Robert J. Ellingson

Cortical electrical responses to visual stimulation in the human infant

Full-term and premature babies have been stimulated on one or more occasions by single and repetitive flashes of light. The responses recorded from the occipital cortex (scalp) differ from those of adults in being of (a) more variable wave-form, (b) more variable (and often higher) amplitude, (c) longer latency, and (d) greater “fatigability”. Developmental changes with increasing age have been demonstrated; the most notable of these are (a) change from a response with initial negative phase in the earliest records of some subjects to the classical response with initial positive phase, (b) decreasing response latency, and (c) increasing ability to respond to more and more rapidly repeated stimuli. Response latency is also inversely correlated with body weight up to about 12 lb. (r = −.80). Curves of response latency vs. age and of response latency vs. body weight are 2-legged rather than monotonic, the breaks in the curves occurring at 4 weeks post-term and 9 lb., respectively. This phenomenon may reflect either a growth spurt in the visual system or different developmental rates in the two parts (scotopic and photopic ?) of the visual system. The physiological evidence appears to be related to anatomical evidence of immaturity and developmental change, but available anatomical data are not detailed enough for close correlation. The human data described are in most respects similar to those reported for cats and rabbits. The visual system of the human infant appears to be physiologically more mature at birth than that of the cat and the rabbit, but the latter develop more rapidly postnatally. Individual differences are as striking in the human as they are in the other two species.

Electroencephalograms of normal, full-term newborns immediately after birth with observations on arousal and visual evoked responses ☆

Abstract 1. 1. EEGs of 277 normal, full-term babies, ages 22 min. to 125 hours, were recorded. Loud auditory stimuli were presented during sleep in 52 cases; single and repetitive light flashes in 65 cases. 2. 2. In general, previous descriptions of EEG patterns during wakefulness and sleep in newborns were confirmed. No relationship was observed in these data between EEG patterns and (a) type of maternal analgesia during labor, (b) type of maternal anesthesia during delivery, or (c) length of 2nd stage of labor. 3. 3. Loud auditory stimuli during sleep may elicit the following generalized responses with or without movement: (a) flattening of tracings, (b) K-type response (rare), or (c) K-type response followed by flattening of tracings. Spontaneous movement during sleep may also be followed by flattening of tracings. 4. 4. Single light flashes to the eyes often elicit evoked potentials in the occipital area. These responses tend to differ from those observed in adults in the following ways: 4.1. (a) they are of more variable wave-form, 4.2. (b) they are of more variable amplitude, 4.3. (c) they show greater “fatiguability”, and 4.4. (d) they are of much longer latency (160–220 msec.). 5. 5. Trains of light flashes at 2 f/sec. or faster tend to elicit responses at the beginning (ON responses) and end (OFF responses) of stimulation. “Driving” effects were observed in only 2 cases, at 2.5–3.5 f/sec. 6. 6. The evoked response data are interpreted as reflecting the physiological immaturity of the newborns nervous system, associated with its anatomical immaturity. The major factor accounting for the long latencies of evoked responses is felt to be slow conduction in the afferent fiber tracts, but retinal and synaptic events may also be contributory. The peculiarities of wave-form and amplitude are felt to be functions of the immature visual cortex.

Variability of visual evoked responses in the human newborn

Abstract 1. 1. Summed visual evoked responses (VERs) were recorded repeatedly during the various phases of the wakefulness-sleep cycle on the first day of life and again 24 h later in six carefully selected full-term human newborns. The obtained VERs were analyzed in terms of wave form changes and amplitudes and latencies of the various wave components. 2. 2. A single subject showed an invariant wave form throughout a recording session. Only the P 2 wave component was always present in all subjects, and it was the only component of relatively invariant latency within subjects. Amplitudes of all components were extremely variable. No relationships could be demonstrated between phases of the wakefulness-sleep cycle or presence of REMs or both on the one hand and (1) presence or absence of any component of the VER, (2) latency of any component of the VER, and (3) peak-to-peak amplitudes. No relationships could be demonstrated among latency and amplitude changes of components of the VER. 3. 3. The following conclusions are reached: (1) The VER of the human newborn is extremely variable. (2) Only the latency of the P 2 component is consistent enough to be used to characterize a subject, but even it does not correlate with its own value a few weeks later. (3) Unless the factors related to its variability can be specified and controlled, the neonatal VER will be of limited value as a tool in clinical measurement or in other individual applications as compared with VERs recorded in older subjects. The principal exceptions would seem to be total absence, extreme distortion and marked and persistent asymmetry of responses. 4. 4. The neonatal VER is, however, very useful for the study of developmental changes in groups and for comparison of groups. 5. 5. It is emphasized that these results do not bear upon the usefulness of the VER beyond the neonatal period.

