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O J Grüsser

Publications and source records attributed to O J Grüsser.

At least 19 recordsLinked to original sources
PubMed2001

Tuning in caudal fastigial nucleus units during natural and galvanic labyrinth stimulation.

Neurons of the caudal fastigial nucleus were investigated by means of single unit recordings. Natural vestibular stimuli were applied as well as galvanic labyrinth polarization. One-third of the neurons showed a convergence of vertical and horizontal canals. More than 80% of the neurons responded to polarization of both the ipsilateral and contralateral canals (binaural responders). Most neurons had a limited response range. Two classes of neurons could be distinguished: up to 1 Hz responders and up to 10 Hz responders. In addition a group of fastigial cells showed a tuning within a small range of frequencies (sharp-tuning responders).

Action Potentials↗
PubMed2001

Saccades guided by somatosensory stimuli.

The accuracy of somatosensory saccades defined by proprioceptive cues with and without an additional tactile stimulus was investigated over a wide range of stimulus amplitudes in 16 normal subjects. The present results confirm that somatosensory saccades are less accurate and more variable than visual saccades. Accuracy was minimal for saccades directed to hand distances of 40-50 deg and increased for larger stimulus amplitudes. The additional application of a tactile cue on the fingertip was not found to influence the accuracy of somatosensory saccades significantly.

Adult↗
PubMed1999

Cortical areas activated by bilateral galvanic vestibular stimulation.

The brain areas activated by bilateral galvanic vestibular stimulation (GVS) were studied using functional magnetic resonance imaging. In six human volunteers, GVS led to activation in the region of the temporoparietal junction, the central sulcus, and the anterior interior intraparietal sulcus, which may correspond to macaque areas PIVC, 3aV, and 2v, respectively. In addition, activation was found in premotor regions of the frontal lobe, presumably analogous to areas 6pa and 8a in the monkey. Since these areas were not detected in previous studies using caloric vestibular stimulation, they could be related to the modulation of otolith afferent activity by GVS. However, the simple paradigm used did not allow separation of the otolithic and semicircular canal effects of GVS. Further studies must be performed to clarify the question of cortical representation of the otolithic information in the human and monkey brain.

Adult↗
PubMed1999

Sigma-optokinetic nystagmus in squirrel monkeys elicited by stationary stripe patterns illuminated by regular and random-interval flash sequences.

Eye position and angular velocity were measured in squirrel monkeys (Saimiri sciureus) by means of the electromagnetic scleral search-coil technique. Horizontal sigma-optokinetic nystagmus (sigma-OKN) was elicited by a stationary, stroboscopically illuminated, periodic, vertical-stripe pattern lining a vertical cylinder. The relationship between the mean slow-phase eye angular velocity, Ve, of sigma-OKN and the product of pattern period, Ps, and flash frequency, f(s), was determined. When Ve approximated k x Ps x f(s) (deg x s(-1)) and k was an integer > or = 1, the sigma-paradigm was fulfilled. Sigma-OKN could be evoked in different "modes", whereby k approximated 1, 2,...n. The sigma-OKN properties of squirrel monkeys were similar to those measured for sigma-OKN in the "stare" mode in man, with the exception of a long-lasting optokinetic afternystagmus (sigma-OKAN) appearing in the monkey. A considerable amount of temporal variability in flash sequence intervals ("temporal noise"), causing retinal error signals that interfered with the sigma-paradigm, was accepted by the visuo-motor system without interruption of sigma-OKN. This observation was explained by the operation of a short memory device for perception of visual motion. The internal gain, g(i), which relates the retinal "error" displacement velocity, Vr, and Ve depended, in turn, on Vr according to a function resembling the known relationship between neuronal activity of NOT (nucleus of the optic tract) nerve cells and Vr. This observation may be taken as direct proof that sigma-OKN can be explained by a centrally preprogrammed relationship between the retinal velocity, Vr, and the OKN slow-phase eye velocity, Ve. It is stipulated that the sum of Vr and efference copy signals generated in cortical or subcortical gaze centers is the essential component controlling the perceived velocity of the sigma-movement, whereby a short-term integrator plays a role for squirrel monkey sigma-OKN. When the flash frequency, f(s), was modulated periodically according to a sinewave or "triangular" function at a rate below 0.5 cycles x s(-1), Ve was found to respond with a corresponding modulation, provided the modulation amplitude did not exceed 50% of the mean flash rate. When the latter occurred, nonlinear responses could be observed. A similar response was found when the speed of "real" optokinetic stimuli was varied sinusoidally. Under these experimental conditions, however, the amplitude of the Ve variation yielded up to 1.0 approximately linear responses.

