Abstract
Rhythm is important in the production of motor sequences such as speech and song. Deficits in rhythm processing have been implicated in human disorders that affect speech and language processing, including stuttering, autism, and dyslexia. Songbirds provide a tractable model for studying the neural underpinnings of rhythm processing due to parallels with humans in neural structures and vocal learning patterns. In this study, adult zebra finches were exposed to naturally rhythmic conspecific song or arrhythmic song. Immunohistochemistry for the immediate early gene ZENK was used to detect neural activation in response to these two types of stimuli. ZENK was increased in response to arrhythmic song in the auditory association cortex homologs, caudomedial nidopallium (NCM) and caudomedial mesopallium (CMM), and the avian amygdala, nucleus taeniae (Tn). CMM also had greater ZENK labeling in females than males. The increased neural activity in NCM and CMM during perception of arrhythmic stimuli parallels increased activity in the human auditory cortex following exposure to unexpected, or perturbed, auditory stimuli. These auditory areas may be detecting errors in arrhythmic song when comparing it to a stored template of how conspecific song is expected to sound. CMM may also be important for females in evaluating songs of potential mates. In the context of other research in songbirds, we suggest that the increased activity in Tn may be related to the value of song for assessing mate choice and bonding or it may be related to perception of arrhythmic song as aversive.
Highlights
Human speech and avian song have many parallels: both are acquired through sensorimotor learning, and when well-formed they are rhythmically structured in time
Summary The present results indicate that arrhythmic song induces greater ZENK expression in the auditory cortical areas, NCM and caudomedial mesopallium (CMM), and the amygdala homolog, Tn, compared to unmanipulated zebra finch song
Greater ZENK expression was induced in CMM in females compared to males across stimulus groups
Summary
Human speech and avian song have many parallels: both are acquired through sensorimotor learning, and when well-formed they are rhythmically structured in time. There is increasing evidence that rhythm plays an important role in speech and language processing. Rhythm perception ability is positively correlated with language and literacy skill [1]. Children with specific language impairment (language delay) have deficits in rhythm processing that include the ability to move in synchrony with a beat [2,3]. A number of other human disorders involve disruptions in timing and/or rhythm processing. Disruptions in aspects of timing or rhythm processing have been observed in patients with attention deficit hyperactivity disorder (reviewed in [9]), schizophrenia (reviewed in [9]), and dyslexia [10]. A better understanding of the neural bases of rhythm processing could elucidate mechanisms associated with a wide range of human developmental and psychiatric disorders
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