胼胝体输入对猫皮层17/18交界区细胞方向和取向选择性的影响

用抑制性神经递质GABA阻断胼胝体输入、用微机控制的运动光棒作为视觉刺激,用金属电极胞外记录技术,研究猫皮层17/18区交界附近细胞方向选择性和取向选择性的变化.在被检测的48个细胞中,50%细胞的方向选择性强度,54.2%细胞的取向选择性强度发生了改变;约20%细胞的最优反应方向或.及最优取向发生了10-30°的偏移;共有56.2%细胞的方向选择性、58.3%细胞的取向选择性受到明确的影响.这些结果表明胼胝体对皮层细胞视觉反应的贡献是多方面的.     

Morphology of the human corpus callosum: the shape of its mediosagittal section

The shape of the corpus callosum was studied on mediosagittal sections of 50 human brains. The terms "facies corticalis" and "facies profunda" are proposed for the sides of corpus callosum. Each of 50 brains had a different shape of callosal mediosagittal section and any available classification was not possible. In 94% of cases, the contour of callosal cortical surface exhibited a posterior depression and in 46% also an anterior one. Other details of callosal morphology influencing its shape on mediosagittal section (transverse folds, circumscribed depressions) were described. The junction of fornix and corpus callosum in 78% was in 3rd and in 14% in 4th quarter of callosal length. The possible significance of these findings for further studies of human brain morphology is discussed.     

Anatomy of corpus callosum in prenatally malnourished rats

The effect of prenatal malnutrition on the anatomy of the corpus callosum was assessed in adult rats (45-52 days old). In the prenatally malnourished animals we observed a significant reduction of the corpus callosum total area, partial areas, and perimeter, as compared with normal animals. In addition, the splenium of corpus callosum (posterior fifth) showed a significant decrease of fiber diameters in the myelinated fibers without changing density. There was also a significant decrease in diameter and a significant increase in density of unmyelinated fibers. Measurements of perimeter's fractal dimensions from sagittal sections of the brain and corpus callosum did not show significant differences between malnourished and control animals. These findings indicate that cortico-cortical connections are vulnerable to the prenatal malnutrition, and suggest this may affect interhemispheric conduction velocity, particularly in visual connections (splenium).     

Functional properties of efferent zones of the motor cortex which project to ipsilateral and contralateral face muscles

In both intact (4 animals) and lesioned (2 preparations with contralateral motor cortex ablation and 1 animal with transection of the rostral two thirds of the corpus callosum) cats, three different types of efferent zones were identified in the face motor cortex by the technique of microstimulation: contralateral, ipsilateral and bilateral efferent zones. The three types of efferent zones had different organizational features such as location, thresholds of effective sites and latencies of motor responses. Mean thresholds of effective sites from ipsilateral and bilateral efferent zones in lesioned animals were not significantly higher than those in intact preparations. In both intact and lesioned animals, neurons endowed with contralateral, bilateral and ipsilateral receptive fields were isolated from the three types of efferent zones.     

Possible phylogenetical significance of the corpus callosum with special reference to the dolphin brain (Stenella graffmani).

The surface area of the corpus callosum was measured in several animals as compared to the brain weight. A general consideration of the importance of this structure on the phylogenetic scale, with special reference to the corpus callosum of the dolphin, Stenella graffmani, is given. Some theoretical considerations about the significance of this structure upon some specialized features are mentioned.     

The extrastriate generators of the EP to checkerboard onset. A source localization approach

The cortical origin of the pattern onset EP has been investigated over a time window which covers the entire positive-negative-positive complex of the pattern onset EP. On the basis of a dipole source localization approach, the position, orientation and strength of the underlying sources of the pattern onset EP were estimated. For large check stimuli, chosen to have a weak edge specific component in the response, still two components are needed to account for the variance of the responses. Each component corresponds to a single dipole source, and both originate in the extrastriate cortex. These components dominate, respectively, the initial and the late positive peaks of the pattern onset EP.The equivalent dipole sources of the two components show different behaviors with respect to the position of the stimulus in the visual field. The topography and behavior of the equivalent dipole source underlying the early positive component suggest an origin in area 18. The invariance with stimulus location of the dipole source underlying the late positive component suggests an origin beyond area 18. The different topographies of the components also account for the differences in surface distribution of the pattern onset EP to large check stimulation of the upper and lower sectors of the visual field.     

