Recently, motor evoked potential(MEP) using cortical surface of transcranial stimulation have been used to monitor the integrity of motor pathways and map motor cortex in human and animal. The primary concept using motor evoked potentials(MEPs) for test of motor pathways was based on the assumtion that pyramidal neurons in the motor cortex are activated by electrical stimulation applied on the cerebral cortex and synchronized compound action potentials are conducted mainly along the corticospinal tracts in the spinal cord. However, the origins and the descending pathways of these MEPs in small animals may be different from those of potentials evoked by intracortical microstimulation because of current spread. Our previous study revealed that the origns of the MEPs in rats differed from those previously believed and may be reticular nuclei. To further clarify those results and localize the intraspinal pathways conduction MEPs, consecutive vertical and/or horizontal sections of the spinal cord were performed at T9 cord level in twelve rats. MEPs were recorded at T2/3 and L2/3 before and after each section and sequential alterations of MEPs were observed. In six rats, the stimulation was alternated between the right and left cortex and the lateralities of conduction pathways were compared. All six cases showed no differences of MEPs and pattern of wave abolition after each section between right and left brain stimulation. The alteration of MEPs after each consecutive section was categorized by analyzing latency shift, amplitude change, and disappearance of waves. We divided a cross section of T9 spinal cord into forty-six squares. If one of the categorized changes occurrd after cutting an area, the appropriate score was given for the area since more change of waves meant more significant contribution of the cut area to conduction of MEPs. The score of twelev rats were summed in each forty-six spots and map showing the distribution of MEPs was constructed. The map revealed that MEPs were conducted along the wide area of ventral and lateral funiculus of the spinal cord but mainly along the medial portion of the ventral funiculus of the spinal cord but mainly along the medial portion of the ventral funiculus and ventral portion of the larteral funiculus through which reticulospinal and vestibulospinal tracts pass. No conduction of MEPs along the corticospinal tracts was confirmed. This finding supports the result of our previous study. However, this extrapyramidal MEP conducted along ventral spinal cord in addition to somatosensory evoked potential(SSEP) which is conducted along posterior funiculus can be useful to monitor the integrity of the whole spinal cord. Moreover, the extrapyramidal MEP can be more useful than pyramidal MEP in rats because the reticular formation plays a more important role in motor function and pyramidal tract is located in posterior funiculus.
Action Potentials ; Animals ; Brain ; Cerebral Cortex ; Efferent Pathways ; Electric Stimulation ; Evoked Potentials, Motor* ; Extrapyramidal Tracts ; Humans ; Motor Cortex ; Neurons ; Pyramidal Tracts ; Rats* ; Reticular Formation ; Spinal Cord

Motor evoked potential(MEP) produced by cortical surface or transcranial stimulation has evolved as a new clinical and experimental tool to monitor the integrity of motor pathways and to map motor cortex. Clinical assessment of motor system using MEP has further advanced with recent development of the magnetic stimulator. The primary concept using MEPs for test of motor pathways was based on the assumption that pyramidal neurons in the motor cortex are activated by electrical stimulation applied on the cerebral cortex and synchronized compound action potentials are conducted mainly along the corticospinal tracts in the spinal cord. However,recent studies indicated that the origins of the Meps in non primates may differ from those previously believed. In order to use MEPs as a clinical or experimental tool, it is essential to clarify the origin of MEPs. Therefore, goals of this study were : (1) to investigate the origin of MEPs, and (2) to design the most reliable but simple method to evoke and monitor MEPs. In a total of fifteen rats, MEPs were produced by cortex to cortex stimulation and were monitored using a pair of epidural electrodes. Using varying stimulus intensities, the amplitudes and latencies of MEPs were statistically analyzed. The latencies and amplitudes of the MEPs in these animals showed surprisingly large standard deviations, which were partially resulted in these animals showed surprisingly large standard deviations, which were partially resulted from convergence of neighboring waves during high stimulation intensities. Wave forms of MEPs were also varied greatly depending on the position of recording electordes. At low stimulus intensities, most consisten MEPs were obtained when the stimulating electrodes were placed on the hard palate and the temporal muscle, not on the motor cortex. This observation indicates that the primary source of MEPs is not the motor cortex in the rat. When the potentials generated by direct stimulation of motor cortex and those generated by reticular nuclei were monitored epidurally in the same preparation using the same electrodes, these potentials generated by different sources actually identical in their latencies and wave forms. However, the threshold stimulus intensities evoking these potentials were quite different in the two metholds. The threshold was much lower to evoke potentails by reticular nuclei stimulation. It suggests that MEPs are geneated by the reticular nuclei or brain structure located in the brain stem. The observation that the motor cortex play no major roles in generating MEPs was confirmed by sequential sections of neural axis from the motor cortex to brain stem in three rats. All these findings suggested that neither direct motor cortex stimulation not transcranial stimulation did evoke MEPs originating from the motor cortex in rat. These stimulating methods activate reticular nuclei by stimulus current spread to the brain stem. Since the reticular formation plays an important role in motor function in rats, MEP originated from reticular nucleus can be an important testing of the motor function in rats. Moreover, transcranial stimulation of the brain is technically easy. This technique producing MEPs originated from reticular nucleus can be useful to monitor the integrity of motor pathways.
Action Potentials ; Animals ; Axis, Cervical Vertebra ; Brain ; Brain Stem ; Cerebral Cortex ; Efferent Pathways ; Electric Stimulation ; Electrodes ; Evoked Potentials, Motor* ; Extrapyramidal Tracts ; Motor Cortex ; Neurons ; Palate, Hard ; Primates ; Pyramidal Tracts ; Rats* ; Reticular Formation ; Spinal Cord ; Temporal Muscle

