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At least 19 recordsLinked to original sources
PubMed1999

Visual evoked oscillatory responses of the human optic tract.

Optic tract oscillatory responses directly recorded during posteroventral pallidotomy were investigated to reveal their features with respect to extracranially recorded visual oscillations and to clarify their contributions to scalp-recorded or far-field visual evoked potentials. Oscillatory responses of the optic tract consisting of early and subsequent late oscillations were recorded in all patients. Early oscillations consist of five negative and positive peaks, and late oscillations consist of two to four negative and positive peaks. The frequency of the first peak of early oscillations (103.0+/-9.2 Hz, n = 14) was significantly lower than that of others (t test, P<0.006), but there were no significant differences among other peaks (t test, P>0.4). This difference was not observed among peaks of late oscillations (t test, P>0.3). As a whole, the frequency of early oscillations (123.9+/-16.7 Hz, n = 70) was significantly higher than that of late oscillations (66.3+/-13.7 Hz, n = 41) (t test, P = 0.0001). Intracerebral recording of the optic responses with the same band filter of scalp-recorded visual evoked potentials (10 Hz to 1 KHz) showed prominent negative (No) and positive (Po) waves, whereas responses obtained over the scalp at Oz and Cz consisted of negative (NI), positive (PI), negative (NII), and positive (PII) waves. Comparisons between No and PI and Po and NII showed overall phase reversal relations between them, but there were significantly different peak latencies between them (t test, P<0.001) except that between Po (116.7+/-11.7 msec, n = 5) and NII of Cz recording (118.4+/-9.4 msec, n = 5) (t test, P<0.3). Our study in conjunction with other studies on visual oscillations revealed that a relatively constant frequency of oscillations is traveling in the subcortical visual system and is probably playing an important role in generating stationary or fixed peaks of the far-field potentials of visual evoked potentials.

Evoked Potentials, Visual↗
PubMed1981

Representation of the visual field in the optic tract and optic chiasma of the cat.

The fibre arrangement in the optic chiasma (OC) and tract (OT) was investigated with anatomical and physiological methods. In silver impregnated material, principal fibre streams can be demonstrated. In the OC, fibre bundles from each eye cross in a regular basket weave pattern, but deviations of single fibres from the predominant stream are often seen. In the OT, fibres run essentially parallel, and crossings of individual fibres are mainly restricted to the periphery of the tract, or around capillaries. Fibres in the upper segment of the OT are of thin, in the lower segments of thick diameter. Individual fibres labelled by HRP injected in the lateral geniculate body (LGB) run essentially parallel over long distances. Ventromedially to the LGB, bifurcations are found with one branch entering the LGB, the other continuing. 57% of OT-fibres had a receptive field (RF) in the contralateral, 43% in the homolateral eye; 60% in the lower, 40% in the upper visual field; and 6% had a RF in the homolateral visual field, mostly near the vertical meridian. Fibres from the central area were underrepresented in our sample. Fibres from the two eyes were mixed. The RFs of consecutively recorded fibres showed a systematic progression only exceptionally. After plotting RFs of a single penetration on a transformed isodensity ganglion cell map of the visual field, the RF's were distributed along elongated paths on this map. In the OT, such paths ran parallel or slightly inclined relative to the horizontal meridian. They were restricted to either the upper or the lower quadrant or to a path along the horizontal meridian. In the OC, the RF-paths mostly crossed the horizontal meridian at an obtuse angle (average 70 degrees). Thus, the visual field representation rotates by nearly 90 degrees from the OC to the OT. In the OC, the central area is located anteriorly, in the OT dorsally, with the upper visual quadrant laterally and the lower medially. Fibres from the two eyes were mixed and, within the range of the scatter, RFs from the homo- and contralateral eye were in register. It is concluded, that the distribution of fibres in the OC and the OT show a basic retinotopic organization superimposed by scatter.

Animals↗
PubMed1997

NMDAR1-like immunoreactive fibers appear in the ipsilateral optic tract during optic nerve regeneration in Rana pipiens.

