerbil.

The effects of spinal transection at T2 upon static and dynamic responses of type I and II neurons in the medial vestibular nucleus after vestibular compensation were investigated in decerebrate Mongolian gerbils (Meriones unguiculatus). Spinal transection in compensated animals resulted in bilaterally depressed spontaneous activity and asymmetry in the response gain of type I neurons, suggesting that tonic spinal inputs contribute to vestibular compensation through effects upon type I neurons.

Adaptation, Physiological↗
PubMed1990

Compensation of horizontal canal related activity in the medial vestibular nucleus following unilateral labyrinth ablation in the decerebrate gerbil. I. Type I neurons.

The spontaneous activity and dynamic responses to two frequencies (1.3 and 0.13 Hz) of sinusoidal angular horizontal head acceleration of type I neurons in the medial vestibular nucleus were recorded bilaterally in decerebrate Mongolian gerbils (Meriones unguiculatus) under three experimental conditions; normal labyrinth intact, acutely following unilateral labyrinthine lesion, and four to seven weeks following labyrinthine lesion. The mean spontaneous activity and number of detected type I neurons decreased immediately ipsilateral to the lesion but recovered significantly with time. In contrast, spontaneous activity on the contralateral side increased during compensation following hemilabyrinthectomy. The mean response gains at both frequencies of head oscillation were depressed bilaterally and asymmetrically acutely following the lesion such that the response gain of cells on the intact side exceeded that of the neurons recorded on the injured side. After compensation the number of detected type I neurons on the side ipsilateral to the injury increased but remained below normal levels. The mean gains remained depressed but became symmetric with compensation as a result of improvement in the response of ipsilateral neurons. The phase of responses were significantly advanced in the compensated animals. Although response gain is not fully restored, the linearity of the dynamic modulation in compensated animals is improved as evidenced by a continuous modulation of the increased spontaneous activity of neurons contralateral to the hemilabyrinthectomy. It is proposed that this effect is related to the concurrent improvement in the linearity of the horizontal vestibulo-ocular response. Electrical cathodal polarization of the vestibular nerve ipsilateral to the ablated labyrinth was utilized to investigate the relationship between recovery of spontaneous activity and dynamic function. Acutely following hemilabyrinthectomy, cathodal polarization restored activity in second-order type I neurons to near normal levels but their response gain to head rotation remained depressed. Similar galvanic stimulation in compensated animals also elevated ipsilateral spontaneous activity. As in the acute preparation, such stimulation did not modify the response gain or phase. Thus, the improvement in response of type I neurons in the compensated gerbil was not a direct consequence of restoration of spontaneous activity on the side of the injury.

Animals↗
PubMed1990

Compensation of horizontal canal related activity in the medial vestibular nucleus following unilateral labyrinth ablation in the decerebrate gerbil. II. Type II neurons.

The spontaneous activity and dynamic responses to sinusoidal horizontal head angular acceleration of type II horizontal semicircular canal related neurons in the medial vestibular nucleus (MVN) were recorded bilaterally in decerebrate Mongolian gerbils (Meriones unguiculatus) under three experimental conditions: normal labyrinths intact, acutely following unilateral labyrinthine lesion, and four to seven weeks following labyrinthine lesion. The number of type II neurons detected contralateral to the lesion was greatly reduced both in the acutely hemilabyrinthectomized animals and following compensation. The gain of the responses was depressed bilaterally acutely following the lesion. A greater reduction in response gain was noted in cells contralateral to the lesion. The gain of the contralateral type II responses increased with time such that in the compensated animal bilaterally symmetric gains were recorded. While the significant changes which occur in the gain of type II neurons with recovery from peripheral vestibular lesions can largely be attributed to type I neurons on the other side of the midline, changes in type I neurons were not entirely reflected in the type II population. The spontaneous activity of type II neurons did not undergo any significant changes following the labyrinthine lesion. We present a model utilizing the dynamic responses to estimate the functional recovery of commissural connections in compensated animals. The overall gain of the contralateral type I to ipsilateral type I commissural polysynaptic pathway appears to improve, while the efficacy in the reverse direction remains depressed, suggesting that modifications in commissural connections, particularly involving the type II to type I connections within the MVN on the injured side, mediate aspects of behavioral recovery.

Animals↗
PubMed1989

A quantitative study of the vestibular commissures in the gerbil.

Direct commissural connections between the bilateral vestibular nuclear complexes (VNC) were investigated in the gerbil using ionophoretic injections of horseradish peroxidase into individual vestibular nuclei. Labelled commissural neurons were counted, the cell counts adjusted by the relative nuclear volume, and the results treated quantitatively. The medial nucleus (MVN) contained the greatest number of commissural neurons. The MVN projected to each of the contralateral vestibular nuclei, but most strongly to the contralateral MVN and superior (SVN) nucleus. The SVN projected modestly to the contralateral VNC. Commissural connections of the descending nucleus were weak. Commissural afferents to the MVN were topographically organized. The crossed fastigiovestibular projection was also investigated.

