Biomedical subjects

Timothy Q Gentner

Publications and source records attributed to Timothy Q Gentner.

6 recordsLinked to original sources

PubMed2006

Recursive syntactic pattern learning by songbirds.

Humans regularly produce new utterances that are understood by other members of the same language community. Linguistic theories account for this ability through the use of syntactic rules (or generative grammars) that describe the acceptable structure of utterances. The recursive, hierarchical embedding of language units (for example, words or phrases within shorter sentences) that is part of the ability to construct new utterances minimally requires a 'context-free' grammar that is more complex than the 'finite-state' grammars thought sufficient to specify the structure of all non-human communication signals. Recent hypotheses make the central claim that the capacity for syntactic recursion forms the computational core of a uniquely human language faculty. Here we show that European starlings (Sturnus vulgaris) accurately recognize acoustic patterns defined by a recursive, self-embedding, context-free grammar. They are also able to classify new patterns defined by the grammar and reliably exclude agrammatical patterns. Thus, the capacity to classify sequences from recursive, centre-embedded grammars is not uniquely human. This finding opens a new range of complex syntactic processing mechanisms to physiological investigation.

Acoustic Stimulation↗

PubMed2005

The effect of auditory distractors on song discrimination in male canaries (Serinus canaria).

Male songbirds such as canaries produce complex learned vocalizations that are used in the context of mate attraction and territory defense. Successful mate attraction or territorial defense requires that a bird be able to recognize individuals based on their vocal performance and identify these songs in a noisy background. In order to learn more about how birds are able to solve this problem, we investigated, with a two-alternative choice procedure, the ability of adult male canaries to discriminate between conspecific song segments from two different birds and to maintain this discrimination when conspecific songs are superimposed with a variety of distractors. The results indicate that male canaries have the ability to discriminate, with a high level of accuracy song segments produced by two different conspecific birds. Song discrimination was partially maintained when the stimuli were masked by auditory distractors, but the accuracy of the discrimination progressively declined as a function of the number of masking distractors. The type of distractor used in the experiments (other conspecific songs or different types of artificial white noise) did not markedly affect the rate of deterioration of the song discrimination. These data indicate that adult male canaries have the perceptual abilities to discriminate and selectively attend to one ongoing sound that occurs simultaneously with one or more other sounds. The administration of a noradrenergic neurotoxin did not impair markedly the discrimination learning abilities although the number of subjects tested was too small to allow any firm conclusion. In these conditions, however, the noradrenergic lesion significantly increased the number failures to respond in the discrimination learning task suggesting a role, in canaries, of the noradrenergic system in some attentional processes underlying song learning and processing.

Acoustic Stimulation↗

PubMed2005

Complementary neural systems for the experience-dependent integration of mate-choice cues in European starlings.

Choice of a particular mate phenotype may arise out of experience with the very phenotypes under consideration. Female European starlings (Sturnus vulgaris) prefer males that sing predominantly long-bout songs over males that sing predominantly short-bout songs, and thus, song-bout length is a phenotypic parameter instrumental in releasing the female's mate choice. The preferred long-bout songs induce higher expression of the immediate early gene (IEG) ZENK in the female auditory telencephalon than short-bout songs do, but this sensitivity to song length depends on the female's recent song experience. Here, we compared the experience-dependent modulation of ZENK with that of another IEG, FOS, and report that ZENK and FOS expression in the caudomedial mesopallium and caudomedial nidopallium show different modulation properties that complement natural variation in song-bout length. As reported previously, ZENK expression was greater in response to novel long-bout than to novel short-bout songs following a 1-week experience with long-bout but not short-bout songs. In contrast, FOS expression was greater in response to novel long-bout than to novel short-bout songs following a 1-week experience with short-bout but not long-bout songs. Thus, the ZENK and FOS signaling pathways are made sensitive to variation in song length by experiences with songs at opposite ends of the starling song-variation continuum, suggesting the presence of complementary neural systems made sensitive in register with the natural axis of phenotypic variation fundamental to the female's mate choice.

