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At least 1,621 records · Page 90Linked to original sources

PubMed2003

Distribution of dendrites of descending neurons and its implications for the basic organization of the cockroach brain.

To determine precisely the brain areas from which descending neurons (DNs) originate, we examined the distribution of somata and dendrites of DNs in the cockroach brain by retrogradely filling their axons from the cervical connective. At least 235 pairs of somata of DNs were stained, and most of these were grouped into 22 clusters. Their dendrites were distributed in most brain areas, including lateral and medial protocerebra, which are major termination areas of output neurons of the mushroom body, but not in the optic and antennal lobes, the mushroom body, the central complex, or the posteroventral part of the lateral horn. The last area is the termination area of major types of olfactory projection neurons from the antennal lobe, i.e., uni- and macroglomerular projection neurons, so these neurons have no direct connections with DNs. The distribution of axon terminals of ascending neurons overlaps with that of DN dendrites. We propose, based on these findings, that there are numerous parallel processing streams from cephalic sensory areas to thoracic locomotory centers, many of which are via premotor brain areas from which DNs originate. In addition, outputs from the mushroom body, central complex, and posteroventral part of the lateral horn converge on some of the premotor areas, presumably to modulate the activity of some sensorimotor pathways. We propose, based on our results and documented findings, that many parallel processing streams function in various forms of reflexive and relatively stereotyped behaviors, whereas indirect pathways govern some forms of experience-dependent modification of behavior.

Animals↗

PubMedDate not supplied

State of synapses of the cortex of cerebral hemispheres on gamma-irradiation.

In adult rats with developing neurological disorders we detected destructive changes in most of the synapses of the brain sensorimotor cortex 1.6-4.3 h after a single dose of gamma-irradiation (200 Gy). All functionally important parts on the axonal and dendritic sides of the synapses had undergone changes: mitochondria, synaptic vesicles, pre- and postsynaptic membranes, synaptic complexes, and subsynaptic consolidations, axonal and dendritic plasma, and their inclusions. These changes possibly cause disconnection of the neurons and provide a structural basis for neurological deficiencies following a high substantial ionizing radiation.

Animals↗

PubMed1996

Functional behavioral homology between rat 5-HT1B and guinea pig 5-HT1D receptors in the modulation of prepulse inhibition of startle.

The serotonin (5-HT) 1B receptor in rats and mice appears to be homologous to the 5-HT1D receptor found in other mammals, such as guinea pigs and humans. The present series of experiments explored the functional similarity between the rat 5-HT1B receptor and the guinea pig 5-HT1D receptor on two behavioral measures known to be influenced by 5-HT1B receptor manipulations in rats: prepulse inhibition of the startle response (PPI) and locomotor activity. Because the 5-HT1B agonist RU 24969 disrupts PPI and stimulates locomotor behavior in rats, it was predicted that the 5-HT1D agonist, SDZ 219-964, would demonstrate a similar behavioral profile in guinea pigs. In support of this hypothesis, SDZ 219-964 was found to disrupt PPI dose-dependently (1.0 and 2.0 mg/kg) without significantly affecting startle amplitude and to increase locomotor activity (0.5-2.0 mg/kg) in guinea pigs. In guinea pigs, RU 24969 failed to affect PPI, although it did increase locomotor activity, indicating that RU 24969 may have activity at the 5-HT1D receptor. As expected, RU 24969 in rats disrupted PPI (2.5 and 5.0 mg/kg) and significantly increased locomotor activity (1.25-5.0 mg/kg). In rats, however, SDZ 219-964 had generalized, stimulatory effects on startle reactivity, without independent effects on PPI or locomotor activity. The spatial patterns of locomotion exhibited by guinea pigs treated with SDZ 219-964 versus those of rats treated with RU 24969 demonstrate important qualitative differences in structure, indicating that the neural substrates subserving these effects may be different. It is concluded that a functional similarity exists between 5-HT1D and 5-HT1B receptors with regard to the modulation of sensorimotor inhibition and, to a lesser extent, locomotor activity.

