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PubMed1996

Relation between heel position and the distribution of forefoot plantar pressures and skin callosities in rheumatoid arthritis.

OBJECTIVE: To investigate the relation between the position of the rearfoot and the distribution of forefoot plantar pressures and skin callosities in rheumatoid arthritis. METHOD: Plantar pressures and callosity patterns were measured in 102 rheumatoid arthritis patients (120 feet with normal heel alignment and 84 feet with valgus heel alignment measured by goniometry) and in 42 (84 feet) age matched healthy adults. Peak pressures (kPa) were measured across the metatarsal heads in-shoe using an FScan system and the distribution of plantar callosities was visually mapped for each foot. RESULTS: Peak pressures were significantly greater at all but the first metatarsal head in the rheumatoid normal heel alignment and healthy adult groups than in the rheumatoid valgus heel group. The feet of both the rheumatoid normal heel group and the healthy adult group behaved the same, the highest peak pressures registering on the central metatarsal heads. However, only in the rheumatoid group were plantar callosities found at these sites. In the rheumatoid valgus heel group, lateral metatarsal heads were frequently non-weightbearing, producing gross loading patterns with a dominant medial distribution. Peak pressures were shifted to the medial fore-foot accompanied by a higher prevalence of callosities. The results, however, failed to establish clearly an association between peak pressures and callus formation. CONCLUSIONS: In rheumatoid arthritis there is an important interrelation between the rearfoot position and forefoot pressure sites.

Adolescent↗
PubMed2001

Relationship between teat-end callosity and occurrence of clinical mastitis.

A longitudinal study in 15 herds, with a total of 2157 cows, was conducted to examine the relationship between teat-end callosity (TEC) and the incidence of clinical mastitis. During the 1.5-yr study period, clinical mastitis was diagnosed by the farmers based on clinical signs. Teat-end callosity was scored every month according to a teat-end callosity classification system, which discriminates between teat-end callosity thickness (TECT) and roughness (TECR). Differences in TECT between healthy and clinical mastitis quarters within infected cows were small but significant 3 mo before (0.13 higher), in the month during which the clinical mastitis occurred (0.08 higher), and in the following 2 mo (0.06 and 0.05 higher). To compare TECT and TECR between cows with and without clinical mastitis, 199 cows with clinical mastitis were paired with control cows based on herd, days in milk, and parity. Clinical mastitis cows had more TEC than their healthy herd mates, particularly when clinical mastitis occurred between the second and fifth months of lactation. Clinical Escherichia coli mastitis in the second or third month of lactation occurred in cows with less TEC than in cows with clinical mastitis caused by other pathogens. Clinical culture-negative, yeast, Klebsiella pneumoniae, and Enterobacter aerogenes mastitis cows had more TECT and TECR than other cows with clinical mastitis in the same month of lactation. Pointed teat ends had higher TECT and TECR than flat or inverted teat ends. Teat-end callosity thickness increased with a higher milk yield at peak production.

Animals↗
PubMed2000

Study of straight metatarsal osteotomy for the treatment of plantar callosities.

BACKGROUND AND AIMS: [corrected] To evaluate the outcome of transverse distal metatarsal osteotomies for intractable plantar callosity without hammer toe deformity and associated toe corns. MATERIAL AND METHODS: Twenty-five plantar callosities were treated in 19 feet of 13 patients (mean age 48 years, 5 male, 8 female) with transverse distal metatarsal osteotomy. RESULTS: Twenty-four of the osteotomies united primarily, one after revision. After a 7-year follow-up, 23 of the callosities had healed, two of them after an oblique reosteotomy. Eight hammer toe deformities had developed in the involved rays of four feet. Eight plantar callosities had developed outside the operated rays in five feet. Hallux valgus was a frequent finding in both operated and non-operated feet. CONCLUSION: It seems that transverse distal metatarsal osteotomy is an effective treatment of intractable plantar callosities. Harmful hammer toe deformities and transfer lesions below adjacent metatarsal heads tend to develop over time.

Callosities↗
PubMed2005

Large-scale maintenance of dual projections by callosal and frontal cortical projection neurons in adult mice.

