Tactile and auditory stimuli repeated at high rates (30-50 per sec) produce similar event related potentials.
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Acoustic Stimulation↗
Biomedical subjects
R Galambos
Publications and source records attributed to R Galambos.
The brainstem auditory evoked potential is a useful diagnostic tool in evaluating risk factors for hearing loss in neonatology.
Fourteen of 100 babies in an intensive care nursery showed abnormal BAEPs. An analysis of the clinical records identified nine risk factors. Neonatal asphyxia appeared to be associated with hearing loss only when repeated episodes of acidosis accompanied it. We conclude that the BAEPs can identify hard-of-hearing babies and estimate the type and amount of peripheral hearing loss. Prolonged perfusion of the cochlea with blood low in pH level may be the most common cause of hearing disorder in our group of nine risk factors.
Brain Stem↗
Auditory brainstem response in dolphins.
We recorded the auditory brainstem response (ABR) in four dolphins (Tursiops truncatus and Delphinus delphis). The ABR evoked by clicks consists of seven waves within 10 msec; two waves often contain dual peaks. The main waves can be identified with those of humans and laboratory mammals; in spite of a much longer path, the latencies of the peaks are almost identical to those of the rat. The dolphin ABR waves increase in latency as the intensity of a sound decreases by only 4 microseconds/decibel(dB) (for clicks with peak power at 66 kHz) compared to 40 microseconds/dB in humans (for clicks in the sonic range). Low-frequency clicks (6-kHz peak power) show a latency increase about 3 times (12 microseconds/dB) as great. Although the dolphin brainstem tracks individual clicks to at least 600 per sec, the latency increases and amplitude decreases with increasing click rates. This effect varies among different waves of the ABR; it is around one-fifth the effect seen in man. The dolphin brain is specialized for handling brief, frequent clicks. A small latency difference is seen between clicks 180 degrees different in phase--i.e., with initial compression vs. initial rarefaction. The ABR can be used to test theories of dolphin sonar signal processing. Hearing thresholds can be evaluated rapidly. Cetaceans that have not been investigated can now be examined, including the great whales, a group for which data are now completely lacking.
Acoustic Stimulation↗
A 40-Hz auditory potential recorded from the human scalp.
Computer techniques readily extract from the brainwaves an orderly sequence of brain potentials locked in time to sound stimuli. The potentials that appear 8 to 80 msec after the stimulus resemble 3 or 4 cycles of a 40-Hz sine wave; we show here that these waves combined to form a single, stable, composite wave when the sounds are repeated at rates around 40 per sec. This phenomenon, the 40-Hz event-related potential (ERP), displays several properties of theoretical and practical interest. First, it reportedly disappears with surgical anesthesia, and it resembles similar phenomena in the visual and olfactory system, facts which suggest that adequate processing of sensory information may require cyclical brain events in the 30- to 50-Hz range. Second, latency and amplitude measurements on the 40-Hz ERP indicate it may contain useful information on the number and basilar membrane location of the auditory nerve fibers a given tone excites. Third, the response is present at sound intensities very close to normal adult thresholds for the audiometric frequencies, a fact that could have application in clinical hearing testing.
Auditory Pathways↗
Holographic assessment of microwave hearing.
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Hearing↗
Electrophysiological signs of split-second decision-making.
When young adults detected auditory stimuli at split-second intervals, different components of the event-related brain potentials showed markedly different speeds of recovery. The P3 component (latency 300 to 350 milliseconds) was fully recovered at intervals of less than 1.0 second, while the N1--P2 components (latencies 100 to 180 milliseconds) were markedly attenuated with stimulus repetition even at longer interstimulus intervals. Thus, the N1--P2 recovers much more slowly than a subject's ability to evaluate signals, whereas the P3 appears to be generated at the same high rates as the decision processes with which it is associated.
Adult↗
Recovery cycles of event-related potentials in multiple detection tasks.
