bluuebunny/crossref_metadata_2025_split huggingface dataset:
Neural encoding of subject–object distance in a visual recognition system
Authors: Nicol  , Brown  , Horn  
Published: March 2003

AbstractDomestic chicks follow a familiar (imprinted) object when it recedes. In behaving, imprinted chicks with no experience of objects at different distances, neuronal activity was recorded from the intermediate and medial part of the hyperstriatum ventrale (IMHV), a brain region crucial for the recognition memory underlying imprinting. We found that (i) some neurones responded equivalently, irrespective of the subject–object distance d (d‐invariant); (ii) other neurones responded differently at different values of d (d‐sensitive); (iii) these response types were found in monocular chicks and in chicks with both eyes exposed; (iv) the action potential shape of d‐invariant neurones was different from that of other neurones and (v) the spontaneous firing rate of some neurones was correlated with locomotor activity. Taken together with previous findings, the results raise the possibility that IMHV has a major role to play in the sensory and motor‐control aspects of imprinting in addition to its mnemonic functions.
Characterization of the multisynaptic neuronal control of the rat pineal gland using viral transneuronal tracing
Authors: Larsen  , Enquist  , Card  
Published: March 2003

AbstractKnowledge of the polysynaptic pathway conveying photic information to the pineal gland is based upon studies employing lesions, knife cuts and classical tracers. In the present investigation we used viral transneuronal tracing to re‐examine the organization of this circuitry. This was accomplished by injecting a neurotropic alpha herpesvirus (pseudorabies virus) into the gland and localizing viral antigen in infected neurones at various postinoculation intervals. This approach is based upon the demonstrated ability of this virus to invade axon terminals, replicate in neurones and pass retrogradely through a multisynaptic circuit. Immunohistochemical localization of viral antigen revealed the progressive appearance of infected neurones in the superior cervical ganglion (SCG), intermediolateral nucleus of the upper thoracic spinal cord (IML), parvicellular subdivisions of the hypothalamic paraventricular nucleus (PVN), and the suprachiasmatic nucleus (SCN). Other infected cell groups known to project to the IML also became infected. Infection of the PVN reproducibly involved neurones in the dorsal, medial and lateral parvicellular subdivisions and preceded the appearance of infected neurones in the SCN and other regions of hypothalamus. Topographic analysis of virus infected neurones within the SCN revealed differential infection of SCN subdivisions that suggested topography in the projection of the SCN to the PVN. Removal of the SCG eliminated infection within the aforementioned circuitry and revealed a parasympathetic innervation from the sphenopalatine ganglion. The data provide further detail on the cellular identity and synaptology of neural circuitry controlling the rhythmic secretion of melatonin by the rat pineal gland.
Prenatal differentiation of mouse vomeronasal neurones
Authors: Tarozzo  , Cappello  , De Andrea  , Walters  , Margolis  , Oestreicher  , Fasolo  
Published: March 2003

AbstractThe vomeronasal organ (VNO) subserves basic chemosensory functions in rodents, mainly related to sexual behaviour. In order to understand early stages of the VNO structural maturation, we have undertaken an immunocytochemical analysis of the VNO of fetal mice. Our results demonstrate that Olfactory Marker Protein (OMP), a marker of differentiated chemosensory cells, is already expressed in vomeronasal neurones and their fibres projecting to the accessory olfactory bulb during the last week of gestation. However, in contrast to the adult, where its expression is restricted to the medial sensory neuronal component of the VNO, during fetal development OMP is also present in cells located in the lateral non‐sensory epithelial component. Some other markers of nasal chemosensory neurones, such as GAP‐43/B‐50, Protein Gene Product 9.5 (PGP 9.5) and carnosine are also transiently expressed in this ectopic site. These results indicate that (i) significant morphological and biochemical maturation of the VNO is achieved before birth; (ii) transient cell populations, sharing the biochemical profile of the vomeronasal chemosensory receptors, occur in ectopic areas during fetal development.
Synaptic clustering of GABAC receptor ρ‐subunits in the rat retina
Authors: Koulen Peter , Brandstätter Johann Helmut , Enz Ralf , Bormann Joachim , Wässle Heinz 
Published: March 2003

