Robert S. Dow

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.

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 Brocas area can enable the cerebellum to improve language skills.

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 Brocas 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.

The influence of the cerebellum on experimental epilepsy

Abstract The cerebellar influence on the cobalt experimental epilepsy has been investigated in unrestrained, unanesthetized rats by stimulation, total removal and temporary cooling of the cerebellum. Cerebellar stimulation generally provoked inhibition of the epileptic waves produced in the brain by cobalt application and depressed the sensory responses in the cerebral cortex. The occasional reversed facilitatory effects of the stimulation are discussed in the light of other peculiar effects of cerebellar stimulation. Total ablation of the cerebellum induced in epileptic rats a hypersynchrony of the background activity of the electrocorticogram and enhanced the clinical and electrocortical manifestations of experimental epilepsy in the unanesthetized rat. A similar tendency to hypersynchrony was occasionally seen in normal rats. The temporary cooling of the cerebellar surface in the unanesthetized, noncurarized rat produced a reversible increase in the spontaneous and sensory activated epileptic manifestations.

The production of cobalt experimental epilepsy in the rat

Abstract Metallic cobalt powder applied to the cerebral cortex of the rat is a consistently effective method of producing a chronic epileptic discharging focus in this species. The ECoG changes consisted of slow waves, sharp waves and spikes and their climax was often accompanied by clonic movements of body musculature. Audio- and photostimulation enhanced both clinical and ECoG manifestations. Possible mechanisms for the epileptic activity of this substance are discussed in the light of the histological changes which are described in detail.

Effects of cerebellar stimulation on cobalt-induced epilepsy in the cat.

Abstract The occurrence of clinical and electrographic focal seizures following cobalt lesions in the contralateral sensori-motor cerebral cortex in the cat has been confirmed. Cerebellar cortical stimulation in the cat was not as effective in influencing these seizures as was cerebellar stimulation in the rat. If an influence was to be seen, it was most apt to be in initiating a seizure. This could occur either during or at the termination of stimulation. If cerebellar cortical stimulation was applied during a seizure, the latter was usually prolonged (but only seen when the stimulus rate was less than 10/sec). Midline cerebellar stimulation sites were more effective than were those located in the hemispheres. Of all areas studied, the pyramis (VIII A) was the stimulus site with the greatest probability of activating a cortical seizure focus. Stimulation of lobulus simplex (VI) seemed most apt to prolong the seizure activity. What evidence is available at this time suggests that the influence of the cerebellum on cobalt experimental epilepsy is more likely to be mediated by way of the reticular activating system rather than via the dentate thalamic projection system.

INFLUENCE OF THE LABYRINTH ON UNITARY DISCHARGE OF THE OCULOMOTOR NUCLEUS AND SOME ADJACENT FORMATIONS.

Abstract The unitary discharge of the oculomotor nucleus and other adjacent mesencephalic formations was recorded in guinea pigs following caloric stimulation of the labyrinth. The oculomotor units usually responded to the vestibular stimulation with rhythmical discharges. The outbursts were separated by periods of total inhibition of the electrical activity. The rhythmical discharges were designated as “quick” or “slow” responses, depending on the duration of each single outburst. Less frequently, labyrinthine stimulation elicited a long-lasting increase in the discharge rate of the oculomotor units (up to 50/sec) with recruitment of new units, which was designated a “continuous activation”. About two-thirds of the units located in the gray substance ventral to the aqueduct, in the reticular formation and in the red nuclei responded to vestibular stimulation with a continuous activation. One-third of the recorded units showed the rhythmical responses, which were also obtained from the medial longitudinal fasciculus. Simultaneous recording of the mesencephalic unitary discharge and the electrical activity of a few fibers of the ipsilateral oculomotor nerve permitted the investigation of the relationship of the nuclear responses to the phases of the eye nystagmus and ocular deviations.

Microelectrode recording of cerebellar and cerebral unit activity during convulsive afterdischarge.

Abstract Cerebellar unitary discharge has been recorded with microelectrodes from cerebellar cortex and nuclei before, during, and after different convulsive patterns induced in curarized rats by electrical stimulation of the brain, by intraperitoneal injection of convulsant drugs (Megimide or Metrazol), and by anoxia. It has been compared simultaneously with the electrical activity of the cerebral cortex (sensorimotor area) recorded either with microelectrodes or with concentric electrodes. Low-voltage, single or repetitive stimulation of sensorimotor area are incapable of modifying the cerebellar unitary discharge. They show an increase in frequency only after strong single shocks or repetitive cerebral stimulation. During anoxia the cerebral units show an acceleration after a short latency and afterwards they become silent. The cerebellar units also show an increase in frequency of discharge but they usually continue to be active even when the cerebrum is silent. After injection of convulsant drugs, such as Megimide and Metrazol, the cerebellar units exhibit first an acceleration of discharge at a time when the electrical activity of the brain is still normal. At a significantly later time the rate of discharge of cerebral units also increases. In some cases each high-voltage slow wave of the cerebral cortex is accompanied by an increase in the frequency of discharge of the cerebellar units. During the clonic period of the convulsive activity the cerebellar units are depressed but they begin to discharge again after the end of the seizure when the cerebral units are totally silent. The cerebellum may actively inhibit cerebral seizure activity.

The role of the cerebellum in the human brain

In replying to the commentaries on our article, we start by recapitulating our proposal about the evolution of human language. How this human language capacity, unique in the animal kingdom, was able to evolve in the brain has not yet been adequately explained 1. Its evolution required that the brain perform rapidly both the motor and cognitive processing that underlie fluent speech. Both such processes can be performed by the models of the cerebellum that we discuss now. On the basis of this modeling, we propose that the evolution of cerebellar capabilities in the human brain could have been a prerequisite for the evolution of human language.

Failures and Successes in a Stroke Program

The activities toward stroke prevention and improving stroke care at Good Samaritan Hospital and Medical Center of Portland, Oregon, for the past ten years are described. The program was multifaceted and included a stroke clinic, a stroke care unit, a course for nurses from throughout the state of Oregon and southwestern Washington, panel discussions and exhibits about stroke care, an educational program for families of stroke patients and satellite clinics at two small communities in Oregon. The presence of this program changed the percentage of patients with strokes of equal severity going home from 13% to 58% at Good Samaritan Hospital and Medical Center and no similar trend could be detected in five other hospitals in Portland during a comparable period. The evaluation of the program revealed that a team approach to stroke care in a special unit improved the care of stroke patients throughout the hospital and was effective in bringing the family into an active role in rehabilitation and patient care. The program also achieved educational goals.