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*

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

PURPOSE: To obtain preliminary data for understanding the central auditory neural pathway by means of functional MR imaging (fMRI) of the cerebral auditory cortex during linguistic and non-linguistic auditory stimulation. MATERIALS AND METHODS: In three right-handed volunteers we conducted fMRI of auditory cortex stimulation at 1.5 T using a conventional gradient-echo technique (TR/TE/flip angle: 80/60/40 degree). Using a pulsed tone of 1000 Hz and speech as non-linguistic and linguistic auditory stimuli, respectively, images-including those of the superior temporal gyrus of both hemispheres-were obtained in sagittal plases. Both stimuli were separately delivered biaurally or monoaurally through a plastic earphone. Images were activated by processing with homemade software. In order to analyze patterns of auditory cortex activation according to type of stimulus and which side of the ear was stimulated, the number and extent of activated pixels were compared between both temporal lobes. RESULTS: Biaural stimulation led to bilateral activation of the superior temporal gyrus, while monoaural stimulation led to more activation in the contralateral temporal lobe than in the ipsilateral. A trend toward slight activation of the left (dominant) temporal lobe in ipsilateral stimulation, particularly with a linguistic stimulus, was observed. During both biaural and monoaural stimulation, a linguistic stimulus produced more widespread activation than did a non-linguistic one. CONCLUSION: The superior temporal gyri of both temporal lobes are associated with acoustic-phonetic analysis, and the left (dominant) superior temporal gyrus is likely to play a dominant role in this processing. For better understanding of physiological and pathological central auditory pathways, further investigation is needed.
Acoustic Stimulation ; Auditory Cortex* ; Auditory Pathways ; Ear ; Linguistics* ; Magnetic Resonance Imaging* ; Neural Pathways ; Plastics ; Temporal Lobe ; Volunteers

OBJECTIVE: To explore plastic changes in the red nucleus (RN) of stroke patients with severe corticospinal tract (CST) injury as a compensatory mechanism for recovery of hand function. METHODS: The moderate group (MG) comprised 5 patients with synergistic hand grasp movement combined with limited extension, and the severe group (SG) included 5 patients with synergistic hand grasp movement alone. The control group (CG) included 5 healthy subjects. Motor assessment was measured by Motricity Index (MI). Diffusion tensor imaging was analyzed using fractional anisotropy (FA) and radial diffusivity (RD) in the individual regions of interest (ROIs)—bilateral internal capsule and anterior pons for CST injury and bilateral RN for rubrospinal tract (RST) injury. RESULTS: The SG showed a significantly lower MI score than the MG mainly due to differences in hand subscores. Significantly reduced FA was observed in both MG and SG compared with CG, while SG showed increased MD and RD in the affected ROIs of CST, and increased FA on the unaffected side compared with CG. However, in the RN ROI, a significantly increased FA and decreased RD on the unaffected side similar to the affected side were found only in the SG. The relative index of FA was lower and RD in SG was higher than in CG in RST. CONCLUSION: The diffusion metrics of RST showed changes in patients with severe CST injury, suggesting that RST may play a role in the recovery of hand function in patients with severe CST injury.
Anisotropy ; Diffusion Tensor Imaging ; Diffusion* ; Extrapyramidal Tracts ; Hand ; Hand Strength ; Healthy Volunteers ; Humans ; Internal Capsule ; Neuronal Plasticity ; Paraplegia ; Plastics ; Pons ; Pyramidal Tracts* ; Recovery of Function ; Red Nucleus* ; Stroke* ; Upper Extremity

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

Although they usually originate from peripheral problems, foot drop is caused by lesions affecting the neural pathway related to dorsiflexor muscles, whether of central or peripheral origin. We present a patient with sudden isolated foot drop caused by a small infarct in the primary motor cortex mimicking a peripheral origin. This report indicates that patients presenting isolated foot drop should be managed carefully and the possibility of both central and peripheral causes should be considered. To our knowledge, this is the first report of sudden isolated foot drop caused by a cortical infarction mimicking lumbar radiculopathy.
Cerebral Infarction* ; Foot* ; Humans ; Infarction ; Motor Cortex ; Muscles ; Neural Pathways ; Paresis ; Pyramidal Tracts ; Radiculopathy*

Recently, brainstem auditory evoked potential is very important for the evaluation of functions of the 8th nerve & brainstem. Especially, it appears that waves I, III, and V primarily represent volume- conducted electrical activity from the acoustic nerve, pons and midbrain, respectively, and that latencies between these three potentials indirectly reflect neural conduction in the corresponding segments of the central auditory pathway. For example, wave I to wave III interpeak latency(I-III IPL) is a measure of conduction in the more caudal segment of the brainstem auditory pathway-acoustic nerve and potomedullary portion-while the III-V IPL is a measure of conduction in the more rostral pontine and midbrain portions of the pathway. This study was undertaken to identify the normal measurements of the waves I, III and V and I-III IPL, III-V IPL in order to for provide basic data for clinical use in diagnosis, monitering in operation and management of patients with brainstem lesions. The literature is reviewed and results compared to the current study.
Auditory Pathways ; Brain Stem* ; Cochlear Nerve ; Diagnosis ; Evoked Potentials, Auditory, Brain Stem* ; Humans ; Mesencephalon ; Neural Conduction ; Pons

