Differential Treatment Response of Proactive and Reactive Partner Abusive Men: Results from a Laboratory Proximal Change Experiment.

Objective: The current study reexamines data from Babcock et al. (2011) proximal change experiment to discern the differential utility of two communication skills-based interventions for proactive and reactive partner violence offenders. Method: Partner violent men were randomly assigned to the Editing Out the Negative skill, the Accepting Influence skill, or to a placebo/timeout and reengaged in a conflict discussion with their partners. Proactivity was tested as a moderator of immediate intervention outcomes. The ability to learn the communication skills, changes in self-reported affect, observed aggression, and psychophysiological responding were examined as a function of proactivity of violence. Results: Highly proactive men had some difficulty learning the Accepting Influence skill and they responded poorly to this intervention. They responded positively to the Editing Out the Negative technique, with less aggression, more positive affect, and lower heart rates. Low proactive (i.e., reactive) men tended to feel less aggressive, more positive, and less physiologically aroused after completing the Accepting Influence technique. Conclusions: This study lends support for tailoring batterer interventions specific to perpetrator characteristics.

Objetivo: El presente estudio reexamina los datos de Babcock et al. (2011) con respecto a un experimento de cambio proximal para discernir la utilidad diferencial de dos intervenciones basadas en habilidades de comunicación para agresores de violencia de pareja proactivos y reactivos. Método: A los agresores se les asignó aleatoriamente a las condiciones habilidad de eliminar lo negativo, habilidad de aceptación de la influencia, o placebo/tiempo fuera y volvieron a participar en una discusión conflictiva con sus parejas. Se evaluó la proactividad como moderadora de los resultados proximales de la intervención. Se examinó la capacidad de aprender habilidades de comunicación, los cambios en el afecto autoinformado, la agresión observada y la respuesta psicofisiológica en función de la proactividad de la violencia. Resultados: Los hombres muy proactivos tuvieron algunas dificultades para aprender la habilidad de aceptación de la influencia y respondieron escasamente a esta intervención. Sin embargo, respondieron positivamente a la técnica de eliminar lo negativo, con menor agresión, más afecto positivo y una frecuencia cardíaca más baja. Los hombres poco proactivos (es decir, reactivos) tendían a sentirse menos agresivos, más positivos y menos activados fisiológicamente después de completar la técnica de aceptación de la influencia. Conclusiones: Este estudio proporciona apoyo a la adaptación de las intervenciones para maltratadores a las características específicas del agresor.

Differential Treatment Response of Proactive and Reactive Partner Abusive Men: Results from a Laboratory Proximal Change Experiment / [La respuesta al tratamiento diferencial de hombres maltratadores proactivos y reactivos: los resultados de un experimento de cambio proximal de laboratorio]

Objective: The current study reexamines data from Babcock et al. (2011) proximal change experiment to discern the differential utility of two communication skills-based interventions for proactive and reactive partner violence offenders. Method: Partner violent men were randomly assigned to the Editing Out the Negative skill, the Accepting Influence skill, or to a placebo/timeout and reengaged in a conflict discussion with their partners. Proactivity was tested as a moderator of immediate intervention outcomes. The ability to learn the communication skills, changes in self-reported affect, observed aggression, and psychophysiological responding were examined as a function of proactivity of violence. Results: Highly proactive men had some difficulty learning the Accepting Influence skill and they responded poorly to this intervention. They responded positively to the Editing Out the Negative technique, with less aggression, more positive affect, and lower heart rates. Low proactive (i.e., reactive) men tended to feel less aggressive, more positive, and less physiologically aroused after completing the Accepting Influence technique. Conclusions: This study lends support for tailoring batterer interventions specific to perpetrator characteristics.(AU)

