No abstract

Using controls and procedures responsive to criticisms of an earlier study by Eason, Harter, and White (1969), two experiments were conducted to test the hypothesis that selectively attending to a given spatial location involves a corticofugally controlled precortical neural filter that differentially screens information arriving from relevant and irrelevant locations. Twelve subjects participated in each experiment. The amplitude of an early evoked potential component believed to arise from striate cortex was greater to attended than to unattended stimuli presented in a given visual field. The amplitude also was greater during focused than during divided attention. In addition to corroborating the 1969 study, the results supported the precortical filtering hypothesis.

Incorporation of strain-specific synthetic DNA tags into yeast Saccharomyces cerevisiae gene-deletion strains has enabled identification of gene functions by massively parallel growth rate analysis. However, it is important to confirm the sequences of these tags, because mutations introduced during construction could lead to significant errors in hybridization performance. To validate this experimental system, we sequenced 11,812 synthetic 20-mer molecular bar codes and adjacent sequences (>1.8 megabases synthetic DNA) by pyrosequencing and Sanger methods. At least 31% of the genome-integrated 20-mer tags contain differences from those originally synthesized. However, these mutations result in anomalous hybridization in only a small subset of strains, and the sequence information enables redesign of hybridization probes for arrays. The robust performance of the yeast genedeletion dual oligonucleotide bar-code design in array hybridization validates the use of molecular bar codes in living cells for tracking their growth phenotype.