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PubMed1996

Somatosensory evoked potential phase reversal and direct motor cortex stimulation during surgery in and around the central region.

In 99 patients with mass lesions in and around the central region, the central sulcus was intraoperatively localized with the use of somatosensory evoked potential (SEP) phase reversal. In 33 of these patients, the motor cortex was directly stimulated and electromyographic responses were recorded from the forearm flexor, thenar, and hypothenar muscles. An additional 25 patients, with subcortical lesions or lesions directly located at the pyramidal tract, were continuously monitored during surgery by motor evoked potentials (MEPs). An exact determination of the central sulcus and tumor localization was possible in all patients; a phase reversal was obtained in 90.8% of the patients, and localization was possible as a result of anatomic structures and the loss of N20 or P20 of SEPs in the other 9.2%. MEPs were obtained in 32 of 33 patients and also in all 25 patients who underwent MEP monitoring at the beginning of tumor removal. From this study, it can be concluded that the combination of SEP phase reversal and modified electrical cortex stimulation is compatible with general anesthesia, although anesthesia was not systematically controlled according to a protocol. Although this study demonstrates that the combined SEP/MEP technique was feasible, it is not yet possible to demonstrate benefit in improving the outcome of patients. Concerning the safety of stimulation, the exact localization of the central sulcus by the noninvasive SEP method, compared with direct electrical stimulation, offered more safety for the patient. The modified technique of direct motor cortex stimulation needed much less charge density than did the common technique. The recording of electromyographic responses instead of movements made objective documentation possible, and the analysis of amplitudes and latencies will supply quantitative information about the motor system.

Adolescent↗
PubMed2004

Post-spike distance-to-threshold trajectories of neurones in monkey motor cortex.

A recently developed method permits calculation of the post-spike distance-to-threshold trajectory from an extracellularly recorded spontaneous spike train, using a transform of the interspike interval histogram. We applied this method to 61 single neurones recorded from the primary motor cortex of an awake behaving monkey; 39 cells were antidromically identified as pyramidal tract neurones (PTNs). The cells fell into three categories. Fifty-three trajectories (37 from PTNs) had statistically significant peaks 10-60 ms after the preceding spike. Six neurones (2 PTNs) had non-peaked trajectories which rose exponentially towards threshold. Two cells (both unidentified) had trajectories which declined monotonically away from threshold with increasing post-spike latency. The peaked trajectories were unlikely simply to be an artefact of changing firing rate, which potentially can invalidate this method. Firstly, computer simulations confirmed that the method could accurately re-create both exponential and peaked trajectories, even in the presence of the same rate modulation as seen experimentally. Secondly, the responses of eight cells to weak single pulse intracortical microstimulation (20 microA) through a nearby electrode were measured. For each cell, including representatives of all three trajectory shapes, the modulation of response probability with post-spike latency was consistent with the trajectory computed from the spontaneous discharge. We also demonstrated that cells showed a peaked trajectory during periods with either high or low spontaneous network oscillations, so that the peaks were likely to be generated in part by single cell properties rather than exclusively by network activity. We conclude that many single neurones in motor cortex have an increased probability of firing a spike around 30 ms after the previous action potential. This could act to enhance synchronized oscillatory discharge among populations of cells at functionally relevant frequencies.

Action Potentials↗
PubMed1993

Brainstem afferents to the rostral (juxtafacial) nucleus paragigantocellularis: integration of exteroceptive and interoceptive sensory inputs in the ventral tegmentum.