Animals↗
PubMed1989

Identification of vestibular efferent neurons in the gerbil: histochemical and retrograde labelling.

The efferent neurons of the gerbil vestibular system were investigated by retrograde tracing techniques and cytochemical staining for acetylcholinesterase (AChE), choline acetyltransferase (ChAT) and a number of peptides. The location, bilateral distribution, cell area and number of neurons in two identified groups of retrogradely labelled cells were described and quantified. The larger of the two groups was located dorsolateral to the facial nerve genu, ventral and medial to the vestibular nuclei. Unilateral tracer injection in the vestibular end organs labelled cells bilaterally in this and the smaller group, which was located immediately ventral to the genu. No cells were found that individually projected bilaterally to both labyrinths. After injections of horseradish peroxidase (HRP) in the utricle or saccule, significantly more cells were located on the contralateral side of the brainstem. The average (+/- SD) cross sectional area of labelled cell bodies associated with the otolith organs was 259.8 (+/- 75.2) microns 2. ChAT immunoreactive and AChE positive cells were found in an area coextensive with the location of the dorsal efferent group. In double-labelling studies, cell bodies in the same group that had been retrogradely labelled with a utricular injection of HRP, were immunocytochemically stained for calcitonin gene-related peptide and met-enkephalin. In contrast, the ventral group of efferents did not have cells that were cytochemically stained for either of the acetylcholine-related enzymes or either peptide. The significance of the existence of peptidergic vestibular efferent neurons is discussed.

Acetylcholinesterase↗
PubMed1989

Projections from the sacculus to the cochlear nuclei in the Mongolian gerbil.

The projections of the saccule, an otolith end organ, to the cochlear nuclei were studied using both transganglionic transport and intracellular injection techniques. Labeled fibers and terminals were observed in the anterior and posterior portions of the ventral cochlear nucleus and the dorsal cochlear nucleus. Most terminals were present in the granule cell domain, especially in the subpeduncular corner between the anteroventral cochlear nucleus and the floccular peduncle of the cerebellum. It has been hypothesized that the cochlea in mammals may have developed phylogenetically from the saccule. The projections from the saccule to the cochlear nuclei were investigated in a mammalian species, the Mongolian gerbil, in an attempt to obtain initial information supporting or refuting this hypothesis. The presence of an otolith end organ projection to the cochlear nuclei in rodents should encourage comparative studies in additional aspects of the evolution of the auditory system.

Animals↗
PubMed1986

Distribution of vestibular afferents that innervate the sacculus and posterior canal in the gerbil.

The central distribution of afferents that innervate the macula of the saccule and the crista of the posterior canal was assessed in the gerbil following the direct injection of horseradish peroxidase (HRP) separately into the sensory neuroepithelia of each peripheral receptor organ. Ganglion cells innervating the posterior canal were located in the caudal part of the inferior ganglion, while those cells innervating the saccule were located in the rostral part of the inferior ganglion, scattered in the superior ganglion, and concentrated at the junction (isthmus) between the two. The paths of the central axons of these two groups of ganglion cells through the vestibular root and their division into ascending or descending pathways were similar. However, the distributions of their terminals were different. The posterior canal projected to medial parts of the vestibular nuclear complex. Terminals were found in the medial and superior vestibular nuclei. The posterior canal also projected to the uvula of the cerebellum. The saccule projected to more lateral-lying brainstem areas. Terminal fields were located in the lateral and descending vestibular nuclei and cell group y. Saccule projections outside the vestibular complex were observed to the lateral cuneate nucleus, the N. gigantocellularis, and the cerebellar cortex. Of the eight areas receiving primary afferent projections from these two organs, only within the medial and descending vestibular nuclei and the cerebellar cortex were overlapping projections observed.

Animals↗
PubMed1986

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Communication↗
PubMed1985

Spontaneous and driven responses of semicircular canal primary afferents in the unanesthetized pigeon.

