The study investigates the expression of long noncoding RNAs (ncRNAs) in the adult mouse brain using in situ hybridization data from the Allen Brain Atlas. Among the 1,328 ncRNAs examined, 849 were found to be expressed in the brain, with most associated with specific neuroanatomical regions, cell types, or subcellular compartments. The genomic context of these ncRNAs revealed diverse origins, including intergenic, intronic, and imprinted loci, often overlapping with or transcribed antisense to protein-coding genes. Comparisons between ncRNA and protein-coding gene expression profiles showed complex relationships, challenging the notion that ncRNAs are merely transcriptional noise or artifacts. The findings suggest that many ncRNAs function intrinsically as RNAs and play significant roles in brain biology, expanding the understanding of the mammalian transcriptome.The study investigates the expression of long noncoding RNAs (ncRNAs) in the adult mouse brain using in situ hybridization data from the Allen Brain Atlas. Among the 1,328 ncRNAs examined, 849 were found to be expressed in the brain, with most associated with specific neuroanatomical regions, cell types, or subcellular compartments. The genomic context of these ncRNAs revealed diverse origins, including intergenic, intronic, and imprinted loci, often overlapping with or transcribed antisense to protein-coding genes. Comparisons between ncRNA and protein-coding gene expression profiles showed complex relationships, challenging the notion that ncRNAs are merely transcriptional noise or artifacts. The findings suggest that many ncRNAs function intrinsically as RNAs and play significant roles in brain biology, expanding the understanding of the mammalian transcriptome.