Integration of sensory-motor information in premotor cortex of rodents occurs largely through callosal and frontal cortical association projections directed in a hierarchically organized manner. Although most anatomical studies in rodents have been performed in rats, mammalian genetic models have focused on mice, because of their successful manipulation on the genetic and cell biological levels. It is therefore important to establish the normal patterns of anatomical connectivity in mice, which potentially differ from those in rats. The goal of this study is to investigate the anatomical development of callosal and frontal premotor projection neurons (CPN and FPN, respectively) in mouse sensory-motor and premotor cortex and to investigate quantitatively the potential laminar differences between these neurons with simultaneous callosal and frontal projections during development. The retrograde tracers Fluoro-Gold and DiI were injected into sensory-motor and premotor cortices, respectively, C57Bl/6 mice at different developmental times (P2, P8, P21, adult). We found that, in contrast to the case in primate and cat, there is widespread overlap in populations of long-distance projection neurons in mice; many projection neurons have simultaneous projections to both contralateral somatosensory cortex and ipsilateral frontal cortex, and a considerable number of these dual projections persist into adulthood. In addition, there are significant laminar differences in the percentage of neurons with simultaneous callosal and frontal projections, and an isolated population of layer V FPN has bilateral projections to both premotor cortical hemispheres. Taken together, our results indicate that a large proportion of individual projection neurons maintains simultaneous callosal and frontal projections in adult mice, suggesting that these dual projections might serve the critical function of integrating motor coordination information with multimodal association areas.

Animals↗
PubMed2007

Callosal axon arbors in the limb representations of the somatosensory cortex (SI) in the agouti (Dasyprocta primnolopha).

The present report compares the morphology of callosal axon arbors projecting from and to the hind- or forelimb representations in the primary somatosensory cortex (SI) of the agouti (Dasyprocta primnolopha), a large, lisencephlic Brazilian rodent that uses forelimb coordination for feeding. Callosal axons were labeled after single pressure (n = 6) or iontophoretic injections (n = 2) of the neuronal tracer biotinylated dextran amine (BDA, 10 kD), either into the hind- (n = 4) or forelimb (n = 4) representations of SI, as identified by electrophysiological recording. Sixty-nine labeled axon fragments located across all layers of contralateral SI representations of the hindlimb (n = 35) and forelimb (n = 34) were analyzed. Quantitative morphometric features such as densities of branching points and boutons, segments length, branching angles, and terminal field areas were measured. Cluster analysis of these values revealed the existence of two types of axon terminals: Type I (46.4%), less branched and more widespread, and Type II (53.6%), more branched and compact. Both axon types were asymmetrically distributed; Type I axonal fragments being more frequent in hindlimb (71.9%) vs. forelimb (28.13%) representation, while most of Type II axonal arbors were found in the forelimb representation (67.56%). We concluded that the sets of callosal axon connecting fore- and hindlimb regions in SI are morphometrically distinct from each other. As callosal projections in somatosensory and motor cortices seem to be essential for bimanual interaction, we suggest that the morphological specialization of callosal axons in SI of the agouti may be correlated with this particular function.

Animals↗
PubMed1981

The ontogeny of the distribution of callosal projection neurons in the rat parietal cortex.

The ontogeny of callosal projection neurons in the rat parietal cortex was examined using the retrograde and anterograde transport of horseradish peroxidase (HRP), as well as Golgi and Nissl stains. From postnatal day 0 (PND 0) to early PND 4, the callosal projection neurons are distributed as two continuous horizontal bands of cells which extend throughout the subplate in layers Va and Vc-upper VIa. Neurons within the cortical plate (CP), however, do not transport HRP from a contralateral injection site until PND 3 to early PND 4, when a few cells at the lower CP border are generally labeled. However, by late on PND 4, and more consistently by PND 5, several changes in the distribution of callosal projection neurons take place. First, cells at all levels of the CP become labeled in a sequential fashion, from the lower border upward. Second, gaps, or areas devoid of HRP, become apparent in layer IV of the barrel field area. Third, in the cortical areas containing the gaps, as well as in other areas which are destined not to be callosally connected in the adult, there is a noticeable decrease in the number of cells labeled with HRP. This decrease continues through PND 15 and possibly into adulthood. The foregoing developmental events are compared to cortical maturation as seen in both Golgi- and Nissl-stained material. By PND 15, the basic adult pattern of callosal projection neurons is established. The neurons reside mainly in layers III and Va, with fewer in layers II and Vc-upper VIa, and fewer still in the other cortical layers. They are aligned in vertical arrays in discrete areas of the cortex.

Aging↗
PubMed1994

Topographical relations between ipsilateral cortical afferents and callosal neurons in the second somatic sensory area of cats.

