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PubMed1997

Functional anatomy of human auditory attention studied with PET.

Positron emission tomography was used to investigate the functional anatomy of selective auditory attention in 17 right-handed male volunteers who submitted to different tasks: silent rest (REST) listening to frequent low- or rare high-pitched tones (LIS) delivered randomly to the right or the left ear, selective auditory attention where subjects had to attend to deviants in one ear, right (ATTR) or left (ATTL). Six subjects had the series REST, LIS, ATTR twice, eight subjects the series REST, LIS, ATTL, and the last three subjects the sereis REST, ATTR, ATTL. Event-related potentials were simultaneously recorded with PET and showed significant task and electrode site effects on the N100 amplitude. When compared to REST, LIS elicited bilateral temporal activations of the Heschl's gyri and the planum temporale, with a significant rightward asymmetry, and of the posterior part of the superior temporal gyrus. Significant right precentral and anterior cingulate gyri normalized regional cerebral blood flow increases were observed in the frontal lobe. Both the ATTR and the ATTL conditions, compared to LIS, activated the supplementary motor area, bilateral precentral, and left postcentral cortices without any temporal cortex activation. In addition, the ATTL condition resulted in a right prefrontal cortex activation. Pooling the 14 subjects revealed an asymmetry in the superior temporal gyrus favoring the cortex contralateral to the attended ear. Two major networks seem thus to be involved during selective auditory attention: (1) a local temporal network, on which selective attention produces a modulation of the functional lateralization, and (2) a frontal network that could mediate the temporal cortex modulation by attention.

Adult↗
PubMed1985

Na-Ca exchange in cardiac tissues.

Our awareness of the importance of Na-Ca exchange in cardiac muscle has progressed from early observations of Na-Ca antagonism in the activation of contractile force. This was followed by demonstrations of actual Na-Ca ion countertransport across cell membranes and later functional studies in which manipulation of intracellular and extracellular Na and Ca concentrations has permitted a better characterization of the exchange process and its contribution to contractile force. The recent development of vesicle preparations from cardiac sarcolemmal membranes has, despite some drawbacks, produced useful information on the electrogenicity of the exchange mechanisms and on the relative affinity of the exchange carrier compared to the ATPase-driven Ca pump. These studies confirmed earlier estimates of the approximate exchange ratio of the Na-Ca countertransport system and have demonstrated its large maximum transport rate capabilities. The application of ion-sensitive microelectrodes in recent years has enabled measurements of the actual ion-activity gradients across the sarcolemmal membrane. These activity gradients together with the membrane potential control the rate and direction of the Na-Ca exchange. Despite the wide range of techniques employed to tackle the problem, the exchange ratio of Na to Ca movement is still in some doubt, with most estimates ranging between 5:2 and 4:1.

Animals↗
PubMed1991

Corticobulbar and corticospinal projections to neck muscle motoneurons in man. A functional study with magnetic and electric transcranial brain stimulation.

The cortical projections to neck muscle motoneurons were studied in normal subjects by electrical and magnetic transcranial brain stimulation. After magnetic stimulation with a large coil, motor evoked potentials were present in about 20% of relaxed and 100% of contracting neck muscles. The latency of these responses was short: about 7 ms in the sternomastoid and splenius and 9 ms in the trapezius muscles. Subtraction of the M-wave latency after stimulation of the accessory nerve at the skull base resulted in a central latency of about 4.5 ms. We suggest that rapid cortical projections connect with neck muscle motoneurons mono or disynaptically. The latency difference between the responses after electrical and magnetic stimulation was smaller in neck than in limb muscles but similar to that seen in masticatory muscles. A small magnetic coil was used to study the pattern of functional lateralization of cortical projections to neck muscle motoneurons; the projections for the sternomastoid and splenius are bilateral but predominantly contralateral, whereas those for the trapezius are exclusively contralateral.

Adult↗
PubMed1978

Sleep habits of children and the identification of pathologically sleepy children.