Spontaneous activity from 120 vestibular semicircular canal (SC) primary afferents and driven responses from 20 SC primary afferents to 2.3-decade bandwidth (0.029-6.152 Hz) sum of sinusoidal angular rotations were characterized in 10 unanesthetized pigeons. The results were compared with those previously gathered from barbiturate anesthetized pigeons. The average spontaneous mean firing rate (MFR) of SC primary afferents in unanesthetized pigeons was found to be 168 impulses per second (I/s), n = 120, and is approximately 80% higher than that for SC primary afferents in anesthetized pigeons [93 I/s, n = 149 (Ref. 9) and 92 I/s, n = 124 (Ref. 22)]. The spontaneous discharge of SC primary afferents from unanesthetized pigeons was classified according to the coefficient of variation (CV) of 512-1,024 interspike intervals (ISIs) into regular (CV less than 0.1), intermediate (0.1 less than or equal to CV less 0.4), and irregular (0.4 less than or equal to CV) categories. The percentages of SC primary afferents falling within each CV category were similar for unanesthetized and anesthetized pigeons (22). The relation between the spontaneous mean ISI and its standard deviation (SD) for SC primary afferents in the unanesthetized pigeon is best described by a power function model, which provides a significantly better fit than does a linear model. The parameters of this power function model are similar for SC primary afferents in unanesthetized and anesthetized pigeons (10). The spontaneous ISIs of individual SC primary afferents in the unanesthetized pigeon were found to be distributed either normally, log-normally, or according to the first passage time of the Wiener-Levy (WL) process. The gain of anterior SC primary afferents at 0.25 Hz is similar for anesthetized (2.93 I X s-1 X deg-1 X s-1, n = 14) (11) and for unanesthetized (3.01 I X s-1 X deg-1 X s-1, n = 14) pigeons. Bode plots constructed from the responses to sum sinusoidal angular accelerations reveal that SC primary afferents in unanesthetized pigeons display a phase lead and gain enhancement at frequencies between 0.6 and 6 Hz.(ABSTRACT TRUNCATED AT 400 WORDS)

Action Potentials↗
PubMed1985

The monkey vertical vestibuloocular response: a frequency domain study.

We studied the vertical vestibuloocular response (VVOR) in seven cynomolgus monkeys. Eye movements were measured by the search coil method. We tested the monkeys by rotating them about their interaural axis, which was colinear with gravity. Each monkey was tested by using a standard rotational paradigm that consisted of discrete sinusoidal oscillations at three frequencies (0.01, 0.1, and 1.0 Hz) and six peak velocities (5, 10, 30, 60, 100, and 150 degrees/S). The standard rotational paradigm was applied twice for each of two conditions. The first condition (EOD) consisted of rotations with the animal's vision occluded; the second condition (EOL) consisted of rotations during which the animal was allowed to view a well-lighted room. Using various statistics, we tested the linearity of the sinusoidal slow-phase velocity component of the VVOR. The largest nonlinearity found was a skewness of approximately 14% in the waveform of f = 0.01 Hz. We did not find an amplitude asymmetry between slow-phase eye velocity upward (SPVU) and slow-phase eye velocity downward (SPVD) greater than 6% for any oscillation. Nonlinearities present in the VVOR during testing with vision occluded (EOD condition) disappeared with the addition of vision (EOL condition). Intensity function plots [peak slow-phase eye velocity vs. peak rotator (head) velocity] revealed that at f = 0.01, 0.1, and 1.0 Hz over the intensity range from +/-30 degrees/s to +/-150 degrees/s, the VVOR is highly linear. The lowest correlation coefficient associated with linear regressions of the intensity function data at each frequency was 0.99. Analyses of frequency response functions for the bandwidth f = 0.01 to 1.0 Hz, revealed the following: 1) mean amplitude ratio (AR) and phase overlap for four different stimulus intensities (30, 60, 100, and 150 degrees/s); 2) no significant differences (Mann-Whitney U test, P greater than 0.05) between any AR or phase value for mean peak SPVU and mean peak SPVD re appropriately directed head velocity; 3) no significant differences (Mann-Whitney U test, P greater than 0.05) between AR and phase values for animals tested and then retested 1 mo later with five intervening standard rotational paradigms; 4) a large effect of vision in producing a VVOR with near-unity gain and near-perfect phase compensation.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1985

Effect of spinal cord transection on spontaneous activity recorded from type I neurons of the medial vestibular nucleus in compensated hemilabyrinthectomized gerbils.

Spontaneous activity was recorded from type I neurons of the medial vestibular nuclei (MVN) in unanesthetized, decerebrate gerbils to determine the effect of spinal cord transection on compensation following labyrinthectomy. Immediately after labyrinthectomy there was an increase in activity of type I neurons on the intact side and an absence of activity on the injured side. Following compensation from labyrinthectomy, the distribution and activity rates approximated those of nonlabyrinthectomized animals. Spinal cord transection resulted in an increase in activity in type I MVN neurons contralateral to the labyrinthectomy in compensated animals and bilaterally in nonlabyrinthectomized animals. These results illustrate that type I neurons apparently are under an indirect inhibitory control from both the contralateral labyrinth and the spinal cord. In compensated animals spinal cord inhibition exists only on the intact side. This suggests that the symmetry in type I activity bilaterally in the compensated animal is in part the result of asymmetric spinal cord input.

Animals↗