N-Methyl-D-aspartate receptor subunit 1-like immunoreactivity (NMDAR1-LI) was investigated in the brain of Rana pipiens during optic nerve regeneration. Following unilateral optic-nerve crush, frogs were tested for prey-catching and optokinetic nystagmus responses to assess return of visual function. At 1, 2, 3 and 5 months after the surgery, NMDAR1-LI was assessed in central visual pathways. At 3 and 5 months, conspicuous ipsilateral NMDAR1-LI fibers were detected in the thalamic and pretectal nuclei, and the time of their appearance coincided with the onset of behavioral recovery. Also, only ipsilateral retinorecipient layers in the optic tectum showed increased NMDAR1-LI during optic nerve regeneration. These results suggest that NMDA receptors may be present on retinal ganglion cell axons and terminals that have been misrouted during regeneration.

Animals↗
PubMed1981

Residual tectal projection from the contralateral central retina of the frog after homolateral optic nerve and main optic tract section. A possible input from the axial optic tract.

After homolateral (right) optic nerve and main optic tract section a residual visual activity originating from the contralateral (left) central retina was recorded in the right optic tectum. Units were classified in three groups according to their receptive field properties: (1) slow-adapting units analogous to class 3 retinal ganglion cells; (2) fast-adapting postsynaptic units; (3) visual neurons. All of these units have in common a receptive field located near the projection of the left eye optic axis. Evidence that these units belong to the same visual pathway (i.e., the axial optic tract) is discussed.

Action Potentials↗
PubMed1990

Topographic disorganization of the optic tracts following long-term optic nerve regeneration: a quantitative image analysis study.

Experiments were designed to find the degree to which regenerated optic axons occupied their previous locations in the optic tracts. Following optic nerve crush and regeneration, either the dorsal, ventral, peripheral, temporal, or nasal part of the retina was ablated. The axons of the remaining retinal ganglion cells (RGCs) were labeled with cobalt. Density of the regenerated dorsal and ventral axons in the dorsal vs. ventral optic tracts was determined digitally. In addition, we determined the density of temporal and nasal axons in the temporal vs. nasal compartments of each optic tract and the density of central axons in the central vs. peripheral compartments of both optic tracts. Regenerated axons were not distributed randomly in the optic tracts. Instead, they were slightly but, significantly biased toward growing through the tract or compartment that they had occupied previously. Still, the pathway specificity exhibited by the regenerated axons was closer to random than it was to the pathway specificity seen in normal animals. Dorsal, ventral, and central RGC axons were significantly better localized to their correct tract or compartment than were temporal or nasal RGC axons. Also, over time, dorsal and ventral axons tended to disappear from incorrectly chosen optic tracts. The slight bias toward choosing the appropriate optic tract or optic tract compartment may be enough to account for the topographic specificity of the regenerated retinotectal projection. Near-randomness of the axonal positions in the tracts argues against the presence of any specific guidance cues in the optic tracts of adult animals. Axonal density was highest in the correct compartment and diminished progressively with increasing distance into the incorrect compartment. Such a gradient of axonal density suggests that regenerating axons "drift" away from their previous positions in the optic pathways.

Animals↗
PubMed1988

Physiological and anatomical identification of the nucleus of the optic tract and dorsal terminal nucleus of the accessory optic tract in monkeys.

Physiological and anatomical criteria were used to clearly establish the existence of a pretectal relay of visual information to the ipsilateral inferior olive in the macaque monkey. After injection of horseradish peroxidase into the inferior olivary nucleus, retrogradely labelled neurons were found in the nucleus of the optic tract (NOT) and the dorsal terminal nucleus of the accessory optic tract (DTN). The labelled cells were distributed in a sparse band arching below the margin of the brachium of the superior colliculus between the dorsal and lateral borders of the brainstem at the caudal edge of the pulvinar. Various types of cells could be distinguished. More superficially the cells were extremely spindle shaped, cells deeper within the midbrain had more compact somata. NOT-DTN neurons in the same region were also found to respond with short latencies to electrical stimulation of both the inferior olive and the optic chiasm. All neurons in the NOT-DTN which were antidromically activated from the inferior olive were also found to have direction specific binocular visual responses. Such neurons were excited by ipsiversive motion and suppressed by contraversive motion, regardless of whether large area random dot stimuli moved across the visual field or small single dots moved across the fovea. Direct retinal input to these neurons was via slowly conducting fibers (3-9 m/s) from the monkey's optic tract conduction velocity spectrum. As shown previously for non-primates, NOT-DTN cells may also in the monkey carry a signal representing the velocity error between stimulus and retina (retinal slip), and relay this signal into the circuitry mediating the optokinetic reflex.

