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PubMedDate not supplied

Distribution of evoked potentials on stimulation of the human pulvinar.

The distribution of the evoked cortical potentials recorded during stereotactic pulvinectomy is analyzed. The evoked cortical potential shows maximal amplitude in the precentral area, with decreasing amplitude in the parietal and anterior temporal area, and minimal amplitude in the occipital area. The pulvinar has been histologically considered to have dense connections with the parietal lobe and no connection with the frontal lobe. However, our results suggest that the pulvinar has a dense functional connection with the frontal cortex, through which the pulvinar plays a role in motor function.

Brain Mapping↗
PubMed1994

Prevalence of abnormal thyroid function tests in connective tissue disease.

The prevalence of thyroid function tests' abnormalities in 170 patients with various connective tissue diseases (CTD) was examined and compared to a group of 100 age- and sex-matched controls. The overall prevalence of diagnosed thyroid disease was 3.5%. Categorizing the patients into 5 "functional groups" by the concurrent thyroid function test/results showed normal thyroid function tests in 14%, isolated elevated TSH levels with normal T4 and T3 levels in 4% and findings consistent with the laboratory diagnosis of primary hypothyroidism in 3%. The "euthyroid sick syndrome" was evidenced in 54% and elevated T4 levels and/or increased or normal T3 values with normal TSH in 25%. Antimicrosomal antibodies were noted in 12 patients (7%), with the highest incidence in systemic lupus erythromatosus patients (10%). patients with mixed connective tissue disease had significantly (p < 0.0005) higher frequency of hypothyroidism, whereas patients with systemic vasculities had higher frequency of hyperthyroxinemia. In conclusion, CTD patients frequently have abnormal results of one or more of thyroid function tests. Hypothyroidism and hyperthyroidism should be considered when evaluating symptoms and signs in CTD and a significant subset of CTD patients appears to be predisposed to the development of hyperthyroidism.

Adolescent↗
PubMed2005

Ribozyme cleavage reveals connections between mRNA release from the site of transcription and pre-mRNA processing.

We report a functional connection between splicing and transcript release from the DNA. A Pol II CTD mutant inhibited not only splicing but also RNA release from the site of transcription. A ribozyme situated downstream of the gene restored accurate splicing inhibited by the CTD mutant or a mutant poly(A) site, suggesting that cleavage liberates RNA from a niche that is inaccessible to splicing factors. Although ribozyme cleavage enhanced splicing, 3' end processing was impaired, indicating that an intact RNA chain linking the poly(A) site to Pol II is required for optimal processing. Surprisingly, poly(A)(-) beta-globin mRNA with a ribozyme-generated 3' end was exported to the cytoplasm. Ribozyme cleavage can therefore substitute for normal 3' end processing in stimulating splicing and mRNA export. We propose that mRNA biogenesis is coordinated by preventing splicing near the 3' end until the transcript is released by poly(A) site cleavage.

Cell Line↗
PubMed1994

Expression of c-fos mRNA and c-fos protein in neocortical transplants placed into excitotoxin-induced lesions in adult rats.

Using anatomical and electrophysiological methods, previous studies from this laboratory demonstrated that fetal neocortical block transplants placed into the excitotoxically ablated cortex of adult rats can establish functional connections with the host central nervous system. In order to further examine functional integration at the level of genomic activation/molecular signaling systems, transplants were analyzed for the presence of c-fos mRNA and Fos protein-labeled cells following a 20-min exposure of the animal to a novel open-field environment. This behavioral testing paradigm, which previously was shown to induce expression of c-fos mRNA in several brain regions including the sensorimotor cortex, was administered at 3 months after grafting. The transplants were found to express c-fos mRNA as well as c-fos protein following novelty exposure. These labeled cells were distributed primarily along the peripheral margin of the grafts. This study therefore suggests that at least some neurons within transplants become integrated with the host pathways at the level of molecular signal transduction.

Animals↗
PubMed2002

Thalamocortical control of feed-forward inhibition in awake somatosensory 'barrel' cortex.

