Munetomo Nakata

Cryptic vascular malformation of the choroid plexus

A 45-year-old man and a 47-year-old woman with cryptic vascular malformations of the choroid plexus in the lateral ventricle are reported. Each patient had an intraventricular hematoma, located in the right trigone and in the anterior part of the left lateral ventricle, respectively. The vascular lesion of one patient was angiographically visualized as find abnormal vessels communicating with the right anterior choroidal artery; in the other, angiography did not reveal the lesion. In the former patient, histological examination of the excised specimen led to a diagnosis of arteriovenous malformation; in the latter, a diagnosis of venous malformation was made. Both patients were successfully treated surgically.

Evaluation of human consciousness level by means of “automated fluctuation analysis” of high frequency electroencephalogram fitted by double Lorentzians

Since Berger’s discovery of the electroencephalogram (EEG), its analysis has been generally restricted to the visual range (upmost 100Hz) and has ignored higher frequency components. One reason should be that there are no reliable methods to distinguish the brain potentials from muscle activity. We have introduced fluctuation analysis, which is popular method especially in the field of basic physiology to clinical electrophysiology. In our previous study, it was declared that power spectral density (PSD) of human high frequency EEG was composed of double Lorentzians and vanished into white level within 1kHz. Then the purpose of this study is to elucidate the “Automated Fluctuation Analysis,” which enables us to evaluate these higher frequency components and its physiological meaning especially focused on conscious level from wakefulness to sleep stage 1. Seventy-four scalp recording EEGs in twenty normal subjects were studied. In short, “Automated Fluctuation Analysis” is made of three steps: amplification of EEG signal, A/D conversion and Fast Fourier Transform by signal processor and extraction of Lorentzian parameters. PSD of high frequency EEG was displayed on log-log graph and the algorithm fit to the following Lorentzian formula were mathematically based on Brown & Dennis. S(f)=S1/ [1+(f/fc1)2] + S2/ [1+(f/fc2)2], where S(f) is PSD (μ V2/Hz) at each frequency (f;Hz), S1 and S2 are the plateau level or zero-frequency power of the initial and second Lorentz, and fc1 and fc2 are the corner or half-power frequency of the initial and second Lorentz, respectively. As results, during wakefulness the PSD of high frequency EEG activity was composed of double Lorentzian fluctuations and the power distribution of S1 value in topographical display was frontal dominant. This pattern of S1 value disappeared and S2 value became lower during sleepiness and the second Lorentz disappeared during sleep.

Why Are Most GABA Agonists Not Effective Antiepileptic Drugs

Abstract: The role of the GABAergic system in the induction and control of seizures remains elusive despite considerable research. In this report, the action of GABA agonists and antagonists is investigated both iontophoretically and intravenously on the trigeminal nucleus model. This technique permitted us to differentiate the direct effect of these drugs on the trigeminal neurons from the action on neurons elsewhere in the central nervous system which impinge on the trigeminal neurons.

Fourier analysis of broad spectral EEG from a fluctuation point of view

It is believed that the EEG is the most reliable method of evaluating brain function, but neither quantitative nor qualitative studies of the EEG have been carried out over the entire range of frequencies. Analysis of limited frequency bands of the EEG has not disclosed the whole of neuronal activity. The aim of this study is to clarify the upper limit of EEG frequency. Our EEG analytic system is composed of a high fidelity preamplifier and signal processor with a frequency response within −3 dB below 20 kHz. Thirty adult cats were used for these experiments. The upper limit of the frequency varied in different structures: 6.9 ± 0.8 kHz (± SEM) in motor cortex, 4.1 ± 0.3 kHz in the hippocampus, 2.9 ± 0.5 kHz in the amygdala, 9.3 ± 0.6 kHz in the ventrolateral nucleus of the thalamus, and 9.9 ± 0.5 kHz in the midbrain reticular formation. Three different types of amplitude spectra were characterized in bilogarithmic graphs. These types are named types f, f + L, and L corresponding to 1/f or Lorentzian fluctuation. In conclusion, the upper limit of frequency and the spectral types correspond to the neuronal specificity of different brain regions. Their physioanatomic significance is discussed.

Afferent Connections of the Neurons in the Foreapos;s Field of H in Cat

Abstract: An anatomicophysiological analysis was made to elucidate afferent connections of the neurons in the Fores field of H (FFH) by horseradish peroxidase retrograde tracing technique and by evoked potential technique. 1) The FFH neurons receive fibers from the neocortex (layer V) and brainstem reticular formations. 2) Physiological projections from the mesencephalic reticular formation to the FFH as well as to the motor cortex were ipsilateral, but those from the pons and medulla oblongata were bilateral. 3) These data will suggest that the FFH neurons are in junction of the corticoreticular connections and play an important role in the maintenance of an epileptic excitability of the neocortical system as suggested by Jinnai and Mukawa.

Histological Changes of the Brain by Experimental Extradural Compression

This experimental study was designed to clarify the effects of long-standing brain compression.