Biomedical subjects

Abigail L Person

Publications and source records attributed to Abigail L Person.

3 recordsLinked to original sources

PubMed2005

Unitary IPSPs drive precise thalamic spiking in a circuit required for learning.

Song learning in birds requires a basal ganglia-thalamo-pallial loop that contains a calyceal GABAergic synapse in the thalamus. Information processing within this circuit is critical for proper song development; however, it is unclear whether activation of the inhibitory output of the basal ganglia structure Area X can drive sustained activity in its thalamic target, the medial portion of the dorsolateral thalamic nucleus (DLM). We show that high-frequency, random activation of this GABAergic synapse can drive precisely timed firing in DLM neurons in brain slices in the absence of excitatory input. Complex IPSP trains, including spike trains recorded in vivo, drive spiking in slices with high reproducibility, even between animals. Using a simple model, we can predict much of DLM's response to natural stimulus trains. These data elucidate basic rules by which thalamic relay neurons translate IPSPs into suprathreshold output and demonstrate extrathalamic GABAergic activation of thalamus.

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PubMed2004

Tonotopic gradients of Eph family proteins in the chick nucleus laminaris during synaptogenesis.

Topographically precise projections are established early in neural development. One such topographically organized network is the auditory brainstem. In the chick, the auditory nerve transmits auditory information from the cochlea to nucleus magnocellularis (NM). NM in turn innervates nucleus laminaris (NL) bilaterally. These projections preserve the tonotopy established at the level of the cochlea. We have begun to examine the expression of Eph family proteins during the formation of these connections. Optical density measurements were used to describe gradients of Eph proteins along the tonotopic axis of NL in the neuropil, the somata, and the NM axons innervating NL at embryonic day 10, when synaptic connections from NM to NL are established. At E10-11, NL dorsal neuropil expresses EphA4 at a higher concentration in regions encoding high frequency sounds, decreasing in concentration monotonically toward the low frequency (caudolateral) end. In the somata, both EphA4 and ephrin-B2 are concentrated at the high frequency end of the nucleus. These tonotopic gradients disappear between E13 and E15, and expression of these molecules is completely downregulated by hatching. The E10-11 patterns run counter to an apparent gradient in dendrite density, as indicated by microtubule associated protein 2 (MAP2) immunolabeling. Finally, ephrin-B2 is also expressed in a gradient in tissue ventral to the NL neuropil. Our findings thus suggest a possible conserved mechanism for establishing topographic projections in diverse sensory systems. These results of this study provide a basis for the functional examination of the role of Eph proteins in the formation of tonotopic maps in the brainstem.

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PubMed2002

Embryonic inner ear cells reaggregate into specific patterns in vitro.

The sensory epithelia of the mammalian inner ear consist of a highly precise pattern of sensory hair cells and supporting cells. The mechanisms regulating this patterning are only beginning to be determined. The present study describes a method for culturing dissociated embryonic inner ear cells and the resulting patterning that occurs in these cultures. The results indicate that developing inner ear cells aggregate into precise patterns on a two-dimensional substrate, suggesting that intrinsic patterning mechanisms remain active in vitro. Using antibodies and scanning electron microscopy to detect hair cells and nonsensory cells, it was determined that only a subset of aggregates contained sensory hair cells. The hair cells were organized into specific patterns and surrounded by supporting cells, similar to the in vivo pattern. Additionally, hair cells increased their immunoreactivity and number of stereocilia over time, suggesting that hair cells continue to mature in vitro. Thus, the study reveals that the cells of the developing inner ear provide the necessary signals that direct sensory hair cells and supporting cells to reassociate into very precise patterns in vitro and that these patterns are reminiscent of the patterning that occurs in vivo.

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