Objetivo: El presente estudio reexamina los datos de Babcock et al. (2011) con respecto a un experimento de cambio proximal para discernir la utilidad diferencial de dos intervenciones basadas en habilidades de comunicación para agresores de violencia de pareja proactivos y reactivos. Método: A los agresores se les asignó aleatoriamente a las condiciones habilidad de eliminar lo negativo, habilidad de aceptación de la influencia, o placebo/tiempo fuera y volvieron a participar en una discusión conflictiva con sus parejas. Se evaluó la proactividad como moderadora de los resultados proximales de la intervención. Se examinó la capacidad de aprender habilidades de comunicación, los cambios en el afecto autoinformado, la agresión observada y la respuesta psicofisiológica en función de la proactividad de la violencia. Resultados: Los hombres muy proactivos tuvieron algunas dificultades para aprender la habilidad de aceptación de la influencia y respondieron escasamente a esta intervención. Sin embargo, respondieron positivamente a la técnica de eliminar lo negativo, con menor agresión, más afecto positivo y una frecuencia cardíaca más baja. Los hombres poco proactivos (es decir, reactivos) tendían a sentirse menos agresivos, más positivos y menos activados fisiológicamente después de completar la técnica de aceptación de la influencia. Conclusiones: Este estudio proporciona apoyo a la adaptación de las intervenciones para maltratadores a las características específicas del agresor.(AU)

Predicting real-world emotion and health from spontaneously assessed linguistic distancing using novel scalable technology.

Individuals who are better at regulating their emotions have been shown to have better physical and mental health outcomes. One promising emotion regulation strategy is psychological distancing, which involves appraising a stimulus with objectivity or spatial/temporal distance. Language-based psychological distancing (linguistic distancing [LD]) refers to the degree to which one implements psychological distancing naturally via language. A crucial, underexamined mechanism that may account for real-world emotion and health self-reports is spontaneous (i.e., implicit) LD. Using HealthSense, a novel, scalable, mobile health assessment application, we collected lexical transcriptions for personally specific negative and positive events as well as emotion and health-relevant data over 14 days (data collected in 2021) and examined how implicit LD during negative and positive events relates to well-being over time. Primary analyses revealed that higher LD during negative events was associated with lower levels of stress as well as greater emotional and physical well-being within persons. LD during positive events on 1 day predicted greater reports of happiness 2 days later within persons. LD during positive events was associated with fewer symptoms of depression and LD during negative events was associated with greater physical well-being among persons. Exploratory analyses revealed that average depression, rumination, and perceived stress across the 2 weeks were significantly negatively associated with LD during negative events between persons. The present results expand understanding of the relationship between LD and mental and physical health risks and motivate future research on low-burden, scalable interventions involving LD. (PsycInfo Database Record (c) 2023 APA, all rights reserved).

Non-suicidal Self-injury History Moderates the Association Between Maternal Emotional Support and Adolescent Affect During Conflict.

Onset of non-suicidal self-injury (NSSI) is most frequent during adolescence. Etiological models indicate that abnormal affective reactivity and regulation within interpersonal contexts is related to heightened NSSI risk. The current study examined the effects of maternal emotional support on adolescent sympathetic nervous system (SNS) activity and observed anger during a conflict discussion among 56 mother-daughter dyads consisting of healthy adolescents and adolescents with a history of self-injury. During the conflict discussion task, maternal emotional support and adolescent anger were coded from behavior, and cardiovascular pre-ejection period was used to index SNS responding. Results demonstrated that maternal emotional support was negatively associated with adolescent anger and SNS activity during the conflict. However, these associations were not significant among adolescents with heightened NSSI history. Maternal emotional support may serve as an interpersonal mechanism for adolescent physiological and behavioral regulation, yet may function differently among adolescents with more frequent NSSI.

Posttraumatic Stress Disorder and Relationship Satisfaction among Firefighters: The Role of Emotion Regulation Difficulties.

Firefighters are exposed to potentially traumatic events throughout their careers, placing them at heightened risk for the development of posttraumatic stress disorder (PTSD). Individuals experiencing PTSD symptoms often experience interpersonal problems and relationship stress, and this may be due to emotion regulation difficulties. The current study examined the association between PTSD symptoms, couple relationship satisfaction, and emotion regulation difficulties among firefighters. Participants were comprised of 188 firefighters (M age = 41.32, SD = 9.25, 97.3% male) who completed an online questionnaire. Results indicated that PTSD symptom severity was negatively associated with relationship satisfaction and positively associated with emotion regulation difficulties. Additionally, there was a significant negative indirect effect of PTSD symptom severity on relationship satisfaction through heightened emotion regulation difficulties. Negative alterations in cognition and mood were especially relevant to emotion regulation difficulties and relationship satisfaction. Findings highlight the importance of understanding associations between PTSD and interpersonal functioning among firefighters. Emotion regulation difficulties may offer a clinically relevant transdiagnostic factor for targeting PTSD symptoms and relationship functioning among firefighters.