Experiments were carried out on the second somatic sensory area (SII) of cats to study 1) the laminar distribution of axon terminals from the ipsilateral first somatic sensory cortex (SI); and 2) the topographical relations between their terminal field and the callosal neurons projecting to the contralateral homotopic cortex. To label simultaneously in SII both ipsilateral cortical afferents and callosal cells, cats were given iontophoretic injections of Phaseolus vulgaris-leucoagglutinin (PHA-L) in the forepaw zone of ipsilateral SI, and pressure injections of horseradish peroxidase (HRP) in the same zone of contralateral SII. The possibility that ipsilateral cortical axon terminals synapse callosal neurons was investigated with the electron microscope by combining lesion-induced degeneration with retrograde HRP labelling. Fibers and terminations immunolabelled with PHA-L from ipsilateral SI were distributed in SII in a typical patchy pattern and were mostly concentrated in supragranular layers. Labelled fibers formed a very dense plexus in layer III and ramified densely also in layers I and II. Labelled axon terminals were both en passant and single-stalked boutons. Counts of 8,303 PHA-L-labelled terminals of either type showed that 82.40% were in supragranular layers. The highest concentration was in layer III (43.99%), followed by layers II (30.32%) and I (8.09%). The remaining terminals were distributed among layers IV (6.96%), V (4.93%), and VI (5.68%). The same region of SII containing anterogradely labelled axons and terminals also contained numerous neurons retrogradely labelled with HRP from contralateral SII. Callosal projection neurons were pyramidal, dwelt mainly in layer III, and were distributed tangentially in periodic patches. Patches of anterograde and retrograde labelling either interdigitated or overlapped both areally and laminarly. In the zones of overlap, numerous PHA-L-labelled axon terminals were seen in close apposition to HRP-labelled pyramidal cell dendrites. Combined HRP-electron microscopic degeneration experiments showed that in SII axon terminals from ipsilateral SI form asymmetric synapses with HRP-labelled dendrites and dendritic spines pertaining to callosal projection neurons. These results are discussed in relation to the layering and function of the SI to SII projection, and to the evidence that SII neurons projecting to the homotopic area of the contralateral hemisphere have direct access to the sensory information transmitted from ipsilateral SI.

Animals↗
PubMed1989

Effects of dark rearing on the development of visual callosal connections.

It is now well established that during normal postnatal development there is a partial elimination of the callosal projections of cortical areas 17 and 18 in the cat and that visual experience early in life can modulate this process. In the present experiments, we quantitatively studied the influence of light, per se, by rearing cats in total darkness. Dark rearing exaggerates the normally occurring partial elimination of immature callosal projections: it causes a significant reduction in the total number of neurons in both the supra- and infragranular layers that send an axon through the corpus callosum and slightly narrows the distribution of these neurons across areas 17 and 18. These data demonstrate that visual stimulation is not necessary either to initiate the partial elimination of immature callosal projections or to stabilize a large fraction of the callosal projections present at birth. However, normal visual stimulation is necessary for the stabilization of the normal complement of callosal projections.

Animals↗
PubMed1991

Interactions between callosal, thalamic and associational projections to the visual cortex of the developing rat.

The patterns of callosal interconnections between the visual cortices of rats display considerable plasticity in response to various neonatal manipulations. In the present study, many neurones in the principal visual thalamic relay nuclei, the dorsal lateral geniculate nucleus (DLG) and to a lesser extent those in the lateral posterior nucleus (LP) were destroyed by injections of the neurotoxin - kainic acid - on the first day of postnatal life. Four weeks later, as demonstrated with the anterograde and retrograde transport of the enzyme horseradish peroxidase (HRP) injected into the occipital lobe of one hemisphere, callosally projecting neurones and terminals were distributed more widely in the retinotopically organized areas 17, 18a and 18b of the visual cortex ipsilateral to the lesioned visual thalamus than in unoperated control animals of the same age. By contrast, in the visual cortex contralateral to the lesioned visual thalamus the areal distribution of callosally projecting neurones and terminals was similar to that of the controls, that is, largely but not exclusively restricted to the common border of areas 17 and 18a. Both in unoperated and operated animals, cells in lamina V of several cytoarchitectonically defined areas that are not retinotopically organized (area 8 in the frontal lobe, area 29d in the retrosplenial limbic cortex and perirhinal areas 35/13 in the temporal lobe) also project to contralateral visual cortices. In areas 8 and 29d, the total numbers, laminar distributions and densities of labelled callosal cells both ipsilateral and contralateral to the kainate-injected visual thalamus were similar to those in the controls. However, in the temporal lobe, the areal distribution of the labelled callosal neurones was more extensive than that in the controls and labelled cells in areas 35/13 of the cortex contralateral to the kainate-lesioned visual thalamus merged with those in the neighbouring areas 20 and 36. By contrast, the areal distribution of associational neurones in area 18a and in nonretinotopically organized areas projecting to area 17 were very similar in controls and in operated animals (neonatal kainate lesion of the visual thalamus, neonatal section of the corpus callosum or both procedures combined). However, in operated animals, the labelled associational neurones projecting from the supragranular laminae (II/III) of area 18a to area 17 constituted a higher proportion of all cells than did those in the unoperated control animals. Thus, overall the number of associational neurones projecting from area 18a to area 17 was slightly increased by the experimental manipulations performed.(ABSTRACT TRUNCATED AT 400 WORDS)

