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M Glickstein

Publications and source records attributed to M Glickstein.

At least 19 recordsLinked to original sources
PubMed2000

How are visual areas of the brain connected to motor areas for the sensory guidance of movement?

Visual areas of the brain must be connected to motor areas for the sensory guidance of movement. The first step in the pathway from the primary visual cortex is by way of the dorsal stream of visual areas in the parietal lobe. The fact that monkeys can still guide their limbs visually after cortico-cortical fibres have been severed suggests that there are subcortical routes that link visual and motor areas of the brain. The pathway that runs from the pons and cerebellum is the largest of these. Pontine cells that receive inputs from visual cortical areas or the superior colliculus respond vigorously to appropriate visual stimuli and project widely on the cerebellar cortex. A challenge for future research is to elucidate the role of these cerebellar target areas in visuo-motor control.

Animals↗
PubMed2000

Functional localisation in the cerebral cortex and cerebellum: lessons from the past.

One of the basic questions about the working of the brain is the extent to which its various functions are localised. In the nineteenth century great advances were made in the study of localisation. The control of speech, movement, and vision was identified with specific regions of the cerebral cortex. Although since the nineteenth century lesions of the cerebellum have been known to produce impaired movement, there has been rather little progress towards answering more detailed questions about the functions of the cerebellum and cerebellar localisation. The experts are still not agreed on what the cerebellum does or how and where it does it. Three examples are given of functions which probably are mediated by the cerebellum; adaptation of the vestibulo-ocular reflex, classical conditioning of the nictitating membrane response, and adaptation of saccadic eye movements. In all three cases the control of these functions has been localised to a specific region of the cerebellar cortex and/or nuclei. The success of localisation studies in the cerebral cortex can serve as a guide. Continued experimentation directed at the question of localisation should prove a fruitful approach to understanding more about the functions of the cerebellum.

Anatomy↗
PubMed2000

Whiskers, barrels, and cortical efferent pathways in gap crossing by rats.

Rats can readily be trained to jump a gap of around 16 cm in the dark and a considerably larger gap in the light for a food reward. In the light, they use vision to estimate the distance to be jumped. In the dark, they use their vibrissae at the farthest distances. Bilateral whisker shaving or barrel field lesions reduce the gap crossed in the dark by about 2 cm. Information from the barrel fields reaches motor areas via cortico-cortical, basal ganglia, or cerebellar pathways. The cells of origin of the ponto-cerebellar pathway are segregated in layer Vb of the barrel field. Efferent axons of Vb cells occupy a central position within the basis pedunculi and terminate on cells in the pontine nuclei. Pontine cells, in turn, project to the cerebellar cortex as mossy fibers. We trained normal rats to cross a gap in the light and in a dark alley that was illuminated with an infra-red source. When the performance was stable, we made unilateral lesions in the central region of the basis pedunculi, which interrupted connections from the barrel field to the pons while leaving cortico-cortical and basal ganglia pathways intact. Whisking was not affected on either side by the lesion, and the rats with unilateral peduncle lesions crossed gaps of the same distance as they did pre-operatively. Shaving the whiskers on the side of the face that retains its input to the pontine nuclei reduced the maximal gap jumped in the dark by the same amount as bilateral whisker shaving. Performance in the light was not affected. Regrowth of the shaved whiskers was associated with the recovery of the maximum distance crossed in the dark. In control cases, shaving the whiskers on the other side of the face did not reduce the distance jumped in the dark or in the light. These results suggest that the cerebellum must receive whisker information from the barrel fields for whisker-guided jumps.

Animals↗
PubMed1999

Saccadic dysmetria and adaptation after lesions of the cerebellar cortex.