Animals↗
PubMed1993

Visual receptive field properties in kitten pretectal nucleus of the optic tract and dorsal terminal nucleus of the accessory optic tract.

1. Neurons in the pretectal nucleus of the optic tract (NOT) and dorsal terminal nucleus of the accessory optic tract (DTN) were recorded in anesthetized and paralyzed kittens on postnatal days 18 to 48 (P18-P48) as well as in adult cats. 2. Spontaneous as well as stimulus driven discharge rates of NOT-DTN neurons in the youngest kittens (P18-P23) are significantly lower than in older kittens (P27-P33) or adult cats. 3. Visual latencies of NOT-DTN neurons in P18-P23 kittens are significantly longer than in P27-P33 kittens. They further decrease as the animals reach adulthood. 4. Already in the youngest animals recorded in this experimental series (P18) NOT-DTN neurons were selective for ipsiversive horizontal stimulus movement. When expressed as the difference between response strength during stimulation in the preferred and the nonpreferred direction, P18-P23 NOT-DTN neurons are less direction selective than NOT-DTN cells in older animals. However, the normalized directional tuning expressed as percent change in discharge rate per degree change in stimulus direction away from the preferred direction (where discharge rate is set 100%) is about equal in all age groups. 5. NOT-DTN neurons in P18-P23 kittens respond to a rather limited range of stimulus speeds with an optimum at approximately 10 degrees/s. In P27-P33 kittens, NOT-DTN neurons increase their responsive range to higher stimulus speeds. As the animals approach adulthood, the range of effective stimulus speeds further broadens to include very low ones. 6. In P18-P23 kittens, the majority of NOT-DTN neurons is exclusively activated by the contralateral eye; only a few neurons receive an additional input from the ipsilateral eye. In P27-P48 kittens, the influence of the ipsilateral eye has significantly increased but with the majority of NOT-DTN cells still being dominated by the contralateral eye. Finally, in adults, a further strengthening of the ipsilateral input leads to a more binocularly balanced input to NOT-DTN cells. 7. Electrical stimulation in areas 17 and 18 did not elicit orthodromic action potentials in NOT-DTN neurons before P27. Thus the cortical input to the NOT-DTN in kittens becomes functional only at 4 wk of age. 8. In conclusion, the significant changes of visual response properties of NOT-DTN neurons coincide with the time when the cortical input to the NOT-DTN becomes functional.(ABSTRACT TRUNCATED AT 400 WORDS)

Accessory Nerve↗
PubMed2001

Postnatal development of the retinal projection to the nucleus of the optic tract and accessory optic nuclei in the hooded rat.

Retinal projections to the nucleus of the optic tract (NOT) and accessory optic nuclei (AON) were studied in the postnatal hooded rat after monocular injection of cholera toxin B subunit (CTB) into the vitreous chamber of the eye. At all postnatal ages, retinal axons were labeled sensitively; they revealed dense projections to the contralateral, and sparse but distinct projections to the ipsilateral, NOT and AON. The CTB labeling enabled the first delineation of the complete morphology of developing retinal axons in the ipsilateral NOT and AON. From postnatal day (P) 1 to P3, axons with complex growth cones were seen, and unbranched collaterals with simple growth cones increased and extended gradually. At P6, complex growth cones disappeared while branched collaterals with simple growth cones as well as small-sized varicosities increased. By P12 (two days before eye-opening) the adult-like pattern of terminal arbors appeared. The branched collaterals with tiny, small-sized varicosities present probably represented developing synaptic boutons. At P16 (after eye opening), the pattern of terminal arbors was well developed, almost to the same extent as in the adult. By contrast, a broadly distributed, transient retinal projection around NOT and AON was gradually eliminated; it started to disappear during the first few postnatal days, and was fully retracted by the time of eye-opening time to a pattern normal for the adult.

Animals↗
PubMed1989

Quantitative analysis of visual receptive fields of neurons in nucleus of the optic tract and dorsal terminal nucleus of the accessory optic tract in macaque monkey.