Sleep disorders and daytime sleepiness have been investigated only minimally in children. The sleep habits of 218 children, ages 10-13 years, were surveyed by a sleep habits questionnaire (SHQ). Our results demonstrate that total night time sleep on school nights begins to fall in early adolescence, whereas it remains relatively stable on non-school nights. Daytime sleepiness is not a common problem in this age group, in contrast to a college age population. We conclude that in adolescence chronic sleep deficits begin to occur which cumulatively affect later functioning. The potential use of the SHQ for depicting pathological sleepiness is also discussed.

Adolescent↗
PubMed1989

Cerebral lateralization as a source of interindividual differences in behavior.

Cerebral laterality can no longer be considered an exclusively human trait, as over the last 15 years there has been an emergence of data to suggest that animal brains are also lateralized. Morphologic, chemical and behavioral indices of brain asymmetry in the rodent have been reported, and it is suggested that variations in the magnitude and direction of these indices are determined by a complex interaction of genetic, hormonal and experiential factors. Interindividual differences in cerebral laterality have been shown to covary with, or predict, individual differences in spatial behavior and stress reactivity, as well as susceptibility to stress pathology and drug sensitivity. Such findings suggest that it is possible to study individual differences in lateralized brain function through the use of animal models.

Animals↗
PubMed1991

Long-term effects of neonatal exposure to isobutylmethylxanthine. I. Retardation of learning with antagonism by mianserin.

Pregnant women regularly ingest the methylxanthines, caffeine and theophylline, during pregnancy and lactation. Also, theophylline is used to treat apnea in premature infants. In this study, rat pups were treated with 3-isobutyl-1-methylxanthine (IBMX), on days 7-10 of life. Transient IBMX treatment during infancy caused a retardation of acquisition of a delayed reinforced autoshaped lever touch response in adulthood. Treated rats required more trials to learn the task, but did not show altered exploratory activity in the operant chambers. Coadministration of the serotonin (5-HT) antagonist mianserin with IBMX was able to attenuate significantly the effects of IBMX in both males and females, even though mianserin treatment alone caused an apparent learning deficit in the males. The results indicate that 5-HT and 5-HT receptors are important during development for normal expression of a specific cognitive function later in life. Furthermore, a 5-HT system appears to play a role in the mechanism whereby perinatal methylxanthine exposure could lead to learning impairments or other undesirable behavioral consequences. The use of IBMX in developing rats may also offer a model for studying the long-term consequences of the expression of opioid withdrawal during the neonatal period, since this agent induces a quasi-morphine withdrawal syndrome (QMWS) in mature rats. It is of interest that mianserin can block or attenuate effects of both quasi- and true morphine withdrawal.

1-Methyl-3-isobutylxanthine↗
PubMed2006

Pleomorphic extra-renal manifestation of the glomerular podocyte marker podocalyxin in tissues of normal beagle dogs.

Podocalyxin (PC) was initially identified as a major sialoprotein on the apical surface of glomerular podocytes to perform the filtration barrier function. Later, it was reported to be expressed in endothelial cells, megakaryotes/platelets, and hemangioblasts, the common progenitor cells of the hematopoietic and endothelial cells. Recently, increasing numbers of reports have indicated that PC is not merely a molecule restricted at renal glomerulus, angiogenic or hematopoietic system. To further elucidate the expression pattern and address the possible physiological role of PC in adult mammals, we conducted an extensive study by immunohistochemistry and immunofluorescence staining on various tissues of healthy adult beagle dogs. By combinatory usage of two different anti-podocalyxin antibodies recognizing distinct epitopes in PC, we have demonstrated that (1) PC is expressed in renal tubules, mesothelium, myocardium, striated muscles in tongue, esophagus and extraocular region, myoepithelial cells in esophagus and salivary glands, neurons, and ependyma, etc.; (2) there are at least three forms of PC proteins, depending upon the accessibility of two different PC antibodies, expressed in different organs/systems; and (3) a particular form of PC is distributed in a vesicle-like compartment in certain organs/systems, such as the central nervous system.

Animals↗
PubMed2004

Spatio-temporal expression of a DAZ-like gene in the Japanese newt Cynops pyrrhogaster that has no germ plasm.