We studied the effects of small lesions of the oculomotor vermis of the cerebellar cortex on the ability of monkeys to execute and adapt saccadic eye movements. For saccades in one horizontal direction, the lesions led to an initial gross hypometria and a permanent abolition of the capacity for rapid adaptation. Mean saccade amplitude recovered from the initial hypometria, although variability remained high. A series of hundreds of repetitive saccades in the same direction resulted in gradual decrement of amplitude. Saccades in other directions were less strongly affected by the lesions. We suggest the following. (1) The cerebellar cortex is constantly recalibrating the saccadic system, thus compensating for rapid biomechanical changes such as might be caused by muscle fatigue. (2) A mechanism capable of slow recovery from dysmetria is revealed despite the permanent absence of rapid adaptation.

Adaptation, Physiological↗
PubMed1999

Cerebellar lesions and prism adaptation in macaque monkeys.

If a laterally displacing prism is placed in front of one eye of a person or monkey with the other eye occluded, they initially will point to one side of a target that is located directly in front of them. Normally, people and monkeys adapt easily to the displaced vision and correct their aim after a few trials. If the prism then is removed, there is a postadaptation shift in which the subject misses the target and points in the opposite direction for a few trials. We tested five Macaque monkeys for their ability to adapt to a laterally displacing prism and to show the expected postadaptation shift. When tested as normals, all five animals showed the typical pattern of adaptation and postadaptation shift. Like human subjects, the monkeys also showed complete interocular transfer of the adaptation but no transfer of the adaptation between the two arms. When preoperative training and testing was complete, we made lesions of various target areas on the cerebellar cortex. A cerebellar lesion that included the dorsal paraflocculus and uvula abolished completely the normal prism adaptation for the arm ipsilateral to the lesion in one of the five monkeys. The other four animals retained the ability to prism-adapt normally and showed the expected postadaptation shift. In the one case in which the lesion abolished prism adaptation, the damage included Crus I and II, paramedian lobule and the dorsal paraflocculus of the cerebellar hemispheres as well as lobule IX, of the vermis. Thus in this case, the lesion included virtually all the cerebellar cortex that receives mossy-fiber visual information relayed via the pontine nuclei from the cerebral cortex. The other four animals had damage to lobule V, the classical anterior lobe arm area and/or vermian lobules VI/VII, the oculomotor region. When tested postoperatively, some of these animals showed a degree of ataxia equivalent to that of the case in which prism adaptation was affected, but prism adaptation and the postadaptation shift remained normal. We conclude that in addition to its role in long-term motor learning and reflex adaptation, the region of the cerebellum that was ablated also may be a critical site for a short-term motor memory. Prism adaptation seems to involve a region of the cerebellum that receives a mossy-fiber visual error signal and probably a corollary discharge of the movement.

Adaptation, Physiological↗
PubMed1998

Cerebellum and the sensory guidance of movement.

By the end of the 19th century the locations of the primary visual and motor areas of the cerebral cortex were well recognized. At that time it was generally assumed that for the visual control of movement visual areas must be linked to motor areas by way of a series of cortico-cortical fibres. Subsequent experimental evidence showed clearly, however, that skilled visuomotor performance is still possible after complete disconnection of interhemispheric and intracortical fibre systems. Preservation of skilled visuomotor performance after such lesions has often been thought to be mediated by ipsilaterally descending motor pathways. However, the evidence indicates that there must also be subcortical pathways that link sensory to motor areas of the brain. One such pathway involves the cerebellum. There is a massive input from cortical and subcortical visual areas to the pontine nuclei. Cells in the pontine nuclei respond vigorously to appropriate visual targets and they distribute their axonal terminals bilaterally in the cerebellar cortex. A cortico-ponto-cerebellar circuit would have remained intact in all cases in the literature in which there was complete disconnection of cortico-cortical fibres between visual and motor cortex. Lesions of the cortical sensory areas that project to the pons or interruption of the fibres within the internal capsule or basis pedunculi, that link cortical sensory areas with the pontine nuclei, can severely impair the sensory guidance of movement. This paper reviews the evidence for sensory input to the cerebellum and the possible role of a cortico-ponto-cerebellar circuit in the sensory guidance of movement.

Animals↗
PubMed1998

Visual control of the arm, the wrist and the fingers: pathways through the brain.