Enzymes of acetylcholine metabolism in the rat inferior colliculus.

Although there is strong evidence for cholinergic projections to the rat inferior colliculus, especially from the pedunculopontine tegmental nucleus (Noftz et al., 2020), there is a lack of information about the quantitative prevalence of the enzymes of acetylcholine metabolism in its various portions. We have used microdissection of freeze-dried sections combined with radiometric assays to map the distributions in the rat inferior colliculus of the activities of choline acetyltransferase (ChAT), which catalyzes synthesis of acetylcholine, and acetylcholinesterase (AChE), which catalyzes its breakdown by hydrolysis. Both enzyme activities were present throughout the inferior colliculus. Average ChAT activity was consistently somewhat higher in the external cortex, excluding its most superficial layer, than in the dorsal cortex or central nucleus. Within the external cortex, ChAT activity was about half as high laterally in its most superficial layer as elsewhere. The distribution of AChE activity was more uniform than that of ChAT. Overall, ChAT activity in the rat inferior colliculus was relatively low, about a fifth of that in whole brain of rat and lower than in other central auditory regions, whereas AChE activity was about two-thirds that of rat whole brain and about average for central auditory regions. The results are compared to previous measurements for cat and hamster inferior colliculus. They are consistent with a modest role for cholinergic neurotransmission in the inferior colliculus, to modulate the activity of its major neuronal types.

Effects of brainstem lesions on amino acid levels in the rat cochlear nucleus.

There is evidence for glutamate, γ-amino butyric acid (GABA), and glycine as neurotransmitters of centrifugal pathways to the cochlear nucleus, but the quantitative extent of their contributions to amino acid neurotransmission in cochlear nucleus regions has not been known. We used microdissection of freeze-dried tissue sections of rat cochlear nucleus, with mapping of sample locations, combined with a high performance liquid chromatography (HPLC) assay, to measure amino acid levels in cochlear nucleus subregions of rats with unilateral lesions of centrifugal pathways to the cochlear nucleus. In rats with lesions transecting all or almost all pathways to the cochlear nucleus from brain stem regions, GABA, aspartate, and glutamate levels were reduced, compared to contralateral values, in almost all ipsilateral cochlear nucleus regions. The largest reductions, in dorsal (DCN), anteroventral (AVCN), and posteroventral (PVCN) cochlear nucleus regions, approached 50% for GABA, 40% for aspartate, and 30% for glutamate. In contrast, glutamine and taurine levels were typically higher in lesioned-side cochlear nucleus regions than contralaterally. Effects on glycine levels were mixed but usually included increased lesioned-side values compared to contralateral, probably reflecting a balance between increases during protein breakdown and decreases of free glycine in transected pathways. More limited lesions transecting just dorsal pathways showed much less effect on amino acid levels. Lesion of the ipsilateral trapezoid body connection plus ipsilateral superior olivary nuclei resulted in decreases of GABA, aspartate, and glutamate levels especially in ventral cochlear nucleus regions. No clear contralateral effects of this lesion could be shown. The results most strongly support centrifugal GABAergic pathways to the cochlear nucleus, providing almost half of GABAergic neurotransmission in most regions. Our results support and extend previously published measurements of lesion effects on GABA uptake and release in cochlear nucleus subdivisions.

Validation of the Emotional Tone Index for Families (ETIF): A Multi-Informant Measure of Emotional Closeness.

Despite the importance of emotional closeness (EC) in families, few researchers have accurately measured the construct in a systemic way. Additionally, existing measures rely on ratings from one informant, typically the mother, to provide information on closeness within the entire family system. We examined EC in 140 individuals (37 families) using the Emotional Tone Index for Families (ETIF), a novel, multi-informant measure that obtains bidirectional information about EC within every family relationship. The parent identified as most familiar with the family also completed two widely used single-informant measures: The McMaster Family Assessment Device and the Family Adaptability and Cohesion Evaluation Scales, version IV. The ETIF exhibited good test-retest reliability, high internal consistency, and concurrent validity with the single-informant measures. Though the primary respondent scores correlated highly with overall family closeness, results revealed only a modest association between closeness ratings within each dyad and parents rated higher levels of closeness toward their children than children rated closeness toward parents. These findings suggest that ratings from multiple informants provide valuable information about discrepancies in perceived closeness between family members and other complex family dynamics that cannot be captured by single-informant measures. Limitations, future directions, and implications for practice are discussed.