AbstractPolyclonal antibodies which recognize the ρ‐subunits of the GABAC receptor were applied to sections of the rat retina. Strong punctate immunoreactivity was found in the inner plexiform layer (IPL), which was shown by electron microscopy to represent a clustering of the GABAC receptors at synaptic sites. During postnatal development diffuse ρ‐immunoreactivity was first observed at postnatal day P3. Distinct labelling of bipolar cells appeared at P7 and punctate, synaptic labelling was observed at P10. In order to show that the ρ‐immunoreactive puncta coincide with the axons of bipolar cells, double immunostainings of retinal sections with an antiserum against syntaxin 3 and with the ρ‐antiserum were performed. The experiments showed that ρ‐immunoreactive puncta are preferentially located on the axon terminals of rod and cone bipolar cells. In order to determine whether GABAC receptor ρ‐subunits coassemble with GABAA receptor subunits, double‐labelling experiments were performed with subunit specific antisera. Punctate, putative synaptic clustering was observed with all antisera applied, however, GABAC receptor expressing puncta did not coincide with GABAA receptor containing puncta. This suggests that there are no synaptic GABA receptors in the retina in which GABAA and GABAC receptor subunits are coassembled. Similar double‐labelling experiments were also performed to find out whether GABAC receptors and glycine receptors are colocalized. They were clustered at different synapses. This suggests that synaptic GABAC receptors consist of ρ‐subunits and are not coassembled with GABAA‐ or glycine‐receptor subunits.
Role of the cerebellum in reaching movements in humans. I. Distributed inverse dynamics control
Authors: Schweighofer Nicolas , Arbib Michael A. , Kawato Mitsuo 
Published: March 2003

AbstractThis study focuses on the role of the motor cortex, the spinal cord and the cerebellum in the dynamics stage of the control of arm movement. Currently, two classes of models have been proposed for the neural control of movements, namely the virtual trajectory control hypothesis and the acquisition of internal models of the motor apparatus hypothesis. In the present study, we expand the virtual trajectory model to whole arm reaching movements. This expanded model accurately reproduced slow movements, but faster reaching movements deviated significantly from the planned trajectories, indicating that for fast movements, this model was not sufficient. These results led us to propose a new distributed functional model consistent with behavioural, anatomical and neurophysiological data, which takes into account arm muscles, spinal cord, motor cortex and cerebellum and is consistent with the view that the central nervous system acquires a distributed inverse dynamics model of the arm. Previous studies indicated that the cerebellum compensates for the interaction forces that arise during reaching movements. We show here how the cerebellum may increase the accuracy of reaching movements by compensating for the interaction torques by learning a portion of an inverse dynamics model that refines a basic inverse model in the motor cortex and spinal cord.
Role of the cerebellum in reaching movements in humans. II. A neural model of the intermediate cerebellum
Authors: Schweighofer Nicolas , Spoelstra Jacob , Arbib Michael A. , Kawato Mitsuo 
Published: March 2003

AbstractThe cerebellum is essential for the control of multijoint movements; when the cerebellum is lesioned, the performance error is more than the summed errors produced by single joints. In the companion paper ( Schweighofer et al. 1998 ), a functional anatomical model for visually guided arm movement was proposed. The model comprised a basic feedforward/feedback controller with realistic transmission delays and was connected to a two‐link, six‐muscle, planar arm. In the present study, we examined the role of the cerebellum in reaching movements by embedding a novel, detailed cerebellar neural network in this functional control model. We could derive realistic cerebellar inputs and the role of the cerebellum in learning to control the arm was assessed.This cerebellar network learned the part of the inverse dynamics of the arm not provided by the basic feedforward/feedback controller. Despite realistically low inferior olive firing rates and noisy mossy fibre inputs, the model could reduce the error between intended and planned movements. The responses of the different cell groups were comparable to those of biological cell groups. In particular, the modelled Purkinje cells exhibited directional tuning after learning and the parallel fibres, due to their length, provide Purkinje cells with the input required for this coordination task. The inferior olive responses contained two different components; the earlier response, locked to movement onset, was always present and the later response disappeared after learning. These results support the theory that the cerebellum is involved in motor learning.
A presynaptic N‐methyl‐d‐aspartate autoreceptor in rat hippocampus modulating amino acid release from a cytoplasmic pool
Authors: Breukel Alexandra I. M. , Besselsen Elly , Da Silva Fernando H. Lopes , Ghijsen Wim E. J. M. 
Published: March 2003