Afferent Pathways↗
PubMed1984

Relation of callosal and striate-extrastriate cortical connections in the rat: morphological definition of extrastriate visual areas.

The main purpose of this study was to correlate the tangential distributions of visual callosal and striate-extrastriate connections in the rat. Cells of origin and terminations of the visual callosal pathway of one hemisphere were labeled by the anterograde and retrograde transport of horseradish peroxidase (HRP) after multiple injections of this enzyme in the contralateral hemisphere, while ipsilateral striate-extrastriate projection fields were revealed by using the autoradiographic method following single injections of 3H-proline in striate cortex. A remarkable complementarity in the distribution of both cortico-cortical pathways was revealed by superimposing in a camera lucida the patterns of callosal and striate-extrastriate projections from consecutive tangential sections processed for HRP and autoradiography, respectively. Projections from striate cortex are distributed into multiple extrastriate fields which are partially or totally surrounded by cortical strips containing dense and overlapping accumulations of labeled callosal cells and terminations. In addition to projections to the following striate recipient areas described in previous reports: posterior (P), posterolateral (PL), lateromedial (LM), laterolateral (LL), anterolateral (AL) and anteromedial (AM); projections to laterointermediate (LI), laterolateral anterior (LLa), anterior (A), medial (M) and pararhinal (PR) areas were defined in the present study. Striate-extrastriate projection fields occupy only a portion of the acallosal islands that contain them, and the location of the fields within these islands correlates with the retinotopic location of the isotope injection in striate cortex. When compared to previous physiological and anatomical maps of extrastriate visual areas in the rat, the present results indicate that the distribution of callosal connections correlates with the borders of extrastriate visual areas, and that the projection from striate cortex into these areas is retinotopically organized. Surprisingly, a direct projection from striate cortex to the head representation region in somatosensory cortex was labeled, a finding that challenges the view that primary sensory areas do not connect directly.

Animals↗
PubMed1997

Callosal connections of the ferret primary auditory cortex.

The callosal connections of ferret auditory cortex were studied by making multiple injections of wheat germ agglutinin-horseradish peroxidase into the middle ectosylvian gyrus or by packing crystals of horseradish peroxidase into the transected corpus callosum. The primary area (AI) had strong callosal connections that arose from somata mainly located in layer III. Other layers contained sparsely distributed cells that projected across the midline. The projecting cells occurred over the whole extent of AI but were not homogeneously distributed in layer III. The axons from these cells terminated mainly in the upper layers of the contralateral cortex, where they converged onto three discrete bands. The three elongated bands lay in a dorsoventral orientation, parallel to the tonotopic axis. They were slightly curved and had a fairly uniform width. The posterior band had a width of about 200 microm, while the anterior and middle bands were more variable and had widths of 300-800 microm. The centre-to-centre distance between the posterior and middle bands was 520+/-60 microm and for the anterior to middle bands was 620+/-210 microm. The retrograde labelling produced by the same injections showed that the cell bodies had a higher density in the terminal bands than in the intervening spaces. The bands of dense callosal connections appear to correspond to the binaural summation columns, which have been clearly demonstrated in the ferret, but direct evidence of this will need to be sought in a future study. The discrete nature of the callosal bands in the ferret appears to make it a suitable species for studying the relationship between callosal terminals and those arising in other areas of the brain and for clarifying the possible existence of separate functional systems within the auditory cortex.

Animals↗
PubMed2002

[Frequency, morphology, pathogenesis and complications of silicotic callosities (phthisis atra). A disappearing disease].

