E.A. Spiegel

Stimulation of Forel's field during stereotaxic operations in the human brain

Abstract 1. 1. Increase or depression of Parkinson tremor may appear on stimulation of the prerubral area; this may be due partly to stimulation of pallidofugal fibers and partly of cerebello-rubro-thalamo-pallidal and of corticofugal fibers that pass through, or synapse in, the field H. 2. 2. Close to the prerubral field there are, in the human brain, cell groups or fibers of the cranial part of the oculomotor nucleus innervating the internal rectus muscle. 3. 3. Various vegetative effects were observed on stimulation of the field H: changes of the pupil, of the vasomotor system, of the heart rate and EKG, and appearance of a galvanic skin reaction. Apparently, hypothalamofugal fibers are stimulated; the participation of indirect stimulation of the hypothalamus cannot be excluded. 4. 4. Cortical recruitment responses could also be elicited; they are apparently chiefly due to stimulation of reticulo-thalamic fibers. A surface positive deflection may precede in records from the frontal lobe and is explained by stimulation of cerebello-rubro-thalamic fibers. 5. 5. This study shows the complexity of Forels field H that contains various systems of different physiologic significance.

Supersensitivity of the sensory cortex following partial deafferentation ☆: Lesion of the ventral posterior thalamic nuclei

Abstract 1. 1. The loss or diminution of the spontaneous electrical discharges of the sensory cortex following lesions or destruction of the ipsilateral ventral posterior thalamic nuclei is often only transitory (experiments in cats). It may be followed by a tendency to periodic burst discharges or by a continuous activity of increased amplitude that may be subject to spontaneous fluctuations. 2. 2. The development of a hypersensitivity of the respective cortical area to toxins such as Mecholyl or Metrazol could be demonstrated. Mecholyl may accentuate an existing or bring to light a latent assymetry of the spontaneous discharges and/or the tendency to burst discharges. 3. 3. Stimulation of sensory nerves (ulnar, sciatic) is still able to elicit evoked potentials (secondary responses of Forbes) in the sensory cortex deprived of its connections with the ventral posterior thalamic nuclei. On bilateral peripheral stimulation with single shocks, one notices that the secondary response is more pronounced in the sensory area corresponding to the thalamic lesion than in the opposite cortex; this difference becomes more marked under the effect of Mecholyl. 4. 4. These findings may have a bearing upon the development of pain and hyperpathia in cerebral lesions extending into the white matter below the sensory cortex.

Cortical responses to rotation. I. Responses recorded after cessation of rotation.

Averaged cortical responses to labyrinthine stimulation induced by sudden cessation of single rotations were studied using a Mnemotron Computer of Average Transients. Following rotation there appeared in cats with the eyelids closed diffuse, slow, sometimes multiphasic responses. They were probably due to excitation of the diffuse thalamic system. In human subjects similar responses could be obtained either diffusely or prevalent or exclusively from the preoccipital and/or parastriate area. The responses observed in posterior parts of the cerebral hemisphere following cessation of rotation appeared also, if the animals were flaxedilized, or the second somatic sensory area was ablated in both hemispheres. Bilateral labyrinthectomy abolished these responses. While the observation of the ocular reactions to labyrinthine stimulation permits one to ascertain the excitability of the vestibulo-ocular reflex arc only, the recording of the cortical responses to rotation may perhaps be developed into a clinical too...

Electrographic study of thalamic impulses to the striatum and pallidum.

Abstract 1. 1. Electrographic studies show that multiple thalamic impulses reach the caudate nucleus and/or globus pallidus. These findings indicate a close relationship between the functional state of the thalamus and that of the striopallidum. 2. 2. Ablation of the frontal lobe or large lesions in the head of the caudate nucleus do not prevent the appearance of pallidal reactions on thalamic stimulation. 3. 3. Possible implications of these findings for the physiopathology of the basal ganglia are discussed.

