Allocentric and egocentric reference frames in the processing of three-dimensional haptic space

In an earlier experiment we showed that selective attention plays a critical role in rabbit eye blink conditioning (Steele-Russell et al. in Exp Brain Res 173:587–602, 2006). The present experiments are concerned to examine the extent to which visual recognition processes are a separate component from the motor learning that is also involved in conditioning. This was achieved by midline section of the optic chiasma which disconnected the direct retinal projections via the brainstem to the cerebellar oculomotor control system. By comparing both normal and chiasma-sectioned rabbits it was possible to determine the dependence or independence of conditioning on the motor expression of the eye blink response during training. Both normal and chiasma-sectioned animals were tested using a multiple test battery to determine the effect of this redirection of the visual input pathways on conditioning. All animals were first tested for any impairment in visual capability following section of the optic chiasma. Despite the loss of 90% of retinal ganglion cell fibres, no visual impairment for either intensity or pattern vision was seen in the chiasma animals. Also no difference was seen in nictitating membrane (NM) conditioning to an auditory signal between normal and chiasma animals. Testing for motor learning to a visual signal, the chiasma rabbits showed a complete lack of any NM conditioning. However the sensory tests of visual conditioning showed that chiasma-sectioned animals had completely normal sensory recognition learning. These results show that NM Pavlovian conditioning involves anatomically separate and independent sensory recognition and motor output components of the learning. This research was supported by S&W research grants ID# 1810 to ISR and ID# 7985 to JAC.     

Right-hemispheric dominance of spatial memory in split-brain mice

Left-right asymmetry of human brain function has been known for a century, although much of molecular and cellular basis of brain laterality remains to be elusive. Recent studies suggest that hippocampal CA3-CA1 excitatory synapses are asymmetrically arranged, however, the functional implication of the asymmetrical circuitry has not been studied at the behavioral level. In order to address the left-right asymmetry of hippocampal function in behaving mice, we analyzed the performance of "split-brain" mice in the Barnes maze. The "split-brain" mice received ventral hippocampal commissure and corpus callosum transection in addition to deprivation of visual input from one eye. In such mice, the hippocampus in the side of visual deprivation receives sensory-driven input. Better spatial task performance was achieved by the mice which were forced to use the right hippocampus than those which were forced to use the left hippocampus. In two-choice spatial maze, forced usage of left hippocampus resulted in a comparable performance to the right counterpart, suggesting that both hippocampal hemispheres are capable of conducting spatial learning. Therefore, the results obtained from the Barnes maze suggest that the usage of the right hippocampus improves the accuracy of spatial memory. Performance of non-spatial yet hippocampus-dependent tasks (e.g. fear conditioning) was not influenced by the laterality of the hippocampus.     

Retinal projections into the Zona Incerta of the rock cavy (Kerodon rupestris): A CTb study

The Zona Incerta is a key neural substrate of higher brain functions. A neural population in the caudal ZI projects into the superior colliculus. This recently has been identified as an important structure for the saccades. Applying CTb, we describe a retinal projection into the caudal ZI and the distribution of its terminal varicosities in the rock cavy, a Brazilian rodent, which has been used as an anatomical model to enhance the comprehension about the phylogeny of the nervous system. Contrary to other investigated rodents, the retinal fibers in the rock cavy lie in the caudal Zona Incerta (ZIc), suggesting a functional specialization in the rock cavy. The high resolution and qualitative analysis of retinal fibers in the present work provide a substrate to interpretation of the visual system, and its phylogenetic pathways among species.     

Ageing of the Aboriginal and Torres Strait Islander population: numerical,structural, timing and spatial aspects

Objectives : To assess levels of numerical, structural, timing and spatial aspects of ageing of the Aboriginal and Torres Strait Islander population. Methods : Population projections for 15 Australian regions were created by a multi‐state cohort‐component model. Results : The older (45‐plus) population grew from 29,815 in 1986 to 167,259 in 2016. In the subsequent 30 years, we project growth to 448,785 people. Growth rates of the older population vary: from 200% in the 60–64‐year‐old group to 800% growth in the 85‐plus age group by mid‐century. This strong numerical ageing is reflected in a shift in structural ageing by about six percentage points. Selected areas outside of capital cities are structurally older than many cities. Numerical ageing is strongest in capital cities and New South Wales. Cohort flow is the primary driver of ageing. Conclusions : Numerical and structural ageing is projected to increase significantly to mid‐century with important spatial variations. Population ageing is largely irreversible. Implications for public health : High numerical growth in the older Aboriginal and Torres Strait Islander population poses implications for increased demand for a range of health and care services. Variations in spatial and timing aspects of ageing indicate demand will peak earlier in some geographical locations relative to others.     

Choleragenoid horseradish peroxidase used for studying projections of some hindlimb cutaneous nerves and plantar foot afferents to the dorsal horn and Clarke's column in the rat

Summary The aim of the present study has been to investigate the spinal projections of cutaneous hindlimb afferents particularly to the deep dorsal horn and to Clarke's column (CC), by using the B-subunit of cholera toxin conjugated to horseradish peroxidase. Injections into three different cutaneous hindlimb nerves in adult rats resulted in dense labeling in the dorsal horn laminae II_i-IV/V, moderate labeling in lamina I and modest labeling in dorsomedial parts of CC. Footpad injections gave similar results, except for a lack of labeling in CC and only weak labeling in laminae I and V. The results suggest that B-HRP should be a useful marker for studying cutaneous myelinated nerve fiber projections to the rat spinal cord.     

