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PubMed2001

[Word generation in bilinguals--fMRI study with implications for language and memory processes].

For over a century the cerebral representation of language functions is a matter of debate. In Neuroscience language is regarded as one of the most lateralized cognitive functions. Thus, while the language which is acquired first in most cases is processed by the left hemisphere some studies in brain damaged but also experimental investigations propose a pivotal role of the right hemisphere in second language processing. By the advent of modern neuroimaging it is now possible to study language lateralization and bilinguality also in healthy subjects. We studied first and second language abilities in a group of bilingual, healthy individuals by means of functional magnetic resonance imaging (fMRI) with a word-fluency paradigm. While we found a predominantly left prefrontal activity during both first and also second language processing an additional right prefrontal activation was registered during the use of second language. Our findings are discussed on the basis of an interaction between language and memory processes.

Adult↗
PubMed2000

Radiation induced cell loss in rat submandibular gland and its relation to gland function.

PURPOSE: To understand early and late radiation-induced loss of function of the submandibular gland, changes in cell number were documented and correlated with data on gland function. Modulation of the radiation effect by sialogogues was used to investigate possible mechanisms of action. MATERIALS AND METHODS: Rats were irradiated with a single dose of 15 Gy of X-rays after pre-treatment with either saline, the muscarinic receptor agonists methacholine or pilocarpine, the adrenergic receptor agonist phenylephrine or methacholine plus phenylephrine. Before and 1-240 days after irradiation, submandibular saliva flow rate was measured. At the same time points and from comparable animals submandibular glands were carefully extirpated, weighed and prepared for light microscopic examination. RESULTS: Soon after irradiation (<30 days) no significant loss of cells was observed, whereas the gland function was severely compromised. Sialogogue pre-treatment attenuated the radiation-induced loss of gland function. At later intervals a considerable loss of acinar cells and to a lesser extent loss of granular convoluted tubule cells were observed. Gland function subsequently declined slowly. Pre-treatment with sialogogues gave transient protection against cell loss and loss of gland function. CONCLUSIONS: The lack of cell loss observed soon after irradiation indicates that the observed reduction in gland function was caused by a compromised functioning of the acini. The later loss of cells is probably due to death of cells that normally proliferate, leading to a further reduced secretory capacity. Protection of gland morphology and function by sialogogues at later times must therefore involve resistance of progenitor cells to radiation-induced cell death.

Adrenergic alpha-Agonists↗
PubMed1999

Psychosis and functioning as risk factors for later suicidal activity among schizophrenia and schizoaffective patients: a disease-based interactive model.

The present research explores the relationship of positive symptoms, negative symptoms, and posthospital functioning to subsequent suicidal behavior over a 7 1/2-year period, and examines whether these patterns vary with diagnosis. The results support a multifactor model of suicide risk. Both psychosis and poor functioning show some relationship to later suicidal activity for both schizophrenic and schizoaffective patients. Psychosis may remain a risk factor for suicidal activity for schizoaffective patients, even when functioning is partialed out. This is in contrast to the schizophrenia patients, for whom funtioning seems to mediate the effects of psychosis on later suicidality. In general, adequacy of overall posthospital functioning mediates the effects of some risk factors on suicidal activity within different diagnostic groups.

Adult↗
PubMed2006

Lobar asymmetries in subtypes of dyslexic and control subjects.

