Projections from visual cortical areas of the superior temporal sulcus to the lateral terminal nucleus of the accessory optic system in macaque monkeys

Visual fixation suppression of caloric nystagmus in progressive supranuclear palsy - A comparison with Parkinson's disease

BACKGROUND

Impairment of visual fixation suppression (VS) in progressive supranuclear palsy (PSP) is not well documented.

OBJECTIVE

To evaluate the usefulness of impaired VS of caloric nystagmus as an index for differential diagnosis between PSP and Parkinson's disease (PD), which is often difficult, especially in the early stage.

METHODS

Subjects comprised 26 PSP patients and 26 PD patients clinically diagnosed at Tokyo Metropolitan Neurological Hospital. We retrospectively investigated VS of caloric nystagmus, horizontal pursuit, saccades, and horizontal optokinetic nystagmus recorded on direct-current-electronystagmography, and neuroradiological findings.

RESULTS

The median of the average VS% was 0% and 50.0% in PSP and PD patients, respectively. In PSP, VS was impaired even in the early stage of disease. We found a significant correlation between VS and velocity of saccades or maximum slow phase velocity of optokinetic nystagmus only in PSP patients. PSP patients with atrophy of the subthalamic nucleus or with decreased blood flow in the frontal lobe showed significantly more severe impairment of VS.

CONCLUSIONS

VS may be a useful biomarker to differentiate patients with PSP from those with PD. Cerebellar networks that connect with the cerebral cortex and basal ganglia may contribute to impaired VS of caloric nystagmus in PSP.

Motion perception during selfmotion: The direct versus inferential controversy revisited

According to the traditional inferential theory of perception, percepts of object motion or stationarity stem from an evaluation of afferent retinal signals (which encode image motion) with the help of extraretinal signals (which encode eye movements). According to direct perception theory, on the other hand, the percepts derive from retinally conveyed information only. Neither view is compatible with a perceptual phenomenon that occurs during visually induced sensations of ego motion (vection). A modified version of inferential theory yields a model in which the concept of extraretinal signals is replaced by that of reference signals, which do not encode how the eyes move in their orbits but how they move in space. Hence reference signals are produced not only during eye movements but also during ego motion (i.e., in response to vestibular stimulation and to retinal image flow, which may induce vection). The present theory describes the interface between self-motion and object-motion percepts. An experimental paradigm that allows quantitative measurement of the magnitude and gain of reference signals and the size of the just noticeable difference (JND) between retinal and reference signals reveals that the distinction between direct and inferential theories largely depends on: (1) a mistaken belief that perceptual veridicality is evidence that extraretinal information is not involved, and (2) a failure to distinguish between (the perception of) absolute object motion in space and relative motion of objects with respect to each other. The model corrects these errors, and provides a new, unified framework for interpreting many phenomena in the field of motion perception.

Difference of climbing fiber input sources between the primate oculomotor-related cerebellar vermis and hemisphere revealed by a retrograde tracing study

The cerebellar flocculus-paraflocculus complex, vermal lobule VII (V-7) and hemispheric lobule VII (H-7) are involved in learning-dependent smooth pursuit eye movement control. To locate the sources of climbing fiber inputs to the H-7 and V-7, we injected retrograde tracers and examined the locations of retrogradely labeled neurons in the inferior olive in 4 monkeys. After the injection of cholera toxin B (CTB) into the H-7, retrogradely labeled neurons were observed abundantly in cell group d, i.e., dorsal cap, of the caudal medial accessory olive (MAO) and ventral lamella of principal olive (PO). After injections of fast blue (FB) into the V-7, retrogradely labeled neurons were observed mainly in cell group b of MAO, but rarely in cell group d or PO. Cell group d is known to receive inputs from the nucleus optic tract (NOT) and project climbing fibers to the flocculus and ventral paraflocculus, and cell group b is known to receive inputs from the superior colliculus. These results suggest that the three oculomotor cerebellar areas may use different visual signals for the control of smooth pursuit: the flocculus-paraflocculus complex and H-7 receive visual climbing fiber inputs derived mainly from the NOT via cell group d, while the V-7 receive visual climbing fiber inputs derived mainly from the superior colliculus via cell group b.