Sperry and his colleagues had shown that section of the corpus callosum blocks the normally strong interocular transfer of visual learning in chiasma sectioned monkeys. Although interhemispheric transfer of learning was blocked, monkeys could be readily trained to use any combination of eye and hand in a task that required rapid visually guided responses. Sperry suggested that there must be a subcortical pathway linking sensory to motor areas of the brain. We tested monkeys in a task which required them to orient their wrist and fingers correctly in order to remove a morsel of food from a slotted disc. Animals in which we made lesions of the dorsal extrastriate visual areas of the parietal lobe were profoundly impaired in performing this task, but showed no deficit in visual discrimination learning. A monkey with an extensive lesion of the ventral, temporal lobe extrastriate areas showed no deficit in the visuomotor task but was profoundly impaired in visual discrimination learning. Lesions of peri-arcuate cortex, a major cortical target of parietal lobe visual areas, produced only a mild deficit which was motor in character. We suggest that the visuomotor deficit caused by parietal lobe lesions is brought about by depriving the cerebellum of its cortical visual input.

Animals↗
PubMed1998

The anatomy of the cerebellum.

Vertebrate cerebella occupy a position in the rostral roof of the 4th ventricle and share a common pattern in the structure of their cortex. They differ greatly in their external form, the disposition of the neurones of the cerebellar cortex and in the prominence of their afferent, intrinsic and efferent connections.

Animals↗
PubMed1997

Mossy-fibre sensory input to the cerebellum.

The role of the spinal and vestibular afferents to the cerebellum in the control of movement first began to be recognized towards the end of the 19th century. By the middle of the present century it was clear that visual and auditory information are also relayed to the cerebellum from the cerebral cortex and brainstem by way of the pontine nuclei. Pontine cells project to the cerebellar cortex where they terminate as mossy fibres. The corticopontine projection arises from cells in lamina V of the cerebral cortex. Cells in the rat primary somatosensory cortex also provide an input to the basal ganglia, but the two populations are largely segregated in distinct sub-laminae. In monkeys, and probably in humans, the cortical visual input to the pontine nuclei arises from the dorsal stream of extrastriate visual areas. Experimental and clinical evidence suggest that damage to this pathway at the cortical level, or interruption of its corticopontine fibres within the internal capsule produce profound disturbance in visuomotor guidance. One of the major pathways through the brain for the visual guidance of movement is relayed from the dorsal stream of extrastriate areas to the cerebellum by way of the pontine nuclei.

Animals↗
PubMed1995

Lodewijk Bolk and the comparative anatomy of the cerebellum.

The cerebellum of mammals is histologically uniform, but it varies greatly in the relative size of its different parts. The Dutch anatomist Lodewijk Bolk studied a large series of mammalian cerebella, and put forward a general scheme of organization that can be applied to all mammals. Bolk also speculated about the functional role of different regions of the cerebellum, based on the idea that there might be a single somatotopically organized representation of the body surface on the cerebellar cortex. Although his idea of a single map is wrong, Bolk's anatomical descriptions are thorough, and his insights are profound. These descriptions formed the basis for much subsequent thinking about the structure of the cerebellum.

Anatomy, Comparative↗
PubMed1995

Subcortical origin of visuomotor apraxia.

Visuomotor apraxia (VMA) is a clinical syndrome characterized by a failure to make use of visual information when performing a target-directed movement. Visuomotor apraxia has traditionally been assumed to result from a disconnection of cortico-cortical fibres between visual and motor areas following occipito-parietal lesions. We describe a patient who developed a permanent contralesional and a temporary ipsilesional visuomotor apraxia as part of a complex neurological syndrome after a right [corrected] thalamic haemorrhage. MRI showed that the suprathalamic white matter was not involved but the most caudal fibres of the internal capsule appeared to be interrupted. To our knowledge this is the first case of a VMA with a lesion restricted to a deep subcortical area indicating that VMA can result from damage to subcortical projections rather than interruption of cortico-cortical fibres.