Reading involves phonologic decoding, in which readers "sound out" a word; orthographic decoding, in which readers recognize a word visually, as in "sight reading"; and comprehension. Because reading can involve multiple processes, dyslexia might be a heterogeneous disorder. This study investigated behavior and gross lobar anatomy in subtypes of dyslexic and control subjects. Subjects aged 18 to 25 years with identified reading problems and a group of healthy controls were given cognitive and behavioral tests and volumetric brain magnetic resonance imaging (MRI). Because atypical cerebral laterality has been proposed as a potential neural risk for dyslexia, dyslexic and control subjects were compared on anatomy of gross lobar regions. On asymmetry quotients, no significant differences were found between groups. Examination of the percentage of total brain volume of each structure revealed that control and dyslexic subjects were significantly different (P = .018). Dyslexic subjects had a larger percentage of brain volume than did the controls in the areas of total prefrontal (P = .003; 9.30% larger) and superior prefrontal (P = .004; 11.48% larger region). A Pearson correlation was performed to investigate whether a relationship existed between behavioral measures and either volumes of total prefrontal and total occipital regions or asymmetry quotients. A significant positive relationship between the left total occipital and word identification performance existed (R = .452, P = .045). Because it is believed by some that dyslexia occurs in varying degrees of severity, and because one of the research questions in this study is whether anatomy relates to severity or to distinct biologic groups, subjects were grouped according to both the nature and distinct pattern of reading or language performance and the degree of deficit. A battery of reading tests revealed five clinical subgroups of control (two) and dyslexic (three) subjects. These subgroups were statistically different on all cognitive and behavioral measures. When asymmetry was investigated across subgroups, significant differences between subgroups were found at the multivariate level (P = .043). Only the phonologic deficit groups (weak phonologic controls, phonologic deficit dyslexic subjects) had atypical asymmetry patterns. This finding suggests that lack of subtyping could have confounded earlier studies and that anomalous asymmetry might be related to phonologic dyslexia, whereas other subtypes might be reflective of environmental factors. Examination of volume at the subgroup level also showed differences between subgroups that might have implications for the nature of compensation. This study supports the concept that anomalous anatomy might reflect anomalous functional cerebral laterality, which could be a risk factor for developmental dyslexia, varying according to the nature of the deficit.

Adolescent↗
PubMed1982

Electromyographic analysis of the functional components of the lateral pterygoid muscle in the rhesus monkey (Macaca mulatta).

Electromyographic recordings (EMG) obtained from intramuscular electrodes inserted in the lateral pterygoid muscle (lat. pt.) of 29 juvenile and adolescent monkeys were assessed in relation to the recorded activity of three jaw elevating muscles, temporalis, masseter and medial pterygoid, and a jaw muscle depressor, the geniohyoid. The lat. pt. was recruited in one of three patterns: (1) only during mandibular depression, (2) during both depression and elevation, or (3) only during elevation of the jaw. The discharge of fibres in the lat. pt. during closing movements occurred bilaterally in 9 of 21 recordings. Simultaneous recordings from the anterior temporalis, medial pterygoid and the ipsilateral lat. pt. indicated completely different discharge patterns of the three muscles. In 9 recording sessions, two pairs of electrodes were placed in the same lat. pt. The discharge patterns from the two pairs were different in 5 of the recordings. In one region, the fibres were active only during depression, whereas in the other region fibres discharged only during elevation of the mandible. The data support the concept of two groups of fibres with separate functions within the lat. pt. and suggest that adaptation to oral respiration utilizes the two groups in distinctive patterns.

Animals↗
PubMed2005

Lateralization of cerebral hemodynamics during Wisconsin Card Sorting Test: a functional transcranial Doppler sonography study.

OBJECTIVE: Studies on lateralization of cerebral metabolism during Wisconsin Card Sorting Test (WCST), a well-known paradigm of category learning, have shown mixed results. Moreover, sorting dimension (number, color and shape) is a cofounder of laterality in WCST. Functional transcranial Doppler sonography (fTCD) has a high temporal resolution and allows the measurement of mean cerebral blood flow velocity (CBFV) in the middle (MCA) and anterior cerebral arteries (ACA), which supply lateral and medial parts of the frontal and parietal lobes, respectively. We used fTCD to investigate CBFV changes occurring in both MCA and ACA during WCST and different sorting dimensions. METHODS: Twenty-one subjects underwent twice two distinct phases of the WCST, namely maintaining a rule (maintaining set) and searching for a new rule (set shifting), during bilateral fTCD of the MCA and ACA. RESULTS: There was a left-sided dominance of CBFV during maintaining set and set shifting in the MCA. CBFV was not associated with test performance. The sorting dimension number caused the highest CBFV increase in both MCA and ACA during maintaining set, and the sorting dimension shape caused lowest CBFV decrease in both MCA during set shifting. CONCLUSIONS: This study confirms results that cerebral blood flow (CBF) lateralizes to the left side during WCST. The 3 sorting dimensions provoked distinct processing speed during maintaining set and set shifting, but caused no effect on hemispheric lateralization. SIGNIFICANCE: Functional transcranial Doppler sonography can be used to assess CBFV during WCST and different sorting dimensions, and the latter modulate reaction time and cerebral hemodynamics.

