Masakazu Konishi

..Comparison of Eigenmannia and barn owls, and their neural systems, has revealed similarities in network designs, such as parallel pathways and their convergence to produce stimulus selectivity necessary for detection of natural stimuli...

..The template method perhaps evolved to free birds from fixed central pattern generators, resulting in the evolution of diverse and complex songs among oscine songbirds. The evolution of human speech may have followed a similar course...

..Thus, the two coding schemes are not alternate methods. Owls can localize sounds by using either the isomorphic map of auditory space in the midbrain or forebrain neural networks in which space is not mapped...

..We recorded extracellularly the responses of LLDa neurons to ITD in anesthetized barn owls and show that this ability is already present in LLDa, raising the possibility that ICcc inherits its noise reduction property from LLDa...

..A network model shows that a linear combination of ICcl responses to ITD-ILD pairs is sufficient to produce the multiplicative subthreshold responses to ITD and ILD seen in ICx...

..Moreover, responses to previous, plastic versions of BOS decayed over time. This indicates that selective tuning to BOS mirrors the vocalization that the bird is currently producing...

..The present study adds complex new connections that expand the traditional song system circuitry into the caudal mesopallium. These new pathways are likely to have broad implications for deciphering how this intricate system works...

..Multiplication worked for the entire range of postsynaptic potentials created by manipulation of ITD...

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..It is, however, not known whether the gating is involved in switching between the premotor and auditory function of neurons in the song control system...

..These findings suggest that in the thalamo-telencephalic auditory pathway, sound localization is subserved by a nontopographic representation of auditory space...

..ICX neurons further enhance this difference in the process of converting membrane potentials to impulse rates. Inhibition also appears to augment the difference between the main and side peaks...

..After normal feedback was restored, these deviations gradually disappeared and the original song was recovered. Thus, adult birds that do not learn new songs nevertheless retain a significant amount of plasticity in the brain...

..Other nonlinear processes improve the spatial tuning of the spike output and reduce the fit to the multiplicative model...

..Gating of auditory input at the junction between the auditory and vocal control system may be essential for regulating auditory feedback signals necessary for song learning and maintenance...

..Thus, there is no need to invoke mechanisms other than neural delays to explain the detection of ITDs by the barn owl's laminaris neurons...

..State-dependent phenomena in downstream nuclei, such as robustus archistriatalis, are likely to be derivatives of those in HVC...

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..One owl always pointed to the direction represented by the smaller of the two ITDs, whereas a second owl always chose the direction represented by the larger ITD (i.e., ITD - T)...

..This bandwidth also enabled higher-order auditory neurons to discriminate between real and illusory sources...

..During the same developmental phase, the BOS was the most effective excitatory stimulus during sleep. The preference for BOS compared to tutor song inverted with sleep/wake state. Thus, song preference shifts with development and state...

..Our findings suggest that the Uva might serve as a hub to coordinate neuromodulatory input into the song system...

..This conclusion is consistent with the recent finding that the combination sensitivity is due to a multiplication of ITD and ILD inputs...

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..The temporal order of syllables resembled the tutor model only in birds released from the noise before 80 d of age but not in older birds. Thus, different schedules and processes may govern the learning of syllable phonology and syntax...

..Antibody staining patterns in the zebra finch show that the protein's expression is developmentally regulated to coincide with the abrupt increase in the volume and cell size of the male's or the estrogen-treated female's song system...

..Our results indicate that the owl's NL neuron uses a "passive soma" design for computational and metabolic reasons...

..These trajectories represent side peaks of neural ITD-tuning curves and successfully predict localization reversals by both owls and human subjects...