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PubMed2001

Transient inhibition of the human motor cortex by capsaicin-induced pain. A study with transcranial magnetic stimulation.

Motor evoked potentials (MEPs) to transcranial magnetic stimulation (TMS) of the left motor cortex were recorded from the right first dorsal interosseous (FDI), abductor pollicis brevis (APB), abductor digiti minimi (ADM), flexor carpi radialis (FCR), extensor carpi radialis (ECR) in 17 normal subjects, before and after painful application of capsaicin on the skin overlying the right FDI and FCR muscles. The amplitude of MEPs from the FDI and FCR was significantly reduced from 20 to 30 min after the application of capsaicin over the FDI and FCR muscles, respectively, then progressively returned to the basal values. A similar trend of MEPs inhibition was observed for APB and FCR muscles, but this reduction was not significant. Indices of peripheral nerve (M-wave) and spinal cord excitability (F and H waves) did not change throughout the experiments. Motor cortex inhibition induced by tonic cutaneous pain is maximal to muscles adjacent to the painful area. This inhibition may be due to the activation of the C fibres which mediate 'slow' nociception and might be important to alert subject to possible phasic nociceptive events that may occur close to the painful area.

Adult↗
PubMed1982

[Electrophysiologic study of Achilles areflexia of aged subjects].

The elderly often presents loss of Achilles tendon reflex. In this electrophysiological study the authors examined 19 patients with loss of the ankle jerk and with no known etiology of peripheral neuropathy. They compared them with 24 subjects who had no areflexia. The study included measurement of the H reflex, of the tendon reflex, of the conduction velocity of Ia fibers and of motor conduction velocity of the tibial nerve. Amplitude of H and tendon response and H/M ratio are diminished in the areflexic group. In 4 cases the H reflex is preserved while the tendon reflex is abolished. The meaning of these impairments is discussed.

Achilles Tendon↗
PubMed1997

On the role of the olivocochlear bundle in hearing: 16 case studies.

Earlier we presented data (Scharf et al. (1994) Hear. Res. 75, 11-26) from a young patient (S.B.) who had undergone a vestibular neurotomy, during which the olivocochlear bundle (OCB) was severed. Those data are complemented by measurements on 15 other patients-some like S.B. with normal audiometric thresholds, none with a loss greater than 35 dB at experimental frequencies. Comparisons of performance for the same ear before and after surgery or between the operated and healthy ears do not provide evidence that the lack of OCB input impairs the following psychoacoustical functions: (1) detection of tonal signals, (2) intensity discrimination, (3) frequency selectivity, (4) loudness adaptation, (5) frequency discrimination within a tonal series, (6) in-head lateralization. Data on single-tone frequency discrimination are equivocal. These mostly negative results apply to listening both in the quiet and, where relevant, in noise. The only clear change in hearing after a vestibular neurotomy is that most patients detect signals at unexpected frequencies better than before. This change suggests an impaired ability to focus attention in the frequency domain. Although limited in scope, our finding that human hearing without OCB input is essentially normal agrees with much of the relevant literature on animal behavior and with the patients' self-reports.

Acoustic Stimulation↗
PubMed2002

Overview of the innervation of the lung.

The autonomic nervous system controls many aspects of airway function, including regulation of airway smooth-muscle tone, mucus secretion from submucosal glands and surface epithelial goblet cells, vascular permeability and blood flow. Recent data suggest that enhanced neural activity may play a key role in the symptomatology and pathophysiology of airway inflammatory diseases.

Afferent Pathways↗
PubMed2026

Decoding mechanoregulation in immunological synapses using biomimetic artificial cells.

Mechanical force-driven signaling has emerged as a key regulator of cell-cell interactions (CCIs), which can enhance immune cell function. However, current biochemical approaches for studying CCIs offer minimal direct control over cellular bulk phenotypes, while synthetic biomaterial systems fail to mimic the dynamic complexity of cells. Here we introduce kpiCells, a biomaterial-based platform that uses a biomimetic membrane-endoplasmic architecture to enable finely tuned phenocopying of cellular states via modular mechanical, chemical and topographical inputs. We demonstrate that kpiCells can engage in physiological CCIs and reproduce critical subcellular features. In T cell systems, kpiCells enable integrated interrogation of afferent mechanosensing pathways and efferent force-exertion pathways, and support measurement of piconewton-scale forces at individual T cell antigen receptors as well as single cell-cell force fingerprints that define activation thresholds. This work establishes kpiCells as a bionic model that enables synthetic material design with the level of functional complexity approaching living cell systems.