Adult↗
PubMed1994

Correlating gamma-aminobutyric acidergic circuits and sensory function in the electrosensory lateral line lobe of a gymnotiform fish.

Electric fish generate an electric field, which they sense with cutaneous electroreceptors. Electroreceptors project topographically onto the medullary electrosensory lateral line lobe (ELL). The ELL of gymnotiform electric fish is divided into four segments specialized to detect different aspects of the electrosensory input; it is also laminated with separate laminae devoted to electroreceptive input, interneurons, projection neurons, and feedback input. We have utilized antisera to glutamic acid decarboxylase (GAD) and gamma-aminobutyric acid (GABA) to map the distribution of GABAergic cells and fibers in the ELL of the gymnotiform fish, Apteronotus leptorhynchus. Six types of GABAergic interneurons are found in ELL: Type 2 granular cells (granular layer) project to pyramidal cells; polymorphic cells (pyramidal cell layer) project to the non-GABAergic type 1 granular cells; ovoid cells (deep neuropil layer) project bilaterally upon basilar dendrites of pyramidal cells; multipolar cells (deep neuropil layer) project bilaterally, probably to dendrites and neurons within the deep neuropil layer; and neurons of the ventral molecular layer and stellate cells (molecular layer) project to apical dendrites of pyramidal cells. GABAergic bipolar cells in the nucleus praeminentialis, a rhombencephalic structure devoted to feedback in the electrosensory system, project in relatively diffuse fashion to pyramidal cells. We hypothesize that the various GABAergic circuits of the ELL can be correlated with specific functions: type 2 granular cells with adaptation, size of receptive field center, and gain; polymorphic cells and type 1 granular cells with regulation of surround inhibition; ovoid cells with common mode rejection; and neurons of the ventral molecular layer with adaptive gain control. The feedback GABAergic input from bipolar cells of n. praeminentialis to pyramidal cells may be part of a searchlight mechanism similar to the one postulated for thalamocortical systems.

Animals↗
PubMed1986

Patterns of intellectual development in later life.

Temporal changes in 16 measures of cognitive and intellectual functioning (11 Wechsler Adult Intelligence Scale subtests, 3 Wechsler Memory Test subscales, 2 measures of reaction time) were studied in the full data set from the First Duke Longitudinal Study of Aging. Patterns of change in these 16 measures were identified through a 'grade-of-membership' analysis -- a general model for identifying patterns in temporal variation that does not require parametric assumptions about the trajectory of change or assumptions about the homogeneity of the sampled population. The analyses showed that the temporal variation of the 16 measures could be described by five latent patterns that reflected the complex patterning of intellectual functioning in extreme late life. The relation of these five patterns of intellectual ability to age was examined, as were the relationships to measures of mental and physical health. These results underline the needs for comprehensive models of health and functioning in later life that describe changes in a multidimensional form.

Aged↗
PubMed2001

[Lateralization and interhemispheric integration of directed attention].

