Colliculus Of Cat Research Articles

Multisensory Integration: A Functional Role for Inter-Area Synchronization?

It has been suggested that synchronization of neural activity in distinct areas of the brain is important in the 'perceptual binding' of the various features relating to a specific object. A recent study has provided new evidence that inter-area synchronization is important in multisensory integration.

Cerebellar fastigial neurons send bifurcating axons to both the left and right superior colliculus in cats

Anesthetized cats were injected with 2% Fast Blue and 0.5% Nuclear Yellow into the intermediate and deep layers of the left and right superior colliculus, respectively. In the right caudal part of the cerebellar fastigial nucleus (cFN), double-labeling was found in 38.5% of the neurons labeled with Fast Blue, and in 11.5% of the neurons labeled with Nuclear Yellow. In the left cFN, 52.2% of the neurons labeled with Fast Blue and 11.0% of the neurons labeled with Nuclear Yellow were double-labeled. The results suggest a role of bifurcating fastigial fibers in cerebellar visual control.

Anatomic Evidence of a Three-Dimensional Mosaic Pattern of Tonotopic Organization in the Ventral Complex of the Lateral Lemniscus in Cat

The ventral complex of the lateral lemniscus (VCLL, i.e., the ventral and intermediate nuclei) is composed of cells embedded in the fibers of the lateral lemniscus. These cells are involved in the processing of monaural information and receive input from the collaterals of the fibers ascending to the inferior colliculus. Whereas tonotopic organization is a feature of all other nuclei of the auditory system, this functional principle is debated in the VCLL. We have made focal injections of the tracer biotinylated dextran amine into different frequency band representations of the inferior colliculus in cat. Retrogradely labeled cells and terminal fibers (collaterals of efferent local axons and other ascending lemniscal fibers) were found in the ipsilateral VCLL. The spatial distribution of the labeling was analyzed using three-dimensional (3-D) reconstruction and computer graphical visualization techniques. A complex topographic organization was found. In all cases, labeled fibers and cells were distributed in multiple clusters throughout the dorsoventral extent of the VCLL. The shape, size, and location of the labeled clusters suggest an interdigitation of clusters assigned to different frequency-band representations. But an overall mediolateral distribution gradient was observed, with high frequencies represented medially and lower frequencies progressively more laterally. We conclude that the clusters may represent discontinuous frequency-band compartments as a counterpart to the continuous laminar compartments in the remaining auditory nuclei. The 3-D orderly mosaic pattern indicates that the VCLL preserves the spectral decomposition originated in the cochlea in a way that facilitates across-frequency integration.

Retinal X-afferents bifurcate to lateral geniculate X-cells and to the pretectum or superior colliculus in cats

The question of whether retinal X-type ganglion cell axons project via axonal bifurcation to both the dorsal lateral geniculate nucleus (LGN) and the pretectum (PT) or the superior colliculus (SC) in the cat, was studied by examining the effects of PT and/or SC stimulation on the LGN cells. X-cells that responded monosynaptically to PT or SC stimulation were encountered as follows: 29%, 26%, and 4% of the tested X-cells responded to stimulation of PT, SC, and both, respectively. For the X-cells activated from the PT or SC, the latency tended to be a little longer than optic chiasm latency. The receptive field centers of the X-cells were located within the receptive fields of the multiple units from the SC whose stimulation could activate the corresponding X-cells. The present results demonstrate that a substantial proportion of the X-type LGN cells receive excitatory inputs from the retinal X-type ganglion cell axons that branch to the PT or the SC.