Animals↗

PubMed1995

Why are vertebrate nervous systems crossed?

Contralateral central nervous control may be an evolutionary consequence of dependence on the image-forming eye, especially in large organisms. As a result of the topological transformation of the visual stimulus in the pupillary eye, the external environmental hemispace impinges directly upon the contralateral internal organismal hemispace. Selective pressure leads to the development of central connections capable of the most rapid and precise functional association of the internal milieu with the organism's environment. The consequence is contralateral central sensorimotor control. Previous hypotheses are discussed, including those based on bilaterality, binocularity the optic chiasm and avoidance behaviors.

Animals↗

PubMedDate not supplied

Neurotoxicity of acrylamide and 2,5-hexanedione in rats evaluated using a functional observational battery and pathological examination.

The clinical effects of two neurotoxicants, acrylamide and 2,5-hexanedione, were compared in rats using a functional observational battery (FOB), which includes a series of home cage and open-field observations, sensorimotor measurements, and physiological parameters. Neurotoxicity was assessed weekly in adult male Long-Evans rats after initiation of IP administration of 9 doses of acrylamide (12, 15, or 50 mg/kg given 3 times a week) and 28 doses of 2,5-hexanedione (150, 225, and 350 mg/kg given daily). Using the FOB, it was possible to detect differences in neurotoxic effects of these two chemicals. Acrylamide significantly affected home cage posture, foot splay and time on the rotarod, whereas 2,5-hexanedione altered hindlimb grip strength and the approach response. Both compounds caused changes in ability to walk, right, and maintain agility on a rotarod within 21 days from initiation of toxicant administration. In addition, both compounds caused dose-dependent decreases in weight gain. Neuropathic changes were detectable at the highest dosages at 21 days in acrylamide-treated rats and at 28 days in rats treated with 2,5-hexanedione. Administration of acrylamide also decreased activities of neural esterases. This study indicated that the FOB could be used to detect evidence of neurotoxicity in rats treated with acrylamide and 2,5-hexanedione, with alterations evident even before pathological changes were induced by 2,5-hexanedione.

Acrylamide↗

PubMed1993

Two forms of apraxia in Alzheimer's disease.

Apraxia was tested in 12 DAT patients with mild to moderate dementia using two assessment procedures: conceptual tasks requiring object use and pantomime knowledge, and tasks based on the imitation of meaningless oral and hand movements. Both object use and pantomime performance were markedly impaired in the DAT group; imitation of hand postures, hand movements and multiple oral movements was also defective while single oral movements could be well imitated. Error analysis revealed several underlying deficits: on conceptual tasks, deficits in object and action knowledge and poor action planning were frequent, whereas impaired recall and coordination of spatial and temporal movement features were found on imitation tasks. A correlation analysis between both types of apraxia showed low and nonsignificant results. These and previous observations suggest that motor control is organized by two functionally separate systems: a conceptual system for purposeful and symbolic motor acts, and a system controlling sensorimotor and spatiotemporal movement features. Both systems may be subject to early damage in Alzheimer's disease.

Aged↗

PubMed1998

Spatial EEG synchronisation over sensorimotor hand areas in brisk and slow self-paced index finger movements.

The changes of spatial EEG synchronisation during brisk and slow voluntary self-paced movements of the right and left index finger were analysed in 12 right-handed and 11 left-handed subjects. EEG was recorded from the left and right sensorimotor area using 24 closely spaced electrodes. A novel measure of spatial EEG synchronisation, omega-complexity, was computed separately for the left and right sensorimotor area in 64 overlapping one-second epochs representing 4.5 s of the pre-movement and 3.5 s of the post-movement period. Omega-complexity was higher, hence spatial synchronisation was lower, in slow than in brisk movements, especially in the right-handed. A sustained increase of omega-complexity was observed during execution of a slow movement. A decrease of omega-complexity which was often associated with a brief burst of spatially synchronised 10-Hz oscillations occurred at the onset of extensor muscle contraction. We suggest that increased spatial EEG synchronisation at movement onset may prevent "spillover" of excitation from the sensorimotor hand area to other cortical regions. During movement, the cortical neuronal assemblies subserve distinct, specialised functions manifesting in increased omega-complexity.

