Even when hearing is intact, the development of perceptual skills can be impaired by removing specific acoustic features from the rearing environment. For example, perceptual deficits are found in songbirds that have been deprived only of song exposure during the juvenile period. When evaluated as adults, birds reared in the absence of adult songs exhibit frequency discrimination deficits. Furthermore, birds reared without hearing sibling or adult vocalizations show poor frequency discrimination and song note recognition (Njegovan and Weisman, 1997 and Sturdy et al., 2001). These studies suggest that the maturation of auditory perception is not simply a matter

of hearing, but requires experience with specific features of the acoustic environment. If the loss of early BMN 673 molecular weight auditory experience degrades behavioral performance, then the opposite manipulation (augmented sound exposure) might be expected to improve perception. Studies that address this issue commonly expose developing animals to a specific acoustic environment, often for a prolonged period. However, the effects are usually assessed by recording from the nervous system (below), and the behavioral impact is not well understood. When developing rats are exposed to a single frequency for 3 weeks and then tested on a frequency discrimination task in adulthood, their perceptual skills selleck chemicals llc display an intricate set of changes. As adults, these animals actually display

poor discrimination at the exposed frequency, yet their discrimination of adjacent frequencies is significantly better than controls (Han et al., 2007). In contrast, when young animals are exposed to noise for days or weeks, behavioral measures reveal diminished or delayed capacities (Philbin et al., 1994, Zhang et al., 2008, Zhou and Merzenich, 2009 and Sun et al., 2011). Because the tone or noise levels used in these experiments appear to be too low to

injure the cochlea, the behavioral impact is probably attributable to central changes (below). A second approach to evaluate how acoustic stimulation influences development is to assess auditory learning. An exceptional series of studies by Gilbert Gottlieb, 1975a, Gottlieb, 1975b, Gottlieb, 1978, Gottlieb, 1980, Gottlieb, 1981 and Gottlieb, 1983) used a biologically relevant form of learning, called vocal imprinting, to examine the role of early MRIP auditory experience in behavioral responses to sound. Devocalized and isolated ducklings do not develop accurate sensitivity to maternal calls, but this perceptual skill is rescued by stimulating the ducklings with natural vocalizations. Preference for the natural call note repetition rate and frequency modulation must be induced or maintained by experiencing those acoustic features. However, merely hearing the right sound may not be sufficient to influence perceptual development; it is often gated by nonauditory factors, such as the state of arousal (Gottlieb, 1993, Sleigh et al.