OBJECTIVE: To investigate the clinical usefulness of the motor cortex mapping using transcranial magnetic stimulation (TMS) in stroke patients. METHOD: Five stroke patients were studied. A piece of cloth which marked at 1 cm interval was fixed on the patient's head. Motor cortex mapping for abductor pollicis brevis muscles (APB) was performed with a butterfly coil or with a round coil if motor cortex mapping was impossible. RESULTS: Ipsilateral motor pathways were discovered from the unaffected motor cortex to the affected APB in patient 1. This patient showed delayed latency and low amplitude of ipsilateral motor evoked potentials (MEP) that seems to be evoked from the descending motor pathway rather than the corticospinal tract. In patient 2 and 3, contralateral motor pathways traveled from the affected hemisphere to the affected APB. The short latency and high amplitude of MEPs seems to be attributed to the corticospinal tract. In patient 4, no MEP was evoked by any hemisphere or magnetic stimulator. We believe that the affected APB had no motor pathway, and it correlated well with the poor motor function of her hand. In patient 5, contralateral pathways from the affected hemisphere to the affected APB were present. In this patient, the parameters of the motor cortex map such as the amplitude of MEP, the number of MEP evoked site, and the excitatory threshold were improved after 2 months, which correlated well with clinical improvement. CONCLUSION: Motor cortex mapping using TMS is clinically useful for the evaluation of the characteristics of motor pathways and the change of motor cortex excitability in stroke patients.
Butterflies ; Efferent Pathways ; Evoked Potentials, Motor ; Hand ; Head ; Humans ; Motor Cortex* ; Muscles ; Pyramidal Tracts ; Stroke* ; Transcranial Magnetic Stimulation*

The purpose of the present study is to find out whether the ophthalmotonic consensual reaction really exists and through what channel the reaction is brought about in rabbits. Twenty-eight pigmented male rabbits were divided into four groups of seven rabbits each, and the intraocular pressure of each eye was measured at designated times in each group with a Mueller electronic tonometer under topical anesthesia (0.5% tetracaine hydrochloride). Retrobulbar anesthesia and compression were performed in each group as follows: Group 1: From 56 minutes to 60 minutes after the experiment had begun, the right eye was compressed for 4 minutes with a 50 gm weight by means of a Baillart ophthalmodynamometer Group 2: About one hour after the experiment had begun, 1.0 cc of 2% procaine hydrochloride was given by retrobulbar injection on the right side. Digital massage after retrobulbar injection was avoided and epinephrine was not employed, because they might influence the intraocular pressure. Group 3: After retrobulbar anesthesia had been performed for the right eye at 40 minutes, this eye was compressed by the above described method from 85 minutes to 90 minutes after the experiment had begun. Group 4: After retrobulbar anesthesia had been performed in the left eye at 40 minutes, the right eye was compressed by the above described method from 86 minutes to 90 minutes after the experiment had begun. The data of each experimental group were analyzed statistically by means of the t-test. Four groups of tonometric studies were done with the following results: 1. After the right eye had been compressed with a 50 gm, weight for 4 minutes, the right intraocular pressure was found to be lowered and then immdiately elevated. The intraocular pressure in the left eye was lowered beginning about 20 minutes after the right eye compression, and this phenomenon may be considered as the ophthalmotonic consensual reaction. 2. After retrobulbar anesthesia with 1.0 cc of 2% procaine hydrochloride had been performed for the right eye, the intraocular pressure was found to be lowered, but that of the left eye showed a slight rise and maintenance of the elevated pressure. 3. When the right eye was compressed after retrobulbar anesthesia had been performed, the grade of rising of the intraocular pressure was lower than when retrobulbar anesthesia had not been performed. The intraocular pressure in the left eye showed no significant change, so it can be postumted that the afferent pathway of the ophthalmotonic consensual reaction was blocked by the retrobulbar anesthesia in the compressed right eye. 4. When the right eye was compressed after retrobulbar anesthesia had been performed previously in the left eye, the change of the intraocular pressure in the right eye showed no difference as when retrobulbar anesthesia had not been performed in the left eye. The intraocular pressure in the left eye showed a similar change as when the right eye had not been compressed, so it can be postulated that the efferent pathway of the ophthalmotonic consensual reaction was blocked by the retrobulbar anesthesia in the non-compressed left eye.
Afferent Pathways ; Anesthesia ; Efferent Pathways ; Epinephrine ; Humans ; Intraocular Pressure ; Male ; Massage ; Procaine ; Rabbits* ; Tetracaine