Artificial Cells↗
PubMed1984

Physiologic stages of vocal reaction time.

A simple vocal reaction time (RT) task was performed by 10 male subjects while measures from intrinsic laryngeal muscles and subglottal air pressure were obtained simultaneously. Based only on each subject's fastest time among 15 trials, RT values were similar to the latencies previously observed in normal subjects. The mean of the subjects' fastest trials was 185 ms (range: 160-250 ms). Shortest latency values obtained for each measure were interarytenoid muscle, 50 ms; thyroarytenoid muscle, 60 ms; posterior cricoarytenoid muscle, 80 ms; subglottal air pressure rise, 125 ms. From these data estimates were made of 115 ms for the shortest respiratory system latency and 25 ms for the minimal central processing time. These data suggest that fastest vocal RTs are determined principally by the temporal constraints involved in activating pulmonary rather than laryngeal structures.

Adult↗
PubMed2004

Spinal cord repair with acidic fibroblast growth factor as a treatment for a patient with chronic paraplegia.

STUDY DESIGN: We present a case of a patient with chronic paraplegia with a complete spinal cord gap resulting from a stabbing injury 4 years ago recovering after an innovative surgical strategy. OBJECTIVES: To demonstrate the clinical outcome of surgical repair with sural nerve graft with fibrin glue containing acidic fibroblast growth factor in a patient with chronic spinal cord injury. SUMMARY OF BACKGROUND DATA: Spinal cord injury usually causes permanent disability, and there had been not effective surgical technique to obtain satisfactory functional motor recovery, particularly in chronic patients. Previous studies have revealed that acidic fibroblast growth factor could promote axonal regeneration and reduce neuronal death in adult rats with spinal cord injury. METHODS: The spinal cord gap at T11 level was bridged with 4 sural nerve grafts that redirected specific pathways from white to gray matter. The grafted area was stabilized with fibrin glue containing acidic fibroblast growth factor. RESULTS: Before the operation, the paraplegia was identified as ASIA-C, with a motor score for the right and left legs of 12 and 0, respectively, a pinprick score of 77, and 77 on a light touch of left side limbs. His functional status improved from being wheelchair-bound to being able to ambulate independently with a walker 2-and-a-half years after surgery. At this stage, paraplegia was ASIA-D, with motor scores for the right and left legs of 15 and 12, respectively, 86 for a pinprick, and 86 for a light touch of left side limbs. CONCLUSIONS: This case demonstrated significant motor recovery attained in a patient with chronic paraplegia following a repair surgery with nerve graft and growth factor.

Adult↗
PubMed1996

Analysis of contributions of acetylcholine and tachykinins to neuro-neuronal transmission in motility reflexes in the guinea-pig ileum.

1. The roles of acetylcholine (ACh) and tachykinins in neuro-neuronal transmission during ascending excitatory and descending inhibitory reflexes were studied by recording intracellular reflex responses of the circular muscle to physiological stimuli. Experiments were carried out in opened segments of guinea pig ileum in an organ bath that was partitioned so that three regions could be independently exposed to drugs. 2. Ascending excitatory reflexes evoked by either distension from the serosal side or compression of the mucosa were depressed by 55% and 85%, respectively, in the presence of hexamethonium (200 microM) and by 30% and 45%, respectively, by a desensitizing concentration of the selective NK3 receptor agonist, senktide (1 microM), in the chamber in which reflexes were initiated. Together, hexamethonium and senktide abolished responses to compression. A residual response to distension persisted. This was abolished by hyoscine (1 microM). 3. Hexamethonium (200 microM) abolished ascending reflexes when applied to the region between the stimulus and the recording sites, or to the recording chamber. 4. Descending reflex responses were reduced by 35% by synaptic blockade in the stimulus chamber with physiological saline containing 0.1 mM Ca2+ plus 10 mM Mg2+. Senktide (1 microM) in the stimulus chamber reduced distension reflexes to the same extent as synaptic blockade, whereas hexamethonium (200 microM) and hyoscine (1 microM) depressed responses by less than 20%. Responses to compression were reduced by 40% by senktide alone, while senktide and hexamethonium together reduced responses by 60%, an effect similar to synaptic blockade. Under these conditions, hyoscine in the stimulus chamber restored reflexes evoked by distension, but did not alter those evoked by mucosal compression. 5. Total synaptic blockade in the intermediate chamber, between stimulus and recording sites, reduced descending reflex responses by more than 90%. In contrast, hexamethonium (200 microM) had no effect and hyoscine (1 microM) reduced only the responses to distension (by 30%). Senktide (1 microM) depressed responses to both stimuli by approximately 80%. 6. Application of hexamethonium (200 microM) to the recording chamber depressed descending reflex responses to distension applied in the near stimulation chamber by 15%, but had no effect on responses to compression in the near chamber or to either stimulus applied in the far chamber. 7. Descending reflexes evoked by near chamber stimuli were unaffected by hyoscine (1 microM) or senktide (1 microM) applied to the recording chamber; hyoscine enhanced reflexes evoked by compression in the far chamber by 50%. 8. For the ascending excitatory reflex pathway, it is concluded that transmission from sensory neurones is mediated by ACh acting via both nicotinic and muscarinic receptors, and by tachykinins acting at NK3 receptors. Transmission from ascending interneurones appears to be predominantly via nicotinic receptors. The descending inhibitory pathways are more complex, and while transmission from sensory neurones involves nicotinic, muscarinic and NK3 receptor-dependent components, transmission from descending interneurones to inhibitory motor neurones is neither cholinergic nor due to tachykinins acting via NK3 receptors.

