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R Porter

Publications and source records attributed to R Porter.

At least 163 records · Page 9Linked to original sources
PubMed1982

[Not Available].

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History, Modern 1601-↗
PubMed1980

Lafora disease: diagnosis by liver biopsy.

We have studied four patients who had a clinical course compatible with Lafora disease. The diagnosis was confirmed in one by the presence of Lafora bodies in central nervous system neurons at autopsy and was supported in another by findings in the cerebral biopsy of a sibling. Our patients had no clinically apparent liver disease, but liver specimens in each instance showed a distinctive histological abnormality, with hepatocytes containing inclusions having a ground-glass appearance. The liver biopsy findings appear to be relatively specific for this disorder and can easily be differentiated from those in other liver diseases.

Adolescent↗
PubMed1980

What is area 3a?

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Afferent Pathways↗
PubMed1980

The monkey globus pallidus: neuronal discharge properties in relation to movement.

1. Recordings were made of the natural discharges of 388 pallidal neurones in awake, free-to-move monkeys in order to describe the discharge properties of such neurones in relation to normal movement performance. 2. Of the 388 neurones, 156 discharged only in association with one direction of movement of the forelimb about a specific joint. If that movement was not taking place the neurone would not discharge. 3. All joints and directions of movement for the upper limb were represented by clusters of cells within the pallidal population. 4. Twenty-nine per cent of neurones co-varied with movement of both contralateral and ipsilateral limb for the same direction of movement about a given joint; distal movements were represented with similar frequency to proximal movements in this group. 5. Afferent information provided by natural stimulation of peripheral receptors did not directly influence either the discharging or non-discharging pallidal neurones. 6. Movement related neurones were regionally organized and were found in the posterior part of the pallidum.

Action Potentials↗
PubMed1980

The discharges during movement of cells in the ventrolateral thalamus of the conscious monkey.

1. Monkeys were trained to perform a stereotyped movement task in return for food rewards. On completion of training a headpiece which allowed microelectrode access to the thalamus for single cell recordings during performances of the task was attached at a surgical operation. The location of each cell studied was determined by histological examination of the fixed brain and precise identification of electrode tracks. 2. Ninety-three of ninety-seven cells discharging in association with arm movements but not responding to natural activation of peripheral receptors in the forelimb were located predominantly in the rostral part of nucleus VPLo and the caudo-ventral part of VLo. These cells appeared to be associated with active movement in one direction of a specific joint. 3. 52% of these 'motor' cells discharged in association with movements of either forelimb. The other 48% discharged in association with movement of the contralateral arm and hand only. 4. Sixty cells responded to stimulation of deep receptors or to passive limb manipulation in the relaxed and cooperative animal. These cells were predominantly located in the ventro-caudal part of VPLo and all the responses were obtained from contralateral receptors. Their discharges during performances of the motor task were indistinguishable from those of 'motor' cells. 5. Ninety-two cells were driven by limb manipulation and by natural activation of superficial cutaneous receptors and these were found predominantly in VPLo and VPLc. All responses were from contralateral receptors. These cells discharged during performance of the motor task; for some of them, their afferent input zones were not being stimulated by contact with the manipulandum when their 'motor' discharges commenced. 6. Although responses in each of the above groups of cells were sought by imposing a sudden perturbation of the limb during the performance of the active movement task, no responses were seen.

Action Potentials↗
PubMed1979

Discharges of intracerebellar nuclear cells in monkeys.

1. Conscious monkeys were trained with food rewards to perform movement tasks with the left forelimb and to accept manipulation of the joints and muscles and natural non-noxious stimulation of the skin of all four limbs. 2. Recordings were made from 217 cells situated in the left interpositus and dentate nuclei of the cerebellum. The identity of seventy-seven cells as cerebellar projection neurones was definitively established by activating them antidromically from the brachium conjunctivum near the contralateral red nucleus. 3. Modulation in the natural activity of 129 of these crebellar nuclear cells (sixty in interpositus; sixty-nine in dentate) occurred in a reproducible manner in temporal association with a phase of the self-paced movement tasks performed by the animal using the ipsilateral arm and hand. The discharges during motor performance of forty-two dentate and forty-five interpositus cells were shown to be associated with movement about a particular joint or region of the forelimb whenever that movement occurred. 4. Cells whose discharges were related to proximal joint movements (shoulder, elbow) and cells related to distal joint movements (wrist, fingers) were encountered in both the dentate and interposed nuclei. 5. The cells were tonically active at rest. Most commonly, accelerations in the discharge were related to movement of a joint or the limb in one direction and a reduction or cessation of activity accompanied movement in the opposite direction. 6. For some cells, variation of the amount of discharge demonstrated during movement performance could be related to the range of the movement or its duration, more activity being characteristic of more prolonged movement performance through larger angles of joint displacement. 7. The dentate and interpositus cells whose discharges were most strongly and consistently related to movements of the forelimb were concentrated in the mid region and caudal half of either nucleus. 8. None of seventy-three dentate neurones examined showed appreciable responses to stimulation of the skin or manipulation of joints and muscles of the fore- or hind limbs and only two cells responded to unexpected perturbation of movement performance. 9. No influence resulting from peripheral afferent input from the ipsilateral forelimb was detected in any interpositus cell whose firing was unchanged during ipsilateral arm movements. 10. Of the sixty interpositus cells whose discharge rates changed during motor performance, twenty-eight were demonstrated to be in receipt of input from receptors in the ipsilateral hand or arm, which could be activated by brisk tapping of the skin and sometimes by gentle squeezing of the forearm. 11. In the passive relaxed animal, manipulation of joints was ineffective in modifying the discharges of most interpositus neurones and, in all cases, prolonged pressure upon the skin elicited only transient responses...