Postnatal development of glutamatergic, GABAergic, and cholinergic neurotransmitter phenotypes in the visual cortex, lateral geniculate nucleus, pulvinar, and superior colliculus in cats

We have analyzed the postnatal development of glutamatergic/aspartergic, GABAergic, and cholinergic neurotransmitter systems in the visual cortical Areas 17 and 18, lateral geniculate nucleus (LGN), pulvinar, and the visual and non-visual parts of superior colliculus (SC) in kittens. High-affinity uptake of D-aspartate (HA D-Asp), glutamate decarboxylase (GAD), and choline acetyltransferase (ChAT) activities were measured as a means of probing the development of the respective transmitter systems. HA D-Asp exceeded the adult level several-fold in all areas during the postnatal period which corresponded with the period of maximal dendritic/axonal branching patterns and synapse densities in the respective regions. GAD exhibited a gradual increase towards adult levels during the first month. The adult level was reached during postnatal week (PNW) 5-6 in Areas 17 and 18, during PNW3 within LGN, pulvinar, and the visual part of SC. In the nonvisual part of SC, the adult GAD level was reached as early as PNW2. ChAT exhibited biphasic developmental profiles in Areas 17 and 18. An initial peak of near adultlike activity in PNW2 was followed by a decline and subsequently by a slow increase towards adult levels during PNW5-17. ChAT developed very slowly in LGN and pulvinar, and in the latter structure only approximately 70% of the adult activity had been attained by PNW17. In both subdivisions of SC, ChAT had reached adult levels during PNW3-5. Dark-rearing from birth until PNW6 moderately attenuated GAD development in all areas and increased ChAT activity in Areas 17 and 18 but did not affect development of HA D-Asp in any part of the kitten visual system. Our neurochemical findings in the developing cat visual system are consistent with available evidence regarding localization of neurotransmitter systems, as well as postnatal changes in terms of cytoarchitectonics, synaptogenesis, functional development, and susceptibility to neonatal dark-rearing in visual pathways.

Characteristics of compensatory processes after unilateral transection of the brachia of the inferior colliculus in cats.

1. Unilateral injury to the brachium of the inferior colliculus resulted in a disturbance of the adequate perception of space, which was indicated by the unidirectionality of orientational and conditioned-reflex responses (in the same direction as the side of injury) to stimuli of various sensory modalities. 2. Appreciable deafferentation of the parietal neocortex on the transection side resulted in a behavioral deficit. 3. Compensation for the function of spatial analysis of nonauditory signals probably occurred due to the restoration of functional (tonusogenic) symmetry between the cortical and subcortical representations of nonauditory-signal analyzers. 4. The restoration of the spatial analysis of auditory stimuli occurred during the first stages of compensation due to the activation of unihemispheric mechanisms in the intact parietal cortex. Later, the parietal cortex on the transection side was involved in this process.

HRP study of the organization of auditory afferents ascending to central nucleus of inferior colliculus in cat.

The ascending auditory projections to central nucleus of inferior colliculus and its ventrolateral and dorsomedial subdivisions (ICVL and ICDM) have been studied in cat using both pressure and electrophoretic injections of horseradish peroxidase (HRP). The results indicate that the predominant ascending projections to inferior colliculus originate in (1) contralateral cochlear nucleus, (2) contralateral and ipsilateral lateral superior olive, (3) ipsilateral medial superior olive, (4) ipsilateral ventral nucleus of the lateral lemniscus, (5) ipsilateral and contralateral dorsal nucleus of the lateral lemniscus, and (6) contralateral inferior colliculus. In addition, ipsilateral cochlear nucleus, ipsilateral and contralateral intermediate nucleus of the lateral lemniscus, ipsilateral, and to a lesser extent contralateral, periolivary nuclei project to inferior colliculus. Of these nuclei, the lateral superior olive projects exclusively to ICVL and ipsilateral cochlear nucleus and contralateral inferior colliculus project mostly, if not exclusively, to ICDM. Many of these projections demonstrate a cochleotopic organization and frequency a nucleotopic organization as well. A cochleotopic organization of the projections is apparent for cochlear nucleus and superior olivary complex. A nucleotopic organization suggests that the heaviest terminations of contralateral inferior colliculus are medial and dorsal in inferior colliculus, of medial superior olive are dorsal and lateral, of superior olivary complex are rostral, of cochlear nucleus are caudal, and of ventral nucleus of the lateral lemniscus are caudal.