A pesar de la importancia de la cercanía emocional en las familias, pocos investigadores han medido con precisión el constructo de una manera sistémica. Además, las herramientas de medición existentes dependen de las valoraciones de un informante, normalmente la madre, para proporcionar información sobre la cercanía dentro de todo el sistema familiar. Analizamos la cercanía emocional en 140 personas (37 familias) usando el Índice de Tono Emocional para las Familias (ITEF), una herramienta de medición novedosa que obtiene información bidireccional sobre la cercanía emocional dentro de cada relación familiar por parte de varios informantes. El progenitor identificado como el más familiarizado con la familia también completó dos evaluaciones de un solo informante ampliamente utilizadas: el Dispositivo de McMaster de Evaluación Familiar (McMaster Family Assessment Device) y las Escalas de Evaluación de la Cohesión y la Adaptabilidad Familiar (Family Adapatability and Cohesion Evaluation Scales), versión IV. El ITEF demostró buena fiabilidad de prueba-reprueba, una alta coherencia interna y validez simultánea con las evaluaciones de un solo informante. Aunque los puntajes del encuestado principal se correlacionaron en gran medida con la cercanía familiar general, los resultados revelaron solo una asociación modesta entre las valoraciones de cercanía dentro de cada díada, y los padres indicaron niveles más altos de cercanía hacia sus hijos de lo que los hijos lo hicieron hacia sus padres. Estos resultados sugieren que las valoraciones de varios informantes proporcionan información valiosa acerca de las discrepancias en la cercanía percibida entre los miembros de la familia y otra dinámica familiar compleja que no puede captarse mediante las mediciones de un solo informante. Se explican las limitaciones, las futuras direcciones y las implicancias para la práctica.

Facial affect recognition moderates the relation between autonomic nervous system reactivity and aggression during dyadic conflict.

Researchers examining physiological factors of emotion have identified differential patterns of physiological reactivity among intimate partner violence perpetrators during interpersonal conflict. Although it is unclear what mechanisms are influencing these distinct physiological patterns, research suggests that perpetrators' ability to decode emotions may be involved. The current study examined how the relation between an individual's physiological reactivity and their aggression during conflict with an intimate partner is influenced by the affect they are exposed to and their affect recognition ability. Sixty-seven heterosexual couples completed self-report measures and participated in a conflict discussion while physiological measures were recorded. The sympathetic nervous system (SNS) was indexed by Skin Conductance Level (SCL) and the parasympathetic nervous system (PNS) by Respiratory Sinus Arrhythmia (RSA). Aggressive affect was coded from video. Additionally, men were administered a facial affect recognition task. Results indicated that observed aggression during the conflict discussion was associated with RSA and SCL suppression, but only for men with moderate to high affect recognition ability. Additionally, the interaction effects between physiological reactivity and affect recognition on male aggression was conditional on their partner exhibiting at least moderate levels of aggressive affect. Findings from our study suggest that the relation between autonomic nervous system reactivity during conflict and aggression toward an intimate partner is conditional on men's ability to decode the facial affect of their partner. For individuals who were able to decode aggressive affect from their partner, aggression was associated with decreased parasympathetic and SNS activation.

Empathy Mediates the Relations between Working Memory and Perpetration of Intimate Partner Violence and Aggression.

Deficits in executive functioning have been associated with aggressive and violent behavior toward intimate partners. However, it is unclear what specific mechanisms are being affected by cognitive deficits that increase an individual's tendency to become aggressive. The current study examined empathy as a mediating factor between deficits in working memory and perpetration of intimate partner aggression and violence. Men in heterosexual relationships (N = 49) were administered a measure of visual-spatial working memory, and questionnaire measures of head injury and empathy. During a second session, men participated in a conflict discussion with their female partner that was coded for aggressive behavior. Female partners also reported on men's physical and psychological abuse. Working memory was positively related to cognitive and affective empathy, and negatively related to men's physical abuse perpetration and observed aggression during the conflict discussion. The effects of working memory on observed aggression during the conflict were fully mediated by cognitive and affective empathy. Additionally, the effects of working memory on reported physical IPV frequency were fully mediated by affective empathy. Deficits in working memory may decrease men's ability to use empathetic processes, resulting in increased aggression and violence toward their intimate partners. Clinically, incorporating empathy training in battering intervention programs may be helpful, especially among men with deficits in cognitive functioning.