The purpose of the present study was to observe whether primary afferent Abeta-fiber is involved in the information transmission between peripheral terminals of adjacent dermatomes. The dorsal cutaneous nerve branches of spinal nerves from T(8) to T(12) segments were cut proximally. One peripheral stump end of the cut nerves was dissected into a few filaments for the examination of mechanoreceptive properties of single Abeta-fibers and their discharges were observed while the other end was stimulated antidromically. Fifty Abeta-units were recorded in forty-two intact rats. After an electrical stimulation (0.45 mA, 0.1 ms, 20 Hz, for 10 s) was delivered to the stimulated nerve, the size of the receptive field of 60.6% (n=33) Abeta-fibers extended. The mean area of receptive fields of all examined units enlarged from 8.94+/-6.51 mm(2) to 20.34+/-16.17 mm(2) (P<0.01) and the shapes of the receptive fields of 81.8% (n=20) units changed from a dot, round or ellipse with its long axis in parallel with the longitudinal axis of the body to an oblique ellipse with the longitudinal axis of the body. The mechanoreceptive threshold of 68.0% (n=50) units decreased with a reduction in mean threshold from 2.37+/-1.24 to 2.29+/-1.24 mN (P<0.05). The duration of these changes in mechano-receptive properties increased from 52.23+/-9.27 to 56.93+/-15.76 min. Meanwhile, increasing discharge was found in 50.0% (n=50) units but lasted only for 1.52+/-0.46 min. The changes in mechanoreceptive properties appeared simultaneously with discharge changes but had longer duration than that of discharge change (P<0.01). Discharges changes usually appeared in those units with the changes in mechanoreceptive properties following an antidromical electrical stimulation of adjacent spinal segment. These results suggest that low-threshold mechanoreceptive Abeta-fibers are affected by antidromical electrical stimulation of the cutaneous nerve from an adjacent spinal segment, indicating that information transmission occurs between the two endings of peripheral afferent nerves from adjacent spinal segments without any involvement of the central nervous system, and that Abeta-fibers are involved in the process of information transmission between peripheral terminals from adjacent spinal segments.
Afferent Pathways ; physiology ; Animals ; Electric Stimulation ; Mechanoreceptors ; physiology ; Neural Conduction ; physiology ; Peripheral Nerves ; physiology ; Rats ; Rats, Sprague-Dawley ; Skin ; innervation ; Spinal Nerves ; physiology

To manifest visual acuity of 20/20 or better, the requirements are good optical imagery, foveal fixation, intact receptor structure and function, and full integrity of the involved neural pathways. Person with hyperopia of 1-10 diopter or astigmatism of 1 diopter may be able to read the line marked 20/20 of Snellen's chart. Non-cycloplegic and cycloplegic subjective manifest refractions were done on 380 normal eyes with visual acuity of 20/20 or more to observe the prevalence, type and degree of the refractive errors. The results were as follows; 1. In non-cycloplegic subjective manifest refraction, 147 eyes(38.7%) had refractive error such as simple hyperopic astigmatism(50.3%), hyperopia(37.4%), simple myopic astigmatism(6.8%) and compound hyperopic astigmatism(5.4%). In cycloplegic subjective manifest refraction, 183 eyes(48.2%) were ametropia such as simple hyperopic astigmatism (49.7%), hyperopia(38.3%), compound hyperopic astigmatism(8.7%) and simple myopic astigmatism(3.2%). 2. As to the type of astigmatisms, "with the rule" astigmatism was 2.5 times more than "against the rule". 3. Average degree of refractive errors were 0.12 diopter in non-cycloplegic refraction and 0.22 diopter in cycloplegic refraction. 4. The degree of hyperopia was less than 1.00 diopter in all cases of noncycloplegic refractions and in most cases(93%) of cycloplegic refractions. 5. Degree of astigmatism were less than 1.00 diopter in the majority(98%).
Astigmatism ; Humans ; Hyperopia ; Neural Pathways ; Prevalence ; Refractive Errors ; Visual Acuity*

The rostral ventromedial medulla (RVM) is a prominent component of the descending modulatory system involved in the control of spinal nociceptive transmission. In the current study, we investigated melanocortin-4 receptor (MC4R) expression in the RVM, where the neurons involved in modulation of nociception reside. Using a line of mice expressing green fluorescent protein (GFP) under the control of the MC4R promoter, we found a large number of GFP-positive neurons in the RVM [nucleus raphe magnus (NRM) and nucleus gigantocellularis pars α (NGCα)]. Fluorescence immunohistochemistry revealed that approximately 10% of MC4R-GFP-positive neurons coexpressed tyrosine hydroxylase, indicating that they were catecholaminergic, whereas 50%-75% of those coexpressed tryptophan hydroxylase, indicating that they were serotonergic. Our findings support the hypothesis that MC4R signaling in RVM may modulate the activity of serotonergic sympathetic outflow sensitive to nociceptive signals, and that MC4R signaling in RVM may contribute to the descending modulation of nociceptive transmission.
Animals ; Female ; Male ; Medulla Oblongata ; cytology ; metabolism ; Mice ; Mice, Transgenic ; Neural Pathways ; cytology ; metabolism ; Neurons, Afferent ; cytology ; metabolism ; Nociception ; physiology ; Receptor, Melanocortin, Type 4 ; genetics ; metabolism ; Serotonergic Neurons ; metabolism ; Tyrosine 3-Monooxygenase ; metabolism