Intracortical inhibition plays a role in shaping sensory cortical receptive fields and is mediated by both feed-forward and feedback mechanisms. Feed-forward inhibition is the faster of the two processes, being generated by inhibitory interneurons driven by monosynaptic thalamocortical (TC) input. In principle, feed-forward inhibition can prevent targeted cortical neurons from ever reaching threshold when TC input is weak. To do so, however, inhibitory interneurons must respond to TC input at low thresholds and generate spikes very quickly. A powerful feed-forward inhibition would sharpen the tuning characteristics of targeted cortical neurons, and interneurons with sensitive and broadly tuned receptive fields could mediate this process. Suspected inhibitory interneurons (SINs) with precisely these properties are found in layer 4 of the somatosensory (S1) 'barrel' cortex of rodents and rabbits. These interneurons lack the directional selectivity seen in most cortical spiny neurons and in ventrobasal TC afferents, but are much more sensitive than cortical spiny neurons to low-amplitude whisker displacements. This paper is concerned with the activation of S1 SINs by TC impulses, and with the consequences of this activation. Multiple TC neurons and multiple S1 SINs were simultaneously studied in awake rabbits, and cross-correlation methods were used to examine functional connectivity. The results demonstrate a potent, temporally precise, dynamic and highly convergent/divergent functional input from ventrobasal TC neurons to SINs of the topographically aligned S1 barrel. Whereas the extensive pooling of convergent TC inputs onto SINs generates sensitive and broadly tuned inhibitory receptive fields, the potent TC divergence onto many SINs generates sharply synchronous activity among these elements. This TC feed-forward inhibitory network is well suited to provide a fast, potent, sensitive and broadly tuned inhibition of targeted spiny neurons that will suppress spike generation following all but the most optimal feed-forward excitatory inputs.

Action Potentials↗
PubMed1981

[Embryonal histogenesis of endothelium].

Development of the mammalian vascular system is characterized by recapitulation of many morpho-functional signs peculiar to certain ancestral forms, as well as by certain aromorphous reorganizations reflecting in histogenesis of endothelium. Prior to the period of the common blood circulation in the mammalian embryos, the endothelium is developing within the endomesenchyme constructed by cells of a peculiar - endothelial - germ, but not of the endomesenchymal cells, as numerous investigators consider. The endothelium is developing as a capacitance tissue which presents by itself an epitheliomorphous duplex selective membrane, functionally connected with blood, tissue fluid and lymph in order metabolism and other functions of the organism's cells and tissues can be performed. Increase in cell number and their proendothelial derivatives at pretissue, tissue and hemoendothelial levels and successive union of recapitularities with the same name at the formation of the endothelial vessels add certain essential features to histogenesis of the endothelium and to its normal reactions. Polymerization and union of the recapitularities with the same name are the ways of integration; they are important ingredients of hereditarily determined differentiation. The latter is realized in the development of hemoendothelial offsprings which appear after the common blood circulation is started. The endothelial genesis in its capacitant form is complemented with blood cells incorporated, the means which is subjected to certain essential evolutional reorganizations. In its turn, this results in appearance of the double tissue hemoendothelial complex possessing features of an elementary organ.

Animals↗
PubMed2003

The articulatory loop: study of the subcortical connectivity by electrostimulation.

Although a cortical network involving Broca's area and the supramarginal gyrus (SMG) was widely studied using neurofunctional imaging, the functional connectivity underlying this so-called articulatory loop remains poorly documented. We describe a patient operated on for a glioma invading the left parietal operculum, using intraoperative electrical functional mapping under local anesthesia. Following the identification of cortical language sites within Broca's area and SMG, the subcortical pathways connecting these regions were detected and preserved during the resection. Postoperatively, the patient presented a slight dysarthria, then recovered. This is the first report of direct tracking of the subcortical connectivity underlying the fronto-parietal articulatory loop, allowing to better understand the pathophysiology of this network and the consequences of its damage.

Adult↗
PubMed1993

Testosterone-induced changes in adult canary brain are reversible.