OBJECTIVE: Electrophysiological studies, which are mostly focused on afferent pathway, have proven that auditory processing deficits exist in patients with schizophrenia. Nevertheless, reports on the suppressive effect of efferent auditory pathway on cochlear outer hair cells among schizophrenia patients are limited. The present, case-control, study examined the contralateral suppression of transient evoked otoacoustic emissions (TEOAEs) in patients with schizophrenia. METHODS: Participants were twenty-three healthy controls and sixteen schizophrenia patients with normal hearing, middle ear and cochlear outer hair cells function. Absolute non-linear and linear TEOAEs were measured in both ears by delivering clicks stimuli at 80 dB SPL and 60 dB SPL respectively. Subsequently, contralateral suppression was determined by subtracting the absolute TEOAEs response obtained at 60 dBpe SPL during the absence and presence of contralateral white noise delivered at 65 dB HL. No attention tasks were conducted during measurements. RESULTS: We found no significant difference in absolute TEOAEs responses at 80 dB SPL, in either diagnosis or ear groups (p>0.05). However, the overall contralateral suppression was significantly larger in schizophrenia patients (p<0.05). Specifically, patients with schizophrenia demonstrated significantly increased right ear contralateral suppression compared to healthy control (p<0.05). CONCLUSION: The present findings suggest increased inhibitory effect of efferent auditory pathway especially on the right cochlear outer hair cells. Further studies to investigate increased suppressive effects are crucial to expand the current understanding of auditory hallucination mechanisms in schizophrenia patients.
Afferent Pathways ; Auditory Pathways ; Case-Control Studies ; Diagnosis ; Ear ; Ear, Middle ; Efferent Pathways ; Hair ; Hallucinations ; Hearing ; Humans ; Noise ; Schizophrenia*

OBJECTIVETo investigate the efferent pathway from the dorsal raphe nucleus to the inner ear.

METHODSEleven adult cats weighing 2.0 - 3.0 kg were used. The animals had no middle-ear disease and their auricle reflex was sensitive to sound. They were divided into experimental group (8 cats) and control group (3 cases). The fluorescent tracer cholera toxin subunit-B (CTB) was injected into cat cochlea and the CTB-labelled neurons of dorsal raphe nucleus (DRN) were identified using an immunofluorescence technique after a survival period of 7 days. For studying other fluorescence labelling, the sections containing CTB-labelled neurons were divided into four groups and incubated in antisera directed against tyrosine hydroxylase (TH), serotonin (5-HT), gamma-aminobutyric acid (GABA) and dopamine B-hydroxylase (DBH), respectively. Single-and double-labelled neurons were identified from the DRN.

RESULTS(1) A subpopulation of dorsal raphe nucleus (DRN) neurons were intensely labelled with CTB and these CTB-labelled neurons were densely distributed in a dorsomedial part of the DRN; (2) Four immunolabelling, TH, 5-HT, GABA and DBH were presented throughout the DRN. Of the total population of CTB-labelled neurons, 100% were TH-labelled neurons (double labelling) and no double-stained neuron with 5-HT, GABA and DBH was observed in the DRN.

CONCLUSIONSThere was a projection from DRN to the inner ear and this pathway might be a dopaminergic projection.

Animals ; Cats ; Ear, Inner ; innervation ; metabolism ; Efferent Pathways ; Neurons ; metabolism ; physiology ; Raphe Nuclei ; metabolism ; physiology

ABSTRACT OBJECTIVES: We report event-related functional magnetic resonance imaging(fMRI) methodology to investigate human brain activity during motor imagery. METHODS: A 1.5 Tesla clinical MR scanner was used in the acquisition of a series of T2* weighted MR images covering the whole brain. Blood oxygenation level-dependent(BOLD) signal changes associated with the imagery event were subsequently detected while healthy right-handed subjects imagined clenching of a right hand cued by auditory stimulus. RESULTS: Group analysis across nine right-handed subjects revealed activations in the medial and superior frontal gyri, cuneus, insula, middle/superior temporal gyri, and anterior cingulate gyri. Bilateral primary motor, premotor and supplementary motor areas exhibited event-related MR signal changes. Although unilateral hand clenching was imagined, bilateral activation of eloquent motor areas was observed. The proposed method also allowed for the visualization of subcortical areas, such as putamen, globus pallidus and thalamus, responsive to the event of motor imagery. CONCLUSION: The major cortical and subcortical areas in the motor pathways were identified and visualized during motor imagery event. Our results suggest that motor imagery and actual movement share common neural substrates.
Brain ; Brain Mapping ; Efferent Pathways ; Globus Pallidus ; Hand ; Humans ; Magnetic Resonance Imaging* ; Oxygen ; Putamen ; Thalamus