Directed attention is a function to direct and shift the focus of awareness adequately to behaviorally relevant sensory events. Healthy subjects direct attention evenly to right and left hemispaces. Unilateral spatial neglect is a failure to respond normally to stimuli on the side opposite a cerebral lesion, which is considered to represent a unilateral disruption of directed attention. The established clinical observation that neglect usually occurs after right hemisphere lesions and the results of functional imaging studies suggest the right hemisphere dominance for directed attention. It is hypothesized that the right hemisphere distributes attention to space bilaterally, whereas the left hemisphere distributes attention primarily to right hemispace. However, patients with callosotomy show no apparent neglect with either right or left hand. Ishiai et al. (2001) reported detailed analyses of eye movements when a patient with a callosal infarction bisected lines. Left unilateral spatial neglect may appear, when use of the right hand induces a rightward bias in the attentional control of the left hemisphere and damage to its cingulate gyrus inhibits interhemispheric integration of attention. By contrast, the disconnected but intact right hemisphere may bisect a line accurately by integrating attention to the extents perceived in the left and right visual fields.

Attention↗
PubMed1988

Corticotectal circuit in the cat: a functional analysis of the lateral geniculate nucleus layers of origin.

1. The dorsal lateral geniculate nucleus (LGN) of the cat is a major thalamic relay between the retina and several visual cortical areas. These cortical areas in turn project to the superior colliculus (SC). The aim of the present experiment was to determine which LGN layers provide a necessary input to the corticotectal circuit. 2. Individual layers of the LGN were reversibly inactivated by microinjection of cobalt chloride during recording of visual responses in the retinotopically corresponding part of the superior colliculus. 3. For cells driven through the contralateral eye, inactivation of layer A or the medial interlaminar nucleus (MIN) had little effect on visual responsiveness in the superior colliculus. In contrast, inactivation of layer C abolished visual responses at one-quarter of the SC recording sites, reduced responses at another quarter, and left half of the recording sites unaffected. 4. For cells driven through the ipsilateral eye, inactivation of layer C1 or the MIN had no effect. Inactivation of layer A1 uniformly reduced visual responses in the superior colliculus and usually abolished them entirely. 5. These results are compatible with previous work showing that cortical input to the SC originates from Y-cells. They indicate that two of the five Y-cell containing layers (A1 and C) provide major inputs to the corticotectal circuit. The results suggest that layer A1 is functionally allied to layer C as well as to layer A.

Animals↗
PubMed1990

Limited lateral thoracotomy. Improved postoperative pulmonary function.

A prospective randomized controlled study was designed to determine differences in early postoperative pulmonary function, pain, and complications between patients undergoing limited lateral muscle-sparing thoracotomy. Fifteen patients underwent standard thoracotomy and 13 underwent limited incision with the same anesthetic technique. During the first 24 hours after operation, there were large decreases in the results of spirometric tests of pulmonary reserve (forced expiratory volume in 1 second and forced vital capacity), but these decrements were consistently significantly smaller in the limited-incision group. Other tests of pulmonary function (mid-expiratory phase forced expiratory flow, alveolar-arterial oxygen gradient, and PaCO2), however, demonstrated similar postoperative changes in both groups. Similarly, there were no differences in pain scores, postoperative morphine requirements, complications, or length of hospital stay. Use of the limited muscle-sparing incision resulted in improved postoperative pulmonary reserve, but this did not translate into differences in other measures of postoperative convalescence.

Female↗
PubMed1995

[The lateralization effect of oxytocin on the functional activity of paired visceral organs in rats].

Following unilateral intranasal oxytocin administration, asymmetric alterations in some functional parameters of the adrenal glands, testis, lungs and heart, occurred. The lateralization of alterations was dependent on the side of oxytocin injection and the side of paired organ arrevgenent. Possible pathways of intranasal oxytocin administration effects on visceral organs as well as causes of their asymmetry, are discussed.

Administration, Intranasal↗
PubMed1994

Cortical point-spread function and long-range lateral interactions revealed by real-time optical imaging of macaque monkey primary visual cortex.