Adult↗

PubMed1998

Is nondipping in 24 h ambulatory blood pressure related to cognitive dysfunction?

OBJECTIVE: Associations between the outcome of 24 h ambulatory monitoring and cognitive performance were studied in order to evaluate the potential relevance of ambulant blood pressure status to brain function. It was hypothesized that a small daytime-night-time difference in mean blood pressure (nondipping) is associated with reduced cognitive performance, in line with studies in hypertensive subjects that have reported associations between nondipping and target-organ damage. METHODS: The study followed a cross-sectional design and was part of a larger research programme on determinants of cognitive aging (Maastricht Aging Study, MAAS). A group of 115 community residents aged 28-82 years was recruited from a general practice population and screened for cardiovascular events and medication use. All underwent 24 h blood pressure monitoring. Cognitive performance was measured with tests of verbal memory, attention, simple speed and information processing speed. RESULTS: Mean daytime or night-time levels of both systolic and diastolic blood pressure were unrelated to cognitive outcome, when age, sex and educational level were controlled for. Differences between mean daytime and night-time blood pressure (based on both narrow and wide measurement intervals for day and night-time periods) were positively associated with memory function (5-9% of additional variance explained) and one sporadic positive association was found on the sensorimotor speed score (4%). Nondippers (n=15) showed lower levels of both memory and sensorimotor speed scores. CONCLUSIONS: Ambulatory blood pressure status was not associated with cognitive performance. A reduced nocturnal blood pressure drop was associated with quite specific cognitive deficits, but the underlying mechanism remains to be determined.

Adult↗

PubMed2003

Distribution of dendrites of descending neurons and its implications for the basic organization of the cockroach brain.

To determine precisely the brain areas from which descending neurons (DNs) originate, we examined the distribution of somata and dendrites of DNs in the cockroach brain by retrogradely filling their axons from the cervical connective. At least 235 pairs of somata of DNs were stained, and most of these were grouped into 22 clusters. Their dendrites were distributed in most brain areas, including lateral and medial protocerebral, which are major termination areas of output neurons of the mushroom body, but not in the optic and antennal lobes, the mushroom body, the central complex, or the posteroventral part of the lateral horn. The last area is the termination area of major types of olfactory projection neurons from the antennal lobe, i.e., uni- and macroglomerular projection neurons, so these neurons have no direct connections with DNs. The distribution of axon terminals of ascending neurons overlaps with that of DN dendrites. We propose, based on these findings, that there are numerous parallel processing streams from cephalic sensory areas to thoracic locomotory centers, many of which are via premotor brain areas from which DNs originate. In addition, outputs from the mushroom body, central complex, and posteroventral part of the lateral horn converge on some of the premotor areas, presumably to modulate the activity of some sensorimotor pathways. We propose, based on our results and documented findings, that many parallel processing streams function in various forms of reflexive and relatively stereotyped behaviors, whereas indirect pathways govern some forms of experience-dependent modification of behavior.

Animals↗

PubMedDate not supplied

[The structural organization and neurochemical mechanisms of the participation of the nucleus accumbens in the interaction of the limbic and motor systems and in the regulation of motor behavior].