Over a period of approximately 30 years we have compared the frequency of Miner's phthisis in the coal mining areas of Aachen and the Ruhr area of Essen and have investigated a total of approximately 600 lungs with silicosis. In cases of silicosis grades II-III and III we found liquefaction in 36% of the callosities but in cases of silicosis I-II and II in only 4-7%. Liquefaction of callosities, or phthisis atra, was found slightly more often in the Ruhr area than in the area of Aachen. If the liquefied silicotic material is expectorated from the bronchial tubes, a cavern-like cavity develops in the lungs, which clinically can often not be differentiated from a tuberculotic cavern. Sometimes silicotic material is transported via the blood vessels and dust particles could often be found microscopically in the liver, spleen or kidneys. In one patient we found silicotic material coming from the bronchial veins with development of arterial embolisms in peripheral arteries of the extremities and brain. The pathogenesis of callosity liquefaction is a consequence of disruption of the blood supply to the surrounding areas of the callosities. In some cases blood vessels in the centre of the callosities are destroyed so that the patient dies after severe haemoptysis.

Humans↗
PubMed2003

On the mechanism of callose synthesis induction by metal ions in onion epidermal cells.

Metal ions induce the synthesis of callose in Allium cepa epidermal cells. Callose is deposited as single knoblike local accumulations, aggregates of knobs, or furrowed clusters tightly attached to the cell wall. The most effective metal is copper, it induces callose formation at micromolar concentrations. Agents acting on inositolphosphate metabolism, phospholipase inhibitors, calcium channel inhibitors, modulators of cytoplasmic calcium, or receptor antagonists influence callose synthesis. It is concluded that metal ions, especially Cu(2+), initiate a signal transduction chain by activation of phospholipases and generation of inositol 1,4,5-trisphosphate, and that callose synthesis is a cellular defence reaction caused by the disturbance of intracellular calcium homeostasis.

Calcium↗
PubMed1983

Thalamic and callosal connections of the rat auditory cortex.

This study was designed to assess the relative distributions of two extrinsic afferent fiber systems in the rat auditory cortex as indicated by the patterns of specific lesion-induced degeneration evident in Fink-Heimer preparations. The auditory cortex consists of cytoarchitectural areas 41, 20 and 36. Lesions were made in the medial geniculate body (MGB) or the corpus callosum in some rats, while in other rats, lesions were made in both the MGB and the corpus callosum. Following the thalamic lesions, degenerating terminals occur throughout the auditory region of cortex, principally in layer IV and deep layer III, but also in layer VI and in the superficial part of layer I. With the exception of the band of degeneration in layer I, the density of the thalamic degeneration is uneven, such that patches of increased density of degeneration are separated by regions with few degenerating terminals. Following lesions of the corpus callosum, degenerating callosal terminals are also evident throughout the auditory region of cortex and they occur in deep layer I through layer III, superficial layer V and in layer VI. The density of the degenerating callosal terminals is not uniform throughout most of area 41, to the extent that there are radially-oriented bands of increased density which appear within the continuous callosal projection. Following the double lesions, degenerating terminals throughout the auditory region are distributed homogeneously within all cortical layers with the exception of deep layer V which is relatively free of degeneration. The results indicate that all regions within the rat auditory cortex are subject to both thalamic and callosal influence, although the input is not completely uniform, for the zones in layers IV and VI which have decreased thalamic input appear to have increased callosal input.

Animals↗
PubMed1990

Post-critical period plasticity of callosal transfer to visual cortex cells of cats following early conditioning of monocular deprivation and late optic chiasm transection.

We studied whether plasticity-induced callosal transfer exists after the critical period for sensitivity of visual cortex cells in kittens postnatally monocularly deprived and in which interocular competition was cancelled by chiasm transection during adulthood. Callosal transfer was studied acutely (n = 3 cats) and chronically (n = 7) following the chiasm transection (OCAMD). For comparison, adult cats in which chiasm transection only was performed (OCA) were also studied acutely (n = 3) and chronically (n = 9). The results were also compared to cats in which monocular deprivation and chiasm transection were simultaneously performed (OCKMD) during development (n = 6) and to normal control cats (n = 18). Unit recording was extracellularly carried out in visual cortex areas 17 and 18 and their boundary region, where the corpus callosum is represented. When no interocular competition was allowed between the non-deprived and the deprived eye via the thalamocortical direct visual pathways on cortical cells, such as in the OCKMD cats, the absolute majority of the cells were ipsilaterally driven, regardless of which hemisphere was studied. Only a minor proportion (4.1%) of the cells had some contralateral input from the non-deprived eye in the hemisphere ipsilateral to the deprived eye, indicating almost no interhemispheric callosal transfer. A slight increase in the proportion of cells callosally driven from the non-deprived eye (9.8%), was found in this hemisphere in cats in which interocular competition was allowed via the direct visual pathways prior to its cancellation by chiasm transection (OCAMD), if studied acutely after the chiasm transection. A remarkable increase in callosal transfer was found in this hemisphere under chronic conditions.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

Long-term callosal lesions and learning of a black-white discrimination by one-eyed rats.