We examined the recovery cycle of the P3 in two different experiments, one in which subjects detected near-threshold (NT) tones and the other in which they detected suprathreshold (ST) tones presented in rapid sucession. In both experiments P3 amplitudes and latencies were decremented at ISIs of 300 msec but fully recovered by 900 msec. The N1 and P2 components elicited by ST tones showed a much more prolonged (> 7.0 sec recovery cycle. These results reveal that the P3 has a recovery cycle which closely resembles that of human decision processes, a recovery cycle far shorter than those of exogenous ERP components previously examined. Sequential changes in P3 amplitude between trials were also investigated. In both experiments P3 amplitudes were largest following signal-absent trials. This suggests that subjects may have modified their expectancies about tone delivery on a trial-by-trial basis. In these experiments the P3 wave was distinguished from the resolution of the CNV on several grounds, including differences in scalp distribution, intra-trial kinetics, effect of previous tone sequences, and distributions among the subjects. These results support the position that P3 is a neurophysiological event distinct from modulations of the CNV. Differences in the amplitude and habituation of P3s produced in the NT and ST experiments suggest that the P3 may be related to decisions which require 'controlled' stimulus processing.
Auditory Threshold↗
Split-second recovery of the P3 component in multiple decision tasks.
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Adolescent↗
Use of the auditory brainstem responses by prematures and newborns infants.
The auditory brainstem response (ABR) yields information on both the neurological and the audiological status of infants, children and adults. We have developed a procedure for extracting each type of information for separate study and we have applied it on 120 prematures and babies (28 to 42 weeks gestation age) in an intensive care unit.
Brain Stem↗
Similarities and differences among the P3 waves to detected signals in three modalities.
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Adult↗
Loudness enhancement and decrement in four paradigms.
When one tone burst (the conditioner) preceeds another (the target) by 100 ms, target loudness is enhanced if the conditioner is more intense and decreased if it is less intense. We show here that similar loudness enhancements and decrements occur when the conditioner follows the target. In all instances, monaural loudness enhancements (in which the conditioner and target are delivered to the same ear) are greater than the dichotic enhancements (in which the conditioner is presented contralaterally), but the decrements, which are smaller than the enhancements, are similar in magnitude. Loudness enhancements and decrements are similar to sequential loudness effects and central tendency effects; the major difference is the relatively very large increases in loudness obtainable in loudness enhancement experiments. We outline a mechanism to account for these loudness phenomena and suggest that this mechanism is responsible for similar perceptual effects that occur in other stimulus dimensions and modalities.
Acoustic Stimulation↗
The auditory brainstem response (ABR) is a useful diagnostic tool in the intensive care nursery.
We present normative data on the auditory brainstem response (ABR) derived from 91 premature infants, and illustrate a simple procedure that uses deviations from these norms to differentiate a hearing disorder from a neurological disorder involving the brainstem. In an infant intensive care unit the procedure identified 11 patients with hearing disorder, 3 with neurological problems, and 3 with both disorders. Serial measurements revealed whether a given infant was developing normally, and, for those with disorders, whether the clinical status was improving or deteriorating. The ABR method, which is noninvasive and performed during natural sleep, provided useful diagnostic information about every infant tested.
Audiometry↗
The auditory brainstem response (ABR) evaluates risk factors for hearing loss in the newborn.
Fourteen of 100 unselected patients in an intensive care nursery were found by the auditory brainstem evoked response (ABR) method to suffer significant hearing loss; of these 8 were ultimately discharged home. Analysis of the 100 clinical records identified 9 risk factors of which most, like low Apgar scores, are already known (Table I). However, neonatal asphyxia appeared to be associated with hearing loss only when repeated episodes of acidosis accompanied it (Table III). We conclude that the ABR readily identifies the hard-of-hearing premature and estimates the type and amount of his peripheral hearing loss, and that physiological events associated with prolonged perfusion of the cochlea with blood low in pH may be the most common cause of hearing disorder in this group.
Acidosis↗
[Neurophysiological characteristics of early auditory waves of the brain stem and their clinical utilization].