The rostral pole of the nucleus paragigantocellularis (PGi), termed juxtafacial PGi, lies medially adjacent to the facial nucleus and lateral to the pyramidal tract and the nucleus gigantocellularis pars alpha in the caudal ventral pons. This narrow region of the ventral pontine reticular formation is an afferent to the nucleus locus coeruleus, and contains neurons which have been implicated in pain processing, cardiovascular regulation, respiratory control and arousal. Here, we studied brainstem afferents to the juxtafacial PGi using retrograde transport of wheat germ agglutinin-conjugated horseradish peroxidase (WGA-HRP) or of a colloidal gold-protein complex. Anterograde transport of WGA-HRP, or of Phaseolus vulgaris leucoagglutinin (PHA-L), was used to confirm and further detail innervation patterns in the juxtafacial PGi. Results revealed that the juxtafacial PGi receives inputs from a variety of nuclei involved in somatosensory, auditory and autonomic function. Retrograde labeling was prominent in the dorsal column nuclei, the inferior colliculus and the paralemniscal zone of the midbrain, as previously reported in other species. We also found afferents to the juxtafacial PGi that were not previously described, including the paramedian reticular formation and the paraolivary reticular formation. Afferents were also identified from the retrofacial PGi, the caudal medullary reticular formation and the dorsal periaqueductal gray, structures implicated in autonomic and pain regulation. These results indicate that inputs to this subregion of the PGi is distinct from that to the more caudal parts of the PGi, and support the view that the juxtafacial PGi may function in the integration and coordination of polymodal (somatic and visceral) sensory events.

Animals↗
PubMed1982

The initiation of voluntary movements by the supplementary motor area.

The hypothesis is formulated that in all voluntary movements the initial neuronal event is in the supplementary motor areas (SMA) of both cerebral hemispheres. Experimental support is provided by three lines of evidence. 1. In voluntary movements many neurones of the SMA are activated probably up to 200 ms before the pyramidal tract discharge. 2. Investigations of regional cerebral blood flow by the radioactive Xenon technique reveal that there is neuronal activity in the SMA of both sides during a continual series of voluntary movements, and that this even occurs when the movement is thought of, but not executed. 3. With voluntary movement there is initiation of a slow negative potential (the readiness potential, RP) at up to 0.8 s before the movement. The RP is maximum over the vertex, i.e. above the SMA, and is large there even in bilateral Parkinsonism when it is negligible over the motor cortex. An account is given of the SMA, particularly its connectivities to the basal ganglia and the cerebellum that are active in the preprogramming of a movement. The concept of motor programs is described and related to the action of the SMA. It is proposed that each mental intention acts on the SMA in a specific manner and that the SMA has an 'inventory' and the 'addresses' of stored subroutines of all learnt motor programs. Thus by its neuronal connectivities the SMA is able to bring about the desired movement. There is a discussion of the manner in which the mental act of intention calls forth neural actions in the SMA that eventually lead to the intended movement. Explanation is given on the basis of the dualist-interactionist hypothesis of mind-brain liaison. The challenge is to the physicalists to account for the observed phenomena in voluntary movement.

Animals↗
PubMed1984

Topographical localization in the motor cortex of the cat for somatic afferent responses and evoked movements.

Microwires chronically implanted in the pericruciate cortex of free-to-move cats were used to record extracellularly from cortical neurones and to deliver intracortical stimulation. Natural stimulation of cutaneous and/or deep mechanoreceptors in limbs and trunk evoked discharges in 89% of 165 neurones, 57% of which were pyramidal tract neurones. Out of 112 cells with receptive fields on the contralateral forelimb, 41% had cutaneous fields, 29% had fields involving deep tissues and 30% were driven from both sources. Cutaneous receptive fields were much commoner than deep ones among cells with fields including the forefoot; this relationship was reversed for cells with more proximal fields. Many more cells had distal than proximal fields. The 'zones' of the forelimb (i.e. foot, wrist, elbow, shoulder) provided input to widespread and overlapping cell populations within the coronal gyrus and the lateral parts of the anterior and posterior sigmoid gyri. Despite the overlap a somatotopy existed with successively more distal limb zones represented successively further laterally in the pericruciate area. Intracortical stimulation (eleven cathodal pulses, duration 0.2 ms, frequency 330 Hz, intensity 35 microA or less) evoked flick movements of the contralateral limbs which were abolished by pyramidectomy. In the forelimb, shoulder movements were commonest and elbow, wrist and digits were represented with decreasing frequency. Both for 35 microA and for threshold stimulation the distributions of the effective electrodes revealed an overlapping somatotopy such that the wrist movements were almost restricted to the coronal gyrus and shoulder movements were most often evoked from the lateral part of the anterior sigmoid gyrus. The movement and receptive field somatotopies overlapped heavily but the former showed a distinct lateral shift relative to the latter. As a result shoulder movements were not uncommonly evoked from the coronal gyrus although the shoulder provided almost no input to cells in that area.