To investigate the germ cell specification in urodeles, we cloned a DAZ-like sequence from the Japanese newt Cynops pyrrhogaster, Cydazl, and raised antibodies specific to Cydazl. Cydazl is a homologue of the human DAZ (deleted in azoospermia), DAZL, and Xenopus dazl genes, which are involved in gametogenesis or germ cell specification. During gametogenesis, expression of Cydazl mRNA and Cydazl protein was detected at first in the small previtellogenic oocytes in females but was not localized as seen in Xenopus and was restricted to secondary spermatogonia prior to meiosis in males. During early embryogenesis, maternal stores of the Cydazl transcript and protein were present in the entire embryos, not localized in any specific region. The zygotic expression was detected in hatching larvae (stage 50) by RT-PCR analysis whereas specific cells expressing Cydazl could not be determined by in situ hybridization at this stage. Strong expression of Cydazl and Cydazl were detected in primordial germ cells (PGCs) that had entered the gonadal rudiment at late stage 59. These results suggest that Cydazl does not function early in development, for the specification of germ cells, but functions later for differentiation of germ cells in the developing gonads during embryogenesis and for meiotic regulation, supporting the previous idea of an intermediate germ cell formation mode in urodeles.

Amino Acid Sequence↗
PubMed1988

Is interhemispheric transfer related to handedness and gender?

Interhemispheric transfer was assessed by five motor, tactile and visual tasks which required the 48 subjects to compare stimuli presented simultaneously on both sides of the body midline. Non-right-handers performed significantly better than consistent right-handers on one motor and one tactile task. Females out-performed males on the visual task and on one tactile task. Better interhemispheric transfer performance by non-right-handers and by females may be related to the reportedly larger corpus callosum regions in these groups and also to the reportedly less strong lateralization of function.

Adult↗
PubMed1996

Diencephalic asymmetries.

Structural asymmetry in diencephalic regions has been reported in a number of studies since the pioneering observations by Kemali and Braitenberg, Atlas of the frog's brain. Springer Verlag: 1969. Anatomical differences between the left and right habenulae have been identified in many lower vertebrate species. While there are few reports of structural asymmetry in the dorsal thalamus, there is evidence that asymmetrical thalamofugal projections can be induced in the visual system of chicks by lateralized sensory stimulation prior to hatching. Finally, there have been consistent reports of differences between and right sides of the hypothalamus in their sensitivity to the effects of circulating gonadal hormones in rats. In most cases, these asymmetries are sex-linked and correspond to a lateralization of function. Although the significance of these diencephalic asymmetries is still enigmatic, their existence indicates that asymmetry is not a phylogenetically recent feature of the brain, and the left-right differences in the brain may be mediated by a common ontogenetic mechanism and may underlie the development of highly specialized functions.

Animals↗
PubMed1991

Gastric vagal fibres distribution and acid secretion induced by portal infusion of D-glucose.

The vagal glucose signal pathway relevant to hepatic portal control of gastric acid secretion was examined in bilaterally adrenalectomized rats. The decrease in acid output after portal glucose injection was blocked by section of the hepatic branch which originates in the ventral vagus trunk below the diaphragm. After cervical vagotomy, the reduction in acid output was the same whether the section had been done on the right or the left side. The acid response was strongly inhibited by prior section of the dorsal vagus trunk at the celiac level. These results suggest that the hepatic glucose signal evoking an inhibitory action on the secretion of gastric acid has a specific pathway from the liver to the stomach, and that there is functional laterality in this pathway.

Animals↗
PubMed1991

An in vivo study of the ontogeny of long-term potentiation (LTP) in the CA1 region and in the dentate gyrus of the rat hippocampal formation.

The influences of stimulus intensity, intratrain frequency, and number of trains were studied for their effects on the development of long-term potentiation (LTP) in the hippocampal formation. LTP was analyzed with full input-output curves for population spike (PS) amplitudes (PS-LTP) calculated from responses elicited in the CA1 region and in the dentate gyrus by monosynaptic activation. A standardized protocol employing a sequence of stimuli was devised to systematically compare LTP in the dentate gyrus to that in the CA1 region in rats of various ages ranging from postnatal day (PN) 6 to adults (PN 60). In adult animals, the degrees of LTP were comparable in the dentate gyrus and CA1 region for the 3 stimulus strengths studied (intensity just subthreshold for PS, intensity giving 1/4 maximal PS, and intensity giving 1/2 maximal PS). LTP developed at different rates in the two regions, reaching adult values about two weeks after birth in CA1 but about 3 weeks after birth in the dentate gyrus. We postulate that differences in the rate of development in CA1 and in the dentate gyrus are related to the later neurogenesis of dentate granule cells and also possibly to a later functional maturation of N-methyl-D-aspartate (NMDA) receptor-channel complexes on these cells.

