Applied Psychophysiology II: Auditory and Visual System Tests, Nervous System Disorders, and Behavior Disorders
Physiological measures have been applied in a variety of clinical situations by psychologists, neurologists, and psychiatrists. Some of the applications have included testing of vision, hearing, and brain responses in retarded individuals, and brain activity in neurological and behavior disorders. Examples of how physiological responses have been used in these various clinical situations, which are of importance to psychologists, audiologists, neurologists, psychiatrists, and others, are briefly described in the next sections.
The Brain Stem Potential. In the adult, the auditory brain stem response is a complex series of waves (see Fig. 16.4). The normal newborn infant shows only Waves I, III, and V in response to the high frequency click stimuli ( Stapells & Kurtzberg, 1991). Wave I is produced by neural activity in the 8th cranial nerve (auditory) and Wave III is generated by activity in the pons of the brain stem. Wave V arises from activity in the midbrain in the vicinity of the inferior colliculus. At-risk infants, that is, those of low birth weight, or those who suffered asphyxia at birth, have shown abnormal brain stem responses ( Majnemer, Rosenblatt, & Ridig, 1988). The latencies between peaks of the brain stem potential were delayed in these infants compared to normal controls. Thus, the brain stem response is a potential diagnostic tool for indicating infants who may have suffered damage to the auditory system.
The use of auditory ERPs to assess hearing deficits in retarded children, infants, and children with multiple handicaps (e.g., those with cerebral palsy) has been increasing in recent years. Because traditional auditory testing requires that subjects indicate verbally or by gesture that they have heard a sound, a technique that can evaluate the integrity of the auditory system without requiring such a response would be of value for testing certain individuals. Rapin ( 1974) observed that the auditory ERP is a powerful physiologic test of hearing because it indicates that stimulation by sound has caused a response to occur in the auditory system and the brain. She found that early diagnosis of hearing deficits with ERPs can allow early remediation. For example, infants have been fitted with hearing aids before the age of 6 months because ERPs showed their hearing to be impaired. Rapin expressed the belief that evoked potential audiometry is too demanding a technique for routine use with cooperative patients, but that it is justified with selected cases, similar to those just mentioned.
Rapin, Graziani, and Lyttle ( 1969) studied behavioral responses to sound and auditory ERPs of 51 children whose mothers had German measles (rubella) during the first 3 months