The accessory optic system: basic organization with an update on connectivity, neurochemistry, and function

The accessory optic system (AOS) is formed by a series of terminal nuclei receiving direct visual information from the retina via one or more accessory optic tracts. In addition to the retinal input, derived from ganglion cells that characteristically have large receptive fields, are direction-selective, and have a preference for slow moving stimuli, there are now well-characterized afferent connections with a key pretectal nucleus (nucleus of the optic tract) and the ventral lateral geniculate nucleus. The efferent connections of the AOS are robust, targeting brainstem and other structures in support of visual-oculomotor events such as optokinetic nystagmus and visual-vestibular interaction. This chapter reviews the newer experimental findings while including older data concerning the structural and functional organization of the AOS. We then consider the ontogeny and phylogeny of the AOS and include a discussion of similarities and differences in the anatomical organization of the AOS in nonmammalian and mammalian species. This is followed by sections dealing with retinal and cerebral cortical afferents to the AOS nuclei, interneuronal connections of AOS neurons, and the efferents of the AOS nuclei. We conclude with a section on Functional Considerations dealing with the issues of the response properties of AOS neurons, lesion and metabolic studies, and the AOS and spatial cognition.

Human motion perception and smooth eye movements show similar directional biases for elongated apertures

Although numerous studies have examined the relationship between smooth-pursuit eye movements and motion perception, it remains unresolved whether a common motion-processing system subserves both perception and pursuit. To address this question, we simultaneously recorded perceptual direction judgments and the concomitant smooth eye-movement response to a plaid stimulus that we have previously shown generates systematic perceptual errors. We measured the perceptual direction biases psychophysically and the smooth eye-movement direction biases using two methods (standard averaging and oculometric analysis). We found that the perceptual and oculomotor biases were nearly identical, suggesting that pursuit and perception share a critical motion processing stage, perhaps in area MT or MST of extrastriate visual cortex.

Can illusory motion disrupt tracking real motion?

When rotating stripes or other periodic stimuli cross the retina at a critical rate, a reversal in the direction of motion of the stimuli is often seen. This illusion of motion perception was used to explore the roles of retinal and perceived motion in the generation of optokinetic nystagmus. Here we show that optokinetic nystagmus is disrupted during the perception of this illusion. Thus, when perceived and actual motion are in conflict, subjects fail to track the veridical movement. This observation suggests that the perception of motion can directly influence optokinetic nystagmus, even in the presence of a moving retinal image. A conflict in the neural representation of motion in different brain areas may explain these findings.

Efferent pathways of the nucleus of the optic tract in monkey and their role in eye movements

To clarify the role of the pretectal nucleus of the optic tract (NOT) in ocular following, we traced NOT efferents with tritiated leucine in the monkey and identified the cell groups they targeted. Strong local projections from the NOT were demonstrated to the superior colliculus and the dorsal terminal nucleus bilaterally and to the contralateral NOT. The contralateral oculomotor complex, including motoneurons (C-group) and subdivisions of the Edinger-Westphal complex, including motoneurons (C-group) and subdivisions of the Edinger-Westphal complex, also received inputs. NOT efferents terminated in all accessory optic nuclei (AON) ipsilaterally; contralateral AON projections arose from the pretectal olivary nucleus embedded in the NOT. Descending pathways contacted precerebellar nuclei: the dorsolateral and dorsomedial pontine nuclei, the nucleus reticularis tegmenti pontis, and the inferior olive. Direct projections from NOT to the ipsilateral nucleus prepositus hypoglossi (ppH) appeared to be weak, but retrograde tracer injections into rostral ppH verified this projection; furthermore, the injections demonstrated that AON efferents also enter this area. Efferents from the NOT also targeted ascending reticular networks from the pedunculopontine tegmental nucleus and the locus coeruleus. Rostrally, NOT projections included the magnocellular layers of the lateral geniculate nucleus (lgn); the pregeniculate, peripeduncular, and thalamic reticular nuclei; and the pulvinar, the zona incerta, the mesencephalic reticular formation, the intralaminar thalamic nuclei, and the hypothalamus. The NOT could generate optokinetic nystagmus through projections to the AON, the ppH, and the precerebellar nuclei. However, NOT also projects to structures controlling saccades, ocular pursuit, the near response, lgn motion sensitivity, visual attention, vigilance, and gain modification of the vestibulo-ocular reflex. Any hypothesis on the function of NOT must take into account its connectivity to all of these visuomotor structures.