Chemical Effects of Kainic Acid Injection into the Rat Superior Olivary Region.

Kainic acid injections have been used to destroy neuron somata in particular regions without damaging fiber tracts. We injected a solution of kainic acid into the region of the rat superior olivary complex in an effort to destroy its cholinergic projections to the cochlea and cochlear nucleus, which derive especially from the lateral superior olivary nucleus and ventral nucleus of the trapezoid body. In the lateral superior olivary nucleus, there were relatively small but fairly consistent decreases of choline acetyltransferase (ChAT) activity, larger decreases of acetylcholinesterase (AChE) activity, and consistent decreases of malate dehydrogenase activity, as a marker for oxidative metabolism. Other superior olivary regions were less affected by the kainic acid injections, but most showed overall significant decreases of AChE activity. Our results suggest that the cholinergic neurons giving rise to the centrifugal pathways to the cochlea and cochlear nucleus are more resistant to the effects of kainic acid than are those that receive major ascending input from the cochlear nucleus and project to higher levels of the auditory system. Comparison with published anatomical studies suggests that this resistance to the effects of kainic acid is related to relatively little glutamatergic input to the somata and proximal dendrites of these neurons. We also found a consistent approximately 16 % decrease of ChAT activity in the injected-side facial nerve root, which is most easily explained as a small effect of kainic acid on the facial nerve fibers passing through the injection site.

Amino acid and acetylcholine chemistry in mountain beaver cochlear nucleus and comparisons to pocket gopher, other rodents, and cat.

The mountain beaver and pocket gopher are two rodents that live mostly underground in tunnel systems. Previous studies have suggested that their cochlear nucleus structure, particularly that of the dorsal cochlear nucleus (DCN), differs significantly from that of other mammals, that the hearing ability of the pocket gopher is deficient compared to that of other rodents, and that the DCN of the mountain beaver is more responsive to slow oscillations of air pressure than to sounds. We conducted some electrophysiological recordings from mountain beaver DCN and then used microchemical methods to map in mountain beaver cochlear nuclei the distributions of amino acids, including the major neurotransmitters of the brain, and enzyme activities related to the metabolism of the neurotransmitter acetylcholine, which functions in centrifugal pathways to the cochlear nucleus. Similar measurements were made for a pocket gopher cochlear nucleus. Responses to tonal stimuli were found in mountain beaver DCN. Distributions and magnitudes of neurotransmitter and related amino acids within mountain beaver and pocket gopher cochlear nuclei were not very different from those of other rodents and cat. However, the enzyme of synthesis for acetylcholine, choline acetyltransferase, had only low activities in the DCN of both mountain beaver and pocket gopher. The chemical distributions in the mountain beaver DCN support a conclusion that it corresponds to just the superficial DCN portion of other mammals. High correlations between the concentrations of γ-aminobutyrate (GABA) and glycine were found for both mountain beaver and pocket gopher cochlear nuclei, suggesting that their co-localization in cochlear nucleus synapses may be especially prominent in these animals. Previous evidence suggests convergence of somatosensory and auditory information in the DCN, and this may be especially true in animals spending most of their time underground. Our results suggest that the enlarged DCN of the mountain beaver and that of the pocket gopher are not very different from those of other rodents with respect to involvement of amino acid neurotransmitters, but they appear to have reduced cholinergic innervation.

Physiological and behavioral effects of interpersonal validation: A multilevel approach to examining a core intervention strategy among self-injuring adolescents and their mothers.

OBJECTIVE: The current study examined how teaching an interpersonal validation-oriented skill from dialectical behavior therapy affects behavioral and biological indices of self-inflicted injury (SII) risk among self-injuring adolescents and their mothers (n = 30 dyads), and typical control mother-daughter dyads (n = 30). METHOD: Behavioral indicators of family functioning (e.g., cohesion, coercion, and invalidation) and a physiological index of emotion dysregulation (respiratory sinus arrhythmia [RSA]) were examined across two conflict tasks (pre- and postskills training). RESULTS: Dyads' subjective affect and observed behavior generally improved when practicing validation. Findings indicate mother-, daughter-, and dyad-level behavior accounted for significant variance in RSA reactivity. CONCLUSIONS: Results demonstrate that teaching a single skill on one occasion can have detectable effects on biosocial functioning, with important implications for the etiology and treatment of SII.

