On chronological changes in the basic EEG rhythm in persons with Down syndrome - with special reference to slowing of alpha waves

The authors tried to know specificity of aging in persons with Down syndrome (DS) from the aspect of electroencephalograph (EEG) frequency changes through the cross-sectional and longitudinal studies, in comparison with normal persons as well as those with mentally retardation except the Down syndrome (non-DS MR). Subjects for a cross-sectional study were 265 persons with DS, 242 with non-DS MR and 239 healthy persons, and subjects for a follow-up study were 28 persons with DS and 14 with non-DS MR, whose EEGs were recorded repeatedly once a year during 8 or 9 years. Resting EEGs from the frontal, central and occipital regions were examined through power spectrum. In the cross-sectional study, the number of subjects with DS who showed dominant component within 8 Hz band of the basic rhythm reached maximum in its appearance rate at 40-44 years of age in the occipital area, but this slowing progressed already at 30-34 years of age. While in non-DS MR, the number of subjects who showed dominant component at 8 Hz reached maximum at 45-49 years of age, and this slowing of the basic rhythm was not so clear as in DS. In the follow-up study for subjects with DS, although the lowering in EEG frequency to 8 Hz took place in various years of age individually, earlier distinct decrease of the frequency was commonly noticed. These earlier steep lowering of EEG frequency was discussed in relation to the senile signs and to the decline of brain function referring to Alzheimer disease.

Brain stem neural mechanisms for vocalization in decerebrate cats

In order to characterize the brain stem circuitry that produces vocalization, the activities of brain stem respiratory neurons were recorded extracellularly during vocalization induced by electrical stimulation of the periaqueductal gray in decerebrate cats. After the onset of stimulation, the respiratory rhythm ceases, and a preparatory inspiration is induced. Following this initial inspiration, vocalization characterized by increased activities of the intrinsic laryngeal adductor and the major expiratory muscles is induced. During vocalization, most of the dorsal respiratory group inspiratory neurons increase their firing rates in phase with an increase of diaphragm activity. Inspiratory neurons with a continuous discharge pattern in the rostral ventral respiratory group increase their firing rates to augment intrinsic laryngeal abductor motoneurons and bulbospinal inspiratory neurons in the dorsal respiratory group. On the other hand, most of the bulbospinal augmenting expiratory neurons in the Bötzinger complex cease firing just after the onset of periaqueductal gray stimulation for the remainder of the stimulation period. These results indicate that at least some part of the coordinated activations of intrinsic laryngeal and respiratory muscles during vocalization are mediated via the central respiratory neurons that produce breathing.

Preliminary study on the effect of rocking on activities of persons with severe mental and physical handicaps

In this preliminary observation, a group of seven mentally and physically handicapped persons of chronological ages ranging from 15.4 yr. to 26.8 yr. experienced 15 sec. of physical rocking. For the further analysis, the poststimulus periods were classified into either those when the subjects' spontaneous head, mouth, and body movements had increased from the prestimulus period or those decreased. The median heart rates recorded in the poststimulus period were not significantly different from those in the prestimulus period on trials on which there was an observable increase in the rates of spontaneous head, mouth, and body movements; however, the median heart rates decreased during those trials on which a decrease in the rates of the movements occurred. Since it is said that rocking heightens arousal of persons with mental and physical handicaps, it is suggested that spontaneously emitted, aimless head, mouth, and body movements attributed to low arousal were reduced by heightened arousal rather than by a decline in participants' activities.

The augmentation of intrinsic laryngeal muscle activity by air-jet stimulation of the nasal cavity in decerebrate cats

The purpose of this study was to examine the functional roles of nasal afferents in modulating the activity of the intrinsic laryngeal muscles. The electromyographic activities of the intrinsic laryngeal muscles and major respiratory muscles were recorded in cats during nasal air-jet stimulation. The activities of brainstem respiratory neurons were also recorded to determine which neurons transmit nasal afferent signals to the intrinsic laryngeal motoneurons. These axonal projections were identified by antidromic activation evoked by stimulation to the spinal cord at C4 level and the laryngeal nerve. The length of the respiratory cycle was prolonged and the diaphragmatic activity was decreased during air-jet stimulation of the nasal cavity. In contrast, the activities of both the intrinsic laryngeal adductor and abductor muscles were increased. Examination of the laryngeal reflexes revealed increase in the activities of intrinsic laryngeal motoneurons during both respiratory phases. Most of the respiratory neurons recorded decreased their peak firing rate during air-jet stimulation, reflecting decreased diaphragmatic activity; however, the peak firing rate of the bulbospinal expiratory neurons in the portion of the ventral respiratory group caudal to the obex did not decrease during stimulation. These findings demonstrate the nasal air-jet stimulation decreases the activities of major inspiratory muscles in order to avoid inspiration of foreign bodies into the nasal cavity and augments the activities of intrinsic laryngeal muscles, enabling prompt elicitation of the laryngeal airway reflex. Our findings also suggest that the nasal afferents suppress the major inspiratory activities by way of brainstem inspiratory neurons, but that the activities of intrinsic laryngeal muscles are controlled through undetermined pathway(s) other than the pathway through respiratory neurons.