1. The visual receptive field properties of neurons in the nucleus of the optic tract (NOT) in the pretectum and the dorsal terminal nucleus (DTN) of the accessory optic tract were analyzed quantitatively in anesthetized, paralyzed macaque monkeys. 2. Visual latencies to reversals in direction of stimulus movement ranged from 40 to 80 ms [61 +/- 13.5 (SD) ms]. 3. All neurons increased their discharge rate during ipsiversive movement and decreased their ongoing activity during contraversive movement of single stimuli or whole-field random dot patterns. The population of neurons in the left NOT-DTN was excited most strongly by leftward movement pointing 4 degrees down; neurons in the right NOT-DTN were excited most strongly by rightward movement pointing 6 degrees down. The mean angle between the directions yielding the highest and the lowest discharge rate in the two populations of NOT-DTN neurons was 177 degrees. 4. The deviation of the preferred excitatory directions from the horizon in individual neurons varied with recording depth. Within the first 500 microns below the midbrain surface, neurons preferred near-horizontal directions, whereas neurons recorded more deeply preferred more oblique directions of stimulus movement. 5. The tuning widths of NOT-DTN neurons in the preferred excitatory direction were very broad. The mean halfwidth defined as the range of directions eliciting responses greater than 50% of the maximum was 127 +/- 25 degrees. 6. Moving a random dot pattern and a single bar of light simultaneously but in opposite directions caused NOT-DTN neurons to increase their discharge rate as soon as one of the two stimuli moved in the ipsiversive direction. The reduction in overall discharge rates when two stimuli moved in opposite directions indicates mainly inhibitory interactions. 7. All NOT-DTN neurons could be activated from both eyes. Interactions between the two eyes were modest and unspecific. Misalignment of the visual axes of the two eyes had no influence on response strength. 8. Optimal speeds of stimulus movement varied widely for different NOT-DTN neurons. The effective range of speeds to elicit direction-selective responses in the total population was very broad (0.1400 degrees/s. With oscillating horizontal stimulation, NOT-DTN neurons followed repetition rates up to 4 Hz at excursions of 40 degrees. Speeds greater than 500 degrees/s were either not effective or resulted in a suppression of ongoing activity in all directions of movement.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1991

Functional projections from striate cortex and superior temporal sulcus to the nucleus of the optic tract (NOT) and dorsal terminal nucleus of the accessory optic tract (DTN) of macaque monkeys.

The nucleus of the optic tract (NOT) and the dorsal terminal nucleus of the accessory optic tract (DTN) have been recognized to be relevant structures for optokinetic and vestibuloocular reflexes. NOT-DTN neurons relay visual information to the vestibular nuclei via the nucleus prepositus hypoglossi and to the flocculus via the dorsal cap of the inferior olive. It has been previously shown that in carnivores the NOT-DTN receives information from primary visual cortical areas in addition to the direct retinal input. In this study we demonstrate the presence and some functional characteristics such as latency and evicacy of considerable cortical projections to the NOT-DTN in macaque monkeys. In anaesthetized and paralyzed monkeys NOT-DTN neurons were identified physiologically and tested for cortical input by electrical stimulation in various cortical areas. Successful sites of stimulation to activate NOT-DTN neurons orthodromically lie in the primary visual cortex (V1) and in the motion-processing areas in the superior temporal sulcus (STS). In contrast, electrical stimulation in area V4 and in parietal areas in most cases did not yield orthodromic responses. Overall latencies of action potentials elicited by stimulation in V1 were 0.5 ms longer than those elicited from STS. These short latency differences between V1 and STS stimulation suggest a direct projection from both V1 and STS to the NOT-DTN. The physiological results were supported by the results of anatomical experiments by using horseradish peroxidase as anterograde tracer. Both injections into V1 and into the lower bank of STS resulted in anterogradely labelled fibers and terminals around the recording sites of direction-specific NOT-DTN neurons. This paper is a first step in clarifying the significance of corticofugal projections from individual areas involved in the analysis of visual motion for the optokinetic reflex.

Animals↗
PubMed1996

Responses of neurons of the nucleus of the optic tract and the dorsal terminal nucleus of the accessory optic tract in the awake monkey.