Quantitative distribution of choline acetyltransferase activity in rat trapezoid body.

There is evidence for a function of acetylcholine in the cochlear nucleus, primarily in a feedback, modulatory effect on auditory processing. Using a microdissection and quantitative microassay approach, choline acetyltransferase activity was mapped in the trapezoid bodies of rats, in which the activity is relatively higher than in cats or hamsters. Maps of series of sections through the trapezoid body demonstrated generally higher choline acetyltransferase activity rostrally than caudally, particularly in its portion ventral to the medial part of the spinal trigeminal tract. In the lateral part of the trapezoid body, near the cochlear nucleus, activities tended to be higher in more superficial portions than in deeper portions. Calculation of choline acetyltransferase activity in the total trapezoid body cross-section of a rat with a comprehensive trapezoid body map gave a value 3-4 times that estimated for the centrifugal labyrinthine bundle, which is mostly composed of the olivocochlear bundle, in the same rat. Comparisons with other rats suggest that the ratio may not usually be this high, but it is still consistent with our previous results suggesting that the centrifugal cholinergic innervation of the rat cochlear nucleus reaching it via a trapezoid body route is much higher than that reaching it via branches from the olivocochlear bundle. The higher choline acetyltransferase activity rostrally than caudally in the trapezoid body is consistent with evidence that the centrifugal cholinergic innervation of the cochlear nucleus derives predominantly from locations at or rostral to its anterior part, in the superior olivary complex and pontomesencephalic tegmentum.

Effects of surgical lesions on choline acetyltransferase activity in the cat cochlea.

Although it is well established that the choline acetyltransferase (ChAT, the enzyme for acetylcholine synthesis) in the mammalian cochlea is associated with its olivocochlear innervation, the distribution of this innervation in the cochlea varies somewhat among mammalian species. The quantitative distribution of ChAT activity in the cochlea has been reported for guinea pigs and rats. The present study reports the distribution of ChAT activity within the organ of Corti among the three turns of the cat cochlea and the effects of removing olivocochlear innervation either by a lateral cut aimed to totally transect the left olivocochlear bundle or a more medial cut additionally damaging the superior olivary complex on the same side. Similarly to results for guinea pig and rat, the distribution of ChAT activity in the cat outer hair cell region showed a decrease from base to apex, but, unlike in the guinea pig and rat, the cat inner hair cell region did not. As in the rat, little ChAT activity was measured in the outer supporting cell region. As previously reported for whole cat cochlea and for rat cochlear regions, transection of the olivocochlear bundle resulted in almost total loss of ChAT activity in the hair cell regions of the cat cochlea. Lesions of the superior olivary complex resulted in loss of ChAT activity in the inner hair cell region of all cochlear turns only on the lesion side but bilateral losses in the outer hair cell region of all turns. The results are consistent with previous evidence that virtually all cholinergic synapses in the mammalian cochlea are associated with its olivocochlear innervation, that the olivocochlear innervation to the inner hair cell region is predominantly ipsilateral, and that the olivocochlear innervation to the outer hair cells is bilateral.

Amino acid and acetylcholine chemistry in the central auditory system of young, middle-aged and old rats.

Older adults generally experience difficulties with hearing. Age-related changes in the chemistry of central auditory regions, especially the chemistry underlying synaptic transmission between neurons, may be of particular relevance for hearing changes. In this study, we used quantitative microchemical methods to map concentrations of amino acids, including the major neurotransmitters of the brain, in all the major central auditory structures of young (6 months), middle-aged (22 months), and old (33 months old) Fischer 344 x Brown Norway rats. In addition, some amino acid measurements were made for vestibular nuclei, and activities of choline acetyltransferase, the enzyme for acetylcholine synthesis, were mapped in the superior olive and auditory cortex. In old, as compared to young, rats, glutamate concentrations were lower throughout central auditory regions. Aspartate and glycine concentrations were significantly lower in many and GABA and taurine concentrations in some cochlear nucleus and superior olive regions. Glutamine concentrations and choline acetyltransferase activities were higher in most auditory cortex layers of old rats as compared to young. Where there were differences between young and old rats, amino acid concentrations in middle-aged rats often lay between those in young and old rats, suggesting gradual changes during adult life. The results suggest that hearing deficits in older adults may relate to decreases in excitatory (glutamate) as well as inhibitory (glycine and GABA) neurotransmitter amino acid functions. Chemical changes measured in aged rats often differed from changes measured after manipulations that directly damage the cochlea, suggesting that chemical changes during aging may not all be secondary to cochlear damage.