Animals↗
PubMed1998

Is there a vestibular cortex?

Very different areas of the primate cortex have been labelled as 'vestibular'. However, no clear concept has emerged as to where and how the vestibular information is processed in the cerebral cortex. On the basis of data from single-unit recordings and tracer studies, the present article gives statistical evidence of the existence of a well-defined vestibular cortical system. Because the data presented here have been verified in three different primate species, it can be predicted that a similar vestibular cortical system also exists in humans.

Animals↗
PubMed1998

Optokinetic reflex in squirrel monkeys after long-term monocular deprivation.

Horizontal optokinetic nystagmus (OKN) as well as neuronal response properties in the nucleus of the optic tract and the dorsal terminal nucleus of the accessory optic system (NOT-DTN) were investigated in three monocularly deprived squirrel monkeys. In two monkeys occlusion of one eye was performed at birth (early) and in the third after 7 weeks (late). In adulthood, in early deprived monkeys monocular horizontal OKN tested through the non-deprived eye was symmetrical and in no way different from normal, i.e. stimulation in the temporonasal and nasotemporal direction elicited equal and robust responses. OKN through the early occluded eye, however, was grossly abnormal with low gain and great variability in the consistency of nasotemporal and temporonasal slow phase eye movements. When in the late deprived monkey the non-deprived eye was occluded a strong spontaneous nystagmus developed despite the deprived eye viewing a stationary pattern. The slow phases were directed from nasal to temporal for the deprived eye. When tested through the non-deprived eye all neuronal responses of the NOT-DTN were normal. The deprived eye's influence on NOT-DTN neurons was extremely weak. No neuron with a moderate or even dominant input from the deprived eye was found after early deprivation. In the late deprived case the deficit was not as severe but still the non-deprived eye was clearly dominating the responses in all neurons tested. Velocity tuning of neurons tested through the non-deprived eye was normal and qualitatively corresponded well to slow phase eye velocity in response to equivalent retinal slip during OKN. Through the early deprived eye, however, velocity tuning was extremely poor. It was somewhat better through the late deprived eye. We suggest that the dramatic deterioration in the optokinetic reflex found after long-term monocular deprivation for the amblyopic eye is probably caused by the almost complete loss of retinal and cortical input driven by that eye to the NOT-DTN. These results are discussed in relation to our previous results in cats and reports in the literature for humans with occlusion amblyopia.

Animals↗
PubMed1997

Co-localization of glycine and calbindin D-28k in the vestibular ganglion of the rat.

Bipolar neurons of the vestibular ganglion (VG) are biochemically heterogeneous. The calcium-binding protein calbindin D-28k (Calb) is present only in a subset of particularly large neurons, and the amino acid glycine (Gly) has been immunocytochemically detected in a group of similarly sized cells. The close correspondence in size and number of cells in these two subgroups suggests that the Calb- and Gly-positive populations may be identical. In order to test this hypothesis, we performed direct and indirect double-labeling for Calb and Gly in the VG of the rat. The results confirm the existence of a distinct subpopulation of Calb-immunoreactive neurons, consisting of the largest cells in the VG. In contrast, the vast majority of neurons in the VG display some degree of Gly immunoreactivity, which gradually decreases from intense to almost unlabeled. Direct evidence is provided that the fraction of cells most heavily labeled by Gly antibodies is not identical with the Calb-positive subpopulation. Although some correlation between soma diameter and labeling intensity exists, Gly immunoreactivity is clearly not restricted to large neurons. The findings imply that the functional mechanisms in which Gly is potentially involved may be shared by a large spectrum of primary vestibular afferents with a broad range of physiological properties.

Animals↗
PubMed1995

Migraine phosphenes and the retino-cortical magnification factor.

Quantitative observations on the shape and position of migraine phosphenes within the visual field were obtained by controlled "perimetric" drawings of the phosphenes performed every 1-2 min during the aura state. The visual field eccentricity of the "fortification" or zig-zag patterns scintillating at about 10 Hz was plotted as a function of observation time. It is well described by an exponential function of time. This exponential function is the product of a first-order linear differential equation determined by the distribution of the retino-cortical magnification factor across the visual field and a constant diffusion speed of the cortical pathophysiological process leading to the migraine phosphene patterns. The observed "particle" size of the phosphene pattern and the width of the scotoma trailing the scintillating phosphenes could also be easily predicted from these assumptions. A model in which the main components are an increase in extracellular potassium concentration, a decrease in extracellular calcium concentration and the constant speed diffusion of the ions along the extracellular space of the stripe of Gennari within the primary visual cortex explains the observations.