The nucleus of the optic tract (NOT) and the dorsal terminal nucleus of the accessory optic tract (DTN) are essential nuclei for the generation of slow-phase eye movements during horizontal optokinetic nystagmus. We recorded from 101 neurons (all directionally selective) in four NOT/DTN of three trained and behaving rhesus monkeys. Neuronal activity increased when stimuli moved ipsiversively with respect to the recording site and decreased below spontaneous activity when stimuli moved contraversively. While the monkey fixated a small spot, some NOT/DTN neurons did not respond at all to the retinal image slip of a whole-field random dot pattern; others showed a monotonic increase of activity to increasing velocities of that stimulus. The velocity range tested was up to 100 degrees/s. During the execution of optokinetic nystagmus, 39 of 73 cells tested showed a velocity-tuned response with an average optimum at 21 degrees/s retinal image slip. Following saccades during optokinetic nystagmus (quick phases), the NOT/DTN neuronal activity briefly attained the level of spontaneous activity, as predicted from the velocity selectivity during optokinetic nystagmus. Immediately upon cessation of optokinetic stimulation in the preferred direction, NOT/DTN activity returned to the spontaneous level and did not reflect the ongoing optokinetic afternystagmus in darkness. Most NOT/DTN neurons displayed direction selectivity also during smooth pursuit. Twenty-one of 50 cells tested (42%) always responded to the retinal slip of the target (target velocity cells), 16 cells (32%) responded to the retinal slip of the background (background velocity cells), and 13 cells (26%) did not respond at all during smooth pursuit. We conclude from our results that the NOT/DTN is an essential structure for the processing of the direction and speed of retinal image slip. This information is then used for the generation and maintenance of slow eye movements, preferentially during horizontal optokinetic nystagmus but also during pursuit eye movements.

Animals↗
PubMed1985

The response of optic tract glia during regeneration of the goldfish visual system. II. Tectal factors stimulate optic tract glia.

After transection, retinal ganglion cell axons of the goldfish will regenerate by growing into a primary target tissue, the optic tectum. To determine what role the target tissue may play in regulating glial cell growth, we measured biosynthetic activity of optic tract glia following excision of the optic tectum and compared it to activity of glia found in the regenerating visual system. Ablation of the tectum reduced glial incorporation of both [3H]thymidine and [35S]methionine. Tectal ablation also led to nearly 80% reduction of amino acids incorporated by oligodendroglia as well as a decrease in the amount of newly synthesized protein found within multipotential glia and within cytoplasmic projections of astroglia. Since the tectal influence upon optic tract glia was detected at a time when tract and tectum are physically separated, we sought to determine if the optic tectum contained soluble glia-promoting factors. A soluble fraction recovered from tecta of the regenerating visual system increased amino acid incorporation within optic tract glia at 2-3-fold above preparations incubated with fractions from control, intact tecta. Comparisons of radiolabeled proteins separated by sodium dodecyl polyacrylamide gel electrophoresis from regenerating and factor-stimulated optic tract were similar and indicated that a soluble tectal fraction promoted biosynthesis of specific glial proteins. Our findings suggest that during regeneration of the goldfish visual system glia are influenced by humoral factor(s) released from the synaptic target site.

Animals↗
PubMed1981

Electrophysiological study of the nucleus of the optic tract that transfers optic signals to the nucleus reticularis tegmenti pontis - the visual mossy fiber pathway to the cerebellar flocculus.

Neuronal activities (n = 43) in the pretectal region in rabbits were recorded. They were orthodromically activated from the optic chiasm (latency, 1.86 +/- 0.35 msec) and antidromically from the ipsilateral nucleus reticularis tegmenti pontis (Nrt) (latency, 0.97 +/- 0.22 msec). Thirty-one (72%) neurons were in the nucleus of the optic tract (NOT), four (9%) in the anterior pretectal nucleus (PA) and seven (16%) in the border between NOT and PA. These findings demonstrate that the NOT is involved in the visual mossy fiber pathways to the flocculus and may contribute to optokinetic eye movements.

Animals↗
PubMed1992

Callosal and superior temporal sulcus contributions to receptive field properties in the macaque monkey's nucleus of the optic tract and dorsal terminal nucleus of the accessory optic tract.

