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PubMed2001

Movement-related cortical potentials associated with progressive muscle fatigue in a grasping task.

OBJECTIVE: The present research was aimed to further address the general empirical question regarding the behavioral and neurophysiological indices and mechanisms that contribute to and/or compensate for muscle fatigue. In particular, we examined isometric force production, EMG, and EEG correlates of progressive muscle fatigue while subjects performed a grasping task. METHODS: Six neurologically healthy subjects were instructed to produce and maintain 70% of maximum voluntary contraction (MVC) for a total of 5 s in a sequence of 120 trials using a specially designed grip dynamometer. Three components of movement-related potentials (Bereitschaftspotential, BP, Motor potential, MP, and Movement-monitoring potential, MMP) were extracted from continuous EEG records and analyzed with reference to behavioral indicators of muscle fatigue. RESULTS: Experimental manipulations induced muscle fatigue that was demonstrated by decreases in both MVC values and mean force levels produced concomitant to increases in EMG root mean square (RMS) amplitude with respect to baseline levels, and EMG slope. EEG data revealed a significant increase in MP amplitude at precentral (Cz and FCz) and contralateral (C3) electrode sites, and increases in BP amplitude at precentral (Cz and FCz) electrode sites. CONCLUSIONS: The increases in EMG amplitude, EMG slope, and MP amplitudes suggest a possible link between the control signal originating in the motor cortex and activity level of the alpha-motoneuron pool as a function of progressive muscle fatigue. Overall, the data demonstrate that progressive muscle fatigue induced a systematic increase in the electrocortical activation over the supplementary motor and contralateral sensorimotor areas as reflected in the amplitude of movement-related EEG potentials.

Adolescent↗
PubMed1998

Spatial and temporal evolution of neuronal activation, stress and injury in lithium-pilocarpine seizures in adult rats.

In order to follow the spatial and temporal evolution of neuronal damage, cellular activation and stress responses subsequent to lithium-pilocarpine seizures of various durations in the adult rat, we analyzed the expression of Fos protein and local cerebral glucose utilization as markers of cellular activation, HSP72 immunoreactivity and acid fuchsin staining as indicators of cellular stress and injury, and Cresyl violet staining for the assessment of neuronal damage. The expression of Fos appeared very early, 2-30 min after the onset of polyspikes and intensified during the following 4 h. Fos immunoreactivity was especially high in the hippocampus, cerebral cortex, amygdala and anterior olfactory nuclei. Local cerebral glucose utilization measured during the second hour of seizures was largely increased (350-580%) over control levels in cortical areas, amygdala, dentate gyrus, caudate nucleus and mediodorsal thalamus. HSP72 immunoreactivity never appeared earlier than 40-50 min after the onset of polyspikes, and was most prominent in hippocampal CA3 area, cerebral cortex (except the piriform cortex) and anterior olfactory nuclei. Acid fuchsin staining was maximal in the piriform cortex and the polymorphic layer of the dentate gyrus. Staining was moderate in the sensorimotor cortex and the amygdala. Neuronal damage was extensive in the piriform and entorhinal cortices, the hippocampal CA3 area and the polymorphic layer of the dentate gyrus, basal amygdala, mediodorsal thalamus and anterior olfactory nuclei. In conclusion, the present study shows that brain regions with the highest expression of Fos and the largest metabolic activation were also highly stained with acid fuchsin and most heavily damaged. Conversely, there is no clear relationship between HSP72 expression, cellular activation and neuronal damage.

Animals↗
PubMed1989

Cerebral glucose utilization in rat brain during phenobarbital withdrawal.