Integration of visual and auditory space in the mammalian superior colliculus.

Recordings of eye movements and single-neurone microelectrode recordings of the superior colliculus in cats show that, for each saccadic movement, their eyes start near to the centre of the orbit so that the coordinates of visual and auditory space are aligned, and complex neural compensation of auditory or visual inputs to the superior colliculus is unnecessary.

Functional organization of the tectothalamic section of the transcollicular visual afferent channel

On the basis of the results of electrical stimulation of the optic tract and upper layers of the superior colliculus in cats anesthetized with pentobarbital maps were compiled of the distribution of evoked potentials of the posterior thalamic nuclear complex, including the pulvinar and n. lateralis posterior, posterior, suprageniculatus, and lateralis dorsalis. Functional projections of the superior colliculus and optic tract to the posterior thalamus were shown to differ from each other. In response to stimulation of the superior colliculus the distribution of projections was more regular than to stimulation of the tract. Fibers running from the optic tract occupy a smaller territory than fibers from the superior colliculus. It is suggested that the transcollicular afferent channel of the visual system is not reduced in the course of evolution but, on the contrary, it acquires connections with the younger thalamic formations of the brain and assume more complex functions.

Suppression by nitrous oxide of visual responses in the cerebellar vermis and superior colliculus of cats anaesthetized with chloralose

Suppression by nitrous oxide of visual responses in the cerebellar vermis and superior colliculus of cats anaesthetized with chloralose

Effects of eye movements upon excitability of the superior colliculus in cats.

Influences of saccadic eye movements upon excitability of cat superior colliculus (SC) were examined in chronic cats carrying implanted electrodes and in encephale isole cats. Excitability of SC was assessed by recording orthodromic responses of SC (SC ortho-response) to electrical stimulation of the optic chiasm. The SC ortho-response consisted of four components; i.e. presynaptic T1 and postsynaptic C1, C2 and C3. Eye movements suppressed the first two components (T1 and C1) and enhanced the latter two (C2 and C3). Retinal impulses caused by movements of images were found responsible for suppression of T1 and C1: 1) This was seen when cats moved eyes seeing external objects in light. In dark, neither T1 nor C1 received any influence from eye movements. 2) By moving visual stimuli rapidly before eyes of paralysed cats the same suppression of T1 and C1 was obtained. Suppression of C1 was deemed as a postsynaptic sign of SC for saccadic suppression. In contrast to suppression of T1 and C1, enhancement of C2 and C3 was dependent upon a central factor: 1) Enhancement of C2 and C3 followed eye movements, independent of the ambient illumination. 2) Saccade-like movements of a slit of light in front of immobilized eyes never induced enhancement of C2 and C3. 3) PRF stimulation, effective to cause saccade-like eye movements, always elicited enhancement of C2 and C3, independent of the ambient condition and even after eyes had been immobilized. This phenomenon was interpreted as indicating that corollary discharges are sent to SC.

Intracochlear Electrical Stimulation: Results of Psychoacoustic Studies in Man and Physiological Studies in Cats

A series of simple psychoacoustic experiments has been conducted on subjects previously implanted with an intracochlear bipolar electrode. With use of simple ac electrical stimulation, subjects heard sounds described as “tones” over a frequency range from about 100 to at least several thousand Hz. The apparent pitch rose rapidly up to 400–600 Hz; at higher frequencies, it changed slowly if at all over a broad range of frequency. The dF was about 1–3 Hz at 100 Hz, 5–10 Hz at 500 Hz, and 50–100 Hz at 1 kHz. Physiological experiments were conducted to determine how sensation heard by these subjects is generated and encoded in the auditory nervous system. Study of single units of the inferior colliculus in cats using standard microelectrode techniques has revealed: (1) Tuning curves of colliculus neurons excited by electrical stimuli were flat, and all were roughly parallel. The normal “place” representation of stimulus frequency is obscured. (2) The period of the stimulus is represented in the time order of discharge of colliculus neurons at frequencies up to 500–600 Hz. (3) With the stimulus electrode employed, the threshold of the acoustic nerve at the cochlear base was 30–40 dB lower than at the cochlear apex. Psychoacoustic and physiological evidence strongly suggests that hearing in these subjects is akin to the described sensation of “periodicity pitch.”

