Olivofloccular circuit in oculomotor control: binocular optokinetic stimulation

The metabolic activation of the olivocerebellar pathway during binocular optokinetic stimulation was studied in the guinea pig, by means of the semiquantitative C-14-2-deoxyglucose (2DG) technique. The experimental group underwent binocular horizontal stimulation, whereas the control animals were either kept in the dark or allowed to view a stationary pattern. The local metabolic activity index in the dorsal cap of the inferior olive was higher on the side contralateral to the eye that had been stimulated in the temporonasal (T-N) direction in the horizontal group; in contrast, the floccular region showed higher activity on the side ipsilateral to the T-N-stimulated eye. These findings support the involvement of the olivocerebellar pathway in the horizontal optokinetic response. A phylogenetic hypothesis is suggested to explain inconsistent results found in the literature

Correlation between amount of retinal afferents to the pretectal nucleus of the optic tract and dorsal terminal accessory optic nucleus and performance of horizontal optokinetic reflex in rat

Intraocular kainic acid injection in Long-Evans rats induces loss of retinal afferents to subcortical visual centers as assessed by the axoplasmic transport of [C-14]valine. The optical terminal fields of the pretectal nucleus of the optic tract (NOT), superior colliculus and accessory optic system (AOS) nuclei appear particularly affected. Since NOT and the AOS dorsal terminal nucleus (DTN) represent the first relay station of the visuomotor pathway mediating horizontal optokinetic nystagmus (HOKR), we have studied the characteristics of HOKR after various degrees of retinal deafferentiation of these nuclei induced by intraocular KA injection. Taking advantage of the arrangement of the primary optic projections to NOT-DTN, that in rats are almost entirely crossed, in each animal, monocular HOKR induced by stimulation of the injected eye was compared to monocular HOKR elicited by stimulation of the intact, ipsilateral eye. Following NOT-DTN optic denervation, HOKR gain always worsened, and in a way, that the greater the deficits of retinal afferents, the greater the HOKR inability to compensate for visual motion. Furthermore, for any given retinal denervation the higher the stimulus velocity, the greater the HOKR deficit. While the correlation between HOKR gain and the amount of retinal afferents to NOT-DTN would seem to indicate a functional homogeneity of the retinal ganglion cells sending axons to these nuclei, the finding that the extent of HOKR impairment also varied with velocity might not support the above view

The interstitial nucleus of the superior fasciculus, posterior bundle (INSFp) in the guinea pig: another nucleus of the accessory optic system processing the vertical retinal slip signal.

As in rabbit, gerbil, and rat, the guinea pig interstitial nucleus of the superior fasciculus, posterior bundle (INSFp) is a sparse assemblage of neurons scattered among the fibers forming the fasciculus bearing this name. Most of the INSFp neurons are small and are ovoid in shape. Interspersed among these, are a few larger, elongated neurons whose density becomes greater and whose shape becomes fusiform in correspondence to the zone of transition from the superior fasciculus to the ventral part of the medial terminal nucleus (MTN). Like the MTN, the INSFp is activated by retinal-slip signals evoked by whole-field visual patterns moving in the vertical direction, as shown by the increase of 14C-2-deoxyglucose (2DG) uptake into this nucleus. At the same level of luminous flux, neither pattern moving in the horizontal direction nor the same pattern held stationary can elicit increases in the INSFp 2DG assumption. The specificity of the observed increases in metabolic rates in INSFp following vertical whole-field motion suggests that this assemblage of neurons relays visual signals used in the control of vertical optokinetic nystagmus

Correspondence between the activation of the nucleus tractus optici and the appearance of optokinetic nystagmus in the albino guinea pig

It is known that albinism is accompanied by several visual disturbances. The anomalous features of the optokinatic eye nystagmus (OKN) found in albino strains of different species have been ascribed to he same visual defects. The occurrence of a clear horizontal OKN in albino Guinea pig led us to investigate activity in the Nucleus of the optic tract (NOT

Neural circuits underlying ketamine induced oculomotor behavior in the rat: 2-deoxyglucose studies