Lombard reflex during PAG-induced vocalization in decerebrate cats

The Lombard reflex occurs when a speaker increases his vocal effort while speaking in the presence of ambient noise. The purpose of this study was to clarify whether the Lombard reflex can be evoked during controlled vocalization in an animal model. In decerebrate cats, repetitive electrical stimulation was applied to the midbrain periaqueductal gray (PAG) to evoke vocalization. Pure tone auditory stimulation was delivered through a loudspeaker. The activities of the laryngeal adductor muscle, diaphragm and external oblique abdominal muscle and the voice intensity were measured during PAG stimulation, in the presence and absence of the auditory stimulation. To clarify the effects of the auditory laryngeal reflex on the activity of laryngeal adductor motoneurons, the amplitude of the laryngeal reflex evoked by single shock stimulation of the superior laryngeal nerve was also measured during respiration, in the presence and absence of auditory stimulation. The sound made by the cats due to PAG-induced vocalization was augmented by exposure to auditory stimulation, and the activities of the laryngeal adductor muscle and external oblique abdominal muscle were also augmented. During respiration, auditory stimulation also increased the amplitude of the laryngeal reflex evoked in the laryngeal adductor muscle. These results demonstrate that the essential neuronal mechanisms for evoking the Lombard reflex exist within the brainstem.

Functional role of ventral respiratory group expiratory neurons during vocalization

The activities of expiratory neurons of the caudal ventral respiratory group (cVRG) (n = 31) were recorded extracellularly during vocalization in unanesthetized, decerebrate cats. Vocalization was induced by electrical stimulation (0.2 ms, 20-80 microA, 100 Hz, lasting for 2-5 s) of the periaqueductal gray (PAG). The firing rates of more than two-thirds of the neurons (24/31) increased during periods of vocalization induced by stimulation of the PAG, with an increase in abdominal muscle activities. The axons of most of these neurons (19/24) projected to the contralateral lumbar spinal cord, and one-third of the bulbospinal neurons (6/19) were orthodromically activated by stimulation of the PAG. Even after sectioning of the axons of bulbospinal cVRG neurons by midsagittal lesion between the obex and the C1 spinal cord, stimulation of the PAG still induced adduction of the vocal cords and vocalization. However, activities of abdominal muscles during vocalization were abolished. These results indicate that the efferent signals for vocalization from the PAG may be relayed at the cVRG neurons and converted into adequate activation of these neurons, contributing to the activation of the abdominal muscles for vocalization.

Activities of expiratory neurones of the Bötzinger complex during vocalization in decerebrate cats

Repetitive electrical stimulation of the midbrain peri-aqueductal grey (PAG) terminates quiet breathing and initiates inspiration that precedes vocalization. To understand the neuronal mechanisms underlying this phenomenon, activities of expiratory neurones (n = 39) of the Bötzinger complex (BOT) were examined in decerebrate cats. Most augmenting expiratory (E-aug) neurones (20/22) of the BOT, including 15 bulbospinal neurones, decreased their activities (9/20) or ceased to discharge (11/20) after the onset of stimulation of the PAG. This suggests that suppression of E-aug neurones of the BOT, which project to phrenic motoneurones, results in disinhibition of these neurones, and, in turn, terminates expiration and initiates inspiration preceding vocalization.

[A device to display moving objects for visual stimulation in the early development: with numerical control of a pulse motor]

In order to observe oculomotor responses to moving objects in infants and the profoundly retarded, a control system of moving objects was developed. The system consists of two parts, the one is to control movement, while the other is to display stimuli. The movement control part is made of a microcomputer, a pulse motor, and a rail, which guides a stimulus carrier with slight friction. The pulse motor rotates 1.8 degrees, according to the input of one pulse. Therefore, the microcomputer can control the velocity of movement of a heavy object exactly. The microcomputer detects the position of a stimulus carrier, counting the number of pulses and receiving signals from switches attached to the rail. The stimuli displaying part controls lighting with respect to the position of a stimulus carrier. Applying this system to a profoundly retarded subject, whose DA was three months, smooth pursuit oculomotor responses at the same velocity as the stimulus were observed in EOG recordings. Measurement of duration of those responses was achieved.

[Spectral analytical study on the developmental properties of EEG in children: variability of EEG in normal and mentally retarded children (author's transl)]

The present study aimed at clarifying the characteristics of variability of the resting arousal EEGs in normal and mentally retarded children. Their ages ranged from 3 to 15 years in 58 normal and from 7 to 18 in 63 retarded. The EEG was recorded monopolarly from six regions of the scalp. The data analysed by a multipurpose digital computer comprised auto-power spectra and a coefficient of variation of power at each frequency. The variability of power at peak within the theta frequency band in both groups of children showed a notably higher value as compared with other frequency bands in all regions. We discussed some of the problems of treating this variability of power as a general characteristic of theta waves or as a developmental one.

[Spectral analytical study on the developmental properties of EEG in children: Generalized and localized components of EEG spectra in the normal and the mentally retarded children (author's transl)]

The purpose of the present study was to elucidate the developmental properties of EEG in the normal and the mentally retarded children through regional differences and regional regional interrelationships. The localized components appearing at 1 or 2 regions tended to show low coherences in relation to the occipital region. The generalized component, observed over all regions, indicated lower coherences in the theta component than in the alpha one. It may be inferred that the theta component shown in the developing children may be differenciated from the component around 10 Hz.