Abstract
Despite being commonly referenced throughout neuroscientific research on songbirds, reports of hemispheric specialization in the processing of song remain controversial. The notion of such asymmetries in songbirds is further complicated by evidence that both cerebral hemispheres in humans may be specialized for different aspects of speech perception. Some studies suggest that the auditory neural substrates in the left and right hemispheres of humans process temporal and spectral elements within speech sounds, respectively. To determine whether songbirds process their conspecific songs in such a complementary, bilateral manner, we performed functional magnetic resonance imaging (fMRI) on 15 isoflurane anesthetized adult male zebra finches (Taeniopygia guttata) while presenting them with (1) non-manipulated, (2) spectrally-filtered (reduced spectral structure), and (3) temporally-filtered (reduced temporal structure) conspecific song. Our results revealed sensitivity of both primary (Field L) and secondary (caudomedial nidopallium, NCM) auditory regions to changes in spectral and temporal structure of song. On the one hand, temporally-filtered song elicited a bilateral decrease in neural responses compared to the other stimulus types. On the other hand, spectrally filtered song elicited significantly greater responses in left Field L and NCM than temporally filtered or non-manipulated song while concurrently reducing the response relative to non-manipulated song in the right auditory forebrain. The latter hemispheric difference in sensitivity to manipulations of spectral structure in song, suggests that there is an asymmetry in spectral and temporal domain processing in the zebra finch auditory forebrain bearing some resemblance to what has been observed in human auditory cortex.
Highlights
The contributions of the left and right cerebral hemispheres to the processing of human speech remain controversial
The refined spectral precision of the right auditory cortex has been demonstrated by these same studies to come at the expense of temporal precision (Robin et al, 1990; Zatorre and Belin, 2001)
The temporal modulation frequency cut-off was set at 5 Hz, which means that all amplitude envelope changes, that are faster than 5 Hz were filtered out
Summary
The contributions of the left and right cerebral hemispheres to the processing of human speech remain controversial. The refined spectral precision (e.g., the ability to detect variations in prosody and speaker identity) of the right auditory cortex has been demonstrated by these same studies to come at the expense of temporal precision (Robin et al, 1990; Zatorre and Belin, 2001). Such a domain-general perspective implies that animals other than humans may possess comparable hemispheric specializations for processing their conspecific communication sounds. Other than the spectral vs. temporal hypothesis for left hemispheric specialization for speech perception described above, alternative possibilities include functional specialization of somatosensory and motor areas determining left hemispheric specialization for speech perception within auditory processing streams (Liebenthal et al, 2013) and speech-selective acoustic sensitivities in the left hemisphere that are indissociable from the articulatory systems that produce speech sounds (McGettigan and Scott, 2012)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