Differential ascending projections from neurons in the cat's lateral cervical nucleus

Extracellular microelectrode recordings were made from single cells of the lateral cervical nucleus (LCN) in cats anaesthetized with chloralose and paralysed with gallamine triethiodide. The cells were tested for antidromic activation from the contralateral medial lemniscus and the contralateral tectum. Seventytwo LCN units were recorded which projected to one or both targets. Sixty (83%) projected through the medial lemniscus, and of these 36 (50% of the total) also projected to the tectum, whereas 24 (33%) projected through the medial lemniscus only; 12 (17%) projected only to the tectum. Twenty-nine units (40%) were excited by moving hairs of the coat but not by pinch of the skin, and 9 (31%) of these projected to the tectum, 11 (38%) through the medial lemniscus and 9 (31%) to both targets. Forty units (56%) were excited by hair movement and noxious pinch, and 3 (7%) of these projected to the tectum, 10 (25%) through the medial lemniscus and 27 (68%) to both targets. Three units (4%) had no discernible receptive fields and they all projected through the medial lemniscus, but not to the tectum. Of the 12 units projecting only to the tectum, 11 had receptive fields completely or partially on the trunk. Units projecting either through the medial lemniscus only, or through the medial lemniscus and also into the tectum, had receptive fields more widely distributed: these included small fields on the fore- and hind feet, on the limbs and also, a minority, on the trunk. Units with glove- or stocking-like receptive fields projected through the medial lemniscus. The results show that while most LCN cells project through the medial lemniscus, those excited by hair movement alone preferentially project either to the tectum or through the medial lemniscus, but not by both routes. The differences in receptive field properties of the differently projecting units are discussed in terms of the possible functions of the spinocervical system.     

A horseradish peroxidase procedure for tracing the central projections of peripheral nerves in exsanguinated anamniotes

This report outlines a procedure for demonstrating the central connections of peripheral nerves in anamniotes by exposing the nerves to horseradish peroxidase (HRP) subsequent to perfusion of the animal with cold saline. The tissue is fixed by immersion after a 6-10 h exposure to the HRP, embedded, sectioned and finally reacted using tetramethylbenzidine as a chromogen. The pattern of afferent projections of the posterior lateral line nerve in the teleost fish Crenicichla as demonstrated by this 'pre-perfused' technique is very similar to the pattern seen when using a standard HRP procedure requiring a post-operative survival period. The utility of the pre-perfused technique is discussed.     

Direct retinal projections of the “non-image forming” system to the hypothalamus,anterodorsal thalamus and basal telencephalon of mink (Mustela vison) brain

Summary The retinal projections of the non-image forming system to the hypothalamus, anterodorsal thalamus and basal telencephalon were visualized in adult mink using the anterograde transport of cholera toxin conjugated to horseradish peroxidase injected intraocularly. A major and nearly symmetrical bilateral input of labeled retinal fibers to the suprachiasmatic nuclei was observed. A dense innervation was also evident in both paraventricular nuclei, and in the anterior, lateral and mediobasal hypothalamus on the side contralateral to the injection. Two projections leaving the optic tract at the level of the lateral hypothalamus or after crossing the geniculate body entered the anterior thalamus and ran in a ventro-dorsal or a caudorostral direction before terminating in the stria terminalis. Fibers were also observed in the horizontal limb of the diagonal band of Broca. These observations are compared to those in other mammalian species and discussed according to their possible implication in photoperiodic signal processing.Abbreviations AC Anterior commissure - AH Anterior hypothalamus - BNST Bed Nucleus Stria Terminalis - DB Diagonal Band of Broca - F Fornix - LH Lateral Hypothalamus - LV Lateral Ventricle; - MBH Mediobasal Hypothalamus - ME Median Eminence - MT Mamillothalamic tract - OC Optic chiasm - OT Optic tract - POA Preoptic Area - PVN Paraventricular nucleus - SCN Suprachiasmatic Nucleus - SM Stria Medullaris - ST Stria Terminalis - V Third Ventricle     

大鼠终纹床核5-羟色胺免疫阳性神经纤维和终支的起源

本文用WGA-HRP逆行束路追踪结合免疫酶组织化学双标记法,对大鼠终纹床核5-羟色胺(5-HT)免疫阳性神经纤维和终支(5-HT纤维)的起源进行了研究。结果如下,终纹床核主要区域的5-HT纤维,除主要起源于中缝背核和中央上核外,尚有部分纤维源自B_9组细胞群和尾侧线形核;在这些发出纤维支配终纹床核的中缝核神经元中,约有1/3为5-HT免疫阳性且主要为同侧;除少数区域外,这些核群内所有类型的5-HT免疫阳性神经元均有部分发出纤维投射到终纹床核。     

Development of the occipital corticotectal projection in the hamster

Summary Anterograde and retrograde labelling with the carbocyanine dye, Di-I, was used to assess the development of the visual cortical projection to the superior colliculus (SC) in pre- and postnatal hamsters. Posterior cortical axons arrive in the SC on postnatal (P-) day one (the first 24 hours after birth = P-0) and begin to arborize in the superficial laminae (the stratum griseum superficiale [SGS] and stratum opticum [SO]) within one day after they enter the tectum. Over succeeding days, the density of the projection increases and numerous labelled fibers are visible throughout the depth of the SGS and SO. Beginning on P-6, there is a decrease in the density of labelled fibers in the upper SGS and by P-10, the laminal distribution of the occipital corticotectal pathway appears adult-like. Anterograde tracing with Di-I also revealed the presence of a few corticotectal fibers that crossed the midline in both the SC and posterior commissures to terminate mainly in the superficial tectal laminae contralateral to the injection site. Crossed corticotectal fibers were visible in hamsters aged between P-3 and P-12. Retrograde tracing with Di-I in hamsters killed between P-3 and P-12 demonstrated that both the ipsilateral and crossed corticotectal projections arose exclusively from pyramidal cells in developing lamina V.