Bunichi Fujimori

EFFECTS OF BRAIN-STEM STIMULATION UPON HIPPOCAMPAL ELECTRICAL ACTIVITY, SOMATOMOTOR REFLEXES AND AUTONOMIC FUNCTIONS.

Abstract In order to understand better the functional significance of hippocampal electrical activity, an attempt has been made to relate its changes with those of somatomotor, sudomotor and vasomotor activities. Experiments were conducted with locally anesthetized cats under Flaxedil. The animals were bilaterally vagotomized in the study of blood pressure. Four types of hippocampal electrical responses to the stimulation of various subcortical brain structures were observed. 1. 1. “Synchronization” (produced by the stimulation of the medial preoptic area, the medial hypothalamic region and the dorsolateral part of the midbrain tegmentum) was associated with facilitation of the monosynaptic gastrocnemius and mono- as well as polysynaptic peroneal reflexes, elevation of blood pressure and facilitation of skin potentials. 2. 2. “Desynchronization A” (elicited by the stimulation of the amygdala and the lateral preoptic area) was associated with inhibition of the gastrocnemius and peroneal reflexes, and depression of blood pressure. The skin potentials could be facilitated with strong stimulation. 3. 3. “Desynchronization B” (elicited by the stimulation of the bulbar ventromedial reticular formation) was associated with inhibition of the gastrocnemius and peroneal reflexes, skin potentials and elevation of blood pressure. However, depression of the latter was obtained after Nembutal administration. 4. 4. “Intermediate response” (elicited by the stimulation of the posterolateral hypothalamic region and the preoptic area) was associated with facilitation of the peroneal reflexes and of the skin potential, and with inhibition of the gastrocnemius reflex. Blood pressure, elevated in the absence of anesthesia, was depressed after Nembutal administration. In view of these experimental results, it is suggested that the slow wave components of hippocampal electrical activity might have a close relationship with somatomotor and vasomotor activities.

Analysis of the electroencephalogram of children by histogram method.

Abstract For the quantitative expression of slow activity of the EEG, the writers analysed the EEGs of 87 children by analyser and histogram methods and two of these EEGs were also analysed by the mathematical method. The histogram method was also applied to the study comparing EEGs of children having sign of some neuropsychiatric condition with those of normal ones and its clinical usefulness was assessed. 1. 1. An Offner type 830 analyser was used and the quantification of each band (delta, theta, alpha and beta) activity was achieved by calculating the percentage of total voltage of the band, that is, the percentage of the square root of the squared sum of every deflection in the band. Although this method of analysis is the most advantageous, there remain some theoretical and technical problems to be solved. 2. 2. The mathematical method of analysis is the most rational one. However, its procedure is too tedious for practical use. The results of these two methods of Fourier analysis (analyser and mathematical methods) coincided fairly well with one another, but the results of these two methods were somewhat different from our impression gained from original record by visual inspection, as slow components were rather emphasized. 3. 3. In the histogram method, standards to measure amplitude and period of each wave were provided in order to exclude subjective criteria. The results of this analysis were to us the most easily understandable ones, as they were the most similar to what is obvious by visual inspection. The procedure of this analysis is rather laborious, but it was found that allowing for 5 per cent error, 20 sec. could appropriately be used instead of 1 min. as the period of analysis. 4. 4. EEGs of 95 mentally deficient Junior High School boys and girls (I.Q. below 80) ranging in age from 13 to 17 years were recorded and 83 EEGs which did not show any specific wave such as “spikes” were analysed by the histogram method in comparison with EEGs of 30 normal Junior High School boys ranging in age from 13 to 15 years. In general, the percentage of slow bands in mentally deficient children were larger than those in normal children and in 47.0 per cent of 83 EEG records from parietal regions, the slow band percentages were abnormally large. The histogram method was also applied to the EEGs of 27 children who suffered from encephalitis japonica and it was found that there existed a fairly good correlation between the percentage of the delta band and the seriousness of the disease. From these results, it may therefore be said that the histogram method is applicable in clinical practice, although it has no theoretical basis.

Exaggeration of knee-jerk following spinal hemisection in monkeys

In 18 monkeys ipsilateral flaccid hemiplegia of the hind-limb was produced by spinal cord hemisection at T8. As a result of systematic observations of various phenomena subsequent to the hemisection for several months, it was found that an ipsilateral marked exaggeration of the knee-jerk gradually developed in 2--3 weeks after the infliction, along with slight atrophy of the hind-limb muscles on the same side. The exaggeration reached a maximum in about 6 weeks and persisted thereafter for several months until the final experiments. The exaggeration of knee-jerk was confirmed by measuring quantitatively photographed trajectories of a small lamp attached to the malleolus, a specially devised hammer being used. The trajectories showed larger amplitudes, shorter rise times and lower thresholds on the hemisected side. Achilles tendon reflex was also observed to be hyperactive. However, there was no evidence of other pathological phenomena such as clonus or Babinskis sign in the present experiment. It was noted that total spinal cord transection one segment below the hemisected site did not abolish the exaggeration of knee-jerk. Another noticeable finding was that quadriceps afferent volleys picked up from the L6 dorsal root following tendon taps were smaller on the hemisected side, in spite of the fact that distinct augmented reflex potentials were observed in the ipsilateral L6 ventral root. These results strongly suggest that the exaggeration of knee-jerk was not induced by a release from tonic supraspinal inhibition nor by augmented quadriceps afferent volleys, but by some neural mechanisms which developed gradually within the lumbo-sacral segments below the hemisected site.

Fast activities and DC potential changes of the cerebral cortex during EEG arousal response

Abstract A quantitative analysis of alpha blocking in seven normal men and of EEG arousal response in 39 cats was made in association with DC potential changes in order to investigate the mechanisms underlying these phenomena. 1. 1. In the alpha blocking, statistically significant decreases not only in α (8–13 c/sec) band but also in θ (4–8 c/sec), β 1 (13–20 c/sec) and β 2 (20–30 c/sec) bands were found irrespective of the intensity of stimulation. 2. 2. Fast activities ( β 2 and β 3 increased in the EEG arousal response induced by strong electrical stimulation as well as by i.v. administration of adrenaline or acetylcholine; no significant change in the fast activities was observed in the EEG arousal response produced by weak electrical stimulation nor, in chronic experiments, following acoustic stimulation. 3. 3. The maximal value of the fast activities and of the largest amplitude of DC potential changes were obtained with stimulation of about 50/sec frequency. 4. 4. There did not seem to be any correspondence between the fast activities and DC potential changes during the EEG arousal response. This would suggest the existence of different mechanisms for these two phenomena.