Acoustic Stimulation↗

PubMed2004

Functional differences in forebrain auditory regions during learned vocal recognition in songbirds.

Converging evidence implicates the auditory forebrain regions caudal medial mesopallium (formerly cmHV) and caudal medial nidopallium in the perceptual processing of conspecific vocalizations in songbirds. Little is known however, about more specific processing within these regions especially during song-based perceptual behaviors. One hallmark of the caudal medial mesopallium and caudal medial nidopallium, areas analogous to mammalian secondary auditory cortical structures, is their robust expression of the immediate-early-gene zenk in response to conspecific songs. Using European starlings operantly trained to recognize the songs of individual conspecifics, we show that the levels and patterns of zenk protein expression in the caudal medial nidopallium and caudal medial mesopallium differ when song recognition demands are placed on the system. In the caudal medial mesopallium, expression is significantly elevated above basal levels during the recognition of familiar songs, the acquisition of novel associations for familiar songs, and the acquisition of novel song discriminations. In the caudal medial nidopallium, however, expression is significantly elevated above basal levels only during the acquisition of novel song discriminations. The results directly implicate the caudal medial nidopallium and caudal medial mesopallium in at least a portion of the auditory processes underlying vocal recognition. Moreover, the observed differences between these regions imply the functional localization (or at least the concentration) of different auditory processing mechanisms within the caudal medial nidopallium and the caudal medial mesopallium.

Acoustic Stimulation↗

PubMed2003

Neuronal populations and single cells representing learned auditory objects.

The neural representations associated with learned auditory behaviours, such as recognizing individuals based on their vocalizations, are not well described. Higher vertebrates learn to recognize complex conspecific vocalizations that comprise sequences of easily identified, naturally occurring auditory objects, which should facilitate the analysis of higher auditory pathways. Here we describe the first example of neurons selective for learned conspecific vocalizations in adult animals--in starlings that have been trained operantly to recognize conspecific songs. The neuronal population is found in a non-primary forebrain auditory region, exhibits increased responses to the set of learned songs compared with novel songs, and shows differential responses to categories of learned songs based on recognition training contingencies. Within the population, many cells respond highly selectively to a subset of specific motifs (acoustic objects) present only in the learned songs. Such neuronal selectivity may contribute to song-recognition behaviour, which in starlings is sensitive to motif identity. In this system, both top-down and bottom-up processes may modify the tuning properties of neurons during recognition learning, giving rise to plastic representations of behaviourally meaningful auditory objects.

Acoustic Stimulation↗

PubMed2002

Recent experience modulates forebrain gene-expression in response to mate-choice cues in European starlings.

Mate-choice decisions can be experience dependent, but we know little about how the brain processes stimuli that release such decisions. Female European starlings (Sturnus vulgaris) prefer males with long-bout songs over males with short-bout songs, and show higher expression of the immediate early gene (IEG) ZENK in the auditory forebrain when exposed to long-bout songs than when exposed to short-bout songs. We exposed female starlings to a short-day photoperiod for one of three durations and then, on an increased photophase, exposed them to one week of long-bout or short-bout song experience. We then examined their IEG response to novel long-bout versus novel short-bout songs by quantifying ZENK protein in two song-processing areas: the caudo-medial hyperstriatum ventrale and the caudo-medial neostriatum. ZENK expression in both areas increased with tenure on short-day photoperiods, suggesting that short days sensitize females to song. The ZENK response bias toward long-bout songs was greater in females with long-bout experience than in females with short-bout experience, indicating that the forebrain response bias toward a preferred trait depends on recent experience with that category of trait. This surprising level of neuroplasticity is immediately relevant to the natural history and fitness of the organism, and may underlie a mechanism for optimizing mate-choice criteria amidst locally variable distributions of secondary sexual characteristics.

Animal Communication↗