AbstractA possible role of the N‐methyl‐d‐aspartate receptor (NMDA‐R) as a presynaptic autoreceptor was investigated using Percoll‐purified hippocampus nerve terminals (synaptosomes). This preparation contained only a neglectable amount of postsynaptic structures. Two main effects of NMDA were observed. First, NMDA dose‐dependently (10–100 μm) and in the absence of Mg2+, stimulated basal release of aspartate and glutamate, but not of GABA. MK801 (10 μm), an open NMDA‐R‐channel blocker, reduced this effect even below control levels, indicating endogenous NMDA‐R activation. By superfusing synaptosomes, which prevents a tonic receptor occupation, also basal GABA release was stimulated by NMDA. The NMDA‐induced potentiation of amino acid superfusate levels was blocked both by MK801 and Mg2+ (1 m
m), was slow in onset and returned to baseline after NMDA‐removal. The NMDA‐effect was also found in the absence of extracellular Ca2+, suggesting that amino acids were released from a non‐vesicular (cytoplasmic) pool. Secondly, in KCl‐depolarized synaptosomes exposed to 1 m
m Mg2+, NMDA did not affect the release of the amino acids. MK801, however, reduced the KCl‐evoked Ca2+‐independent release of aspartate and glutamate, but not of GABA.
l‐trans‐PDC, the selective inhibitor of the glutamate/aspartate transporter, prevented this MK801‐effect, suggesting a coupling between NMDA‐Rs and these transporters.These data provide evidence for a presynaptic NMDA autoreceptor in rat hippocampus. We speculate on the role of this NMDA‐R to depolarize the presynaptic membrane by Na+‐entry, which may induce reversal of amino acid transporters and thereby releasing amino acids from a cytoplasmic pool.
Eye position encoding in the macaque posterior parietal cortex
Authors: Bremmer  , Pouget  , Hoffmann K. ‐P. 
Published: March 2003

AbstractIn two previous studies, we had demonstrated the influence of eye position on neuronal discharges in the middle temporal area, medial superior temporal area, lateral intraparietal area and area 7A of the awake monkey ( Bremmer et al. 1997a , b). Eye position effects also have been found in visual cortical areas V3A and V6 and even in the premotor cortex and the supplementary eye field. These effects are generally discussed in light of a coordinate transformation of visual signals into a non‐retinocentric frame of reference. Neural network studies dealing with the eye position effect succeeded in constructing such non‐retinocentric representations by using model neurones whose response characteristics resembled those of ‘real’ neurones. However, to our knowledge, response properties of real neurones never acted as input into these neural networks. In the present study, we thus investigated whether, theoretically, eye position could be estimated from the population discharge of the (previously) recorded neurones and, if so, we intended to develop an encoding algorithm for the position of the eyes in the orbit. The optimal linear estimator proved the capability of the ensemble activity for determining correctly eye position. We then developed the so‐called subpopulation encoding of eye position. This algorithm is based on the partition of the ensemble of neurones into two pairs of subpopulations. Eye position is represented by the differences of activity levels within each pair of subpopulations. Considering this result, encoding of the location of an object relative to the head could easily be accomplished by combining eye position information with the intrinsic knowledge about the retinal location of a visual stimulus. Taken together, these results show that throughout the monkey’s visual cortical system information is available which can be used in a fairly simple manner in order to generate a non‐retinocentric representation of visual information.
Adaptation in patterns of c‐fos expression in the brain associated with exposure to either single or repeated social stress in male rats
Authors: Martinez Manuela , Phillips Peter J. , Herbert Joe 
Published: March 2003