Action Potentials↗
PubMed1987

Modification of EEG asymmetry induced by auditory biofeedback loop during REM sleep in man.

Several studies have emphasized the relationship between (1) rapid eye movement sleep (REM sleep) and learning, and (2) between REM sleep and asymmetry in EEG activity. Since we have shown that obtaining operant conditioned responses via auditory biofeedback during REM sleep is feasible, we demonstrate here that REM contingent auditory stimulations (white noise stimulation or interruption of a continuous white noise stimulation) lead to differential changes in phasic and tonic components of REM sleep. Whereas during baseline nights a relative right activation is found in the medium bands of EEG frequencies, our procedure seems to induce a systematic interhemispheric change during experimental nights. A new approach to the information processing hypothesis during REM sleep is proposed in terms of functional lateralized modifications of the EEG.

Acoustic Stimulation↗
PubMed1990

Ear dominance and laterality of cortical activation identified by event-related desynchronization mapping.

Lateralized cortical functioning was assumed to be involved in ear dominance for pitch information. Left ear dominant (LED), right ear dominant (RED) subjects and individuals with no distinct ear preference (NED) were examined by means of the event-related desynchronization-mapping method during stimulation with a dichotic listening test. Contrary to expectations ED-groups did not systematically show greater involvement of the hemisphere contralateral to the dominant ear. RED were characterized by a response-dependent cortical activation pattern, LED exhibited a marked ipsilateral desynchronization focus if they showed preference for the dominant ear. In the NED group an early asymmetrical activation distribution was observed during the perception interval, which was concentrated ipsilaterally to the preferred ear.

Acoustic Stimulation↗
PubMed1988

Hemisphere differences for components of mental rotation.

The hemispheric functional lateralization of components of mental rotation performance was investigated. Twenty right-handed males were presented with rotated alphanumerics and unfamiliar characters in the left or right visual field. Subjects decided if the laterally presented stimulus was identical to or a mirror image of a center standard stimulus. Reaction time and errors were measured. Previous mental rotation findings were replicated and the visual field variable produced significant effects for both dependent measures. An overall right visual field advantage was observed in the latency data, suggesting a left hemisphere superiority for at least one component process of the task. A significant interaction in the error data showed that alphanumerics produced less errors in the right visual field than in the left visual field, consistent with a left hemisphere superiority for processing verbal symbolic material. No such hemispheric difference in accuracy was found for unfamiliar characters.

Adult↗
PubMed1989

Regional cerebral blood flow characteristics and variations with age in resting normal subjects.

Regional cerebral blood flow (rCBF) was measured during resting in 97 normal subjects, 19-68 years old. The results showed that the mean CBF level decreased progressively with age. The decrease was more prominent in frontotemporal and inferior Rolandic areas bilaterally. Frontal areas showed the highest values in all age groups. This hyperfrontality weakened somewhat with age. Mean CBF in the right hemisphere was significantly higher than in the left, as was flow in superior frontal, inferior frontal, and parietal areas. These asymmetries were age invariant. The age-related decrease of rCBF is interpreted as reflecting aging of the brain per se, although the influence of asymptomatic brain disease can not be ruled out. The flow asymmetries are interpreted as being related to functional lateralization of some aspects of attentional activation.

Adult↗
PubMed1979

EEG asymmetries in recognition of faces: comparison with a tachistoscopic technique.

Twelve field-dependent and twelve field-independent women, who had previously shown opposite superiorities in a tachistoscopic face recognition task, returned to the laboratory for a session in which FEG asymmetry was measured during two facial and two verbal recognition tasks. Although task-related EEG asymmetries were observed, there was no effect of cognitive style on either direction or amount of asymmetry. These results suggest a lack of comparability among different methods of assessing individual differences in lateral functions.

Adolescent↗