Animals↗
PubMed2004

Unilateral frontal lobe contusion and forelimb function: chronic quantitative and qualitative impairments in reflexive and skilled forelimb movements in rats.

Traumatic brain injury induced by mechanical impacts of the head can be modeled in rats in order to investigate acute and chronic therapy. Because frontal lobe contusion affects the neural representation of the forelimb in both the neocortex and basal ganglia, the purpose of the present experiments was to examine the chronic changes in reflexive and skilled forelimb induced by the injury. Contusions produced a cavity in the sensorimotor cortex, accompanied by shrinkage of the pyramidal tract, loss of cells in the dorsolateral striatum, and enlargement of the lateral ventricle. There were substantial individual differences in lesion size despite use of two different contusion forces, but all rats receiving contusions displayed chronic forelimb deficits. Reflexive tests of forelimb use (limb posture, placing, and support) indicated that impairments were most pronounced in the forelimb contralateral to the lesion. Tests of limb preference indicated that the contusion rats displayed a forelimb asymmetry: they were more likely to lean on their ipsilateral-to-lesion forelimb for support when rearing in a test cylinder, and this impairment was amplified in a home cage test. They also displayed a preference for the forelimb ipsilateral to the lesion when reaching for food, although both forelimbs were equally impaired on measures of success when reaching for food from a tray and reaching for a single food pellet on a shelf. A qualitative analysis from frame-by-frame video records indicated that when reaching for single pellets, impairments in forelimb use primarily affected the contralateral-to-lesion limb, especially limb aiming, supination, and food pellet release. Impairments in the ipsilateral-to-lesion forelimb were generally, but not exclusively, secondary to postural abnormalities. The wide range of chronic impairments in forelimb use following contusion injuries are discussed in relation to the anatomical and behavioral origins of the impairments and the potential use of forelimb tests in the assessment of therapy for traumatic brain injury to the frontal cortex.

Animals↗
PubMed1993

Critical timing of sensorimotor cortex lesions for the recovery of motor skills in the developing cat.

Forelimb movements and motor skills were studied in adult cats in order to determine the effect of brain damage inflicted at different postnatal ages. The unilateral lesion included the cortical areas from which the pyramidal tract originates in cat: areas 4 and 6 corresponding to the motor cortex; areas 3, 2 and 1 corresponding to the primary somatosensory cortex; and part of area 2 prae-insularis corresponding to the secondary somatosensory cortex. Forelimb performance of a food-retrieving task requiring proximal as well as distal muscles was assessed by comparing the limb contralateral to the damaged hemisphere (affected limb) with the limb contralateral to the intact hemisphere (non-affected limb) that appeared to perform the task as well as both limbs of control animals. In simple task-related movements, all operated animals were rapidly able to achieve the goal with the affected limb, whatever the age at lesion. In complex tasks, the ability to achieve the goal with the affected limb decreased with increasing age at lesion. Recovery of distal skills, i.e. grasping and wrist rotation, did not occur in animals operated on after the 23rd postnatal day (PND), and recovery of proximal skills, i.e. amplitude and precision of the reaching movement, did not occur in animals operated on after the 45th PND. The critical time for the recovery of distal skills lies somewhere between the 23rd and 30th PND, whereas for the recovery of proximal skills it lies somewhere between the 45th and 60th PND. These critical dates for the recovery of motor skills support the Kennard doctrine. Different critical times for proximal and distal skills may be explained in terms of different stages of sensorimotor development in kitten. It is hypothesised that recovery only occurs if brain damage is inflicted before maturation of the nervous system underlying a given motor skill.

Animals↗
PubMed2003

Motor cortical and other cortical interneuronal networks that generate very high frequency waves.

