Persistence and generalization of adaptive changes in auditory localization behavior following unilateral conductive hearing loss.

Introduction: Sound localization relies on the neural processing of binaural and monaural spatial cues generated by the physical properties of the head and body. Hearing loss in one ear compromises binaural computations, impairing the ability to localize sounds in the horizontal plane. With appropriate training, adult individuals can adapt to this binaural imbalance and largely recover their localization accuracy. However, it remains unclear how long this learning is retained or whether it generalizes to other stimuli. Methods: We trained ferrets to localize broadband noise bursts in quiet conditions and measured their initial head orienting responses and approach-to-target behavior. To evaluate the persistence of auditory spatial learning, we tested the sound localization performance of the animals over repeated periods of monaural earplugging that were interleaved with short or long periods of normal binaural hearing. To explore learning generalization to other stimulus types, we measured the localization accuracy before and after adaptation using different bandwidth stimuli presented against constant or amplitude-modulated background noise. Results: Retention of learning resulted in a smaller initial deficit when the same ear was occluded on subsequent occasions. Each time, the animals' performance recovered with training to near pre-plug levels of localization accuracy. By contrast, switching the earplug to the contralateral ear resulted in less adaptation, indicating that the capacity to learn a new strategy for localizing sound is more limited if the animals have previously adapted to conductive hearing loss in the opposite ear. Moreover, the degree of adaptation to the training stimulus for individual animals was significantly correlated with the extent to which learning extended to untrained octave band target sounds presented in silence and to broadband targets presented in background noise, suggesting that adaptation and generalization go hand in hand. Conclusions: Together, these findings provide further evidence for plasticity in the weighting of monaural and binaural cues during adaptation to unilateral conductive hearing loss, and show that the training-dependent recovery in spatial hearing can generalize to more naturalistic listening conditions, so long as the target sounds provide sufficient spatial information.

Congenital and infantile benign skin lesions affecting the hand and upper extremity, part 2: nonvascular neoplasms.

This article is part 2 of a 2-part series presented to aid the hand surgeon in becoming familiar with dermatological lesions that may be present on the upper extremity during infancy. The discussion focuses on nonvascular neoplasms grouped into the following categories: epithelial, melanocytic, histiocytic, dermal, fibroblastic, and adipocytic neoplasms. Diagnostic tips are offered, including clinical photographs, to help differentiate between these lesions. In addition, the recommended treatment for each is discussed.

Congenital and infantile skin lesions affecting the hand and upper extremity, part 1: vascular neoplasms and malformations.

Many dermatologic conditions may be present on a newborn infant's upper extremity that can evoke concern for parents and/or primary caregivers. Although the pediatrician typically remains the first care provider, often these children are referred to specialists to diagnose and treat these lesions. Hand surgeons should be familiar with different infantile skin lesions on an upper extremity. Some lesions are best observed, whereas others require treatment with nonoperative measures, lasers, or surgical interventions. A 2-part series is presented to aid the hand surgeon in becoming familiar with these lesions. This part 1 article focuses on vascular neoplasms and malformations. Particular attention is paid to the multiple types of hemangiomas and hemangioendotheliomas, telangiectasias, angiokeratomas, as well as capillary, venous, and lymphatic malformations. Diagnostic tips and clinical photographs are provided to help differentiate among these lesions. In addition, the recommended treatment for each is discussed.

Benign subungual tumors.

A variety of benign and malignant processes may affect the subungual region; however, most are relatively rare lesions. We present a review of the current literature regarding benign tumors affecting the subungual region.