The phenobarbital withdrawal syndrome in rats is characterized by tremors, arched back, weight loss and hyperactivity. This syndrome is shown to be associated with both general and localized increases in cerebral glucose utilization. An increase in glucose utilization (significant at the P less than or equal to 0.001 level) was observed in 72% of the 57 structures examined. Increases in glucose utilization of greater than or equal to 180% of control values were noted in structures associated with the motor system (columns in the frontal sensorimotor cortex, globus pallidus, dentate nucleus of the cerebellum and ovoid areas in the cerebellar vermis), thalamic nuclei (lateral and posterior), dorsal lateral geniculate, mammillary body, cingulate cortex, locus ceruleus, and cerebellar flocculus and paraflocculus. The structures showing the greatest increase in glucose utilization were cerebellar paraflocculus (257% of control), columns in the frontal sensorimotor cortex (247% of control) and ovoid areas in the cerebellar vermis (223% of control). Areas of the brain that have been described as cell body areas for serotonergic (raphe), noradrenergic (locus ceruleus), dopaminergic (substantia nigra, zona compacta) and GABAergic (globus pallidus) neurons also showed increases in glucose utilization. The pattern of cerebral glucose utilization accompanying the phenobarbital withdrawal syndrome in rats contrasts with that for morphine withdrawal and exhibits both similarities and differences with respect to ethanol withdrawal.

Animals↗
PubMed1987

Alterations in regional energy metabolism in rat brain produced by small and by large doses of apomorphine: possible relations to autoreceptors.

Dose-dependent changes in behavioural patterns and in local cerebral glucose utilization (LCGU) following subcutaneous application of apomorphine were measured in conscious, unrestrained rats by means of a scoring system and of the autoradiographic [C14]2-deoxyglucose technique, respectively. The behavioural patterns of akinesia, ptosis, yawning and penile erections were scored. Akinesia and ptosis were most prominent after 0.02 and 0.07 mg/kg apomorphine but not after 0.18 mg/kg. Maximal scores for yawning and penile erections were obtained after 0.07 mg/kg. LCGU was not significantly changed after 0.07 mg/kg except for decreases in the cingulate cortex and hypothalamus. Apomorphine 0.5 mg/kg decreased LCGU in the cingulate, parietal and occipital cortex, anteromedial and lateral thalamus and lateral habenula but increased it in laminae IV and VI of the sensorimotor cortex, in the parafascicular nucleus of the thalamus, and in some parts of the basal ganglia and related nuclei. Similar changes in LCGU occurred after 2.0 mg/kg apomorphine, which also increased LCGU in the ventral tegmental area. The lower dose did not produce changes in LCGU opposite to those occurring after larger doses. The data obtained with LCGU do not support the idea that behavioural effects after low doses of apomorphine are elicited by activation of dopamine autoreceptors.

Animals↗
PubMed1998

The functional emergence of prefrontally-guided working memory systems in four- to eight-year-old children.

The neural processes that underlie the functional emergence of human cognitive functions, particularly those associated with the prefrontal cortex (PFC), are of growing interest to developmental psychologists and neuroscientists. Specifically, working memory functions have been correlated with PFC activity in nonhuman primates and adult humans but have not been extensively studied in children. We examined the developmental emergence of functions involved in working memory through the use of the Cambridge Neuropsychological Test Automated Battery (CANTAB), a computerized battery of nonverbal visually-presented neuropsychological tests designed to dissociate frontal from temporal lobe behavioral functions. Participants were normal children, aged 4-8 (n = 181) and a small group of young adults (n = 24) who completed measures of Spatial Memory Span, Spatial Working Memory, the Tower of London planning task, Visual Pattern and Spatial Recognition tasks, and a Set-Shifting task. Findings indicate a general age-related progression in ability levels on frontal lobe tasks, with 4-year-olds performing worse than 5- to 7-year-olds on all measures. Eight-year-olds are superior to younger children in their ability to solve complex problems but have not yet reached adult levels of performance on the most difficult items of the Tower of London and Spatial Working Memory tasks. We conclude that the development of working memory functions proceeds dimensionally, starting with refinement of basic perceptual and sensorimotor functions and culminating with the physiological maturation of widespread neural networks that integrate complex processing demands inherent to working memory tasks.

Adolescent↗
PubMed1986

Communicative, sensorimotor, and language skills of young children with Down syndrome.

