Altered Auditory BOLD Response to Conspecific Birdsong in Zebra Finches with Stuttered Syllables

How well a songbird learns a song appears to depend on the formation of a robust auditory template of its tutor's song. Using functional magnetic resonance neuroimaging we examine auditory responses in two groups of zebra finches that differ in the type of song they sing after being tutored by birds producing stuttering-like syllable repetitions in their songs. We find that birds that learn to produce the stuttered syntax show attenuated blood oxygenation level-dependent (BOLD) responses to tutor's song, and more pronounced responses to conspecific song primarily in the auditory area field L of the avian forebrain, when compared to birds that produce normal song. These findings are consistent with the presence of a sensory song template critical for song learning in auditory areas of the zebra finch forebrain. In addition, they suggest a relationship between an altered response related to familiarity and/or saliency of song stimuli and the production of variant songs with stuttered syllables

Neural representation of spectral and temporal features of song in the auditory forebrain of zebra finches as revealed by functional MRI

Song perception in songbirds, just as music and speech perception in humans, requires processing the spectral and temporal structure found in the succession of song-syllables. Using functional magnetic resonance imaging and synthetic songs that preserved exclusively either the temporal or the spectral structure of natural song, we investigated how vocalizations are processed in the avian forebrain. We found bilateral and equal activation of the primary auditory region, field L. The more ventral regions of field L showed depressed responses to the synthetic songs that lacked spectral structure. These ventral regions included subarea L3, medial-ventral subarea L and potentially the secondary auditory region caudal medial nidopallium. In addition, field L as a whole showed unexpected increased responses to the temporally filtered songs and this increase was the largest in the dorsal regions. These dorsal regions included L1 and the dorsal subareas L and L2b. Therefore, the ventral region of field L appears to be more sensitive to the preservation of both spectral and temporal information in the context of song processing. We did not find any differences in responses to playback of the bird's own song vs other familiar conspecific songs. We also investigated the effect of three commonly used anaesthetics on the blood oxygen level-dependent response: medetomidine, urethane and isoflurane. The extent of the area activated and the stimulus selectivity depended on the type of anaesthetic. We discuss these results in the context of what is known about the locus of action of the anaesthetics, and reports of neural activity measured in electrophysiological experiments

Olfactory Responses to Natal Stream Water in Sockeye Salmon by BOLD fMRI

Many studies have shown that juvenile salmon imprint olfactory memory of natal stream odors during downstream migration, and adults recall this stream-specific odor information to discriminate their natal stream during upstream migration for spawning. The odor information processing of the natal stream in the salmon brain, however, has not been clarified. We applied blood oxygenation level-dependent (BOLD) functional magnetic resonance imaging to investigate the odor information processing of the natal stream in the olfactory bulb and telencephalon of lacustrine sockeye salmon (Oncorhynchus nerka). The strong responses to the natal stream water were mainly observed in the lateral area of dorsal telencephalon (Dl), which are homologous to the medial pallium (hippocampus) in terrestrial vertebrates. Although the concentration of L-serine (1 mM) in the control water was 20,000-times higher than that of total amino acid in the natal stream water (47.5 nM), the BOLD signals resulting from the natal stream water were stronger than those by L-serine in the Dl. We concluded that sockeye salmon could process the odor information of the natal stream by integrating information in the Dl area of the telencephalon

Noninvasive fMRI investigation of interaural level difference processing the rat auditory subcortex

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Neural correlates of vocal learning in songbirds and humans

Animal models, songbirds particularly, are increasingly used to study the human capacity for speech and language. In the light of understanding both language evolution and individual language acquisition these models are highly valuable, provided that they are studied within a valid comparative framework. In the past few decades, non-invasive methods such as functional Magnetic Resonance Imaging (fMRI) and Near-InfraRed Spectroscopy (NIRS) have become available for human as well as animal brain research. In the studies discussed in this thesis, fMRI is employed to unravel the neural correlates of vocal learning in the human and songbird brain. Specifically, fMRI in both songbirds and humans is used to study the neural mechanisms underlying birdsong learning and human artificial grammar learning. In a series of fMRI studies investigating these neural mechanisms in adult and juvenile zebra finches and human adults, this thesis compares the neural substrates of song learning in birds with those of language learning in humans. Studies in both species show correlations between behavioral learning of song or speech and neural activity. These results contribute to the songbird model for human vocal learning.Language Use in Past and Presen

Artificial grammar learning in primates :behaviour and neuroimaging

PhD ThesisNeuroimaging studies have shown that natural language processes engage left hemisphere perisylvian brain regions. Artificial Grammars (AG), which are designed to emulate aspects of language syntactic structure, recruit comparable brain areas. Nonhuman animals have been shown to learn a range of different AGs. However, no data is currently available regarding the brain areas that support these processes. In this thesis, I combined behavioural artificial grammar learning (AGL) and fMRI experiments to generate insights regarding language evolution, and as a first step to developing animal model systems for aspects of language processing. These experiments provide novel evidence that nonhuman primates are able to learn a non-deterministic AG, designed to emulate some of the variability of the structure of sentences in natural language, and demonstrated notable correspondences between the brain regions involved in macaque and human AGL. I developed a quantitative method to compare AGL abilities across species and studies, and a novel eye-tracking technique with which to collect objective behavioural data. Using this technique, and a refined version of a traditional video-coding paradigm, I demonstrated that Rhesus macaques notice violations of the AG structure and that these results could not be explained by reliance on simple cues. Common marmosets also showed evidence of AGL however, these results may have been driven by simple learning strategies. Comparative fMRI experiments showed that, in humans, violations of the AG activated a number of perisylvian brain regions associated with language processing, including the ventral frontal cortex (vFC), temporal and temporo-parietal regions, although not Broca’s area (BA44/45). In Rhesus macaques, comparable patterns of activation were seen in the ventral frontal cortex and temporo-parietal regions. Additional activation in BA44/45 in macaques provides interesting insights into the evolution of this region. These experiments provide novel evidence regarding the AGL capabilities of nonhuman primates, and the brain areas that support them, suggesting that some language related functions may represent generic, rather than language specific processes. Therefore, some of the brain regions involved in AGL in both species might share a common evolutionary heritage, and therefore Rhesus macaques might represent a valuable animal model system for aspects of language processing

Control of Vocal Production in Budgerigars (Melopsittacus undulatus)

Budgerigars engage in dynamic vocal interactions with conspecifics, learn their vocalizations in a rich social environment, and rely to some extent on auditory feedback to acquire and maintain normal vocal output. However, little is known about the exact role of sensory input and sensory feedback in the control of vocal production in these birds. For example, we know that these birds learn best in a social environment that contains both auditory and visual information, yet we know very little about how this information guides and influences vocal production. Although we suspect that budgerigars rely on auditory feedback for the learning and maintenance of vocal behavior, we do not know whether there are refined, compensatory feedback mechanisms similar to that of humans. Finally, we do not know whether, or to what extent, calls can be modified in structure during learning. This dissertation describes a series of experiments that use more highly controlled and regimented conditions than previous studies with songbirds to investigate the control of vocal production in budgerigars and to provide a more detailed description of some of the mechanisms underlying vocal learning in budgerigars