AbstractIntraspecific confrontation between male rats represents a biologically relevant form of social stress. C‐fos expression has been used to map the pattern of neural activation following either a single (acute) or repeated (10 times) exposure of an intruder male to a larger male in the latter’s home cage. These conditions induce high levels of aggressive interaction.Sixty minutes after a single defeat, there was intense c‐fos expression (quantified using image analysis) in restricted areas of the basal forebrain (including lateral septum, bed nucleus of stria terminalis, lateral preoptic area, lateral hypothalamic area, paraventricular nucleus, and medial and central amygdala) as well as in the autonomic and monoaminergic nuclei of the brainstem (central grey, dorsal and median raphe, locus coeruleus and nucleus of the solitary tract). After the tenth defeat, this pattern was modified despite persistently high levels of aggression. Some areas in the forebrain (bed nucleus of stria terminalis, paraventricular nucleus and medial amygdala) continued to express increased c‐fos; others (the septum, lateral hypothalamic area, lateral preoptic area and central amygdala) no longer expressed c‐fos. The brainstem response was equally varied: the central grey and the raphe nuclei continued to respond after repeated defeat, whereas the solitary nucleus and locus coeruleus did not. On the other hand, there was no change in the behaviour of intruder rats after repeated defeat.This study shows the pattern of adaptation at a cellular level in the basal forebrain and brainstem to repeated defeat. As in our previous studies of repeated restraint, modulation in the expression of c‐fos following repeated stress is highly regionally specific, suggesting that differential neural processing is involved in adaptation to social stress.
Functional diversity of synaptic AMPA/KA receptors from rat as revealed by subtype‐specific antagonists
Authors: Weigand Erik , Keller Bernhard U. 
Published: March 2003

AbstractSubtype‐specific pharmacological compounds represent important tools to identify the molecular components of synaptically activated glutamate receptors in central neurones. Here, we utilized a collection of subtype‐specific antagonists and modulators to investigate the functional profile of glutamate receptors in identified synapses in thin slices of the cerebellum, hippocampus and brain stem. During whole‐cell patch‐clamp recordings α‐amino‐3‐hydroxy‐5‐methyl‐4‐isoxazolepropionate/kainate (AMPA/KA) receptor‐mediated synaptic currents (EPSCs) in cerebellar Purkinje cells were (i) prolonged by 100 μm cyclothiazide, (ii) not significantly changed after preincubation in 10 μm concanavalin A, (iii) not affected by 1 μm Evans Blue or polyamine toxin analogue N‐(4‐hydroxyphenylpropanolyl)‐spermine (NHPPS), but (iv) significantly reduced by high (≥ 100 μm) concentrations of Evans Blue. These pharmacological properties were distinct from those observed in hippocampal granule cells and brain stem interneurones and markedly different from those of recombinant glutamate receptor channels GluR1–GluR6 previously investigated in heterologous expression systems.
Incorporation of mouse neural progenitors transplanted into the rat embryonic forebrain is developmentally regulated and dependent on regional and adhesive properties
Authors: Olsson Martin , Bjerregaard Kristoffer , Winkler Christian , Björklund Monte Gates anders , Campbell Kenneth 
Published: March 2003