The transition from preverbal to verbal communication of retarded and nonretarded children was explored in a prospective, longitudinal study. Mental development was tested at ages 13 months and at 2 and 3 years. At age 2 years, the MA of the retarded subjects matched the MA of the nonretarded at 13 months. Sensorimotor development of the retarded children at 2 and 3 years of age was assessed by the Uzgiris-Hunt scales. Splitting the sample according to whether or not the retarded subjects had reached Sensorimotor Stage 6 at age 3 yielded differential results on concurrent language skills. Pragmatic skills measured at age 2 for the retarded subjects were deficient as compared with such skills assessed at 13 months for the nonretarded subjects. Results seem to support the postulate of a skill-specific homology in the transition from preverbal to verbal communication.

Child Development↗
PubMed2001

Selective and long-term learning impairment following neonatal hypoxic-ischemic brain insult in rats.

We examined four different learning and memory tasks in rats which had been subjected to left carotid artery ligation followed by 2 h hypoxia (8% oxygen) when they were 7 days old. The examination began on the 4th week after insult and continued to 18 weeks post-insult. Compared with the control group, the hypoxic-ischemic group showed significant learning impairments in choice reaction time tasks relating to the attention process, and in plus-maze tasks and water maze tasks which examine long-term reference memory. In eight-arm radial maze tasks representing both short-term working memory and long-term reference memory, inferiority of the hypoxic-ischemic group was transient. Results of the sensorimotor test were normal in the hypoxic-ischemic group although slight flexion and twisting in the right forelimb was observed in 30% of the hypoxic-ischemic group when suspended by the tail. These abnormalities did not affect the results of learning tests. Findings of the study indicate that left-side brain damage produced by hypoxia-ischemia at 7 days of age resulted in selective and long-lasting learning and memory impairment.

Animals↗
PubMed2006

Tactile spatial attention enhances gamma-band activity in somatosensory cortex and reduces low-frequency activity in parieto-occipital areas.

We investigated the effects of spatial-selective attention on oscillatory neuronal dynamics in a tactile delayed-match-to-sample task. Whole-head magnetoencephalography was recorded in healthy subjects while dot patterns were presented to their index fingers using Braille stimulators. The subjects' task was to report the reoccurrence of an initially presented sample pattern in a series of up to eight test stimuli that were presented unpredictably to their right or left index finger. Attention was cued to one side (finger) at the beginning of each trial, and subjects performed the task at the attended side, ignoring the unattended side. After stimulation, high-frequency gamma-band activity (60-95 Hz) in presumed primary somatosensory cortex (S1) was enhanced, whereas alpha- and beta-band activity were suppressed in somatosensory and occipital areas and then rebounded. Interestingly, despite the absence of any visual stimulation, we also found time-locked activation of medial occipital, presumably visual, cortex. Most relevant, spatial tactile attention enhanced stimulus-induced gamma-band activity in brain regions consistent with contralateral S1 and deepened and prolonged the stimulus induced suppression of beta- and alpha-band activity, maximal in parieto-occipital cortex. Additionally, the beta rebound over contralateral sensorimotor areas was suppressed. We hypothesize that spatial-selective attention enhances the saliency of sensory representations by synchronizing neuronal responses in early somatosensory cortex and thereby enhancing their impact on downstream areas and facilitating interareal processing. Furthermore, processing of tactile patterns also seems to recruit visual cortex and this even more so for attended compared with unattended stimuli.

Adult↗
PubMed1976

Activation-induced restoration of sensorimotor functions in rats with dopamine-depleting brain lesions.

Bilateral electrolytic lesions of the lateral hypothalamus or intraventricular 6-hydroxydopamine injections produced substantial depletions of striatal dopamine in rates. All animals with brain damage showed marked sensorimotor impairments. However, they began to move and respond appropriately to environmental stimuli when placed in a sink of water, in a shallow ice bath, or among a colony of cats or rats. A reversal of the sensorimotor dysfunctions was still apparent shortly after the animals were removed from each activating situation. However, the terapeutic effects dissipated rapidly, and by 4 hr after an exposure the rats responded as poorly as they had prior to activation. These findings are strikingly similar to the "paradoxical kinesia" seen in parkinsonism, a clinical disorder attributed to degeneration of central dopamine-containing neurons. Collectively, they suggest the importance of activation in maintaining responsiveness to senory stimuli in rats following dopamine-depleting brain lesions.