Processing of retinal images is carried out in the myriad dendritic arborizations of cortical neurons. Such processing involves complex dendritic integration of numerous inputs, and the subsequent output is transmitted to multiple targets by extensive axonal arbors. Thus far, details of this intricate processing remained unexaminable. This report describes the usefulness of real-time optical imaging in the study of population activity and the exploration of cortical dendritic processing. In contrast to single-unit recordings, optical signals primarily measure the changes in transmembrane potential of a population of neuronal elements, including the often elusive subthreshold synaptic potentials that impinge on the extensive arborization of cortical cells. By using small visual stimuli with sharp borders and real-time imaging of cortical responses, we found that shortly after its onset, cortical activity spreads from its retinotopic site of initiation, covering an area at least 10 times larger, in upper cortical layers. The activity spreads at velocities from 100 to 250 microns/msec. Near the V1/V2 border the direct activation is anisotropic and we detected also anisotropic spread; the "space constant" for the spread was approximately 2.7 mm parallel to the border and approximately 1.5 mm along the perpendicular axis. In addition, we found cortical interactions between cortical activities evoked by a small "center stimulus" and by large "surround stimuli" positioned outside the classical receptive field. All of the surround stimuli used suppressed the cortical response to the center stimulus. Under some stimulus conditions iso-orientation suppression was more pronounced than orthogonal-orientation suppression. The orientation dependence of the suppression and its dependency on the size of some specific stimuli indicate that at least part of the center surround inhibitory interaction was of cortical origin. This findings reported here raise the possibility that distributed processing over a very large cortical area plays a major role in the processing of visual information by the primary visual cortex of the primate.

Animals↗
PubMed1984

Critical periods for functional and anatomical compensation in lateral suprasylvian visual area following removal of visual cortex in cats.

Previous experiments have found that neurons in the cat's lateral suprasylvian (LS) visual area of cortex show functional compensation following removal of visual cortical areas 17, 18, and 19 on the day of birth. Correspondingly, an enhanced retino-thalamic pathway to LS cortex develops in these cats. The present experiments investigated the critical periods for these changes. Unilateral lesions of areas 17, 18, and 19 were made in cats ranging in age from 1 day postnatal to 26 wk. When the cats were adult, single-cell recordings were made from LS cortex ipsilateral to the lesion. In addition, transneuronal autoradiographic methods were used to trace the retino-thalamic projections to LS cortex in many of the same animals. Following lesions in 18- and 26-wk-old cats, there is a marked reduction in direction-selective LS cortex cells and an increase in cells that respond best to stationary flashing stimuli. These results are similar to those following visual cortex lesions in adult cats. In contrast, the percentages of cells with these properties are normal following lesions made from 1 day to 12 wk of age. Thus the critical period for development of direction selectivity and greater responses to moving than to stationary flashing stimuli in LS cortex following a visual cortex lesion ends between 12 and 18 wk of age. Following lesions in 26-wk-old cats, there is a decrease in the percentage of cells that respond to the ipsilateral eye, which is similar to results following visual cortex lesions in adult cats. However, ocular dominance is normal following lesions made from 1 day to 18 wk of age. Thus the critical period for development of responses to the ipsilateral eye following a lesion ends between 18 and 26 wk of age. Following visual cortex lesions in 2-, 4-, or 8-wk-old cats, about 30% of the LS cortex cells display orientation selectivity to elongated slits of light. In contrast, few or no cells display this property in normal adult cats, cats with lesions made on the day of birth, or cats with lesions made at 12 wk of age or later. Thus an anomalous property develops for many LS cells, and the critical period for this property begins later (between 1 day and 2 wk) and ends earlier (between 8 and 12 wk) than those for other properties.(ABSTRACT TRUNCATED AT 400 WORDS)

Aging↗
PubMed1999

Visualization of defective mitochondrial function in skeletal muscle fibers of patients with sporadic amyotrophic lateral sclerosis.

