Auditory physiology and behavior in RB/1bg, RB/3bg, and their F1 hybrid mice (Mus musculus): influence of genetics, age, and acoustic variables on audiogenic seizure thresholds and cochlear functions

In the early 1950s, Frings and Frings began a process of selection for audiogenic seizure susceptibility and resistance in albino mice. The present study was conducted to examine behavioral and cochlear functions in the inbred descendants of these mice. The cochlear action potential (AP) thresholds of the susceptible RB/1bg inbred mice were abnormally high, and the resistant inbred RB/3bg mice had normal AP audiograms. The F1 hybrid showed heterosis for its cochlear function. Only the RB/1bg was susceptible to audiogenic seizures on the first acoustic exposure. Thresholds for the successive components of their audiogenic seizures were determined in response to narrow bands of noise. These paralleled the AP thresholds of RB/1bg mice (r = .89). This RB/1bg mouse showed little age-related cochlear loss, which probably accounts for its robust sensitivity to audiogenic seizures over most of its lifespan. Earlier studies had demonstrated that the susceptible RB line had a robust AP, but little or no cochlear microphonic (CM). The susceptible RB/1bg had well-defined AP and CM responses at low frequencies. The nonsusceptible RB/3bg mice were more resistant to acoustic priming than another mouse (CBA/J) strain with a similar audiometric profile.     

Social interaction patterns of geriatric home and community residents

Thirty elderly nursing home residents and ten community residing older adults were observed in group settings. Their behavior was assessed for dependent personal maintenance, independent personal maintenance, and appropriate and inappropriate behaviors. Responses by staff and peers to these behaviors were classified as positive, negative, or ignore. The frequency of occurrence of these behaviors as well as the relationship of resident to peer or staff behaviors were analyzed. Results indicate that community-residing elders' behaviors differ from nursing home residents' in quantity rather than quality of interactions. There was a lower frequency of behaviors in the nursing home residents. Though older adults respond differentially to various behaviors of other nursing home residents, staff responses were consistent regardless of residents' behavior. These results suggest that geriatric home residents' behavior can be characterized as withdrawn rather than dependent.     

Biological basis of the stress response.

Chronic, as well as acute emotional arousal, is a consequence of various types of social interaction, i.e., those between mother and infant and between controlling dominant and less effective subordinate. The neurohumoral accompaniments of this social stress include the sympathetic adrenal medullary and hypothalamic pituitary adrenal responses. A common ensuing pathophysiological state involves a chronic increase of blood pressure. Although Selye's General Adaptation Syndrome presupposed the same response to a variety of stimuli; recent work shows that specific perceptions of control result in different patterns of neuroendocrine activation. A challenge perceived as easy to handle will elicit an active coping response and release of the neurosympathetic system's norepinephrine. Testosterone will rise as the subject savors success. With increasing anxiety this active coping shifts to a more passive mode and the behavior becomes less assured as the animal loses control. The norepinephrine/epinephrine ratio decreases as epinephrine, prolactin, renin and fatty acids rise. As the outcome becomes still less certain and distress grows, adrenocorticotropic hormone and cortisol levels arise. Thus, the effort required on the one hand and the degree of frustration conflict and uncertainty on the other, determine the ratio of catecholamines to corticoids. With severe emotional trauma, brain dysfunction may occur. These effects can be lasting, and corticoids paradoxically return to normal as the behavior changes to that of post-traumatic stress disorder. Repression and denial set in and the organism responds with decreased concern of impaired attachment and increased irritability.