Binocular interaction in the striatal cortex of rats during changes in intensity of a monocular stimulus

Binocular interaction was investigated by the evoked potentials method in symmetrical centers of the rat striatal cortex before and after division of the corpus callosum. One eye was always stimulated by flashes of average intensity and the other by flashes of varied intensity. Contralateral facilitation was shown to be increased with an increase in the strength of stimulation. Ipsilateral facilitation was found to exist and to change into ipsilateral depression. In all cases contralateral effects were stronger than ipsilateral. The reciprocity of contralateral and ipsilateral influences in the striatal cortex is emphasized. Division of the corpus callosum leads to strengthening of the contralateral and ipsilateral facilitatory and depressive influences. Depressive ipsilateral influences are found after callosotomy in response to weaker stimuli than before the operation.Biological Institute, Leningrad University. Translated from Neirofiziologiya, Vol. 5, No. 2, pp. 122–127, March–April, 1973.     

Tests of genetic allelism between four inbred mouse strains with absent corpus callosum.

Inbred mouse strains that lack the corpus callosum connecting the cerebral hemispheres in the adult differ from the C57BL/6J strain at several relevant but unknown loci. To identify at least one major locus that influences axon guidance, different strains showing phenotypically similar defects were crossed to test for allelism. If the F1 hybrid between two strains with the same brain defect is phenotypically normal, it is much more likely that the two strains will differ at fewer loci than will an acallosal strain and C57BL/6J. This approach proved to be very informative. Five reasonable models of inheritance involving two or three loci were assessed, and the data justified rejection of all but one hypothesis. A total of 479 mice were obtained from four inbred strains prone to absence of the corpus callosum (BALB/cWah1, BALB/cWah2, I/LnJ, and 129/ReJ), one normal strain (C57BL/6J), and 11 F1 hybrids among them. Because the size of forebrain axon bundles is generally greater in mice with larger brains, and because whole brain size is certainly polygenic, the phenotypically normal groups were used to derive a standard index of the degree of corpus callosum deficiency relative to brain size. Results demonstrated clearly that the hybrid between BALB/cWah1 and 129/ReJ is normal, whereas the crosses among the BALB/c substrains and I/LnJ yielded many mice with deficient corpus callosum. I/LnJ crossed with 129/ReJ also produced some animals with callosal defects. The data were consistent with a model in which the difference between BALB/c and 129/ReJ involves two loci, whereas the defect in I/LnJ involves homozygosity at three loci, which impairs development more severely.(ABSTRACT TRUNCATED AT 250 WORDS)     

Corpus callosum morphology in capuchin monkeys is influenced by sex and handedness

Sex differences have been reported in both overall corpus callosum area and its regional subdivisions in humans. Some have suggested this reflects a unique adaptation in humans, as similar sex differences in corpus callosum morphology have not been reported in any other species of primate examined to date. Furthermore, an association between various measurements of corpus callosum morphology and handedness has been found in humans and chimpanzees. In the current study, we report measurements of corpus callosum cross-sectional area from midsagittal MR images collected in vivo from 14 adult capuchin monkeys, 9 of which were also characterized for hand preference on a coordinated bimanual task. Adult females were found to have a significantly larger corpus callosum: brain volume ratio, rostral body, posterior midbody, isthmus, and splenium than adult males. Left-handed individuals had a larger relative overall corpus callosum area than did right-handed individuals. Additionally, a significant sex and handedness interaction was found for anterior midbody, with right-handed males having a significantly smaller area than right-handed females. These results suggest that sex and handedness influences on corpus callosum morphology are not restricted to Homo sapiens.     

Hippocampal commissure defects in crosses of four inbred mouse strains with absent corpus callosum

It is known that four common inbred mouse strains show defects of the forebrain commissures. The BALB/cJ strain has a low frequency of abnormally small corpus callosum, whereas the 129 strains have many animals with deficient corpus callosum. The I/LnJ and BTBR T+ tf/J strains never have a corpus callosum, whereas half of I/LnJ and almost all BTBR show severely reduced size of the hippocampal commissure. Certain F1 hybrid crosses among these strains are known to be less severely abnormal than the inbred parents, suggesting that the parent strains have different genetic causes of commissure defects. In this study, all hybrid crosses among the four strains were investigated. The BTBR × I/Ln hybrid expressed almost no defects of the hippocampal commissure, unlike its inbred parent strains. Numerous three‐way crosses among the four strains yielded many mice with no corpus callosum and severely reduced hippocampal commissure, which shows that the phenotypic defect can result from several different combinations of genetic alleles. The F2 and F3 hybrid crosses of BTBR and I/LnJ had almost 100% absence of the corpus callosum but about 50% frequency of deficient hippocampal commissure. The four‐way hybrid cross among all four abnormal strains involved highly fertile parents and yielded a very wide phenotypic range of defects from almost no hippocampal commissure to totally normal forebrain commissures. The F2 and F3 crosses as well as the four‐way cross provide excellent material for studies of genetic linkage and behavioral consequences of commissure defects.     