Calcium↗
PubMed1994

Corticofugal connections between the cerebral cortex and brainstem vestibular nuclei in the macaque monkey.

The distribution of cortical efferent connections to brainstem vestibular nuclei was quantitatively analysed by means of retrograde tracer substances injected into different electrophysiologically identified parts of the brainstem vestibular nuclear complex of five Java monkeys (Macaca fascicularis). Three polysensory vestibular areas were found to have a substantial projection to the vestibular nuclei: area 2v located at the tip of the intraparietal sulcus, the parietoinsular vestibular cortex (PIVC) covering the most occipital part of the granular insula (Ig) and the retroinsular area (Ri or reipt), and the dorsolateral part of the somatosensory area 3a ("area 3aV" neck/trunk region). From physiological recording experiments, these three cortical fields were known to contain many neurons responding to stimulation of semicircular canals as well as to optokinetic (area 2v, PIVC) and somatosensory stimuli (PIVC, area 3a). These three regions form the inner cortical vestibular circuit. Besides these polysensory vestibular cortical fields, three other circumscribed cortical regions of the macaque brain were also found to project directly to the brainstem vestibular nuclei: a circumscribed part of the postarcuate premotor cortex (area 6pa), part of the agranular and the adjacent dysgranular cortex located around the cingulate sulcus (area 6c/23c), and a predominantly visual (optokinetic) association field located at the fundus of the lateral sulcus (area T3). These areas are known to have connections with the structures of the inner cortical vestibular circuit. Only a few efferent connections to the brainstem vestibular nuclei were found for the different parts of cytoarchitectonic area 7. Significant differences were found between the efferent innervation patterns of the axons originating in the six cortical areas mentioned and ending in the various compartments of the vestibular nuclear complex. Vestibular nuclei with a dominant output to the gaze motor system of the brainstem receive efferent connections preferably from the parietoinsular vestibular cortex. Vestibular structures with their primary output to skeletomotor centers, however, receive stronger efferent connections from areas 6pa and 3a. The ventrolateral nucleus, which sends efferent axons to both the oculomotor and skeletomotor systems of the brainstem and the spinal cord, also receives its main cortical efferents from the somatomotor area 6 and from area 3aV. Through these connections the cortical somatomotor system may directly influence vestibuloocular and vestibulocollic reflexes. It is speculated that the corticofugal connections to the vestibular brainstem nuclei are predominantly inhibitory, suppressing vestibular reflexes during cortically controlled goal-directed movements.

Animals↗
PubMed1994

Vision and cognition in the natural philosophy of Albert the Great (Albertus Magnus).

Albert the Great (Albertus Magnus, ca. 1197-1280) descended from a nobleman's family in Upper Suebia and studied natural philosophy and theology at the University of Padova, where he joined the Dominican order. Confronted with Aristotelian thought mainly in its Arabic modification (Avicenna, Al-Farabi, Averroes, Alhazen, Costa ben Luca and others) from his days in Padova, he elaborated in several books on the principles of natural philosophy, biology, brain and sense functions and psychology in addition to his theological and exegetic works. His observations and concepts on vision are discussed in detail. It is pointed out that Albert discovered some phenomena of vision not before known such as vestibular nystagmus and rod monochromacy, i.e. total colour blindness accompanied by photophobia. Based on clinical observations Albert also postulated a decussation of the optic nerve fibres at the optic chiasm. Albert's concept of higher order cognitive function is discussed and some of his explanations of dreams and neuropsychiatric disease on the basis of his cognitive model are mentioned. Albert's thoughts on vision and other sense perceptions, higher brain functions and cognition are considered as progressive elaborations of Galenic concepts as adapted by some Patristic theologians and the Arabic natural scientists and philosophers of the 9th-11th century.

Cognition↗
PubMed1994

Recovery from motion adaptation is delayed by successively presented orthogonal motion.

Following a period of adaptation to a pattern moving in a particular direction, a subsequently viewed stationary pattern appears to move in the opposite direction for some time: the movement after effect (MAE). The MAE lasts longer when the test pattern is not immediately or not continuously presented after adaptation. This phenomenon is called storage. So far research indicates that storage only occurs when textured visual stimulation is absent during part of the test phase or if the processing of a stationary test stimulus is prevented (e.g. by binocular rivalry). We present evidence that storage-like phenomena can occur even while a textured and moving visual stimulus is phenomenally present. We adapted binocularly to uni-directional motion of a random-pixel array M1 for 60 sec. This stimulus was immediately followed by another moving pattern M2. Its motion direction was orthogonal to that of M1. The presentation time of M2 was the independent variable. A stationary pattern was presented immediately after presentation of M2. The direction of the resulting integrated uni-directional MAE was measured. For short presentation times of M2 there is an integrated uni-directional MAE, which shows an interaction of the output of units stimulated by both moving patterns. However, it appeared that the effect of M1 on the direction of this combined uni-directional MAE is much longer present than would be expected from the MAE duration of M1, when tested in isolation.