Action Potentials↗
PubMed1979

Supplementary motor area in the monkey: activity of neurons during performance of a learned motor task.

1. Recordings were made of the natural discharges of neurons in the supplementary motor area (SMA) of conscious monkeys trained to perform stereotyped motor task, pulling a horizontal lever, with either hand. 2. Of the total population of cells, 80% showed modulation of their activity during particular movements of either limb. Many cells had a similar pattern of modulation regardless of whether the contralateral or ipsilateral hand was used. Of the remaining 20%, some cells were related to leg or body movements or to visual experience. 3. Cells whose activity was related to movements of distal joints were found in approximately equal numbers to those whose discharges occurred with proximal movements. 4. Only 5% of cells tested sent their axons into the pyramidal tract, and only 14% of units investigated showed responses to passive manipulation of the limbs. The effective afferent input usually was of a rather complex kind. 5. The findings suggest that the discharges of a large number of neurons in SMA are changing during particular movements of either arm, and that only a small number of cells receive peripheral afferent sensory input. These results contrast with those obtained in the primary motor area and suggest a different role for SMA in the control of movement.

Animals↗
PubMed1979

[Not Available].

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History, Modern 1601-↗
PubMed1978

Deficient influence of peripheral stimuli on precentral neurones in monkeys with dorsal column lesions.

1. Four male monkeys (M. fascicularis) were trained in a movement performance task which involved pulling a horizontal lever into a target zone and then collecting, from one of a variety of positions, a small food reward. The same animals were also trained to sit quietly and accept passive manipulation and natural stimulation of the arm and hand while remaining relaxed. 2. After complete bilateral section of the cuneate fasciculi or division of a major part of these dorsal column afferents at C1-C2 or at C5 level, the animals were still able to perform movement tasks normally. Disturbance of discrimination ability was revealed after vision was occluded it the animal was required to detect differences in texture with only a small cutaneous area in contact with the object (e.g. using only the tip of the index finger). Contactual-placing reactions could be performed in the absence of vision and the movements the animal made in these reactions were well controlled and appropriately directed. Minimal disturbance of contact placing was noticed if the surface touched was on the hand or fingers or if the reaction involved crossed placing. 3. An examination of the natural discharges of 342 percentral neurones revealed that the patterns of activity exhibited in relation to complex movements were indistinguishable from patterns recorded in normal monkeys carrying out similar tasks. 4. Discharges of ninety-one of 321 precentral neurones could be produced by appropriate natural stimuli delivered within the cell's afferent input zone at the periphery. The zone from which a given cell could be influenced was usually limited and its location could be on any part of the contralateral forelimb. However, all but nine of these responses were found in animals in which a small proportion of the cuneate fibres remained intact. In an animal with histologically proven complete section of the cuneate faciculi very few (nine of 171) precentral neurones were influenced by natural activation of peripheral receptors in the forelimb. The zones from which these few afferent inputs were found could all have been proximal to the level of the cuneate lesion. 5. The very small number of responding pre-central neurones found in an animal with complete section of the cuneate fasciculi made it likely that the dorsal columns provide the major pathway for effects from circumscribed peripheral receptors in the forelimb to influence precentral neurones. However, even in an animal with complete interruption of cuneate fibres, a proportion of post-central neurones could still be influenced by natural activation of peripheral receptors within restricted regions of the forelimb. Hence the 'sensory' cortex was still in receipt of afferent projections which could be revealted readily by the tests used. 6...

Action Potentials↗