Brain nuclei that control song are larger in male canaries, which sing, than in females, which sing rarely or not at all. Treatment of adult female canaries with testosterone (T) induces song production and causes song-control nuclei to grow, approaching the volumes observed in males. For example, the higher vocal center (HVC) of adult females approximately doubles in size by 1 month following the onset of T treatment. Male HVC projects to a second telencephalic nucleus, RA (the robust nucleus of the archistriatum), which projects in turn to the vocal motor neurons. Whether HVC makes a similar connection in female canaries is not known, although HVC and RA are not functionally connected in female zebra finches, a species in which testosterone does not induce neural or behavioral changes in the adult song system. This experiment investigated whether HVC makes an efferent projection to RA in normal adult female canaries, or if T is necessary to induce the growth of this connection. In addition, we examined whether T-induced changes in adult female canary brain are reversible. Adult female canaries received systemic T implants that were removed after 4 weeks; these birds were killed 4 weeks after T removal (Testosterone-Removal, T-R). Separate groups of control birds received either (a) T implants for 4 weeks which were not removed (Testosterone-Control, T-C) or (b) empty implants (Untreated-Control, O-C). Crystals of the fluorescent tracer DiI were placed in the song-control nucleus HVC in order to anterogradely label both efferent targets of HVC, RA and Area X. Projections from HVC to RA and Area X were present in all treatment groups including untreated controls, and did not appear to differ either qualitatively or quantitatively. Thus, formation of efferent connections from HVC may be prerequisite to hormone-induced expression of song behavior in adult songbirds. The volumes of RA and Area X were measured using the distribution of anterograde label as well as their appearance in Nissl-stained tissue. RA was larger in T-treated control birds than in untreated controls. Experimental birds in which T was given and then removed (T-R) had RA volumes closer in size to untreated controls (O-C). Because the volume of RA in T-treated controls (T-C) was larger than that of birds that did not receive T (O-C), we conclude that the volume of RA increased in both T-C and T-R birds but regressed upon removal of T in T-R birds.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1991

The impact of intracerebral retinal transplants on types of behavior exhibited by host rats.

Retinae transplanted over the midbrain of newborn rats establish functional connections with host brain centers, which provide a substrate for several distinct visual functions. These responses provide insight into the relationship between anatomy and behavior under normal conditions and after brain injury, as well as into the strategies used by an animal to extract significant information from its visual environment.

Animals↗
PubMed2006

Independent component model of the default-mode brain function: Assessing the impact of active thinking.

The "default-mode" network is an ensemble of cortical regions, which are typically deactivated during demanding cognitive tasks in functional magnetic resonance imaging (fMRI) studies. Using functional connectivity, this network can be conceptualized and studied as a "stand-alone" function or system. Regardless of the task, independent component analysis (ICA) produces a picture of the "default-mode" function even when the subject is performing a simple sensori-motor task or just resting in the scanner. This has boosted the use of default-mode fMRI for non-invasive research in brain disorders. Here, we studied the effect of cognitive load modulation of fMRI responses on the ICA-based pictures of the default-mode function. In a standard graded working memory study based on the n-back task, we used group-level ICA to explore the variability of the default-mode network related to the engagement in the task, in 10 healthy volunteers. The analysis of the default-mode components highlighted similarities and differences in the layout under three different cognitive loads. We found a load-related general increase of deactivation in the cortical network. Nonetheless, a variable recruitment of the cingulate regions was evident, with greater extension of the anterior and lesser extension of the posterior clusters when switching from lower to higher working memory loads. A co-activation of the hippocampus was only found under no working memory load. As a generalization of our results, the variability of the default-mode pattern may link the default-mode system as a whole to cognition and may more directly support use of the ICA model for evaluating cognitive decline in brain disorders.

Adult↗
PubMed2001

Serotonin excites tuberomammillary neurons by activation of Na(+)/Ca(2+)-exchange.

We have studied the effects of serotonin on the histaminergic neurons in the hypothalamic tuberomammillary nucleus. Intracellular recordings of the membrane potential were made with sharp electrodes from superfused rat hypothalamic slices. We found that serotonin increased the firing rate of the neurons to 224% of the control rate and depolarized them dose-dependently. Insensitivity to tetrodotoxin indicated a postsynaptic effect, which was unrelated to any conductance change. The involved receptor appeared to be a 5-HT2C receptor. The depolarization was strongly dependent on temperature and replacement of extracellular Na(+) with Li(+) or with N-methyl-D-glucamine suppressed the depolarization. Pretreatment with Ni(2+), 2',4'-dichlorobenzamil or KB-R7943 strongly attenuated the effect. These features indicate that the depolarization is the result of activation of an electrogenic Na(+)/Ca(2+)-exchanger which leads to an net inward current. These results support the view that the Na(+)/Ca(2+)-exchanger can play a role in determining the excitability of neurons. The results also provide a functional connection between two transmitter systems, the histaminergic and serotonergic, which modulate many physiological functions in the brain.