Acetylcholine↗
PubMed1995

Anatomic and behavioral aspects of frontal-subcortical circuits.

Frontal-subcortical circuits provide a comprehensive framework for understanding the anatomy, biochemistry, and pharmacology of behavior. The three principal behaviorally relevant circuits originate in the dorsolateral prefrontal cortex, orbitofrontal cortex, and anterior cingulate cortex, respectively. Circuit-specific marker behaviors associated with each circuit are executive dysfunction (dorsolateral prefrontal-subcortical circuit), disinhibition and OCD (orbitofrontal-subcortical circuit), and apathy (medial frontal-subcortical circuit). Environmental dependency is common to all prefrontal-subcortical syndromes and may reflect disruption of working memory. Depression, mania, and psychosis are mediated by structures involved in prefrontal-subcortical circuits and are circuit-related but not circuit-specific behaviors. The actions of PCP, LSD, serotonergic antidepressants, anxiolytics, sedative-hypnotics, antipsychotic agents, and ethanol may all be partially or primarily mediated through transmitter systems and receptor effects expressed through frontal-subcortical circuits.

Afferent Pathways↗
PubMed1985

The primate premotor cortex: past, present, and preparatory.

The concept of a separate premotor cortical field involved in the cerebral control of movement went out of favor among neurophysiologists during the quarter century from 1952 to 1977, but recent studies have led to its rehabilitation. The premotor cortex appears to be one of at least three fields within the motor cortex, two others being the primary motor cortex and the supplementary motor cortex. Several proposals have been presented concerning the functional specializations of the premotor cortex. Although no specific hypotheses have very strong support at present, the best evidence favors a role for premotor cortex in the preparation for and the sensory guidance of movement.

Afferent Pathways↗
PubMed1986

Altered synaptic transmission in dentate gyrus of rats reared in complex environments: evidence from hippocampal slices maintained in vitro.

Pre- and postsynaptic responses to activation of medial perforant path (MPP) axons were examined in hippocampal slices taken from rats reared for 3-4 wk in relatively complex (EC) or individual cage (IC) environments. Three types of extracellular field potentials were recorded in the infrapyramidal blade of the dentate gyrus: 1) granule cell population spikes (PSs), which reflect the number and synchrony of discharging granule cells (2), 2) population excitatory postsynaptic potentials (EPSPs), which reflect the amount of excitatory synaptic current flow into dendrites (28), and 3) presynaptic fiber volleys (FVs), which reflect the number of activated axons (28). Stimulation of the MPP evoked significantly larger PSs in slices taken from EC rats. There was no significant effect of rearing environment on PS/EPSP relationships. The slopes of EPSPs recorded at the site of synaptic activation in the dentate molecular layer and at the major current source in the dentate granule cell layer were significantly greater in slices taken from EC rats. The presynaptic FV was recorded at the site of synaptic activation in the molecular layer. FV amplitude did not differ significantly as a function of rearing environment. To examine possible differences in tissue impedance, granule cells were activated by stimulating granule cell axons in the dentate hilus and recording the antidromic PS in the granule cell layer. Antidromic PS amplitude was not significantly affected by rearing environment. The relative permanence of the experience-dependent alterations in synaptic transmission was assessed by comparing slices taken from rats that had been reared for 4 wk in complex environments followed by 3-4 wk in individual cages with those from rats reared for 7-8 wk in individual cages. There were no significant differences in MPP synaptic transmission between these groups of animals. The results suggest that experience in a relatively complex environment is associated with greater MPP synaptic transmission arising from an increased synaptic input to granule cells; the greater MPP synaptic transmission associated with behavioral experience can occur independent of behavioral state, influences from extrahippocampal brain regions and intrahippocampal inhibitory activity; and the experience-dependent synaptic alterations in the dentate gyrus are transient, in contrast to experience-dependent morphological alterations described in occipital cortex. The possible relationship of these alterations to the phenomenon of long-term enhancement is discussed.