Convulsions in tuberous sclerosis controlled byelimination of impulses originating in the basal ganglia

Summary Control of major and minor seizuresin a 10-year-old boy with tuberous sclerosis is reported. In conjunction with roentgenographic studies a striatal focus was located by depth electroencephalography, and circumscribed lesions were produced in this area and the corresponding ansa lenticularis. The recording as well as the coagulating electrodes were inserted by means of the steroencephalotome. The practical and theoretical implications of these observations are discussed.

The effect of bulbocapnine upon the spontaneous electric activity of the brain and its reactivity to afferent stimuli

Abstract 1. 1. In catalepsy producing doses bulbocapnine has a slight depressive effect upon the electric activity of the cerebrum, that may be detected in the prosencephalon, diencephalon and mesencephalon. It affects chiefly the fast activity. Only occasionally slow waves or transitory excitatory states were seen with the doses used. 2. 2. In the cataleptic state the reactivity of the cortex and various subcortical areas (hypothalamus, reticulate substance of the midbrain, cerebellar cortex) to afferent impulses is preserved, or even increased. 3. 3. Simultaneous recordings from cortex and various subcortical areas reveal rather variable differences in the degree in which these regions may be affected, indicating that some degree of independence of the functional states of these regions may exist.

The striatoamygdaloid system

Abstract Using a Computer of Average Transients, it could be shown in cats that repeated stimulation of the caudate nucleus was able to elicit responses in the amygdala. These responses persisted despite extensive lesions of the globus pallidus, septum, nucleus ventralis anterior thalami or degeneration of the corticofugal fibers originating in the frontal lobe and motor area. They were abolished by coagulation around the tip of the stimulating electrode. The experiments suggest a functional relationship between the striatum and parts of the limbic system.

Stimulation and elimination of the anterior thalamic nuclei in man and cat

Summary1. Stimulation of the anterior nucleus in anesthetized cats and man induces slowing or arrest of respiration. The effect upon the blood pressure in cats is variable, though a depressor effect is frequently observed.2. Stimulation of the anterior nucleus in unanesthetized cats produces a “reaction of alertness” (the head is raised, the eyes are opened, the animal looks around and starts to walk), probably by activating hypothalamic mechanisms.3. These reactions persist in cats after ablation of the cingular gyrus and of the fornix.4. The inhibition of respiration observed on stimulation of the cingular gyrus is not prevented by elimination of the anterior nucleus. Efferent impulses from the cingular gyrus seem to reach the lower centers partly by a pathway coursing outside the anterior nucleus and partly by fibers synapsing in this nucleus.5. Bilateral lesions of the anterior nuclei in cats produce a brief state of catalepsy followed by a transient period of reduced reactivity to threatening or painful stimuli.

The influence of stimulation of the hypothalamus and of the dorsomedial nucleus upon experimental bradykinesia and akinesia.

Abstract In an attempt to analyze mechanisms able to counteract bradykinesia and akinesia, alumina cream was injected into the caudate nucleus of cats, a procedure able to produce initially a marked slowing and eventually nearly complete cessation of spontaneous movements. In various stages following the alumina cream injection, the hypothalamus or the dorsomedial nucleus were stimulated through previously implanted electrodes. Such stimulations were able to increase the speed of the locomotor activity or to initiate locomotion in catatonic animals. Electrocoagulation around the foci of stimulation prevented such effects. Lesions of the dorsomedial nuclei, however, prevented the effect of hypothalamic stimulation only if relatively low voltages were used.

Cortical Responses to Rotation II.: Responses Recorded at the Onset of Rotation from the Second Somatic Sensory and Posterior Areas

Using a Mnemotron computer a method has been developed permitting one to study in cats the cortical responses appearing when angular acceleration is started. According to this method the entrance of labyrinthine impulses is not restricted to the second somatic sensory area (S2) but extends posteriorly, chiefly into parts of the auditory cortex and into the so-called association cortex (gyrus suprasylvius medius). At least in some of the experiments the anterior part of the gyrus ectosylvius posterior and the posterior corner of the gyrus suprasylvius medius (part of the second visual area) showed responses of relatively short latency. General muscle paralysis or bilateral ablation of S2 did not prevent such responses in posterior parts of the hemisphere, while bilateral labyrinthectomy abolished them.