Amiloride↗
PubMed1999

Neuronal overexpression of APPL, the Drosophila homologue of the amyloid precursor protein (APP), disrupts axonal transport.

The two pathological hallmarks of Alzheimer's disease, amyloid plaques and neurofibrillary tangles, involve two apparently unrelated proteins, the amyloid precursor protein (APP) and Tau. Although it is known that aberrant processing of APP is associated with Alzheimer's disease, the definitive role of APP in neurons is not yet clear. Tau regulates microtubule stabilization and assembly in axons and is, thus, an essential component of the microtubule-associated organelle transport machinery. Although several groups have reported physical interaction between APP and Tau, and induction of Tau phosphorylation by APP and beta-amyloid peptide, the functional connection between APP and Tau is unclear. To explore the possibility that the functions of these two proteins may somehow converge on the same cellular process, we overexpressed APPL, the Drosophila homologue of APP, along with Tau in Drosophila neurons. Panneural coexpression of APPL and Tau resulted in adults that, upon eclosion, failed to expand wings and harden the cuticle, which is suggestive of neuroendocrine dysfunction. We analyzed axonal transport when Tau and APPL were coexpressed and found that transport of axonal cargo was disrupted, as evidenced by increased retention of synaptic proteins in axons and scarcity of neuropeptide-containing vesicles in the distal processes of peptidergic neurons. In an independent approach, we demonstrated genetic interaction and phenotypic similarity between APPL overexpression and mutations in the Kinesin heavy chain (Khc) gene, the product of which is a motor for anterograde vesicle trafficking.

Amyloid beta-Protein Precursor↗
PubMed2002

Effects of DSP4 and dizolcipine on connectivity of solid E19 cortical grafts to ablated SmI region of adult rats; an in vivo electrophysiological study.

The functional connectivity of an embryonic graft implanted into the lesioned somatosensory cortex and the effect of DSP4 (a selective noradrenergic neurotoxin to noradrenergic terminals) and dizolcipine (a non-competitive NMDA receptor antagonist), was studied electrophysiologically. The forepaw representational area of the rat primary somatosensory cortex was lesioned unilaterally and, 3-4 weeks later, tissue from the same region of E19 rat embryos was implanted into the cavity. At 7-9 months later, the rats were anaesthetized and single unit activity was recorded from the grafts in response to contralateral forepaw, ipsilateral hindpaw and contralateral hindpaw stimulation and compared with that obtained in control rats, in rats pretreated with dizolcipine immediately after lesioning and in rats given DSP4 24 h before transplantation. Neurones within the graft were integrated into the host brain and developed a pattern of representation similar to that of intact rats, but with a reduced proportion of neurones exhibiting short-latency response to contralateral forepaw stimulation and an increased proportion responding to stimulation of more than one paw. Pretreatment with dizolcipine did not increase short-latency responses to stimulation of contralateral forepaw stimulation however pretreatment with DSP4 reduced such responses and increased proportion of inhibitory responses. It was concluded that the noradrenergic system plays an important role in establishing host-graft connectivity. The importance of further pharmacological studies on host-graft connectivity and the relation of such connections to neural plasticity were discussed.

Adrenergic Agents↗
PubMed2003

Connections among symptoms of obsessive-compulsive disorder and posttraumatic stress disorder: a case series.

Theoretical, clinical, and empirical implications of the functional connections between symptoms of obsessive-compulsive disorder (OCD) and posttraumatic stress disorder (PTSD) are abundant. As such, four cases are presented here of men and women who met criteria for comorbid OCD and PTSD. All had been diagnosed with treatment-resistant OCD and were seeking treatment from an OCD specialty clinic or institute, all reported a history of traumatic experiences prior to the onset of OCD, and all appeared to demonstrate negative treatment outcomes. Upon examination, it appeared that symptoms of OCD and PTSD were connected such that decreases in OCD-specific symptoms related to increases in PTSD-specific symptoms, and increases in OCD-specific symptoms related to decreases in PTSD-specific symptoms. Speculations about the function of OCD symptoms in relation to post-traumatic psychopathology are put forth; and theoretical, research, and treatment implications are discussed.