The mitochondrial function in skeletal muscle was investigated in skeletal muscle biopsies of 26 patients with sporadic amyotrophic lateral sclerosis (ALS) and compared with investigations of 28 age-matched control muscle samples and biopsies of 6 patients with spinal muscular atrophy (SMA) and two patients with Tay-Sachs disease. In comparison to the control, SMA and Tay-Sachs biopsies, we observed in the ALS samples a significant about two-fold lower activity of complex I of mitochondrial respiratory chain. To visualise the distribution of the mitochondrial defect in skeletal muscle fibers we applied confocal laser-scanning microscopy and video fluorescence microscopy of NAD(P)H and fluorescent flavoproteins. The redox change of mitochondrial NAD(P)H and flavoproteins on addition of mitochondrial substrates, ADP, or cyanide were determined by measurement of fluorescence intensities with dual-photon UV-excitation and single-photon blue excitation. In skeletal muscle fibers of ALS patients with abnormalities of mitochondrial DNA (multiple deletions, n=1, or lower mtDNA levels, n=14) we observed a heterogeneous distribution of the mitochondrial defects among individual fibers and even within single fibers. In some patients (n=3) a mitochondrial defect was also detectable in cultivated skin fibroblasts. These findings support the viewpoint that the observed impairment of mitochondrial function in muscle of certain ALS patients is caused by an intrinsic mitochondrial defect which may be of pathophysiological significance in the etiology of this neurodegenerative disease.

Adult↗
PubMed1993

Functional organization of the ventral lateral geniculate complex of the tree shrew (Tupaia belangeri): II. Connections with the cortex, thalamus, and brainstem.

Connections of the ventral lateral geniculate complex (GLv) in the tree shrew were traced by anterograde and retrograde transport of WGA-HRP. The results buttress earlier findings that GLv in this species is composed of two main divisions, lateral and medial, each of which differs in its connections with the brainstem and cerebral cortex. The connections of the lateral division (GLv) suggest that it participates in visuosensory functions: it receives input from the retina, striate cortex, pretectum, and retino-recipient layers of the superior colliculus. These connections help clarify the identification of the internal and external subdivisions of GLv inasmuch as projections from both the superior colliculus and pretectum terminate in the external subdivision and each, in turn, receives a projection from the internal subdivision. Connections of the medial division suggest that this part of the nucleus is involved with visuomotor functions. Thus, the medio-caudal subdivision projects to the pontine nuclei, the prerubral field and the central lateral nucleus. The medio-caudal subdivision also receives projections from the lateral cerebellar nucleus, so that the GLv-ponto-cerebello-GLv loop involves mainly one subdivision of GLv. The medio-rostral subdivision receives projections from the pretectum and parietal cortex. Its output is directed primarily at the intermediate and deep layers of the superior colliculus. All of these targets of GLv, the pons, prerubral field, and deep layers of the superior colliculus, are known to play a role in the coordination of head and eye movements. Additional connections of GLv with the vestibular nuclei, intralaminar nuclei, hypothalamus, and facial motor nucleus are also described.

Animals↗
PubMed1996

Cortical activation in the human brain during lateral saccades using EPISTAR functional magnetic resonance imaging.

The location of the human cortical substrate underlying simple horizontal saccadic eye movements was investigated using echoplanar functional magnetic resonance imaging (fMRI) in young healthy volunteers. Echoplanar imaging with signal targeting and alternating radiofrequency (EPISTAR), a novel perfusion technique, measured signal intensity changes in one to four contiguous 10-mm slices centered to include both striate cortex and putative frontal eye fields during horizontal saccade and fixation conditions. Subtraction images of self-paced visually guided saccadic versus fixation conditions showed bilateral marked and statistically significant localized signal increases in the precentral region (Brodmann areas 4, 6) and peristriate cortex (areas 17, 18, 19) and qualitative increases in the superior medial frontal region, as identified by a Talairach-Tournoux generalized template in the brain slices that were scanned. Additional parietal activation occurred during a target-guided saccade task. Our data (i) support the localization of the human FEF, as identified by simple, nonexploratory saccadic eye movements, in the precentral motor strip and premotor cortex, (ii) show individual variability in the exact anatomical location of saccade-related activations, and (iii) confirm that the EPISTAR technique can demonstrate localized signal increases during a behavioral task.

Adult↗