Tectal activity and eye movements during paradoxical sleep in cats

Phasic negative waves, similar to ponto-geniculo-occipital (PGO) waves, simultaneous with eye movements occurred in the superior colliculus in cats during the desynchronised EEG of paradoxical sleep. The frequency of PGO-like waves in the superior colliculus was about 25% lower than in the lateral geniculate body during the period of eye movements due to absence of 8/sec bursts common in the lateral geniculate body. Eye movements were evoked by stimulating the superior colliculus by rectangular pulse trains, and were accompanied by PGO-like waves in the lateral geniculate body and in the contralateral superior colliculus. During periods of paradoxical sleep, when no spontaneous rapid eye movements and PGO waves occurred, the effect of superior colliculus stimulation decreased. The phasic waves in the superior colliculus are associated apparently with the mechanism of rapid eye movements during paradoxical sleep. They resemble, but are not identical with, the phasic waves recorded under similar conditions in the lateral geniculate body.

The effect of body tilt upon the transfer- and output function of neurons of the cat's superior colliculus.

The influence of body tilt upon the reactions to a visual stimulus was tested in 54 single neurons of the cat's colliculus superior. The statistical analysis did not reveal modification of neuronal reactions by body tilt. In a second series of experiments we studied the influence of body position on eye position, which had been induced by focal electrical stimulation of the colliculus superior. Again, the body tilt did not modify the electrical stimulation effect. Our results suggest, that tonic vestibular stimuli do not influence the excitability of neurons of the superior colliculus.

Electrophysiological investigation of the noise stability of the auditory system during sound localization

Single unit activity was investigated in the inferior colliculi of cats anesthetized with chloralose and urethane in experiments simulating sound localization in the presence of direct and reflected signals. In more than half of the neurons with specific angular sensitivity the reflected signal either caused no change in the response to the direct signal or augmented angular sensitivity to the direct signal. In about one-quarter of the neurons studied the special characteristics of the response to a direct signal, located at a certain angle were abolished by a reflected signal, i.e., the reflected signal interfered with assessment of the angle. Changes in the other neurons were more complex: depending on the combination of angles of the direct and reflected signals, no change, augmentation of angular sensitivity, or its diminution could be observed in the same neuron. It must be particularly emphasized that the responses of about half of the neurons studied to a direct signal were changed only if the direct and reflected signals were separated by particular time intervals. This fact suggests that the reflected signal can help to determine the distance of the sound source from the animal.

Effect of acoustic stimuli on unit activity of inferior colliculus in cats

Effect of acoustic stimuli on unit activity of inferior colliculus in cats

Central pathways of vision.