Uterine region-dependent differences in responsiveness to prostaglandins in the non-pregnant porcine myometrium

To clarify the uterine region-dependent distribution of prostanoid receptors, we compared the mechanical responses to selective prostanoid receptor agonists (FP, EP3, DP, EP2) and naturally occurring prostaglandins (PGF2alpha PGE2, PGD2) in longitudinal and circular muscles isolated from three different regions (cornu, corpus and cervix) of the non-pregnant porcine uterus. Expression levels of FP receptor and cyclooxygenase (COX-1 and COX-2) in the respective regions were also examined using RT-PCR and Western blotting. The contractile responses to fluprostenol (an FP agonist) and PGF2alpha in both longitudinal and circular muscles were strongest in the cornu but weak in the corpus and cervix. Expression levels of mRNA and protein of FP receptor were highest in the cornu, consistent with the contractile responses. ONO-AE-248 (an EP3 agonist) caused contraction of both muscle layers, but region-related difference in responsiveness was observed only in the longitudinal muscle. ONO-AE1-259 (an EP2 agonist) inhibited spontaneous contraction of the myometrium, and inhibition was conspicuously stronger in the cervix. PGE2 caused contraction (<100 nM, cornu > corpus = cervix) and inhibition (>300 nM, cornu = corpus < or = cervix) of contractility depending on the concentration in both muscle layers. BW245C (a DP agonist) inhibited the spontaneous contraction, and region-dependent different responsiveness was marked in the longitudinal muscle (cervix = corpus > cornu). COX-1 but not COX-2 was detected in the non-pregnant porcine uterus. Expression level of COX-1 was different in the longitudinal muscle (cornu > corpus = cervix) but the same in the circular muscle. SC-560 inhibited the spontaneous contraction of longitudinal muscles in all regions. The results of the present study indicate that there are region-related heterogeneous distributions of contractile (FP and EP3, cornu > cervix) and relaxant (EP2 and DP, cervix > cornu) prostanoid receptors and COX-1 in the porcine uterus. The results also suggest involvement of endogenous PGs in the regulation of spontaneous uterine contractility. Region-related differences in COX-1 and prostanoid receptors might be necessary to produce a gradient of uterine motility decreasing from the cornu to the cervix that manages movement of luminal contents.     

Age-related Changes of Elements in Human Corpus Callosum and Relationships Among These Elements

To elucidate compositional changes of the corpus callosum with aging, the authors investigated age-related changes of elements and relationships with their element contents in the corpus callosum. After ordinary dissection by medical students at Nara Medical University was finished, the genu, trunk, and splenium of the corpus callosum were resected from the subjects ranging in age from 58 to 94 years. The element contents of the corpus callosum were determined by inductively coupled plasma-atomic emission spectrometry. The contents of Ca, P, S, Mg, Zn, Fe, and Na did not change significantly in the genu, trunk, and splenium of the corpus callosum with aging. Regarding the relationships among the element contents, significant correlations were found among the contents of Ca, P, S, Mg, and Fe in all of the genu, trunk, and splenium of the corpus callosum with some exceptions.     

Behavioral asymmetry in BALB/cCF mice with corpus callosum abnormalities]

The possible homology between anomalies of the corpus callosum in mice and in humans remains questionable. The small number of existing behavioural studies in mice have not shown effects, at the behavioural level, of the absence or reduction in size of the corpus callosum. We therefore examined the development, during the first 3 weeks of postnatal life, of a number of simple reflex and integrative responses in the members of a sample of 101 BALB/cCF mice; at autopsy carried out at 50 days of age, 29 mice showed anomalies of the corpus callosum (total absence or an area less than 0.75 mm2). Asymmetry of the development of these responses was measured either as the proportion of animals showing asymmetrical appearance of responses on the left and right sides, and as the delay between appearances on the left and right sides in "asymmetrical" mice. Both measures decreased over the first 15 postnatal days, at the same rate in normal and abnormal mice; in each case the decrease is better described by a second-order, quadratic, function than by a simple linear function. We therefore conclude that the integrity of the corpus callosum is not necessary for the normal maturation of sensorimotor behaviour in mice, and suggest that this conclusion may possibly be explained by the relatively recent appearance of mice in the mammalian radiation.     