To assess the functional contribution of the cortical input to the receptive field properties of nucleus of the optic tract (NOT) and dorsal terminal nucleus (DTN) neurons, a first set of experiments evaluated the response properties of NOT-DTN cells in monkeys with split corpus callosum. With respect to visual latency, direction specificity, directional tuning width, velocity tuning, ocular dominance, and binocular interaction, they were indistinguishable from NOT-DTN neurons in normal monkeys. However, a clear difference was found regarding the extent of the receptive fields. Whereas, in normal monkeys, NOT-DTN receptive fields include the contralateral hemifield and the fovea as well as substantial parts of the ipsilateral visual field, receptive fields in callosum-split monkeys stop abruptly at, or close to, the vertical 0-meridian and do not extend into the ipsilateral visual field. In addition, the location of the highest sensitivity within the receptive fields in callosum-split monkeys is shifted away from the vertical 0-meridian in comparison to normal animals. In a second set of experiments, we antidromically identified cortical neurons within the superior temporal sulcus that project to the NOT-DTN. These neurons were found in area MT mostly near the border of MTp or MSTl. All of them are direction selective for ipsiversive stimulus movement, and their receptive fields extend substantially into the ipsilateral visual hemifield. Neurons with other preferred directions did not project to the NOT-DTN. These results contribute to the explanation of the ipsiversive directional deficits in slow eye movements after cortical lesions, as well as the asymmetries in optokinetic nystagmus with hemifield stimulation after transection of the corpus callosum. The more general implication of the results is that a particular function of a cortical area can only be understood by knowing its subcortical connections.

Animals↗
PubMed1990

Fibre organization of the monkey's optic tract: I. Segregation of functionally distinct optic axons.

The fibre organization of the monkey's optic tract was examined by implanting pellets of horseradish peroxidase into different locations within the tract, or into the superior colliculus and pretectum. Retinae were examined for the distribution, size, and morphological types of retrogradely labelled ganglion cells; optic tracts were examined for the distribution of anterogradely and retrogradely labelled axonal profiles; and lateral geniculate nuclei were examined for the distribution of anterogradely labelled processes within distinct geniculate laminae. Localized implants in the optic tract produced retrograde labelling of ganglion cells across wide regions of the retinal surface. The maximum density of labelled cells was always substantially less than the total ganglion cell density known to be present at those retinal loci. Distinct retinal ganglion cell types were labelled from differing regions within the optic tract: implants into the deep (dorsal) portion of the tract, far removed from the outer, pial, surface, retrogradely labelled predominantly P beta retinal ganglion cells, whereas implants into the superficial (ventral), subpial, part of the tract retrogradely labelled primarily the other retinal ganglion cell types, i.e., the P alpha, P gamma, and P epsilon cells. Within any given class of axon, there is a mapping of the centroperipheral retinal axis across the deep-to-superficial dimension of the tract, but this retinotopy is extremely coarse. Anterograde labelling of axonal terminations within the lateral geniculate nucleus showed a corresponding specificity for distinct geniculate laminae, the deep implants labelling the parvocellular laminae, superficial implants labelling the magnocellular laminae. Implants into the visual centres of the midbrain produced retrograde axonal labelling rostral to the lateral geniculate nucleus only in the superficial part of the optic tract. These results demonstrate that the monkey's optic tract is not a simple topographic mapping of retinal eccentricity. Rather, the primary organizational principle is that of a segregation of functionally distinct optic axon classes. As fibre order in the mammalian optic tract is also a chronological index of axonal arrival during development, the present results provide specific predictions about the temporal order of ganglion call genesis and axonal addition within the visual pathway. They also provide an anatomical basis for the functionally selective visual impairments that may arise following local damage to the optic tract in humans.

Animals↗
PubMed1982

Histopathology of experimental optic tract hemianopia.

Optic nerve and retinal degeneration were studied histopathologically following surgical resection of the right optic tract of a rhesus monkey (Macaca mulatta). 7 months following resection, well-developed patterns of degeneration were seen bilaterally in optic nerves and retinas. The lesions correlated well with clinical studies done on the animal, and with lesions reported in 1 case in man. The experimental results indicate that the rhesus monkey would make a good model to study optic nerve and retinal degeneration.

Animals↗