The magnocellular nucleus of the anterior neostriatum is a forebrain nucleus of passerine birds that accumulates testosterone and makes monosynaptic connections with other telencephalic nuclei that control song production in adult birds. Lesions in the magnocellular nucleus disrupted song development in juvenile male zebra finches but did not affect maintenance of stable song patterns by adult birds. These results represent an instance in which lesions of a discrete brain region during only a restricted phase in the development of a learned behavior cause permanent impairment. Because cells of the magnocellular nucleus accumulate androgens these findings raise the possibility that this learning is mediated by hormones.

Connections of a telencephalic vocal-control nucleus, the lateral magnocellular nucleus of the anterior neostriatum (lMAN), were studied in adult male zebra finches. Anterograde transport of horseradish peroxidase (alone or conjugated to wheat germ agglutinin) revealed that neurons in lMAN project to another forebrain song-control nucleus, the robust nucleus of the archistriatum (RA). RA is known to project onto the hypoglossal motor neurons that innervate the vocal organ. Retrograde transport of HRP from lMAN labeled a large thalamic nucleus, the medial portion of the dorsolateral nucleus of the thalamus (DLM). DLM in turn receives input from another nucleus of the song-control system, area X of the parolfactory lobe. We confirmed results of previous studies showing that area X receives a projection from the ventral area of Tsai (AVT) in the midbrain. In addition, we replicated results of previous experiments with canaries showing that the song-control nucleus HVc (caudal nucleus of the ventral hyperstriatum) receives input from three sources: the medial magnocellular nucleus of the anterior neostriatum (mMAN), the interfacial nucleus (NIf), and the uvae-form nucleus (Uva) of the thalamus. HVc neurons project to area X and to RA. In summary, there is a path from AVT in the midbrain, to area X, to DLM, and then to lMAN; HVc projects to X and hence indirectly to lMAN. We do not yet know the afferent connections of AVT. Thus, lMAN receives indirect input from a variety of other sources, including other regions known to be involved with vocal control.

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When deciding whether or not to regulate a chemical, regulatory bodies often evaluate the degree to which the public may be exposed by evaluating the chemical's occurrence in food and drinking water. As part of its decision-making process, the United States Environmental Protection Agency (USEPA) evaluated the occurrence of perchlorate in public drinking water by sampling public water systems (PWSs) as part of the first implementation of the Unregulated Contaminant Monitoring Rule (UCMR 1) between 2001 and 2005. The objective of this paper is to evaluate the current representativeness of the UCMR 1 dataset. To achieve this objective, publicly available sources were searched to obtain updated perchlorate data for the majority of large PWSs with perchlorate detections under UCMR 1. Comparison of the updated and UCMR 1 perchlorate datasets shows that the UCMR 1 dataset is no longer representative because the extent and degree of occurrence has decreased since implementation of UCMR 1. Given this finding, it seems appropriate for regulatory bodies engaged in decision-making processes over several years to periodically re-evaluate the conditions that prompted the regulatory effort, thereby ensuring that rules and regulations address actual conditions of concern.