Projections from visual areas of the cerebral cortex to pretectal nuclear complex, terminal accessory optic nuclei, and superior colliculus in macaque monkey

The purpose of this study was to analyze the projections from visually related areas of the cerebral cortex of rhesus monkey to subcortical nuclei involved in eye-movement control; i.e., the pretectal nuclear complex, the terminal nuclei of the accessory optic system (AOS), and the superior colliculus (SC). The anterograde tracer 3H-leucine was pressure injected bilaterally into the cortex of six monkeys (for a total of 12 cases) involving the primary visual cortex (area 17); the medial prestriate cortex (medial 18/19); dorsomedial area 19; the caudal portion of the cortex of the superior temporal sulcus, upper bank (cytoarchitectural area OAa) and lower bank (area PGa); the lower bank of the caudal lateral intraparietal sulcus (area POa); and the inferior parietal lobule (area 7). The results revealed that the pretectal nucleus of the optic tract received inputs from medial prestriate cortex, dorsomedial part of area 19, OAa, and PGa. The posterior pretectal nucleus received sparse projections from area 7 and the cortex lining the intraparietal sulcus (dorsomedial part of area 19 and POa). The pretectal olivary nucleus was targeted by neurons in cortex of dorsomedial area 19, and the anterior pretectal nucleus was targeted by neurons in both dorsomedial 19 and area 7. The nuclei of the AOS (dorsal terminal; lateral terminal; and interstitial nuclei of the superior fasciculus, posterior and medial fibers) received projections exclusively from areas OAa and PGa. Furthermore, in one case with PGa injection, the medial terminal nucleus, dorsal portion, was also labeled. The visual cortical areas studied projected differentially upon the SC laminae. The primary visual area 17 projected only to the superficial laminae, i.e., stratum zonale (SZ), stratum griseum superficiale (SGS), and stratum opticum (SO). On the other hand, the medial portion of the prestriate cortex and caudal OAa and PGa targeted the superficial and intermediate laminae, i.e., SZ, SGS, SO, and stratum griseum intermediale (SGI), whereas caudal area POa projected primarily to the intermediate layer SGI. Rostral area 7 (mainly 7b) neurons terminated in the stratum album intermediale (SAI); no SC terminals were found in a case in which caudal area 7 (mainly 7a) was injected.

Pattern of striate cortical projections to the pretectal complex in the guinea pig

The primary goal of this study was to determine whether the striate cortex (Oc 1) of the guinea pig projects to the pretectal nucleus of the optic tract (NOT), the first postretinal station of the horizontal optokinetic pathway, and, if so, to analyze the anatomical organization of this cortico-NOT projection. Other goals of this investigation are to identify other pretectal nuclear projections from the visual cortex in the guinea pig, and to determine whether there is any visuotopic organization in this pathway. Axonal tracers (biocytin or 3H-leucine) were injected into the striate cortex (Oc 1), and the tissue processed with histochemical or light autoradiographic techniques. All subcortical terminal labeling is ipsilateral in the basal ganglia and thalamic nuclei. Furthermore, projections are traced to the ipsilateral brainstem, including two areas of the pretectal complex: (1) one in the NOT, extending in some cases to the adjacent lateral portion of the posterior pretectal nucleus (PPN), and (2) one in the pars compacta of the anterior pretectal nucleus (APNc). The terminal fields in the APN are consistently located rostrally in the dorsolateral portion of the nucleus, independently of the injection site in Oc 1, whereas in the NOT the terminal fields shift slightly after injections placed in different locations in the striate cortex. A correlation of the injection sites in Oc 1 and terminal fields in the NOT reveals a loose topographic organization in the cortico-NOT projection; accordingly, the rostrocaudal axis of the striate cortex projects to the lateromedial axis of the NOT, with a 90 degrees rotation, whereas lateral parts of the striate cortex project diffusely throughout the rostrocaudal extent of the NOT. These data show for the first time that the NOT in the guinea pig receives a substantial projection from the visual cortex. Given the fact that in the guinea pig the optokinetic nystagmus shares some of the characteristics found in cat and monkey (i.e., consistent initial fast rise in the slow phase velocity and reduced asymmetry in monocular stimulation), the present findings lend support to the hypothesis that a cortical input to the NOT is a necessary condition for these oculomotor properties to be present.