Variability of visual evoked potentials in human infants and adults

Abstract Visual evoked potentials (VEPs) were recorded in 6 normal 12–13-week-old infants and 4 young adults during wakefulness and sleep in 2 recording sessions approximately one week apart. VEP configuration as well as latency and amplitude of response components were examined with attention to relationships with the wakefulness-sleep cycle and intra- and intersession consistency. Results were compared with previously published data from newborns. The following conclusions have been reached: 1. 1. In newborns VEP configuration tends to be unreliable during wakefulness and active sleep between days. It tends to be reliable during quiet sleep between days in some subjects, but quite unreliable in others. 2. 2. In 3-month-old infants VEP configuration tends to be unreliable during wakefulness and drowsiness (stages W and 1) between days, but to be more reliable during slow wave sleep (SWS; stages 2–4) between days. 3. 3. In adults VEPs tend to be reliable during both wakefulness and sleep, but especially during SWS. 4. 4. Overall, VEPs are more reliable within sessions than between days, are more reliable for adults than for infants, and are slightly more reliable for 3-month-old infants than for newborns. 5. 5. Regardless of stage of the wakefulness—sleep cycle VEPs are a great deal more homogeneous across the occipital area of the head (leads O1, OZ, O2) in adults than in infants or newborns, while the latter 2 groups are not different from one another. 6. 6. In all groups (newborns, 3-month-old infants, and adults) the latency of the early components of the VEP (P0–P2) are relatively stable and are invariant with respect to the wakefulness-sleep cycle. However, components P0, N0 and P1 are often not seen. 7. 7. In newborns and 3-month-old infants the latencies of the later components of the VEP (N2, P3, N3) are variable but unrelated to the wakefulness-sleep cycle. In adults the latencies of the later components are variable and are related to the wakefulness-sleep cycle: (1) During stage W a sequence of rhythmic sinusoidal waves (“sensory after-discharge”) tends to follow the P3 component; (2) components N2 and P3 increase in latency during slow wave sleep; (3) component N3 appears during slow wave sleep, seeming to develop as a consolidation of the first waves of the sensory after-discharge. 8. 8. In newborns and 3-month-old infants the P2 components is the most often identifiable and the most stable, and is the best “marker” component. In adults P3 is the best “marker” component. 9. 9. The VEP of the 3-month-old infant has not matured as much over that of the newborn as was expected on the basis of changes in P2 latency and collateral electrophysiological findings.

Studies of the Electrical Activity of the Developing Human Brain

Publisher Summary This chapter is limited to a report on the observations that have been made in the course of a longitudinal study of the development of brain electrical activity from birth in human subjects. The study was begun in 1955. Its original objectives were to provide descriptive data on normal and abnormal developmental changes in EEG patterns from birth through the early years of life, and to determine if the EEG might prove useful in prognosticating congenital developmental abnormalities, which often become manifest only some weeks or months after birth. Most recording is by the bipolar technique. Over 3/4 of the subjects were stimulated on one or more occasions with single and repetitive flashes of light from a stroboscope. Auditory stimuli, consisting of handclaps early in the study and electronically generated clicks, later were also administered to a number of subjects. Although the overall study is not yet complete, the data available are so extensive that a condensed summary is all that is possible in this chapter. This is attempted in three sections here: (1) the development of EEG patterns from 24 weeks of age after conception through the end of the first year from term, (2) cerebral responses to stimulation, and (3) findings in subjects displaying developmental abnormalities.

The Study of Brain Electrical Activity in Infants

Publisher Summary This chapter describes the descriptive aspects of the developmental electrophysiology of the human brain. Much relevant data derived from animal studies are found in the literature. It remains for future investigations to relate such data systematically to anatomical development and other physiological and behavioral processes in the developing infant. Critical periods could be sought; for example, the available data suggest that at age 3–4 months the visual system is ready to participate in complex perceptual processes. It is the epoch during which the dominant occipital rhythm appears and just prior to which the latency of visual evoked responses approaches the adult level; anatomical studies show striking development of occipital cortical neurons between birth and 3 months. It should be possible to devise or adapt test situations involving a range of visual-motor performances from the simplest to the more complex with which to measure the capacity of the infant visual system before, during, and after this probable critical period. Further information is obviously needed on the physiological development of the auditory and somesthetic sensory systems as well as of high level motor functions. Developmental relationships among the conventionally designated “systems” of the brain and the development of interaction among these systems have been studied less. Such studies will be of great importance, because complex behavior, such as conditioning and learning, necessarily involves constant interaction of widespread portions of the nervous system.