Volumes of cochlear nucleus regions in rodents.

The cochlear nucleus receives all the coded information about sound from the cochlea and is the source of auditory information for the rest of the central auditory system. As such, it is a critical auditory nucleus. The sizes of the cochlear nucleus as a whole and its three major subdivisions - anteroventral cochlear nucleus (AVCN), posteroventral cochlear nucleus (PVCN), and dorsal cochlear nucleus (DCN) - have been measured in a large number of mammals, but measurements of its subregions at a more detailed level for a variety of species have not previously been made. Size measurements are reported here for the summed granular regions, DCN layers, AVCN, PVCN, and interstitial nucleus in 15 different rodent species, as well as a lagomorph, carnivore, and small primate. This further refinement of measurements is important because the granular regions and superficial layers of the DCN appear to have some different functions than the other cochlear nucleus regions. Except for DCN layers in the mountain beaver, all regions were clearly identifiable in all the animals studied. Relative regional size differences among most of the rodents, and even the 3 non-rodents, were not large and did not show a consistent relation to their wide range of lifestyles and hearing parameters. However, the mountain beaver, and to a lesser extent the pocket gopher, two rodents that live in tunnel systems, had relative sizes of summed granular regions and DCN molecular layer distinctly larger than those of the other mammals. Among all the mammals studied, there was a high correlation between the size per body weight of summed granular regions and that of the DCN molecular layer, consistent with other evidence for a close relationship between granule cells and superficial DCN neurons.

Cochlear damage affects neurotransmitter chemistry in the central auditory system.

Tinnitus, the perception of a monotonous sound not actually present in the environment, affects nearly 20% of the population of the United States. Although there has been great progress in tinnitus research over the past 25 years, the neurochemical basis of tinnitus is still poorly understood. We review current research about the effects of various types of cochlear damage on the neurotransmitter chemistry in the central auditory system and document evidence that different changes in this chemistry can underlie similar behaviorally measured tinnitus symptoms. Most available data have been obtained from rodents following cochlear damage produced by cochlear ablation, intense sound, or ototoxic drugs. Effects on neurotransmitter systems have been measured as changes in neurotransmitter level, synthesis, release, uptake, and receptors. In this review, magnitudes of changes are presented for neurotransmitter-related amino acids, acetylcholine, and serotonin. A variety of effects have been found in these studies that may be related to animal model, survival time, type and/or magnitude of cochlear damage, or methodology. The overall impression from the evidence presented is that any imbalance of neurotransmitter-related chemistry could disrupt auditory processing in such a way as to produce tinnitus.

Effects of cochlear ablation on amino acid levels in the rat cochlear nucleus and superior olive.

Amino acids have important roles in the chemistry of the auditory system, including communication among neurons. There is much evidence for glutamate as a neurotransmitter from auditory nerve fibers to cochlear nucleus neurons. Previous studies in rodents have examined effects of removal of auditory nerve input by cochlear ablation on levels, uptake and release of glutamate in cochlear nucleus subdivisions, as well as on glutamate receptors. Effects have also been reported on uptake and release of γ-aminobutyrate (GABA) and glycine, two other amino acids strongly implicated in cochlear nucleus synaptic transmission. We mapped the effects of cochlear ablation on the levels of amino acids, including glutamate, GABA, glycine, aspartate, glutamine, taurine, serine, threonine, and arginine, in microscopic subregions of the rat cochlear nucleus. Submicrogram-size samples microdissected from freeze-dried brainstem sections were assayed for amino acid levels by high performance liquid chromatography. After cochlear ablation, glutamate and aspartate levels decreased by 2 days in regions receiving relatively dense innervation from the auditory nerve, whereas the levels of most other amino acids increased. The results are consistent with a close association of glutamate and aspartate with auditory nerve fibers and of other amino acids with other neurons and glia in the cochlear nucleus. A consistent decrease of GABA level in the lateral superior olive could be consistent with a role in some lateral olivocochlear neurons. The results are compared with those obtained with the same methods for the rat vestibular nerve root and nuclei after vestibular ganglionectomy.