Time-related changes in oculomotor function and of metabolic activity patterns in selected brain networks, as assessed by the quantitative 2-deoxyglucose technique, were investigated in Long-Evans rats following intraperitoneal administration of a ketamine anesthetic dose. During ketamine-induced anesthesia a nystagmic-like behavior was present, characterized by unidirectional slow ocular drifts with superimposed paroxystic bursts of quick (saccadic-like) eye movements; all quick movements were executed in the horizontal direction, were strictly confined to an ocular hemifield of vision, and were followed by a backward (centripetal) drift. A metabolic hyperactivity was found in the dorsomedial shoulder region of the frontal cortex, corresponding to the rat saccadic cortical generator area, whereas functional activity levels were decreased in cerebellum and in several brainstem regions, including portions of the reticular formation and medial vestibular nuclei, putatively indicated as the locus of the oculomotor neural integrator. Starting 2 h after drug injection, a gradual recovery of oculomotor function occurred, with the disappearance of slow ocular drifts. However, an almost uninterrupted sequence of individual saccades was still present. Significant metabolic increases were found at this time in the cingulate and frontal cortex, basal ganglia, superior colliculus, paramedian reticular formation and oculomotor nuclei, the cerebellar vermis and paraflocculus. In medial vestibular nuclei, metabolic levels were undistinguishable from controls. These results suggest different concentration-dependent actions of ketamine on cortical and subcortical circuits involved in saccade generation and gaze holding. These effects are likely to be related at least in part to antagonism of N-methyl-D-aspartate receptor-mediated functions

Vertebral alveolar echinococcosis-a case report, systematic analysis, and review of the literature.

Alveolar echinococcosis caused by Echinococcus multilocularis is an infrequent zoonosis with a high degree of disability, morbidity, and mortality, especially in disease clusters of the northern hemisphere. The diagnosis is complicated by extended incubation time, diverse clinical manifestations, and mimicking of differential diagnoses. The primary organ affected is the liver, but extrahepatic disease is possible, with vertebral involvement in only a few dozen cases described worldwide. Although vertebral alveolar echinococcosis seems to be rare, it might be under diagnosed, and it might be seen more often as the number of people with immunocompromised conditions increases. Recognition of this syndrome is crucial, because advances in medical and surgical management strategies since the introduction of benzimidazole in 1976 have controlled and relieved symptoms in most cases. In this Grand Round, we present the case of a 75-year-old woman who was referred for biopsy of a lumbar lesion 3 months after she was diagnosed with chronic myeloid leukaemia. The diagnosis of hepatic alveolar echinococcosis with metastasis to the lumbar spine and paravertebral region as well as the brain was confirmed by biopsy, PCR, and serology. The patient was given albendazole and referred for palliative surgery with the aim of pain control. Clinical features of the case are presented and discussed in the context of the literature. This case and review illustrate the complexity of extrahepatic alveolar echinococcosis manifestations and the necessity of an interdisciplinary approach

Pathologist computer-aided diagnostic scoring of tumor cell fraction: A Swiss national study.

Tumor cell fraction (TCF) estimation is a common clinical task with well-established large inter-observer variability. It thus provides an ideal testbed to evaluate potential impacts of employing a computer-aided diagnostic (TCFCAD) tool to support pathologists' evaluation. During a National Slide Seminar event, pathologists (n=69) were asked to visually estimate TCF in 10 regions of interest (ROI) from hematoxylin and eosin (H&E) colorectal cancer images intentionally curated for diverse tissue compositions, cellularity, and stain intensities. Next, they re-evaluated the same ROIs while being provided a TCFCAD created overlay highlighting predicted tumor versus non-tumor cells, together with the corresponding TCF percentage. Participants also reported confidence levels in their assessments using a 5-tiers scale, indicating no confidence to high confidence, respectively. The TCF ground truth (GT) was defined by manual cell-counting by experts. When assisted, inter-observer variability significantly decreased, showing estimates converging to the GT. This improvement remained even when TCFCAD predictions deviated slightly from the GT. The standard-deviation of estimated TCF to the GT across ROIs was 9.9% vs 5.8% with TCFCAD, p < 0.0001. The intraclass correlation coefficient increased from 0.8 to 0.93 (CI95% [0.65, 0.93] vs [0.86, 0.98]) and pathologists stated feeling more confident when aided (3.67 ± 0.81 vs. 4.17 ± 0.82 with CAD). TCFCAD estimation support demonstrated improved scoring accuracy, inter-pathologist agreement and scoring confidence. Interestingly, pathologists also expressed more willingness to use such a CAD tool at the end of the survey, highlighting the importance of training/education to increase adoption of CAD systems