Adaptation, Ocular↗
PubMed1993

Connections from the neocortex to the vestibular brain stem nuclei in the common marmoset.

Monosynaptic projections from the cerebral cortex to the vestibular nuclei were studied in the common marmoset monkey (Callithrix jacchus) by injecting fluorescent dextrans into the brain stem vestibular nuclei. The injection sites were determined by single unit vestibular responses identified later histologically. During the recordings sinewave rotation in pitch, roll or yaw or steady tilt was applied. The most notable loci of labelling were found inside the primary sensory cortex, the cortex deep down along the posterior lateral sulcus, the premotor region and the anterior cingulate cortex. From studies in other primates these cortical areas are known to process vestibular information. Their connections with the vestibular nuclei may serve as an internal feedback modulating the vestibular brain stem activity.

Animals↗
PubMed1993

Corticofugal projections to the vestibular nuclei in squirrel monkeys: further evidence of multiple cortical vestibular fields.

Single- and multiple-unit recordings were made from nerve cells located in the different nuclei of the brainstem vestibular nuclear complex (VNC) of anaesthetized squirrel monkeys (Saimiri sciureus) by conventional stereotaxic techniques. After neurons responding to semicircular canal stimulation in a yaw, roll, or pitch direction or to otholith stimulation were identified, small amounts of retrograde tracer substances were deposited at the recording sites. Up to three different tracers were administered to different parts of the VNC in the same animal (Fast Blue, HRP-WGA, and Rhodamine-dextranes). After adequate survival times, the animals were sacrificed. Following histological processing, the cortical grey matter was screened systematically for cells labelled with the retrograde tracers (fluorescence microscopy or light microscopy for HRP processing). Labelled nerve cells which clearly project to the VNC directly were found predominantly in the cytoarchitectonic layer 5 of seven different cortical areas: 1) The parieto-insular vestibular cortex PIVC, which in squirrel monkeys consists mainly of the medial area Ri and parts of the anterior area Ig; 2) area 7ant, which presumably corresponds to the macaque area 2v; 3) area 3aV, a vestibular field of area 3a; 4) the temporal area T3 bordering on area Ri; 5) the premotor area 6a; and 6, 7) the areas 6c and 23c of the anterior cingulate cortex. The PIVC, area 7ant, and area 3aV form the "inner cortical vestibular circuit" (Guldin et al.: J. Comp. Neurol. 326:375-401, '92), while the other cortical areas mentioned also have direct projections to the structures of the inner cortical vestibular circuit. It is speculated that the direct projections of the cortical vestibular structures to the brainstem vestibular nuclei regulate the vestibulo-ocular, the vestibulo-spinal, and the optokinetic reflexes mediated through the VNC, thus preventing counteractions of these reflexes during voluntary, goal-directed head movements or locomotion.

Animals↗
PubMed1993

Gaze motor asymmetries in the perception of faces during a memory task.

In 33 male and female adult volunteers, eye position recordings were performed by means of an infrared reflection technique. Slides of randomly shuffled black-and-white photographs (7.5 x 10 degrees) of faces and vases were projected for 6 or 20 sec respectively in a visual memory task. In each series, 10 slides of art nouveau vases and of the "inner part" of masked Caucasian faces were used. During recording the head was fixed by a bite-board. (a) For faces the preferred targets of the centre of gaze were the eyes, the mouth and nose region, for vases the contours and some prominent ornaments. (b) Left-right asymmetries in the gaze-movement sampling strategy appeared with faces, but not with vases. In faces, the overall time that the centre of gaze remained in the left half of the field of gaze was significantly longer than in the right half. (c) When, however, the amplitude of the gaze excursions into the left and right halves of the inspected items was taken as a measure and normalized, a preference for the right gaze field was observed. (d) The relative left-right bias during face inspection was stronger with the 6 sec than with the 20 sec inspection period and significantly stronger in female than in male subjects for the 6 sec tasks. (e) Left/right inversion of the face stimuli did not abolish the side bias. Thus the asymmetric sampling strategy when faces were inspected as compared to vases was due to "internal" factors on the part of the subjects. It is hypothesized that a left-right asymmetry in hemispheric visual data processing for face stimuli was the cause of a left-right asymmetry in gaze motor strategies when faces were inspected.