OBJECTIVE: To evaluate the reorganization of descending motor pathways of trunk muscles in stroke patients. METHOD: Nine patients with unilateral hemispheric stroke were enrolled. Their mean age was 56 years. Transcranial magnetic stimulation (TMS) was applied to unaffected and affected motor cortices in turn and bilateral electromyographic recordings were made from rectus abdominis, external oblique abdominal, and 4 th and 9 th thoracic erector spinae muscles during resting. The onset latency and peak-to-peak amplitude of motor evoked potential (MEP) were measured for each muscle on both sides. RESULTS: Stimulation of the unaffected hemisphere evoked contralateral responses in all patients. Ipsilateral responses were more common in TMS of affected hemisphere. Ipsilateral but not contralateral MEPs were obtained in TMS of affected hemisphere. CONCLUSION: These results demonstrated that the variable availability of bilateral crossed and uncrossed corticomotorneuronal projections among patients could be related with the inconstant occurrence of trunk weakness after unilateral hemispheric stroke.
Efferent Pathways ; Evoked Potentials, Motor ; Humans ; Muscles ; Rectus Abdominis ; Stroke ; Transcranial Magnetic Stimulation

Since the development of magnetic stimulation as a way of assessing the functions of corticospinal pathways, diseases involving central motor pathways have been investigated by motor evoked potentials(@). However, studies correlating MEP findings and the neurological deficits were rarely carried out in patients with stroke. In this study, transcranial magnetic stimulation of the motor cortex and lower cervical area was performed in 50 patients with acute stroke and 23 healthy volunteers. Follow-up tests were performed in 22 patients about I month@ later. The amplitudes of @ were significantly reduced (P=0.0001), and central motor conduction time (CMCT) was significantly delayed (P=0.0004) in stroke patients compared to the normal controls. The abnormalities of MEP were closely related to the initial motor deficits. The cortical MEP findings in patients with cortical infarction and pontine infarction were more severe than those obtained in patients with subcortical I lesion. Initial MEP findings showed good correlation with the final functional outcome of the patients. The shortened latencies of follow-up MEP were significantly (P=0.0266) related to the improvement of the patients' motor deficit. These results illustrate that the results of magnetic stimulations are related to the prognosis of patients with stroke, and suggest that MEP may be I used in the monitoring their neurological or functional progress.
Efferent Pathways ; Evoked Potentials, Motor* ; Follow-Up Studies ; Healthy Volunteers ; Humans ; Infarction ; Motor Cortex ; Prognosis ; Stroke* ; Transcranial Magnetic Stimulation

BACKGROUND: The afferent and efferent pathways of fentanyl cough response (FCR) and central organization are poorly understood at present. The aim of this study was to investigate the pretreatment effects of morphine, propofol, atropine, and midazolam on FCR. METHOD: The 120 healthy patients were randomly assigned to six equal pretreatment groups. They received 2ug/kg fentanyl rapidly through a peripheral venous catheter. The patients in each group were pretreated before the time necessary for peak plasma levels with different drugs as follows: group 1, no premedication; group 2, morphine 0.05 mg/kg iv; group 3, morphine 0.05 mg/kg iv naloxone 0.01mg/kg iv; group 4, propofol 0.5 mg/kg iv; group 5, atropine 0.01 mg/kg iv; group 6, midazolam 0.05 mg/kg iv. The patients were observed for any coughing or side effects, including oxygen desaturation, bronchoconstriction, chest wall rigidity and seizure. RESULT: 40% of patients in group 1 (control) had a cough response to fentanyl. Group 2 (morphine) and group 3 (morphine naloxone) showed a reduced FCR of 10%. The incidence of coughing was 60% of the patients in group 4 (propofol), 30% in group 5 (atropine), and 40% in group 6 (midazolam). These were not statistically significant. CONCLUSION: FCR is not altered by pretreatment with propofol, atropine, or midazolam, but morphine inhibits cough response and this antitussive effect was not antagonized by naloxone.
Atropine* ; Bronchoconstriction ; Catheters ; Cough* ; Efferent Pathways ; Fentanyl* ; Humans ; Incidence ; Midazolam* ; Morphine* ; Naloxone ; Oxygen ; Plasma ; Premedication ; Propofol* ; Seizures ; Thoracic Wall