A remarkable feature of motor cortical organization in higher mammals is that a brief electrical stimulus elicits in the pyramidal tract and corticospinal tract an unrelayed direct (D) wave followed by multiple indirect (I) waves at frequencies as high as 500-700 Hz. This review presents some conclusions regarding very high frequency synchronous activity in mammalian cortex: (1) Synchrony in repetitive I discharges is extraordinary in humans and monkeys, less in cats and still less in rats, being there represented by a delayed broad wave; such phylogenetic trends have important implications for the suitability of lower mammalian species for studies of high frequency cortical networks in the human brain; (2) The evidence from microstimulation at different cortical depths and pial cooling favors a vertically oriented chain of interneurons that centripetally excite corticospinal neurons as the basis for inter-I wave periodicity and synchrony; (3) Significantly, the I wave periodicity is conserved despite wide changes in stimulus parameters; (4) Synchronous high frequency activity similar to that of I waves can be recorded from other neocortical areas such as visual and somatosensory cortex; however, evidence is still lacking that the output neurons of these cortical regions have synchronized discharges comparable to I waves; (5) In limbic cortices, the frequency of synchronous neural activity is lower than that in motor cortex or related cortices and periodicity is not conserved with changes in stimulus parameters, indicating a lack of the neocortical interneuronal substrate in limbic cortex; (6) We propose that the very high frequency synchronous activity of motor cortical output reflects a computational function such as a "clock," quantizing times at which inputs would interact preferentially yielding synchronous output discharges. Such circuitry, if a general feature of neocortex, would facilitate rapid communication of significant computations between cortical regions.

Animals↗
PubMed2001

Investigation into non-monosynaptic corticospinal excitation of macaque upper limb single motor units.

There has been considerable recent debate as to relative importance, in the primate, of propriospinal transmission of corticospinal excitation to upper limb motoneurons. Previous studies in the anesthetized macaque monkey suggested that, compared with the cat, the transmission of such excitation via a system of C3-C4 propriospinal neurons may be relatively weak. However, it is possible that in the anesthetized preparation, propriospinal transmission of cortical inputs to motoneurons may be depressed. To address this issue, the current study investigated the responses of single motor units (SMUs) to corticospinal inputs in either awake (n = 1) or lightly sedated (n = 3) macaque monkeys. Recordings in the awake state were made during performance of a precision grip task. The responses of spontaneously discharging SMUs to electrical stimulation of the pyramidal tract (PT) via chronically implanted electrodes were examined for evidence of non-monosynaptic, presumed propriospinal, effects. Single PT stimuli (up to 250 microA; duration, 0.2 ms, 2 Hz) were delivered during steady discharge of the SMU (10-30 imp/s). SMUs were recorded from muscles acting on the thumb (adductor pollicis and abductor pollicis brevis, n = 18), wrist (extensor carpi radialis, n = 29) and elbow (biceps, n = 9). In all SMUs, the poststimulus time histograms to PT stimulation consisted of a single peak at a fixed latency and with a brief duration [0.74 +/- 0.25 (SD) ms, n = 56], consistent with the responses being mediated by monosynaptic action of cortico-motoneuronal (CM) impulses. Later peaks, indicating non-monosynaptic action, were not present even when the probability of the initial peak response was low and when there was no evidence for suppression of ongoing SMU activity following this peak (n = 20 SMUs). Even when repetitive (double-pulse) PT stimuli were used to facilitate transmission through oligosynaptic linkages, no later peaks were observed (16 SMUs). In some thumb muscle SMUs (n = 8), responses to PT stimulation were compared with those evoked by transcranial magnetic stimulation, using a figure-eight coil held over the motor cortex. Responses varied according the orientation of the coil: in the latero-medial position, single peak responses similar to those from the PT were obtained; their latencies confirmed direct excitation of CM cells, and there were no later peaks. In the posterio-anterior orientation, responses had longer latencies and consisted of two to three subpeaks. At least under the conditions that we have tested, the results provide no positive evidence for transmission of cortical excitation to upper limb motoneurons by non-monosynaptic pathways in the macaque monkey.

Anesthesia↗
PubMed1998

Corticoreticular pathways in the cat. I. Projection patterns and collaterization.