The review of own and literature data devoted to structural and neurochemical organization of the nucleus accumbens (Acc) as well as spatial organization of their projection fibers in comparison with nucleus caudatus (neostriatum) has been presented. The facts concerned with correlations revealed between both the cell clusters and histochemical compartments as well as the compartmental organization of afferent and efferent striatal connections were analyzed. The presented data propose the existence of sensorimotor and limbic parts of the dorsal and ventral striatum, which are involved in the parallelly functioning systems. The common and different signs of these two systems and its role in the regulation of the movement behaviour has been proposed. A lot of attention also was payed to the Acc and the neostriatum interaction. The many pathways by which Acc can influence neostriatum functions and therefore the motor activity controlled by the neostriatum are discussed. It was shown that the Acc can influence on the striatal synaptic DA release. The sign of this influence depended upon DA/glutamic acid interactions in the Acc. It was stressed that the influence of Acc on striatal DA-ergic system is very likely mediated via kainate/quisqualate (but not NMDA) inputs of the neostriatum. The balance of DA-ergic mechanisms of neostriatum and Acc as important basis of animals adequate behaviour in conditioning situation was proposed. The disbalance of these mechanisms could leads to pathology.

Afferent Pathways↗

PubMed1977

Stabilization of the thalamocortical motor system by cerebellar stimulation.

Epilepsy typifies instability in a complex control system. We have previously identified parameters of the thalamocortical motor system of the cat which correlate with epileptiform activity and are controlled by common anticonvulsants. This study is concerned with the control of such parameters by cerebellar stimulation, potencially promoting stability within the motor system. Under computer control, stimuli were delivered to both ventrolateral thalamus and cerebellar cortex, with multichannel recording of evoked responses obtained from sensorimotor cortex. Cortical evoked responses were plotted as an excitability curve (mean response amplitude as a function of pulse interval) or a family of threshold curves (mean response amplitude as a function of stimulus amplitude at various fixed intervals). The present study reveals that cerebellar epidural stimulation can reduce both the height and duration of the excitability curve, as well as increase the response threshold and reduce the saturation level of the threshold curve. The degree and direction of these parameter changes are dependent on the frequency, polarity, and amplitude of cerebellar stimulation, with the amount of parameter change exceeding that achieved by monotoxic doses of anticonvulsants. These data suggest that control of parameters related to excitability and threshold in the thalamocortical motor system may be the means by which cerebellar stimulation accomplishes control of clinical seizures.

Animals↗

PubMedDate not supplied

[Respiratory insufficiency in adults with diphtheric polyneuropathy].

Twenty-five adult patients with grave diphtheric polyneuropathy after toxic diphtheria were followed up. Two symptom complexes of neurologic disorders leading to the development of peripheral respiratory failure of different severity were distinguished: 1) predominating glossopharyngeal paralysis and 2) combination of glossopharyngeal paralysis with grave generalized sensorimotor polyneuropathy (with pareses and paralyses of the respiratory muscles). The major quantitative parameters of pulmonary functions associated with various manifestations of respiratory failure are characterized. The significance of information on the type of dysfunction of vocal cords is emphasized. A high efficacy of a complex of respiratory reanimation used in the treatment of patients with peripheral respiratory failure is demonstrated.

Adult↗

PubMed1999

Principles of applied neurogastroenterology: physiology/motility-sensation.

Many of the symptoms characteristic of the functional gastrointestinal disorders (FGID) are consistent with dysfunction of the motor and/or sensory apparatus of the digestive tract. Those aspects of sensorimotor dysfunction most relevant to the FGID include alterations in: gut contractile activity; myoelectrical activity; tone and compliance; and transit, as well as an enhanced sensitivity to distension, in each region of the gastrointestinal tract. Assessment of these phenomena involves a number of techniques, some well established and others requiring further validation. Using such techniques, researchers have reported a wide range of alterations in sensory and in motor function in the FGID. Importantly, however, relationships between such dysfunction and symptoms have been relatively weak, and so the clinical relevance of the former remains unclear. Moreover, the proportions of patients in the various symptom subgroups who display dysfunction, and the extent and severity of their symptoms, require better characterization. On a positive note, progress is occurring on several fronts, especially in relation to functional dyspepsia and irritable bowel syndrome, and based on the data gathered to date, a number of areas where further advances are required can be highlighted.