Animals↗
PubMed1979

Preterm infant interaction with the caregiver in the first year of life and competence at age two.

Caregiver-infant interactions were studied for 50 preterm infants and their primary caregivers. Naturalistic observations in the home were made when the infants were 1, 3, and 8 months of age. The social transactions in the first year were related to competence at age 2, thereby extending a previous report showing a moderate association between caregiver-infant interaction and competence at 9 months. The frequency of early social transactions was predictive of the infant's competence at age 2 on the Gesell Developmental Schedules, a sensorimotor scale, a measure of receptive language, and the Bayley Mental Scale. Early social transactions were as predictive of 2-year competence as were caregiver-child transactions at age 2. The study suggests that social transactions as early as 1 month reflect some quality of the relationship between the caregiver and the infant that is important to the child's later mental performance.

Child Development↗
PubMed2000

Experience-dependent structural plasticity in cortex heterotopic to focal sensorimotor cortical damage.

Structural plasticity following focal neocortical damage in adult rats has recently been found to be sensitive to postinjury rehabilitative training. Experience on a complex motor skills task, the acrobatic task, after unilateral lesions of the forelimb representation region of the sensorimotor cortex (FLsmc) enhanced synaptic structural changes in the cortex contralateral and homotopic to the lesions. Using tissue from this previous study, the present study examined whether a heterotopic region of the sensorimotor cortex of either hemisphere, the hindlimb representation area (HLsmc), would undergo structural changes following unilateral FLsmc lesions and whether these changes would also be sensitive to postinjury training on the acrobatic task. Stereological methods for light and electron microscopy were used to assess structural changes in lesion or sham-operated rats following 28 days of postoperative acrobatic training or simple repetitive exercise (motor controls). In the HLsmc contralateral to the lesions of rats receiving acrobatic training, there was a subtle, but significant, increase in cortical volume and in layer II/III neuropil and dendritic volume per neuron in comparison to shams. In rats receiving simple exercise after the lesions, these changes were not significantly different from shams. Acrobatic training also prevented a loss of cortical volume in the HLsmc adjacent to the lesion in comparison to shams. These data suggest that behavioral training following cortical injury facilitates structural plasticity in behaviorally relevant areas of the neocortex other than the homotopic cortex contralateral to the lesion. This structural plasticity might be relevant to the development of behavioral compensation after cortical injury.

Animals↗
PubMed2005

Analysis of the role of 5-HT1A receptors in spatial and aversive learning in the rat.

The role of the brain 5-HT1A receptor in cognition was examined in the water maze (WM) and passive avoidance (PA) tasks in the male rat. Pre-training administration of the 5-HT1A receptor agonist 8-OH-DPAT impaired WM performance and facilitated PA retention at low doses (0.01 and 0.03 mg/kg) and impaired PA retention at higher doses (0.1-1.0 mg/kg). The 5-HT1A receptor antagonist NAD-299 produced a dose-dependent facilitation of PA retention. In contrast, the 5-HT1A receptor antagonists NAD-299 and WAY-100635 failed to alter acquisition and retention in the WM. The impairments in WM and PA (but not facilitation in PA) induced by 8-OH-DPAT were blocked by NAD-299. Furthermore, NAD-299 prevented the PA impairments induced by the muscarinic antagonist scopolamine or the NMDA receptor antagonist MK-801. In contrast, NAD-299 and WAY-100635 failed to attenuate the WM impairment induced by scopolamine, probably due to the failure of 5-HT1A receptor blockade to attenuate the sensorimotor disturbances induced by scopolamine. These results indicate that 5-HT1A receptor stimulation and blockade result in opposite effects in two types of cognitive tasks in the rat, and that 5-HT1A receptor blockade can facilitate some aspects of cognitive function, probably via modulation of cholinergic and glutamatergic transmissions. This suggests that 5-HT1A receptor antagonists may have a potential role in the treatment of human degenerative disorders associated with cognitive deficits.