Aged↗
PubMed1994

Visual pontocerebellar projections in the macaque.

The cerebellum plays an important role in the visual guidance of movement. In order to understand the anatomical basis of visuomotor control, we studied the projection of pontine visual cells onto the cerebellar cortex of monkeys. Wheat germ agglutinin horseradish peroxidase was injected into the dorsolateral pons two monkeys. Retrogradely labelled cells were mapped in the cerebral cortex and superior colliculus, and orthogradely labelled fibers in the cerebellar cortex. The largest number of retrogradely labelled cells in the cerebral cortex was in a group of medial extrastriate visual areas. The major cerebellar target of these dorsolateral pontine cells is the dorsal paraflocculus. There is a weaker projection to the uvula, paramedian lobe, and Crus II, and a sparse but definite projection to the ventral paraflocculus. There are virtually no projections to the flocculus. There are sparse ipsilateral pontocerebellar projections to these same regions of cerebellar cortex. In nine monkeys, we made small injections of the tracer into the cerebellar cortex and studied the location of retrogradely filled cells in the pontine nuclei and inferior olive. Injections into the dorsal paraflocculus or rostral folia of the uvula retrogradely labelled large numbers of cells in the dorsolateral region of the contralateral pontine nuclei. Labelled cells were found ipsilaterally, but in reduced numbers. Injections outside of these areas in ventral paraflocculus or paramedian lobule labelled far fewer cells in this region of the pons. We conclude that the principal source of cerebral cortical visual information arises from a medial group of extrastriate visual areas and is relayed through cells in the dorsolateral pontine nuclei. The principal target of pontine visual cells is the dorsal paraflocculus.

Animals↗
PubMed1994

Cerebellar agenesis.

Lesions of the cerebellum produce profound deficits in movement. Since there is demonstrable recovery from partial lesions, some have asserted that the cerebellum may not be necessary for normal movement. It is even alleged that people may not manifest any motor symptoms despite total cerebellar agenesis. The literature points to a different conclusion. Cerebellar agenesis is always associated with profound motor deficits. A case of cerebellar agenesis of a man who died in 1951 is discussed. Evidence is presented that it is this case which gave rise to part of the oral tradition which alleges that normal movement is possible despite total cerebellar agenesis. In this brain an MRI scan revealed a small residual cerebellum. Moreover, despite an oral tradition to the contrary, there is absolutely no evidence about the motor capacities of this man during his life.

Adolescent↗
PubMed1992

The organisation of fibres within the rat basis pedunculi.

The organisation of corticofugal fibres within the basis pedunculi of rats was studied using wheat germ agglutinin-horseradish peroxidase as an orthograde tracer. Following cortical injections, labelled fibres were distributed within the cerebral peduncle in an orderly way. Fibres which originate from cells in the frontal cortex maintain a position in the ventromedial part of the basis pedunculi. Fibres from the occipital and temporal cortex travel in the most dorsolateral part. Somatosensory fibres travel between these two. The extent of labelled fibres within the peduncles is correlated with the relative density of corticopontine cells arising from different areas of the cerebral cortex.

Animals↗
PubMed1992

The cerebellum and motor learning.

Lesions of the cerebellum and its associated circuitry abolish or impair several types of motor learning. It is controversial whether these lesions damage the motor memory or its performance. Recent work is evaluated in the light of the original suggestions by Marr, Albus and Gilbert that the cerebellar cortex is a preferred locus for reflex plasticity and motor learning.

Afferent Pathways↗
PubMed1991

Paradoxical movement in Parkinson's disease.

Patients with Parkinson's disease, although impaired, can sometimes move effectively under visual guidance. The stimuli that often elicit such paradoxical movement are similar to those that relay visual information to the cerebellum. We suggest that many instances of paradoxical movement may be explained by the fact that the pathways relaying those visual stimuli can bypass the damaged basal ganglia and allow an intact cerebellar circuit to be used for visuomotor control.

Cerebellum↗