Colonic Diseases, Functional↗

PubMed2002

Sensorimotor control of the spine.

The spinal viscoelastic structures including disk, capsule and ligaments were reviewed with special focus on their sensory motor functions. Afferent capable of monitoring proprioceptive and kinesthetic information are abundant in the disc, capsule and ligament. Electrical stimulation of the lumbar afferents in the discs, capsules and ligaments seem to elicit reflex contraction of the multifidus and also longissimus muscles. The muscular excitation is pronounced in the level of excitation and with weaker radiation 1 to 2 levels above and below. Similarly, mechanical stimulation of the spinal viscoelastic tissues excites the muscles with higher excitation intensity when more than one tissue (ligaments and discs for example) is stimulated. Overall, it seems that spinal structures are well suited to monitor sensory information as well as to control spinal muscles and probably also provide kinesthetic perception to the sensory cortex.

Afferent Pathways↗

PubMedDate not supplied

[Functional organization of monosynaptic interneuronal connections in the cerebral cortex].

A study of monosynaptic intraneuronal connections was performed in micro-regions of sensorimotor and autitory cortical areas in cats. Certain definite characteristics were found in the joint activity of neurones which persisted after the regime of microsystem activity was changed. Neurones with a lower spike amplitude discharge earlier and elicite discharges in neurones with a greater spike amplitude; feed-backs are inhibitory. It is suggested that in both cortical areas there exist microsystems with similar organization composed of different types of neurones.

Animals↗

PubMed2006

Conscious and unconscious sensory inflows allow effective control of the functions of the human brain and heart at the initial ageing stage.

The authors of the present article based their assumption on the concept that the sensory systems are the "windows to the brain" through which various functions of the human organism can be controlled. Comprehension of the fundamental mechanisms of the optimization of the sensory systems, brain, and cardiac functions has increased based on the prolonged sensory flows using conscious and unconscious aromatherapy and multimodal sensory activation. Sensory flow evoked stable systemic responses, including adaptive alteration of psycho-emotional state, attention, memory, sensorimotor reactions, intersensory interaction, visual information processing, statokinetic stability, and autonomic heart rhythm control. The efficacy and expediency of the use of sensory flow for non-medicinal correction of vital functions of the human organism at the initial stages of ageing was revealed.

Afferent Pathways↗

PubMed2007

Motor imagery and stroke rehabilitation: a critical discussion.

Motor disorders are a frequent consequence of stroke and much effort is invested in the re-acquisition of motor control. Although patients often regain some of their lost function after therapy, most remain chronically disabled. Functional recovery is achieved largely through reorganization processes in the damaged brain. Neural reorganization depends on the information provided by sensorimotor efferent-afferent feedback loops. It has, however, been shown that the motor system can also be activated "offline" by imagining (motor imagery) or observing movements. The discovery of mirror neurones, which fire not only when an action is executed, but also when one observes another person performing the same action, also show that our action system can be used "online" as well as offline. It is an intriguing question as to whether the information provided by motor imagery or motor observation can lead to functional recovery and plastic changes in patients after stroke. This article reviews the evidence for motor imagery or observation as novel methods in stroke rehabilitation.

Cognition↗

PubMed2004

Plasticity of the spinal neural circuitry after injury.

Motor function is severely disrupted following spinal cord injury (SCI). The spinal circuitry, however, exhibits a great degree of automaticity and plasticity after an injury. Automaticity implies that the spinal circuits have some capacity to perform complex motor tasks following the disruption of supraspinal input, and evidence for plasticity suggests that biochemical changes at the cellular level in the spinal cord can be induced in an activity-dependent manner that correlates with sensorimotor recovery. These characteristics should be strongly considered as advantageous in developing therapeutic strategies to assist in the recovery of locomotor function following SCI. Rehabilitative efforts combining locomotor training pharmacological means and/or spinal cord electrical stimulation paradigms will most likely result in more effective methods of recovery than using only one intervention.

Animals↗