This paper summarizes and compares the projection patterns and the receptive fields of cortical neurons in areas 4 and 6 that project to the pontomedullary reticular formation (PMRF). A total of 326 neurons were recorded in area 4 and 129 in area 6 in four awake, unrestrained cats that were chronically implanted with arrays of electrodes in the PMRF and the pyramidal tract (PT). In area 4, 47% of the neurons projected to the caudal PT but not to the PMRF (PTNs); 19% were activated only from the PMRF [corticoreticular neurons (CRNs)], whereas 27% were activated from both the PT and the PMRF (PTN/CRNs). More PTN/CRNs conducted at velocities >20 m/s (82%) than did CRNs (23%). In area 6, only 19% of the neurons were identified as PTNs, 12% were PTN/CRNs and 31% were CRNs; a further 38% could not be activated from either structure. Collateral branches within the PMRF conducted at maximum velocities of 20 m/s (average = 6.5 m/s). No significant differences in the conduction velocities of the collateral branches were found either between fast and slow PTNs or between area 4 and area 6 neurons. A large proportion of neurons in area 4 (85/173, 49%) were activated by passive manipulation of the more distal, contralateral forelimb, with approximately equal numbers being classed as PTNs, PTN/CRNs and CRNs. Most neurons in area 6 for which a receptive field could be found were excited by lightly touching or tapping the face and neck; a receptive field could not be determined for 39% of the area 6 neurons compared with only 5% of those in area 4. Finally, there was evidence that neurons in quite widespread areas of the pericruciate cortex, including both areas 4 and 6 projected onto similar, restricted regions of the PMRF. The fact that the cortical projection from area 4 to the PMRF includes a high percentage of fast PTNs with a receptive field on the distal forelimb is consistent with the view that this projection may serve to integrate movement and the dynamic postural adjustments that accompany them. The fact that the cortical projection from area 6 to the PMRF is primarily from slow PTNs with receptive fields on the face, neck and back is consistent with a role for this cortical area in adjusting the general posture of the animal on which movements are superimposed.

Animals↗
PubMed2003

Synchronization in monkey motor cortex during a precision grip task. II. effect of oscillatory activity on corticospinal output.

Recordings from primary motor cortex (M1) during periods of steady contraction show oscillatory activity; these oscillations are coherent with the activity of contralateral muscles. We investigated synchronization of corticospinal output neurons with the oscillations, which could provide the pathway for their transmission to the spinal motoneurons. One hundred seventy-six antidromically identified pyramidal tract neurons (PTNs) were recorded from M1 in three macaque monkeys trained to perform a precision grip task. Local field potentials (LFP) were simultaneously recorded. All analysis was confined to the hold period of the task, where our previous work has shown that there is the strongest oscillatory activity. Coherence was calculated between LFP and PTN discharge. Significant coherence was seen in three bands, with frequencies of 10-14, 17-31, and 34-44 Hz. Coherence values were low, with the majority of PTN-LFP coherences having a peak lower than 0.05. The phase of coherence was approximately -pi/2 radians for each band (with LFP polarity defined as negative upward), although there was some dispersion of phase across the population of PTNs. Coherence was also calculated between pairs of PTNs that had been simultaneously recorded. Where there was significant coherence, it was also generally smaller than 0.05. The phase of PTN-PTN coherence clustered around zero radians. A computer model was constructed to assist the interpretation of the experimental results. It simulated an integrate-and-fire neuron responding to synaptic inputs. A fraction of the synaptic inputs was synchronized with a simulated LFP; the remainder were uncorrelated with it. The model showed that coherence between the LFP and the output spike train considerably underestimated the fraction of synchronized inputs. Additionally, for a given fraction of synchronized inputs, coherence was smaller for high- compared with low-frequency bins. Cell discharge rate also influenced the spike-LFP coherence: coherence was higher for simulations in which the cell discharged at a faster rate. Thus although levels of PTN-LFP coherence seen experimentally were low, a considerable proportion of the input to the PTN must be synchronized with the global oscillatory activity recorded by the LFP. The low LFP-PTN coherences do however indicate that cortical oscillations are transmitted with only low fidelity in the discharge of a single PTN. Using further computer simulations, it was demonstrated that a small population of PTNs could encode the cortical oscillatory signal effectively, since the action of averaging across the population improves the signal:noise ratio. The oscillations will therefore be effectively transmitted to spinal motoneurons, and this has important consequences for the possible role of oscillations in motor control of the hand.