Adult↗
PubMed1992

Cortico-cortical connections and cytoarchitectonics of the primate vestibular cortex: a study in squirrel monkeys (Saimiri sciureus).

The cortical connections of two vestibular fields [parieto-insular vestibular cortex (PIVC) and area 3aV] were studied in the squirrel monkey (Saimiri sciureus) by means of retrograde tracer techniques. Small iontophoretic or pressure injections of horseradish peroxidase (HRP), wheat-germ-HRP, Nuclear Yellow, and Fast Blue were administered to the cytoarchitectonic areas Ri (PIVC), 3aV, the parieto-temporal association area T3, the granular insula (Ig), and the rostral part of area 7 (7ant). The injection sites were physiologically characterized by means of microelectrode recordings and vestibular, optokinetic, or somatosensory stimulation: Area Ri is the region of the parieto-insular vestibular cortex (PIVC) as defined in macaques. The neck-trunk region of area 3a (area 3aV) also contains many neurons responding to stimulation of semicircular canal receptors. Some neurons of area T3 bordering on the PIVC also receive vestibular signals, but most neurons in area T3 responded preferentially to large-field optokinetic stimulation and not to vestibular stimulation. In none of the areas mentioned were responses to otolith stimulation found. The PIVC receives inputs from frontal and parietal cortical areas, especially areas 8a, 6, 3a, 3aV, 2, and 7ant. Area T3 receives signals from the insular and retroinsular cortex, various parts of area 7, visual areas of the parieto-occipital and parieto-temporal regions (area 19) and from a sector of the upper bank of the temporal sulcus (STS-area). The cortical afferents to area 3aV stem from areas 24, 4, 6, 7ant, from other parts of the primary somatosensory cortex, the secondary somatosensory cortex (SII), the retroinsular cortex (Ri), and the granular insula (Ig). In the border region of the areas 2 and 7ant, labelled neurons appeared after injections into both the PIVC and the area 3aV. This region is presumably the homologue to the vestibular area 2v of the macaque brain. In all regions cells within the contralateral cortex were less frequently labelled than cells in the homologous structures of the ipsilateral hemisphere. The cortical system for processing vestibular information about head-in-space movement consists mainly of the reciprocally interconnected areas PIVC and 3aV, and most likely of border regions of area 2 and 7ant. This "inner cortical vestibular circuit" also receives signals from two other cortical sensory systems, the somatosensory-proprioceptive system mediated by the primary somatosensory cortex and the visual movement system (optokinetic or visual flow signals). These visual movement signals reach PIVC via area 19 and area T3.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1992

Thalamic connections of the vestibular cortical fields in the squirrel monkey (Saimiri sciureus).

The afferent thalamic connections to cortical fields important for control of head movement in space were analysed by intracortical retrograde tracer injections. The proprioceptive/vestibular area 3aV, the neck-trunk region of area 3a, receives two thirds of its thalamic projections from the oral and superior ventroposterior nucleus (VPO/VPS), which is considered as the proprioceptive relay of the ventroposterior complex (Kaas et al., J. Comp. Neurol. 226:211-240, 1984). The parieto-insular vestibular cortex (PIVC, area retroinsularis, Ri) receives its main thalamic input from posterior parts of the ventroposterior complex and from the medial pulvinar. Anatomical evidence is presented that the posterior region of the ventroposterior complex is a special compartment within this principal somatosensory relay complex. The parietotemporal association area T3, mainly involved in visual-optokinetic signal processing, receives a substantial input from the medial, the lateral, and the inferior pulvinar. Dual tracer experiments revealed that about 5% of the thalamic neurons projecting to 3aV were spatially intermingled with neurons projecting to areas PIVC or T3. This spatial intermingling was distributed over small but numerous, circumscribed thalamic regions, called "common patches," which were found mainly in the intralaminar nuclei, the posterior group of thalamic nuclei, and the caudal parts of the ventroposterior complex. The "common patches" may indicate a functional coupling of area 3aV with the PIVC or area T3 on the thalamic level. In control experiments thalamic projections to the granular insula Ig and the anterior part of area 7, two cerebral structures connected with the vestibular cortical areas, were studied. Some overlap in the thalamic relay structures projecting to these areas with those projecting to the vestibular cortices was found. A quantitative evaluation of thalamic regions projecting to different cortical structures was performed by constructing so-called "thalamograms." A scheme was developed that describes the afferent thalamic connections by which vestibular, visual-optokinetic, and proprioceptive signals reach the vestibular cortical areas PIVC and 3aV.

Animals↗