Dataset Information

Input clustering in the normal and learned circuits of adult barn owls.

ABSTRACT: Experience-dependent formation of synaptic input clusters can occur in juvenile brains. Whether this also occurs in adults is largely unknown. We previously reconstructed the normal and learned circuits of prism-adapted barn owls and found that changes in clustering of axo-dendritic contacts (putative synapses) predicted functional circuit strength. Here we asked whether comparable changes occurred in normal and prism-removed adults. Across all anatomical zones, no systematic differences in the primary metrics for within-branch or between-branch clustering were observed: 95-99% of contacts resided within clusters (<10-20 ?m from nearest neighbor) regardless of circuit strength. Bouton volumes, a proxy measure of synaptic strength, were on average larger in the functionally strong zones, indicating that changes in synaptic efficacy contributed to the differences in circuit strength. Bootstrap analysis showed that the distribution of inter-contact distances strongly deviated from random not in the functionally strong zones but in those that had been strong during the sensitive period (60-250 d), indicating that clusters formed early in life were preserved regardless of current value. While cluster formation in juveniles appeared to require the production of new synapses, cluster formation in adults did not. In total, these results support a model in which high cluster dynamics in juveniles sculpt a potential connectivity map that is refined in adulthood. We propose that preservation of clusters in functionally weak adult circuits provides a storage mechanism for disused but potentially useful pathways.

SUBMITTER: McBride TJ

PROVIDER: S-EPMC4465939 | biostudies-literature | 2015 May

REPOSITORIES: biostudies-literature

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Input clustering in the normal and learned circuits of adult barn owls.

McBride Thomas J TJ DeBello William M WM

Neurobiology of learning and memory 20150218

Experience-dependent formation of synaptic input clusters can occur in juvenile brains. Whether this also occurs in adults is largely unknown. We previously reconstructed the normal and learned circuits of prism-adapted barn owls and found that changes in clustering of axo-dendritic contacts (putative synapses) predicted functional circuit strength. Here we asked whether comparable changes occurred in normal and prism-removed adults. Across all anatomical zones, no systematic differences in the ...[more]

PMID: 25701706

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Project description:BackgroundThe intensification of agricultural practices over the twentieth century led to a cascade of detrimental effects on ecosystems. In Europe, agri-environment schemes (AES) have since been adopted to counter the decrease in farmland biodiversity, with the promotion of extensive habitats such as wildflower strips and extensive meadows. Despite having beneficial effects documented for multiple taxa, their profitability for top farmland predators, like raptors, is still debated. Such species with high movement capabilities have large home ranges with fluctuation in habitat use depending on specific needs.MethodsUsing GPS devices, we recorded positions for 134 barn owls (Tyto alba) breeding in Swiss farmland and distinguished three main behavioural modes with the Expectation-Maximization binary Clustering (EMbC) method: perching, hunting and commuting. We described barn owl habitat use at different levels during the breeding season by combining step and path selection functions. In particular, we examined the association between behavioural modes and habitat type, with special consideration for AES habitat structures.ResultsDespite a preference for the most common habitats at the home range level, behaviour-specific analyses revealed more specific habitat use depending on the behavioural mode. During the day, owls roosted almost exclusively in buildings, while pastures, meadows and forest edges were preferred as nocturnal perching sites. For hunting, barn owls preferentially used AES habitat structures though without neglecting more intensively exploited areas. For commuting, open habitats were preferred over wooded areas.ConclusionsThe behaviour-specific approach used here provides a comprehensive breakdown of barn owl habitat selection during the reproductive season and highlights its importance to understand complex animal habitat preferences. Our results highlight the importance of AES in restoring and maintaining functional trophic chains in farmland.

Project description:Inhibition of return (IOR) is the reduction of detection speed and/or detection accuracy of a target in a recently attended location. This phenomenon, which has been discovered and studied thoroughly in humans, is believed to reflect a brain mechanism for controlling the allocation of spatial attention in a manner that enhances efficient search. Findings showing that IOR is robust, apparent at a very early age and seemingly dependent on midbrain activity suggest that IOR is a universal attentional mechanism in vertebrates. However, studies in non-mammalian species are scarce. To explore this hypothesis comparatively, we tested for IOR in barn owls (Tyto alba) using the classical Posner cueing paradigm. Two barn owls were trained to initiate a trial by fixating on the center of a computer screen and then turning their gaze to the location of a target. A short, non-informative cue appeared before the target, either at a location predicting the target (valid) or a location not predicting the target (invalid). In one barn owl, the response times (RT) to the valid targets compared to the invalid targets shifted from facilitation (lower RTs) to inhibition (higher RTs) when increasing the time lag between the cue and the target. The second owl mostly failed to maintain fixation and responded to the cue before the target onset. However, when including in the analysis only the trials in which the owl maintained fixation, an inhibition in the valid trials could be detected. To search for the neural correlates of IOR, we recorded multiunit responses in the optic tectum (OT) of four head-fixed owls passively viewing a cueing paradigm as in the behavioral experiments. At short cue to target lags (<100 ms), neural responses to the target in the receptive field (RF) were usually enhanced if the cue appeared earlier inside the RF (valid) and were suppressed if the cue appeared earlier outside the RF (invalid). This was reversed at longer lags: neural responses were suppressed in the valid conditions and were unaffected in the invalid conditions. The findings support the notion that IOR is a basic mechanism in the evolution of vertebrate behavior and suggest that the effect appears as a result of the interaction between lateral and forward inhibition in the tectal circuitry.

Dataset Information

Input clustering in the normal and learned circuits of adult barn owls.

Publications

Input clustering in the normal and learned circuits of adult barn owls.

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