Their functions in gener al. -Blindness, total with the exception of the ability to distinguish sudden lightening of a dark room from sudden darken­ ing of a light one, has been shown to last at least 20 years after a lesion restricted to the occipital poles of the cerebral hemispheres in man (7). Op­ tokinetic nystagmus remains absent. Such lasting blindness contrasts with the well-known substantial return of vision after similar lesions in monkeys and, still more, in nonprimate mammals. The extra striate and presumably extrageniculate vision that does thus return has been found to be little af­ fected by lesions of the superior colliculus in cats (83) and rats (36) but much affected in monkeys by lesions that destroy the 'accessory optic sys­ tem', i.e. fibres that terminate in the nucleus paralemniscalis (65). The visual neglect or lack of orienting reactions produced by lesions of the dorsal midbrain has been found to be conspicuous in hamsters (73) and slight in monkeys (2). It i s accompanied by almost no defect in formal tests of pattern discrimination, but there is in monkeys a defect of discrimi­ nation of rates of movement (2). The controversy as to whether the signifi­ cant parts of the causal lesions are collicular, tegmental, or both has not been satisfactorily resolved. Their anato my. - Sefton (74) has elegantly proved that the great major­ it y of retinocollicular fibres in the rat are collaterals of retinogeniculate fibres. The direct mapping of the retin a on the colliculus in the cat has been reexamined by anatomical means (32), and its indirect mapping through the striate cortex by electrical recording (78). The two maps are at least roughly concordant, but it is not yet possible to say if they are exactly so. Responses to electrical stimulation of the optic nerve have been recorded at various depths in the superior colliculus of cats (68) and rats (75). The

Recurrent collateral inhibition of visual cortical cells projecting to superior colliculus in cats

Using cats, with eyes intact or enucleated chronically, the visual cortical cells projecting to the superior colliculus (SC) (VCSC cells) were identified on the basis of antidromic responses to stimulation of SC. They were most frequently encountered in the junctional part of the lateral and postero-lateral gyri and that of the middle and suprasylvian gyri. Repetitive shocks of SC induced in the VCSC cells a long-sustained depression of excitability which was preceded by refractoriness resulting from the cell-body discharge. This depressed excitability, revealed as a suppression of ortho- and antidromic firings and also as a blockade of spontaneous discharges, was attributed to the recurrent collateral inhibition mediated by inhibitory interneurons.

Projections of the inferior colliculus in cat.

AbstractProjections of the feline inferior colliculus were studied using the Nauta‐Laidlaw method to demonstrate degenerating axons. A subtentorial stereotaxic approach was used to avoid corticofugal degeneration. Direct connections from the inferior colliculus to the anterior midline cerebellar cortex were observed. There is a topographical relationship of fibers of the brachium of the inferior colliculus and parabrachial region to the superior colliculus. A definite projection to the superior colliculi including a pathway through its commissure was found from the parabrachial region. A projection exists from the inferior colliculus to the dorsolateral portion of the central gray as far as the pretectum. There is a projection along the medial portion of the superior colliculus to the pretectum. Projections to the midbrain reticular formation, central gray and superior colliculi were substantial. Thalamic projections include a distribution of fibers to the magnocellular and rostral portion of the principal divisions of the medial geniculate body and to the lateral posterior thalamic nucleus. The rostral connections of the inferior colliculus with areas other than the medial geniculate body indicate that it may function in roles in addition to that of a mass somatomotor reflex center. Possible roles of the inferior colliculus in attention, habituation, and integration of corticovisual and auditory impulses are suggested.

Unit responses of the inferior colliculus in cats to lateralization of repetitive acoustic stimuli

1. Unity activity of the inferior colliculus during a series of short noise bursts (duration of bursts 2 msec, frequency 20–30 Hz, duration of series 600–700 msec) was investigated in cats anesthetized with chloralose and urethane. The following properties of unit activity were established during repetitive stimulation: a prolonged discharge throughout the series; lowering of the threshold of the response compared with that to a single noise burst of duration 2 msec and a continuous noise of duration 600–700 msec; a sharp increase in latency of the response and its dispersion at the threshold. These properties were characteristic of neurons of both phasic and tonic type. 2. During lateralization of a series of clicks of the same frequency and duration of the series, only two-thirds of the neurons respond by changes in spike activity to the first stimuli in the series and to its subsequent part. In one-third of the neurons, only the response to the subsequent part of the series is changed, the response to the first stimuli remaining unchanged. 3. The results suggest the existence of neurons capable of detecting the direction of movement of a source of sound.