8-Hydroxy-2-(di-n-propylamino)tetralin↗
PubMed1980

[Caffeine and smoking-induced changes in the behavior of car drivers].

The authors examined changes in the behaviour of car drivers under the effect of coffeini matrii benzoici in doses of 250 mg (125 mg pure caffeine) and 500 mg (250 mg pure caffeine) in a single experimental group who had been exposed, prior to that, to a zero control experiment. The behaviour changes were examined immediately after the smoking of 5 cigerettes in a row. The experimental subjects' reaction was investigated using the determination set, their attention--using a modified Block test. 125 mg pure caffeine proved to have an excitatory effect on most of the group, with an overall improvement in performance, brightening up of mental processes, with the rate of mistakes dropping, attention and reaction improving in comparison with the proceding zero experiment. A dose of 250 mg caffeine had an inhibitory effect on most of the probands with the overall quality of performance deteriorating in all of the group; the quality of attention was worse, too, while reaction showed a moderate degree of improvement as a result of transfer. The experiment involving smokers after a dose of 5 cigarettes showed a deterioration in the capacity for concentration and a higher rate of errors in the performance of sensorimotor task while the reaction capacity remained normal.

Attention↗
PubMed2001

Brain areas involved in interlimb coordination: a distributed network.

Whereas behavioral studies have made significant contributions toward the identification of the principles governing the coordination of limb movements, little is known about the role of higher brain areas that are involved in interlimb coordination. Functional magnetic resonance imaging (fMRI) was used to reveal the brain areas activated during the cyclical coordination of ipsilateral wrist and foot movements. Six normal subjects performed five different tasks that were presented in a random order, i.e., isolated flexion-extension movements of the right wrist (WRIST) and right foot (FOOT), cyclical coordination of wrist and foot according to the isodirectional (ISODIR) and nonisodirectional (NON-ISODIR) mode, and rest (REST). All movements were auditory paced at 66 beats/min. During the coordination of both limb segments, a distributed network was identified showing activation levels in the supplementary motor area (SMA), cingulate motor cortex (CMC), premotor cortex (PMC), primary sensorimotor cortex (M1/S1), and cerebellum that exceeded the sum of the activations observed during the isolated limb movements. In addition, coordination of the limb movements in different directions was associated with extra activation of the SMA as compared to movements in the same direction. It is therefore concluded that the SMA is substantially involved in the coordination of the nonhomologous limbs as part of a distributed motor network. Accordingly, the long-standing exclusive association that has been made between this medial frontal area and bimanual (homologous) coordination needs to be abandoned and extended towards other forms of interlimb coordination (nonhomologous).

Adult↗
PubMed2003

Self-inflicted tourniquet paralysis mimicking acute demyelinating polyneuropathy.

Tourniquet paralysis is an uncommon complication of surgery, and self-inflicted tourniquet paralysis has never been documented to our knowledge. We report a patient with bilateral self-induced tourniquet paralysis of the lower extremities, whose symptoms were initially attributed to an acute demyelinating sensorimotor polyneuropathy based on clinical presentation and electrodiagnostic study. After investigations failed to reveal a cause, he was found to have placed tourniquets on his legs because of a rare obsession with limb amputation known as apotemnophilia. Significant spontaneous partial resolution of clinical symptoms was noted after 6 weeks. Electrophysiologic evidence of segmental demyelination of multiple motor nerves localized to the same region may help to distinguish this condition from other forms of acute demyelinating polyneuropathy.

Acute Disease↗
PubMed2000

Effect of thyroid hormone deficiency on developmental expression of goalpha gene in the brain of neonatal rats by competitive RT-PCR and in situ hybridization histochemistry.