Variability of auditory evoked potentials in human newborns.

Abstract Auditory evoked potentials (AEPs) were recorded in 6 normal full-term newborns throughout sleep cycles on 2 consecutive days. AEP configuration, latencies, and voltages were examined and analyzed with attention to relationships with the wakefulness-sleep cycle and intra-and intersession consistency. The following conclusions have been reached: 1. 1. Previous reports of AEP differences between active and quiet sleep were confirmed. The late components of the AEP tend to be of higher voltage and longer latency during quiet sleep. The AEP of wakefulness tends to resemble that of active sleep. 2. 2. The AEP consists of 7 components. Component P2 (latency approximately 250 msec) is far the most consistently detected. Its latency and voltage are reasonably stable both within and between recording sessions, taking state into account. 3. 3. The AEP of the full-term newborn is more mature than the visual evoked potential by several criteria.

Development of EEG and daytime sleep patterns in trisomy-21 infants during the first year of life: Longitudinal observations

Abstract Daytime EEG-polygraph recordings were obtained weekly from birth to 12–13 weeks, and at 26 and 52 weeks of age in 7 Trisomy-21 infants. The babies remain alive and are relatively well at ages 20–53 months. All 81 EEGs obtained were within normal limits for age. Derived data were compared with similar data from 17 normal full term infants. The trace alternant pattern disappeared later in the Trisomy-21 than in the control group (mean ages 55.6 days vs. 33.4 days post term; P P P P Sleep spindle bursts during slow wave sleep were less abundant in the Trisomy-21 group than in the control group throughout the first year (2.96 vs. 4.08 bursts/min; P P P P Developmental quotients at 8 months of age were significantly negatively correlated with age at disappearance of trace alternant, age at appearance of rolandic sleep spindles, and age at disappearance of frontal sharp waves. The present results demonstrate significant retardation in the maturation of brain electrical activity in Trisomy-21 infants, which is correlated with delayed early behavioral development, but not with the presence of conventional signs of EEG abnormality.

Clinical electroencephalographic observations on institutionalized mongoloids confirmed by karyotype

Abstract Two hundred and seventy-nine EEGs were recorded on 202 institutionalized mongoloid patients, ages 1 month to 63 years, whose diagnoses had been confirmed by karyotype. The EEGs were analyzed by conventional impressionistic clinical interpretation. The following conclusions are drawn, based upon the results of the present study and predominant findings reported in the literature: 1. 1. The rate of EEG abnormality in mongoloids is greater (20–25%) than that in the general population. 2. 2. Rates of EEG abnormality in mongoloids are age-related. The highest rates are found during childhood (prior to 14 years of age). Abnormality rates during young adulthood are no higher than those for the general population. They appear to rise prematurely in the 5th and 6th decades, consistent with clinical and pathological observations of acceleration of aging processes in mongoloids. 3. 3. The rate of so-called seizure activity in mongoloids is elevated (9%). Ninety percent of records with “seizure activity” are obtained on subjects under 14 years of age. They are usually not associated with a history of seizures. In general, EEG abnormalities are not well correlated with specific behavioral or neurological signs and symptoms in mongoloids. 4. 4. There is no conclusive evidence that rates or types of EEG abnormality are different in patients with the rarer trisomy 21 mosaic and D/G translocation karyotypes than in patients with the trisomy 21 karyotype.

EEG during Masturbation and Ejaculation

The occurrence of a distinctive EEG pattern specifically related to sexual arousal and orgasm would provide a reliable and convenient means of identifying such events in the laboratory and would also provide clues to cerebral structures involved in the processes.EEG-polygraph recordings were obtained under rigorously controlled conditions in four normal male subjects during masturbation and ejaculation. The EEG data were subjected to both impressionistic and quantitative analyses. They showed no remarkable changes during the sequence of relevant physiological responses. The sole effect was a slight depression of alpha activity, a well-known nonspecific effect associated with changes in attention and arousal. Examination of the literature shows little agreement among reported results of studies of EEG changes during orgasm. It is likely that at least some reported changes were artifactual. It is concluded that the case for the existence of EEG changes specifically related to sexual arousal and orgasm remains unproven.