We know from our previous studies that mature rats with monocular enucleation at birth (OEBs), as well as animals enucleated at maturity (OETs), were unable to learn a black-white discrimination when they were trained after lesions of the visual cortex contralateral to the remaining eye. Since it is well known that synaptic reorganization takes place in the adult rat brain through reactive synaptogenesis following deafferentation, we wondered if long-term callosal lesions in OEBs and OETs would bring out such synaptic reorganization in the visual cortex and, consequently, affect the outcome of the discrimination mentioned above. In the present study, two experiments were carried out: in Experiment 1 the previous experiment was replicated in that OEBs and OETs of 3 months of age were trained on the discrimination 10 days following unilateral visual cortex lesions; in Experiment 2, effects of callosal lesions made 10 weeks earlier either at 3 weeks of age or 13 weeks of age were investigated. The results were: 1) the findings of the previous experiment were confirmed; 2) the long-term callosal lesions facilitated the acquisition of discrimination in OEBs but not in OETs; 3) the facilitative effects were more prominent in OEBs with callosal lesions at 3 weeks of age than in those at 13 weeks of age. The findings were discussed in relation to possible synaptic reorganization produced in the visual cortex ipsilateral to the remaining eye following callosal lesions made 10 weeks earlier and also in relation to reorganization of the uncrossed visual pathways resulting from monocular enucleation at birth.

Aging↗
PubMed1988

In vivo visualization of callosal pathways: a novel approach to the study of cortical organization.

I describe here the successful visualization of interhemispheric callosal connections in the live mammalian cortex. The development of this method was prompted by the finding that fluorescent tracer labeling of groups of cortical neurons, when done under optimal conditions, is sufficiently intense to be visible even in the whole brain preparation. The new approach could provide a useful tool for enhanced precision in localizing cortical modules in vivo. In a typical experiment, rats had their left cortical hemisphere extensively injected with the fluorescent tract-tracer bisBenzimide (BB). After appropriate survival, the right cortical hemisphere was illuminated with UV light and the fluorescing callosal pattern could be discerned under the network of blood vessels even with the unaided eye. The pattern, although diffuse, was grossly similar to the pattern of callosal connections as seen in flattened, sectioned cortex. Features that could be discerned were: the main callosal band straddling the lateral border of area 17, several rings and bands in extrastriate areas 18a and 18b, and a major band straddling the lateral border of area 3. The vitally visualized callosal pattern was used to guide injections of either wheat germ agglutinin conjugated to HRP (WGA-HRP) or rhodamine-labeled microspheres (RLM) into precisely localized sites in occipital cortex. There were numerous instances of doubly labeled neurons stained both with BB and WGA-HRP or RLM, suggesting that uptake of BB combined with UV exposure did not hinder the ability of stained neurons to take up and transport a second tracer. It is suggested that vital tract tracing be used as a tool for enhanced precision in studies of cortical connectivity.

Animals↗
PubMed1990

A slice preparation preserving the callosal projection to contralateral visual cortex.

Due to the curved path they follow, the visual callosal projections to areas OC1 and OC2 of the rat visual cortex have been inaccessible to studies using brain slices. In this paper we describe a new slice preparation in which a curved cutting blade was used to obtain slices in which callosal fibers projecting to OC1 or OC2 are preserved. Stimulation of the contralateral white matter resulted in EPSPs recorded in layer II/III and V cells of OC2 studied with intracellular recording. Current source density analysis of extracellular field potentials collected in OC1 and OC2 revealed laminar current sink patterns paralleling the laminar distribution of callosal terminations reported by Miller and Vogt (Dev. Brain Res., 14 (1984) 304-309). Exposure of slices to 2 mM kynurenic acid reversibly abolished current sinks in OC1 recorded in response to callosal stimulation indicating that glutamate receptors mediate the response of OC1 to callosal afferent activity. This new slicing technique can be readily adapted to study other systems in the nervous system in which neural processes follow curved trajectories.

Animals↗