Afferent Pathways↗
PubMed1990

Forcing of coupled nonlinear oscillators: studies of intersegmental coordination in the lamprey locomotor central pattern generator.

1. This paper reports the results of an investigation of the basic mechanisms underlying intersegmental coordination in lamprey locomotion, by the use of a combined mathematical and biological approach. 2. Mathematically, the lamprey central pattern generator (CPG) is described as a chain of coupled nonlinear oscillators; experimentally, entrainment of fictive locomotion by imposed movement has been investigated. Interpretation of the results in the context of the theory has allowed conclusions to be drawn about the nature of ascending and descending coupling in the lamprey spinal CPG. 3. Theory predicts and data show that 1) the greater the number of oscillators in the chain, the smaller is the entrainment frequency range and 2) it is possible to entrain both above and below the rest frequency at one end but only above or below at the other end. 4. In the context of the experimental results, the theory indicates the following: 1) ascending coupling sets the intersegmental phase lags, whereas descending coupling changes the frequency of the coupled oscillators; 2) there are differences in the ascending and descending coupling other than strength; and it also suggests that 3) coupling slows down the oscillators.

Afferent Pathways↗
PubMed2001

Properties and interconnections of trigeminal interneurons of the lateral pontine reticular formation in the rat.

Numerous evidence suggests that interneurons located in the lateral tegmentum at the level of the trigeminal motor nucleus contribute importantly to the circuitry involved in mastication. However, the question of whether these neurons participate actively to genesis of the rhythmic motor pattern or simply relay it to trigeminal motoneurons remains open. To answer this question, intracellular recordings were performed in an in vitro slice preparation comprising interneurons of the peritrigeminal area (PeriV) surrounding the trigeminal motor nucleus (NVmt) and the parvocellular reticular formation ventral and caudal to it (PCRt). Intracellular and extracellular injections of anterograde tracers were also used to examine the local connections established by these neurons. In 97% of recordings, electrical stimulation of adjacent areas evoked a postsynaptic potential (PSP). These PSPs were primarily excitatory, but inhibitory and biphasic responses were also induced. Most occurred at latencies longer than those required for monosynaptic transmission and were considered to involve oligosynaptic pathways. Both the anatomical and physiological findings show that all divisions of PeriV and PCRt are extensively interconnected. Most responses followed high-frequency stimulation (50 Hz) and showed little variability in latency indicating that the network reliably distributes inputs across all areas. In all neurons but one, excitatory postsynaptic potentials (EPSPs) or inhibitory postsynaptic potentials (IPSPs) were also elicited by stimulation of NVmt, suggesting the existence of excitatory and inhibitory interneurons within the motor nucleus. In a number of cases, these PSPs were reproduced by local injection of glutamate in lieu of the electrical stimulation. All EPSPs induced by stimulation of PeriV, PCRt, or NVmt were sensitive to ionotropic glutamate receptor antagonists 6-cyano-7-dinitroquinoxaline and D,L-2-amino-5-phosphonovaleric acid, while IPSPs were blocked by bicuculline and strychnine, antagonists of GABA(A) and glycine receptors. Examination of PeriV and PCRt intrinsic properties indicate that they form a fairly uniform network. Three types of neurons were identified on the basis of their firing adaptation properties. These types were not associated with particular regions. Only 5% of all neurons showed bursting behavior. Our results do not support the hypothesis that neurons of PeriV and PCRt participate actively to rhythm generation, but suggest instead that they are driven by rhythmical synaptic inputs. The organization of the network allows for rapid distribution of this rhythmic input across premotoneuron groups.

Afferent Pathways↗