AbstractDuring development, telencephalic neural progenitors acquire positional specification and give rise to distinct structures such as the striatum and cortex. Here, we examine, in vivo, the influence of developmental stage, cell‐surface molecules and regional differences along the dorso‐ventral and antero‐posterior axes on the selective incorporation of neural progenitors derived from different regions of the developing brain, utilizing a cross‐species in utero transplantation paradigm. Striatal progenitors derived from the embryonic day (E) 12–14 mouse lateral ganglionic eminence (LGE) were observed consistently to incorporate into the developing striatum as early as 24–48 h following intraventricular injection into the E15–17 rat host. By removing cell‐surface molecules from the LGE progenitors, the pattern of incorporation was remarkably different with no preferential striatal incorporation. Cortical progenitors with intact cell‐surface molecules, by contrast, displayed little telencephalic (including striatal) incorporation as compared with precursors from the LGE. However, both progenitors from cortex and LGE incorporated widely into diencephalic and mesencephalic structures. The capacity for integration of precursors derived from the LGE and cortex gradually decreased during development of the host and was minimal in the postnatal day (P) 1 host. Unlike the telencephalic precursors, the vast majority of progenitors derived from the midbrain and cerebellar primordium (with cell‐surface molecules intact) incorporated into diencephalic and midbrain nuclei with only a few cells observed in the telencephalon. These results demonstrate that incorporation of neural progenitors across the ventricular wall in the embryonic host is strictly developmentally regulated, dependent on their position along the antero‐posterior axes and in the case of progenitors from the LGE is mediated by cell‐surface molecules expressed on the transplanted cells.
Long‐term protection of the rat nigrostriatal dopaminergic system by glial cell line‐derived neurotrophic factor against 6‐hydroxydopamine in vivo
Authors: Sullivan  , Opacka‐Juffry  , Blunt  
Published: March 2003

Glial cell‐line‐derived neurotrophic factor (GDNF) has been shown to enhance the survival of dopaminergic neurones both in vitro and in vivo, and to protect the rodent dopaminergic system from neurotoxic damage. However, most previous studies have only examined the short‐term protective effects of GDNF. We have investigated the long‐term effects of GDNF on a 6‐hydroxydopamine (6‐OHDA)‐induced lesion of the rat medial forebrain bundle (MFB), which results in complete and irreversible destruction of the nigrostriatal pathway, and is a robust model of Parkinson’s disease.GDNF was administered ipsilaterally above the substantia nigra and into the lateral ventricle immediately before a unilateral 6‐OHDA injection into the MFB. The effects of GDNF were examined in vivo by behavioural testing and positron emission tomography (PET) at weekly intervals, for 12 weeks. GDNF prevented the development of amphetamine‐induced rotations at all time‐points. PET studies, using [11C]‐RTI‐121 as a tracer for the dopamine transporter, indicated that GDNF prevented 6‐OHDA‐induced reduction of dopamine reuptake sites in the ipsilateral striatum. Post‐mortem neurochemical analysis at 13 weeks after surgery found that GDNF significantly inhibited 6‐OHDA‐induced loss of dopamine, 3,4‐dihydroxyphenylacetic acid and homovanillic acid in the ipsilateral striatum. Immunocytochemistry showed that GDNF reduced 6‐OHDA‐induced loss of tyrosine hydroxylase‐positive neurones in both the substantia nigra pars compacta and ventral tegmental area. We have shown that a single treatment with GDNF can confer long‐term protective effects against a 6‐OHDA lesion, which suggests that this factor may be useful for the treatment of Parkinson’s disease.
Possible involvement of gradients in guidance of receptor cell axons towards their target position on the olfactory bulb
Authors: Gierer Alfred 
Published: March 2003

AbstractThere is increasing evidence for directional guidance of growing axons by molecular gradients in target tissues. Aside from biochemical studies on gradients and their role, the capability of axons to approach their target position from different aspects of a two‐dimensional field is itself an indication for guidance by gradients. According to this criterion, such guidance is expected to be involved not only in map‐formation in the visual system but also in targeting of receptor cell axons in the olfactory bulb. In this paper, physico‐chemical concepts of visual mapping are adapted to olfactory targeting. In both cases there must be sophisticated processing of graded cues in the growing tip of the axon for growth cone navigation. In visual map formation, a target position is determined by influences of cues depending on the position of axonal origin; in olfactory targeting, however, these influences are expected to be based on properties of the receptor‐cell‐specific molecules (possibly including the receptor molecule itself), as well as by gene regulation affecting the levels of expression. According to this concept, the main role of molecules expressed in a receptor‐cell‐type specific manner is not matching specific counterparts on the target tissue, but instead quantitative modulation of growth cone steering for sensing the direction towards the target position.