The activity of 2'',3''-cyclic nucleotide 3''-phosphohydrolase in the corpus callosum, subcortical white matter, and spinal cord in infants dying from sudden infant death syndrome

Abstract: The activity of 2',3'-cyclic nucleotide 3'-phos-phohydrolase (CNPase) has been determined in corpus callosum, subcortical white matter, and spinal cord of infants whose death was attributed to the sudden infant death syndrome (SIDS), and compared with enzyme activity in other cases in which the cause of death was not associated with respiratory distress. In nearly half the SIDS cases, CNPase activity and oligodendroglial cell numbers were reduced before the onset of myelination, but only in the corpus callosum. In other SIDS cases, enzyme activity and cell numbers were the same as in non-SIDS cases. If the expression of CNPase activity reflects glioblast differentiation to oligodendrocytes with myelinating potential, then this transformation is abnormal in certain SIDS cases, as also evidenced in cases of prolonged neonatal respiratory insufficiency and gives rise to a subsequent deficit of myelin in the corpus callosum.     

When the Sun Prickles Your Nose: An EEG Study Identifying Neural Bases of Photic Sneezing

Background

Exposure to bright light such as sunlight elicits a sneeze or prickling sensation in about one of every four individuals. This study presents the first scientific examination of this phenomenon, called ‘the photic sneeze reflex’.

Methodology and Principal Findings

In the present experiment, ‘photic sneezers’ and controls were exposed to a standard checkerboard stimulus (block 1) and bright flashing lights (block 2) while their EEG (electro-encephalogram) was recorded. Remarkably, we found a generally enhanced excitability of the visual cortex (mainly in the cuneus) to visual stimuli in ‘photic sneezers’ compared with control subjects. In addition, a stronger prickling sensation in the nose of photic sneezers was found to be associated with activation in the insula and stronger activation in the secondary somatosensory cortex.

Conclusion

We propose that the photic sneeze phenomenon might be the consequence of higher sensitivity to visual stimuli in the visual cortex and of co-activation of somatosensory areas. The ‘photic sneeze reflex’ is therefore not a classical reflex that occurs only at a brainstem or spinal cord level but, in stark contrast to many theories, involves also specific cortical areas.     

Relative coordination to unknown "weak zeitgebers" in free-running blind individuals

Light is the primary synchronizer of the human biological clock. In more than half of those blind individuals who completely lack light perception, the absence of photic input to the hypothalamic circadian pacemaker results in rhythms that free-run (blind free-runners [BFRs]) with a period typically greater than 24 h. The remainder are entrained, although sometimes at an abnormal phase angle. It is presumed that weak as-yet-to-be-identified time cues provide the necessary resetting stimulus in these entrained individuals. These weak zeitgebers might be expected to modulate the observed circadian period in blind people who are not actually entrained by them. The authors report here the results from 5 BFRs (average linear regression period +/-SD of 24.31 +/- 0.06 h) who had high-resolution (many and frequent) phase assessments. All 5 subjects demonstrated a similar and reproducible pattern of changes in observed period (period response curves) indicative of relative coordination. The precise shape of the period response curve to weak zeitgebers has implications for the entrainment of BFRs using exogenous melatonin administration or other nonphotic stimuli. Sighted individuals may also be affected by such weak zeitgebers, which may be obscured by the stronger light/dark cycle.     

Developmental Changes in the Corpus Callosum from Infancy to Early Adulthood: A Structural Magnetic Resonance Imaging Study

Previous research has reported on the development trajectory of the corpus callosum morphology. However, there have been only a few studies that have included data on infants. The goal of the present study was to examine the morphology of the corpus callosum in healthy participants of both sexes, from infancy to early adulthood. We sought to characterize normal development of the corpus callosum and possible sex differences in development. We performed a morphometric magnetic resonance imaging (MRI) study of 114 healthy individuals, aged 1 month to 25 years old, measuring the size of the corpus callosum. The corpus callosum was segmented into seven subareas of the rostrum, genu, rostral body, anterior midbody, posterior midbody, isthmus and splenium. Locally weighted regression analysis (LOESS) indicated significant non-linear age-related changes regardless of sex, particularly during the first few years of life. After this increase, curve slopes gradually became flat during adolescence and adulthood in both sexes. Age of local maximum for each subarea of the corpus callosum differed across the sexes. Ratios of total corpus callosum and genu, posterior midbody, as well as splenium to the whole brain were significantly higher in females compared with males. The present results demonstrate that the developmental trajectory of the corpus callosum during early life in healthy individuals is non-linear and dynamic. This pattern resembles that found for the cerebral cortex, further suggesting that this period plays a very important role in neural and functional development. In addition, developmental trajectories and changes in growth do show some sex differences.     

