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R S Dow

Publications and source records attributed to R S Dow.

At least 19 recordsLinked to original sources
PubMed1993

Cognitive and language functions of the human cerebellum.

Traditionally, the human cerebellum has been regarded as a motor mechanism, but this view of its function is being challenged by a growing body of data on the non-motor functions of the cerebellum. Some of these data are presented in this article, which reviews neuroanatomical, neuroimaging and behavioral reports of cerebellar involvement in cognitive and language functions. The article proposes that this functional expansion is a consequence of specific cerebellar structural changes that evolved during hominid evolution and that could have been a prerequisite for the evolution of human language.

Cerebellum↗
PubMed1991

The human cerebro-cerebellar system: its computing, cognitive, and language skills.

In this review of the human cerebro-cerebellar system, the focus is on the possible contributions of the cerebellum to cognitive and language functions. The role of the cerebellum in these human functions has tended to be obscured by the traditional preoccupation with the motor functions of the cerebellum, which have been widely observed in other vertebrates as well. In the human brain, some phylogenetically new parts evolved and enlarged in the cerebellum, concomitantly with the enlargement of association areas in the cerebral cortex. Anatomical evidence and behavioral evidence combine to suggest that this enlarged cerebellum contributes not only to motor function but also to some sensory, cognitive, linguistic, and emotional aspects of behavior. The anatomical evidence derives from the modularity of the cerebellum, whose cortical nerve cells are organized into longitudinal micro-modules, which are arrayed perpendicular to the cortical surface and parallel to each other. The number of these micro-modules increased when the cerebellum enlarged, which enlarged the computing capabilities of the network. (From principles underlying the processing of information, it is known that when modules with modest processing capabilities are assembled in large numbers in parallel, the resulting network can achieve remarkably powerful computing capabilities.) Such cerebellar computing capabilities can be utilized in the different areas of the cerebral cortex to which the cerebellum sends signals. The cerebellar output connections convey signals through the thalamus to the cerebral cortex in segregated channels of communication, which preserve the modularity of the cerebellum. Through these channels, modules in the lateral cerebellum can send signals to new cognitive and language areas of the cerebral cortex, such as Broca's area in the prefrontal cortex. The anatomy of the human cerebro-cerebellar system therefore suggests that the cerebellum can contribute to the learning not only of motor skills but also of some cognitive and language skills. Supporting this anatomical evidence is the mounting behavioral evidence, obtained both in normal brains and in clinical studies, which indicates that the lateral cerebellum is indeed involved in some cognitive and language functions.

Brain↗
PubMed1989

Stance dependence of automatic postural adjustments in humans.

This study investigated the effect of initial stance configuration on automatic postural responses in humans. Subjects were tested in both bipedal and quadrupedal stance postures. The postural responses to horizontal translations of the supporting surface were measured in terms of the forces at the ground, movement of the body segments, and electromyographic (EMG) activity. Postural responses to the same perturbations changed with initial stance posture; these responses were biomechanically appropriate for restoring centre of mass. A change in stance configuration prior to platform movement led to a change in both the spatial and temporal organization of evoked muscle activation. Specifically, for the same direction of platform movement, during bipedal stance muscles on one side of the lower limb were activated in a distal to proximal sequence; during quadrupedal stance, muscles on the opposite side of the lower limb were activated and in a proximal to distal sequence. The most significant finding was an asymmetry in the use of the upper limbs and the lower limbs during postural corrections in quadrupedal stance. Whereas antagonists of the upper limb were either co-activated or co-inhibited, depending on the direction of translation, lower limb antagonists were reciprocally activated and inhibited. Human subjects in a quadrupedal stance posture used the lower limbs as levers, protracting or retracting the hips in order to propel the trunk back to its original position with respect to the hands and feet. Postural responses of the subjects during quadrupedal stance were remarkably similar to those of cats subjected to similar perturbations of the supporting surface. Furthermore, the same predominance of lower limb correction is characteristic of both species, suggesting that the standing cat is a good model for studying postural control in humans.

Adult↗
PubMed1989

Reappraising the cerebellum: what does the hindbrain contribute to the forebrain?