The auditory brainstem electric response yields information on both the neurological and the audiological status of infants and adults. These early waves have particular properties as: non-habituation, absence of latency modifications between sleep, awake state, or under high doses of barbiturates. We have developed a procedure for extracting each type of information by measuring the latencies of wave I (auditory nerve) and wave V (inferior colliculus), then the speed of conduction between these two waves.
Adult↗
Brain stem evoked response audiometry in newborn hearing screening.
Brain stem evoked response audiometry (BERA) has been used as an auditory screening procedure in three groups of newborn infants. Group 1 consisted of 220 normal-term infants who were tested within 72 hours of birth; no hearing abnormalities were uncovered (386 ears), and their threshold responses (for clicks) lay between a 10- and 20-dB hearing level (re: adult). Group 2 consisted of 75 newborns who were treated in an intensive care unit for one to 14 weeks; four were found to have severe sensorineural hearing loss (seven ears) at the time of discharge. Group 3 consisted of a group of 325 infants, 1 year or older, who had previously been discharged from the same intensive care unit; of these infants, an additional four showed severe sensorineural hearing loss. All abnormalities that were identified by BERA were subsequently confirmed by conventional audiometric measures. The estimate of an incidence of severe hearing loss in one of 50 infants who required intensive care in the neonatal period calls for careful testing of this population.
Audiometry↗
Middle-ear structures contribute little to auditory perception of microwaves.
The contribution of the ossicles (middle-ear bones) to auditory perception of microwaves was evaluated by the brain-stem evoked response (BER). Amplitude and latency of BERs were recorded from guinea pigs that were stimulated at various intensities by acoustic pulses coupled to the auditory canal or via bone conduction, and by microwave pulses. Blocking of the external ear, middle-ear damping, and middle-ear destruction produced little change in the BERs that were elicited by microwave pulses. Results indicate that activity in the central auditory pathway as induced by pulsed microwaves only requires stimulation of the cochlea. Conduction of pressure waves through the bones of the calvarium appears to be the mechanism responsible in perception of pulsed microwaves.
Animals↗
Cortical responses from adults and infants to complex visual stimuli.
Event-related potentials (ERPs) time-locked to the onset of visual stimuli were extracted from the EEG of normal adult (N = 16) and infant (N = 23) subjects. Subjects were not required to make any response. Stimuli delivered to the adults were 150 msec exposures of 2 sets of colored slides projected in 4 blocks, 2 in focus and 2 out of focus. Infants received 2-sec exposures of slides showing people, colored drawings or scenes from Disneyland, as well as 2-sec illuminations of the experimenter as she played a game or of a TV screen the baby was watching. The adult ERPs showed 6 waves (N1 through P4) in the 140--600-msec range; this included a positive wave at around 350 msec that was large when the stimuli were focused and smaller when they were not. The waves in the 150--200-msec range, by contrast, steadily dropped in amplitude as the experiment progressed. The infant ERPs differed greatly from the adult ones in morphology, usually showing a positive (latency about 200 msec)--negative(5--600msec)--positive(1000msec) sequence. This ERP appeared in all the stimulus conditions; its presence or absence, furthermore, was correlated with whether or not the baby seemed interested in the stimuli. Four infants failed to produce these ERPs; an independent measure of attention to the stimuli, heart rate deceleration, was demonstrated in two of them. An electrode placed beneath the eye to monitor eye movements yielded ERPs closely resembling those derived from the scalp in most subjects; reasons are given for assigning this response to activity in the brain, probably at the frontal pole. This study appears to be one of the first to search for cognitive 'late waves' in a no-task situation. The results suggest that further work with such task-free paradigms may yield additional useful techniques for studying the ERP.
Adolescent↗
Clinical applications of the auditory brain stem response.
The auditory brain stem response is a powerful new tool for the detection and quantification of hearing impairment, especially in the pediatric population. It gives exact information about the functional status of the cochlea and brain stem pathways. The technique distinguishes recruiting from nonrecruiting losses, predominantly high frequency from flat losses, and retrocochlear from peripheral disorders. The recent introduction of bone conducted stimuli should soon permit the unambiguous separation of conductive and sensorineural losses.
Adult↗