Magnetic Resonance Findings of the Corpus Callosum in Canine and Feline Lysosomal Storage Diseases

Several reports have described magnetic resonance (MR) findings in canine and feline lysosomal storage diseases such as gangliosidoses and neuronal ceroid lipofuscinosis. Although most of those studies described the signal intensities of white matter in the cerebrum, findings of the corpus callosum were not described in detail. A retrospective study was conducted on MR findings of the corpus callosum as well as the rostral commissure and the fornix in 18 cases of canine and feline lysosomal storage diseases. This included 6 Shiba Inu dogs and 2 domestic shorthair cats with GM1 gangliosidosis; 2 domestic shorthair cats, 2 familial toy poodles, and a golden retriever with GM2 gangliosidosis; and 2 border collies and 3 chihuahuas with neuronal ceroid lipofuscinoses, to determine whether changes of the corpus callosum is an imaging indicator of those diseases. The corpus callosum and the rostral commissure were difficult to recognize in all cases of juvenile-onset gangliosidoses (GM1 gangliosidosis in Shiba Inu dogs and domestic shorthair cats and GM2 gangliosidosis in domestic shorthair cats) and GM2 gangliosidosis in toy poodles with late juvenile-onset. In contrast, the corpus callosum and the rostral commissure were confirmed in cases of GM2 gangliosidosis in a golden retriever and canine neuronal ceroid lipofuscinoses with late juvenile- to early adult-onset, but were extremely thin. Abnormal findings of the corpus callosum on midline sagittal images may be a useful imaging indicator for suspecting lysosomal storage diseases, especially hypoplasia (underdevelopment) of the corpus callosum in juvenile-onset gangliosidoses.     

The cortical EEG in the acallosal mouse

The congenital absence of the corpus callosum has recently been found to occur among some mice of the ddN strain in our laboratory. Morphologically, the absence of corpus callosum was classified into two types. One was complete agenesis of corpus callosum, and the other revealed partial agenesis (genu or splenium, or both). In this experiment, the differences of cortical EEG spectral characteristics were studied on the normal, hypogenesis and acallosal mice. A total of 75 male and female adult mice were used. Under light ether anesthesia, five stainless steel electrodes (0.29 mm) were implanted stereotaxically in the bilateral cerebral cortex and cerebellum at a depth of 1.0 mm. After one week recovery period, the correlations of EEG of five combinations, such as homotopic anterior vs. posterior, left vs. right hemispheres, crossed contralateral, and homotopic anterior and posterior to the reference electrode, were analysed with a signal processor. In the complete acallosal mice (n = 11), the correlation coefficients were significantly lower (p less than 0.05), in the crossed contralateral, left vs. right hemispheres, and homotopic posterior to reference. In the hypogenesis of corpus callosum (n = 7), however, they were no significant differences in the correlation compared with normal mice (n = 57). At the end of experiment, the brain was removed and fixed with 10% formalin, then it was cut in half along the midsagittal plane. The midsagittal section was used to examine an outline of the corpus callosum.     

Latent inhibition and extinction of passive avoidance in mice C57BL/6J AND DBA/2J

The study was carried out in mice C57BL/6J and DBA/2J for comparative analysis of two interference processes: latent inhibition and extinction of passive avoidance produced with an unconditioned aversive stimulus of different parameters (0.5 and 0.25 mA). With a strong training to new stimulus, impairment of extinction has been detected only in mice DBA/2J. Reduction in the strength of punishment during training was accompanied by acceleration of extinction in mice C57BL/6J and its appearance in mice DBA/2J. The learning of passive avoidance in strong and weak reinforcement was the same for both strains of mice. Interline differences were found also in the analysis of latent inhibition. With strong and weak training to conditional stimulus, lost of novelty by repeated an 8-fold pre-exposures to the experimental chamber, in DBA/2J mice, in contrast to C57BL/6J, latent inhibition was disrupted. In addition, DBA/2J mice showed impairment of extinction with weak training to non-relevant stimulus.