Goalpha is a guanine nucloetide-binding regulatory protein alpha subunit which is mainly distributed in the central nervous system, but it has not previously been reported how it is regulated by thyroid hormone in the brain of neonatal rat at transcriptional levels. In this report, we used quantitative competitive reverse transcriptional PCR to quantify the effects of TH deficiency on Goalpha gene expression in the brain of neonatal rat at mRNA levels. It was found that Goalpha mRNA levels in the brain of 14-day-old rats significantly increased over 3-fold after induction of perinatal hypothyroidism, and declined markedly after treatment of thyroxine replacement. In situ hybridization histochemistry was further employed to observe the time-course and spatial expression of Goalpha gene in the brain of neonatal rats affected by thyroid hormone deficiency during the developmental period. The data showed that perinatal hypothyroidism can enhance Goalpha mRNA levels in the temporal cortex, sensorimotor cortex, piriform cortex, amygdala, hippocampal CA1-4 subfields, dentate gyrus, arcuate nucleus (AR) and ventromedial hypothalamic nucleus (VMH) of hypothalamus, but not in the striate cortex, cingulate cortex, claustrum, caudate/putamen and thalamus in the brain of rat at 7-21 days post-partum. The results suggest that up-regulation of Goalpha gene expression may be one kind of common mechanism responsible for neurological deficits in some brain areas arising from thyroid hormone deficiency in the critical periods of neonatal rats.

Animals↗
PubMed2002

Fierce: a new mouse deletion of Nr2e1; violent behaviour and ocular abnormalities are background-dependent.

A new spontaneous mouse mutation named fierce (frc) is deleted for the nuclear receptor Nr2e1 gene (also known as Tlx, mouse homolog of Drosophila tailless). The fierce mutation is genetically and phenotypically similar to Nr2e1 targeted mutations previously studied on segregating genetic backgrounds. However, we have characterized the fierce brain, eye, and behavioural phenotypes on three defined genetic backgrounds (C57BL/6J, 129P3/JEms, and B6129F1). The data revealed many novel and background-dependent phenotypic characteristics. Whereas abnormalities in brain development, hypoplasia of cerebrum and olfactory lobes, were consistent on all three backgrounds, our novel finding of enlarged ventricles in 100% and overt hydrocephalus in up to 30% of fierce mice were unique to the C57BL/6J background. Developmental eye abnormalities were also background-dependent with B6129F1-frc mice having less severe thinning of optic layers and less affected electroretinogram responses. Impaired regression of hyaloid vessels was observed in all backgrounds. Furthermore, retinal vessels were deficient in size and number in 129P3/JEms-frc and B6129F1-frc mice but almost entirely absent in C57BL/6J-frc mice. We present the first standardized behavioural tests conducted on Nr2e1 mutant mice and show that C57BL/6J-frc and B6129F1-frc mice have deficits in sensorimotor assays and are hyperaggressive in both sexes and backgrounds. However, C57BL/6J-frc mice were significantly more aggressive than B6129F1-frc mice. Overall, this extensive characterization of the fierce mutation is essential to its application for the study of behavioural, and brain and eye developmental disorders. In addition, the background-dependent differences revealed will enable the identification of important genetic modifiers.

Aggression↗
PubMed1984

Common origin of linguistic and movement abilities.

We start with the view that the development of systems of symbols is rooted in the regulation of cellular processes and the behavior of unicellular animals. Animals would thereafter start to externalize these internal symbol systems, to coordinate movements with each other. We propose that the brains of multicellular animals can be understood as a continuing elaboration of the early chemical symbol systems of unicellular animals: the labile symbols of the unicellular animal are replaced by hormones, more stable chemical compounds, and nerves that are seen as more stable and more specific routes of activation; and brains developed layers of symbols such that the domain of a symbol is not a set of bodily processes but rather a set of brain processes. Human language is very much in the "style" of the rule-governed symbol manipulation required by all behaving animals, although unique in its complexity. We suggest that the essential question is not how humans have evolved symbolic and linguistic abilities from a primitive sensorimotor brain but rather how do symbols come to exist in biological systems and what is useful and necessary about a system of symbols for the coordination of action within animals and among animals.

Animals↗