Animals↗
PubMed1994

Motor cortical activity during voluntary gait modifications in the cat. II. Cells related to the hindlimbs.

1. To determine whether the motor cortex is involved in the modification of the hindlimb trajectory during voluntary adjustments of the locomotor cycle, we recorded the discharge patterns of 72 identified pyramidal tract neurons (PTNs) within the hindlimb region of pericruciate area 4 during a task in which cats stepped over obstacles attached to a moving treadmill belt. Data were also recorded from representative flexor and extensor muscles of the fore- and hindlimbs contralateral to the recording site. 2. To step over the obstacles, the cats increased flexion sequentially at the knee, ankle, and then the hip to bring the leg above and over the obstacle. This flexion movement was followed by a strong extension of the whole limb that repositioned the foot on the treadmill belt. These changes in limb trajectory were associated with large changes in the level of the activity of many flexor and extensor muscles of the hindlimb, and especially of the knee flexor, semitendinosus. On the basis of the time of onset of the knee and ankle extensor muscles in those steps when the limb was the first to be brought over the obstacle, the swing phase of the modified step cycle was subdivided into two parts, Phase I and Phase II, which correspond respectively to the flexion of the limb (F) and the initial extension (E1). 3. The temporal sequence of the movement was the same whether the hindlimb was the first (lead) or second (trail) to step over the obstacle, although the relative time between flexion at the three joints was changed in the two conditions. 4. Seventy-two PTNs were recorded from the posterior bank of the cruciate sulcus during the voluntary gait modifications. Sixty-three (63/72) of these PTNs had receptive fields that were confined to the contralateral hindlimb, or were recorded from penetrations in which such cells were found. Nine (9/72) PTNs had receptive fields on both the contralateral fore- and hindlimbs. Microstimulation applied through the recording electrode evoked, in all cases, brief twitch responses only in contralateral hindlimb musculature. 5. Forty-two (42/63) of those PTNs with receptive fields confined to the hindlimb showed a significant increase in their discharge frequency when the limb contralateral to the recording site was the first to step over the obstacle (lead limb). Twenty-nine PTNs (29/63) discharged maximally during the swing phase (18 in Phase I and 11 in Phase II), including two PTNS that also increased their discharge frequency during stance.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1993

Motor cortical activity during voluntary gait modifications in the cat. I. Cells related to the forelimbs.

1. The discharge patterns of 91 identified pyramidal tract neurons (PTNs), located within the forelimb region of area 4 of the cat motor cortex, were recorded during the voluntary modifications of gait needed to step over obstacles attached to a moving treadmill belt. Recordings were made simultaneously from flexor and extensor muscles acting around the shoulder, elbow, wrist, and digits of the forelimb contralateral to the recording site. 2. Analysis of the changes in electromyographic (EMG) activity during the gait modification showed increases in the activity of most flexor muscles of the shoulder and elbow, as well as in the wrist and digit dorsiflexors, when the contralateral forelimb was the first to pass over the obstacle. This period of augmented activity could be subdivided into two parts: one associated with the initial flexion of the limb that was needed to bring it above and over the obstacle (phase I), and the second associated with increased wrist dorsiflexor muscle activity before foot contact (phase II). 3. The discharge frequency of a total of 57/91 (63%) of the recorded PTNs was significantly increased during the gait modification when the limb contralateral to the recording site was the first to step over the obstacle; six of these neurons also showed a significant decrease in their discharge in a different part of the step cycle. In a further 21/91 (23%) neurons, discharge frequency was only decreased, whereas the remaining 13/91 (14%) PTNs showed similar patterns of activity both during control walking and during the gait modifications. 4. Most of those neurons (47/57) in which significant increases in firing frequency were observed, discharged maximally during the period of increased activity of the physiological flexor muscles. Twenty-three of these cells (23/47) discharged maximally in phase I, and 12 (12/47) in phase II. A third population of PTNS (12/47) started to increase their discharge in the stance phase of the step cycle immediately preceding the modified cycle. Seven (7/57) PTNs increased their discharge during the stance phase of the modified cycle, and the remaining three could not be classified as being preferentially related to any one part of the step cycle. 5. The frequency modulation of 41/57 PTNs was less when the leg contralateral to the recording site was the second to encounter the obstacle. In many neurons there was also an appreciable change in the time in the step cycle that peak discharge occurred. These changes in amplitude and timing paralleled the changes observed in the temporal relationships of the muscles.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1990

Experimental studies on spinal cord function using evoked action potentials.