Although the cerebellum has traditionally been regarded as a motor mechanism, recent behavioral evidence indicates that the human cerebellum is involved in a wider range of functions: in learning, in planning, in judging time, in some emotional and cognitive disorders such as autism, and in some normal mental activities such as the cognitive processing of words. This evidence suggests that the traditional view of cerebellar function now needs to be reassessed and enlarged to include nonmotor as well as motor functions in the human brain. Whereas the cerebellar connections to frontal motor areas enable the cerebellum to improve motor skills, cerebellar connections to adjacent association areas of the prefrontal cortex can enable the cerebellum to improve mental skills, and cerebellar connections to Broca's area can enable the cerebellum to improve language skills.

Animals↗
PubMed1988

Contribution of electrophysiological studies to cerebellar physiology.

Electrical stimulation and the recording of electrical potentials have made important contributions to the classic formulations of cerebellar function. These electrical methods also have contributed to a re-appraisal, now underway, of the cerebellar role in the human brain. Beyond its accepted role in motor function, the cerebellum seems to contribute to some nonmotor functions. It is now known to communicate with the prefrontal cortex as well as with the motor cortex of the frontal lobe, and it seems to be involved in some prefrontal cognitive and language functions as well as in motor function. Investigations of cerebellar involvement in such functions are now being carried out, with encouraging results. If confirmed by further clinical evidence, this broader concept of cerebellar function would explain the mystery of why the most lateral parts of the cerebellum enlarged dramatically in the human brain, concomitantly with the enlargement of the cerebral association areas.

Adult↗
PubMed1987

Cerebro-cerebellar learning loops in apes and humans.

In the cerebro-cerebellar system of anthropoid apes and humans, the cerebellum seems able to contribute not only to motor skills but also to mental and language skills. Anatomical evidence suggests that in these species the cerebellum can function at two different hierarchical levels. At a lower level, the cerebellum can supply signals to the frontal motor areas for effecting the manipulation of muscles. At a higher level, the cerebellum can supply signals to some prefrontal areas for effecting the manipulation of symbols. At both levels, the cerebellum can function in essentially the same way: when incoming information is processed repeatedly in the neural loops in which the cerebellum is embedded, the cerebellum can learn to generate new sequences of signals, which constitute new programs for carrying out learned procedures. If cerebellar programs are used in the frontal motor areas (area 4 and are 6), motor manipulations can be effected rapidly and skillfully. Similarly, if cerebellar programs are used in some prefrontal areas (e.g., area 8 and the inferior frontal convolution), mental and language manipulations could be effected rapidly and skillfully. The cerebellum, in its contributions to these mental and language functions, as in its contributions to motor function, could serve as an adaptive mechanism whose signals enable the frontal cortex to execute learned procedures optimally. In the absence of such cerebellar signals, the frontal cortex would have to perform these procedures less rapidly and fluently. Modern testing techniques can reveal such a subtle difference in performance. These techniques are therefore now being used to test human subjects, in an attempt to validate or refute this broadened concept of cerebellar function. If the new concept is validated, it can provide powerful explanations for some unresolved mysteries about the human brain.

Animals↗
PubMed1986

Does the cerebellum contribute to mental skills?

Although it has been known for half a century that unique structures evolved in the cerebellum of anthropoid apes and became greatly enlarged in the human brain, the function of these structures still remains unknown. In an attempt to explain their function, a new concept of cerebellar capabilities is proposed, which is based both on neural evidence and on information-processing theory. The phylogenetically newest structures of the cerebellum may contribute to mental skills in much the same way that the phylogenetically older structures contribute to motor skills. In both cases, the cerebellum can send signals from the dentate nucleus to the cerebral frontal cortex via the thalamus. Signals from the older part of the dentate nucleus certainly help the frontal motor cortex to effect the skilled manipulation of muscles, and signals from the newest part of the dentate nucleus may help the frontal association cortex to effect the skilled manipulation of information or ideas. How such mental skills could have evolved in higher primates in the course of phylogenetic and ontogenetic development is shown. The validity of this new concept of cerebellar function can be tested on humans by means of tomographic brain scans.

Animals↗