Linear vection in the central visual field facilitated by kinetic depth cues

Illusory self-motion (vection) is thought to be determined by motion in the peripheral visual field, whereas stimulation of more central retinal areas results in object-motion perception. Recent data suggest that vection can be produced by stimulation of the central visual field provided it is configured as a more distant surface. In this study vection strength (tracking speed, onset latency, and the percentage of trials where vection was experienced) and the direction of self-motion produced by displays moving in the central visual field were investigated. Apparent depth, introduced by using kinetic occlusion information, influenced vection strength. Central displays perceived to be in the background elicited stronger vection than identical displays appearing in the foreground. Further, increasing the eccentricity of these displays from the central retina diminished vection strength. If the central and peripheral displays were moved in opposite directions, vection strength was unaffected, and the direction of vection was determined by motion of the central display on almost half of the trials when the centre was far. Near centres produced fewer centre-consistent responses. A complete understanding of linear vection requires that factors such as display size, retinal locus, and apparent depth plane are considered.

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.

Preoccipital cortex receives a differential input from the frontal eye field and projects to the pretectal olivary nucleus and other visuomotor-related structures in the rhesus monkey

The bidirectional axonal transport capabilities of the horseradish peroxidase (HRP) technique facilitated the study of the frontal-eye-field (FEF) input and pretectal output of two regions of extrastriate preoccipital cortex (POC). Following horseradish peroxidase (HRP) gel implants into the middle and dorsal POC in two rhesus monkeys, the middle POC implant demonstrated retrograde frontal cortical labeling largely restricted to the inferior frontal eye field (iFEF) and adjacent inferior prefrontal convexity, whereas the dorsal POC implant showed labeling in the caudal ventral bank of the superior ramus of the arcuate sulcus (sas) and middle-to-dorsal region of the rostral bank of the concavity of the arcuate sulcus (dorsal FEF). Prominent anterogradely labeled efferent preoccipital projections were observed to the ipsilateral pretectal olivary nucleus (PON) and to a lesser extent the anterior pretectal nucleus. Although the middle POC case had heavier projections to the lateral PON, the dorsal case projected more heavily to the medial PON. In addition, both implants demonstrated subcortical connections with the lateral and dorsal inferior pulvinar nuclei, central superior lateral thalamic intralaminar nucleus, caudate nucleus, and middle-to-ventral claustrum. However, while the middle POC implant had efferent projections to the superficial superior colliculus (SC), pregeniculate nucleus (PGN), lateral terminal accessory optic nucleus (LTN), and dorsolateral pontine nucleus (DLPN), resembling those previously reported for the middle temporal (MT) visual area (Maunsell & Van Essen, 1982; Ungerleider et al., 1984), the dorsal implant had projections to the lateral intermediate SC, zona incerta (ZI), PGN, a notably lesser projection to the LTN, and basilar pontine projections to the lateral and lateral dorsal pontine subnuclei (not including the extreme dorsolateral DLPN). These preliminary results suggest that the preoccipital cortex, which reportedly functions in pupillary constriction, accommodation, and convergence, entertains connections with the PON and other visuomotor-related structures, and thus could act as an intermediary in the pathway between the iFEF and PON, and provide a possible explanation for pupillary effects that occur with stimulation of the FEF (Jampel, 1960) and within the contex of other oculomotor activities. The findings shed light on certain differences in connections of middle vs. dorsal POC with visuomotor-related nuclei, and appear to suggest that the middle region, which receives input from the iFEF, has greater access to the optokinetic (OKN) system by virtue of its projection to the LTN, and to the smooth-pursuit system b