Biomedical subjects

Dan D Stettler

Publications and source records attributed to Dan D Stettler.

2 recordsLinked to original sources

PubMed2006

Axons and synaptic boutons are highly dynamic in adult visual cortex.

While recent studies of synaptic stability in adult cerebral cortex have focused on dendrites, how much axons change is unknown. We have used advances in axon labeling by viruses and in vivo two-photon microscopy to investigate axon branching and bouton dynamics in primary visual cortex (V1) of adult Macaque monkeys. A nonreplicative adeno-associated virus bearing the gene for enhanced green fluorescent protein (AAV.EGFP) provided persistent labeling of axons, and a custom-designed two-photon microscope enabled repeated imaging of the intact brain over several weeks. We found that large-scale branching patterns were stable but that a subset of small branches associated with terminaux boutons, as well as a subset of en passant boutons, appeared and disappeared every week. Bouton losses and gains were both approximately 7% of the total population per week, with no net change in the overall density. These results suggest ongoing processes of synaptogenesis and elimination in adult V1.

Animals↗

PubMed2002

Lateral connectivity and contextual interactions in macaque primary visual cortex.

Two components of cortical circuits could mediate contour integration in primary visual cortex (V1): intrinsic horizontal connections and feedback from higher cortical areas. To distinguish between these, we combined functional mapping with a new technique for labeling axons, a recombinant adenovirus bearing the gene for green fluorescent protein (GFP), to determine the extent, density, and orientation specificity of V1 intrinsic connections and V2 to V1 feedback. Both connections cover portions of V1 representing regions of visual space up to eight times larger than receptive fields as classically defined, though the intrinsic connections are an order of magnitude denser than the feedback. Whereas the intrinsic connections link similarly oriented domains in V1, V2 to V1 feedback displays no such specificity. These findings suggest that V1 intrinsic horizontal connections provide a more likely substrate for contour integration.

Adenoviridae↗