Experiments were carried out on cats to determine the use of conductive evoked spinal cord action potentials in diagnosing motor function of the spinal cord. Direct stimulation from the dura produced three negative wave potentials, N1, N2 and N3. The intraspinal pathway of N2 and N3 was the dorsal column. The pathways of N1, determined by dorsal and ventral epidural recording, were the dorsilateral funicle and the extrapyramidal tracts. A collision experiment between potential N1 and pyramidal tract action potential did not reflect the function of the tract as the amplitude of the action potential was too small. Nevertheless, it is considered that conductive evoked spinal cord action potentials could become a valuable method of assessing spinal cord function as they reflect the function of the extrapyramidal tracts, as well as of the dorsilateral funicle and the dorsal column.

Action Potentials↗
PubMed1997

The distribution and dynamic density of oligodendroglial cytoplasmic inclusions (GCIs) in multiple system atrophy: a correlation between the density of GCIs and the degree of involvement of striatonigral and olivopontocerebellar systems.

The distribution and dynamic density of oligodendroglial cytoplasmic inclusions (GCIs) were studied based on 30 cases of multiple system atrophy (MSA), including striatonigral degeneration (SND), olivopontocerebellar atrophy (OPCA) and Shy-Drager syndrome. GCIs were widely spread throughout the central nervous system, including the striatonigral and olivopontocerebellar systems. Inclusion-bearing cells appeared to be oligodendrocytes which usually had larger and lighter nuclei than those of normal-looking oligodendrocytes. The distribution of GCIs was similar in all cases, irrespective of the degrees of OPCA and SND, but the frequency of GCIs varied from case to case. We classified all the cases into two categories based on the degree of neuropathological changes of SND (mild and severe) and, independently, into three groups based on that of OPCA (minimal, moderate and severe), i.e., a total of six groups. An association between the frequency of GCIs and the severity of the lesions was obtained. For example, many GCIs were seen the cerebellar white matter in the cases in which OPCA was not histologically confirmed. More GCIs were seen in the cases with moderate OPCA. In the cases with severe OPCA, GCIs were rarer and smaller, in proportion to the devastation of fibers; no GCIs were seen in the cases with more severe OPCA. The incidence of GCIs showed a positive correlation to the severity of OPCA but not that of SND in the corticopontine tracts, of both OPCA and SND in the pyramidal tracts, and of SND but not of OPCA in the pencil fibers of the putamen. It is suggested that GCIs may represent either a change synchronous with neuronal degeneration or a phenomenon preceding neuronal changes, especially in the cerebellar white matter. Thus, they may represent the early changes in MSA and may be a useful neuropathological hallmark for diagnosis of MSA, even in cases with minimal OPCA and SND.

Aged↗
PubMed1980

Clinicopathological studies of oculo cerebrorenal syndrome of Lowe, Terrey and MacLachlan.

A thirty-three-year-old male with Lowe's syndrome had cataract; nystagmus, buphthalmos, prominent frontal bossing, growth and mental retardation, aminoaciduria, proteinuria, rickets, areflexia, genu valgum, piercing cry and head-banging being among the presenting features. The rickety changes improved over a period of years with the administration of vitamin D2. Pathological changes include: (1) tubular damage in the kidneys and hypertrophies of Bowman's capsules; (2) small brain with ventricular dilatation with thickened meninges, small corpus callosum, small size of pyramidal tracts and medial leminisci, neurofibrillary tangles in the pyramidal cells of the Ammon's horn and frontal lobe; (3) eye changes of buphthalmos, congenital cataracts and thickening of Descemet's membrane; (4) testicular atrophy--both testes showing peritubular fibrosis with an increase of fibrous tissue in the interstitial tissue. Azoospermia was present linked with poor development of spermatogonia and spermatocytes. The lumina of the seminiferous tubules were filled with foamy exudate.

Adolescent↗