Adult↗
PubMed1995

Bilateral connections from ventral group inspiratory neurons to phrenic motoneurons in the rat determined by cross-correlation.

We examined the functional connections from inspiratory neurons in the ventrolateral medulla to phrenic motoneurons in 11 Sprague-Dawley rats with intact vagi anaesthetized with sodium pentobarbital and paralysed with pancuronium bromide. Cross-correlation histograms were computed between the extracellular activity of 70 of these neurons and the discharge of the phrenic nerves; 38 contralateral only, 10 ipsilateral only and 22 bilaterally. A total of 22 peaks were detected in the cross-correlation histograms. These were classified as indicating common activation or synaptic connection according to their latencies to onset, and those suggesting connections as monosynaptic or paucisynaptic according to their half-amplitude widths. Nine peaks suggesting monosynaptic excitation of phrenic motoneurons were detected for 7 ventral group inspiratory neurons; 4 with contralateral connections and not tested for ipsilateral connections, 2 with bilateral connections, and 1 with a monosynaptic contralateral connection and a paucisynaptic ipsilateral connection. Four peaks suggesting paucisynaptic excitation of phrenic motoneurons were detected for 3 ventral group inspiratory neurons; 1 with bilateral connections, 1 with a contralateral connection only, and 1 (previously mentioned) with a paucisynaptic ipsilateral connection and a monosynaptic contralateral excitation. The remaining 9 peaks were classified as due to a common activation of the phrenic motoneurons and the ventral group inspiratory neurons. Cross-correlation histograms were also computed between the left and right phrenic nerve discharges in 5 rats and all displayed central broad peaks indicative of common activation, possibly due to excitation from bilaterally projecting medullary inspiratory neurons. We concluded that there is a substantial bilateral excitation of phrenic motoneurons by inspiratory neurons in the ventral medullary group of the rat.

Animals↗
PubMed1998

Methylene blue supravital staining: an evaluation of its applicability to the mammalian brain and pineal gland.

Methylene blue supravital staining of mammalian brain reveals typical staining patterns in different brain regions. Within the cerebellum of the mouse, the dye showed a peculiar affinity for the somata and the axons of Purkinje cells. Additionally, large polymorphic neurons characterized by long descending axons were detected within the granular layer and the white matter. These cells might represent another type of projection neuron. In the stratum pyramidale and stratum oriens of the murine hippocampus, a subpopulation of non-pyramidal cells, i.e. intrinsic interneurons, were selectively stained. Additionally, a labelling of perineuronal nets of extracellular matrix covering single cells could be achieved; this phenomenon might be due to the occurrence of strong anionic residues which attract the cationic dye. Therefore, perineuronal nets might also trap other cations and play an important role in the control of cell excitability. The electron microscopic investigation revealed drop-like dye accumulations within the cytoplasm and a staining of material at the site of the plasma membrane. Throughout the pineal gland, a network of a subpopulation of polymorphic cells with manifold long processes could be visualized. Syncytial connections of cells seemed to occur. The oxygen-dependent selective staining is probably functionally connected with the generation of oxygen radicals and subsequent oxidative stress for the cells. This reaction indicates a certain vulnerability to hypoxia; therefore, the intracellular dye-uptake might be interpreted as an early sign of metabolic disturbance.

Animals↗
PubMed2004

[Repetitive transcranial magnetic stimulation in depression; stimulation of the brain in order to cure the psyche].

Transcranial magnetic stimulation (TMS) is a non-invasive approach to briefly stimulate or inhibit cortical brain areas. A novel approach entails the delivery of repetitive TMS pulses (rTMS) at a fixed frequency. In rTMS cortical activity is altered beyond the period of actual stimulation. The changes occur locally as well as at a distance in functionally connected brain areas. These features render rTMS a suitable tool to study normal brain functions and the pathophysiology of brain diseases. Furthermore, it is expected that rTMS could be used as a novel therapy for neurological or psychiatric diseases characterised by abnormal cortical activation. This possibility has been studied mostly in patients suffering from depression, where rTMS has been used to restore normal activity in the hypoactive prefrontal cortex. Despite statistically significant therapeutic effects in small sized trials, the clinical implications are still limited.

Depressive Disorder↗