The function of SCN1B (sodium voltage-gated channel beta subunit 1, ENSG00000105711) is as follows. Regulatory subunit of multiple voltage-gated sodium (Nav) channels directly mediating the depolarization of excitable membranes (PubMed:40768348). Navs, also called VGSCs (voltage-gated sodium channels) or VDSCs (voltage-dependent sodium channels), operate by switching between closed and open conformations depending on the voltage difference across the membrane. In the open conformation they allow Na(+) ions to selectively pass through the pore, along their electrochemical gradient (PubMed:40768348). The influx of Na+ ions provokes membrane depolarization, initiating the propagation of electrical signals throughout cells and tissues (PubMed:14622265, PubMed:15525788, PubMed:18464934, PubMed:19710327, PubMed:29992740, PubMed:36696443, PubMed:8125980, PubMed:8394762). The accessory beta subunits participate in localization and functional modulation of the Nav channels (PubMed:15525788, PubMed:19710327, PubMed:29992740). Modulates the activity of SCN1A/Nav1.1, SCN2A/Nav1.2, SCN3A/Nav1.3, SCN4A/Nav1.4, SCN5A/Nav1.5, SCN8A/Nav1.6, SCN9A/Nav1.7 and SCN10A/Nav1.8 (PubMed:14622265, PubMed:15525788, PubMed:18464934, PubMed:30765606, PubMed:36696443, PubMed:8125980, PubMed:8394762). {ECO:0000269|PubMed:14622265, ECO:0000269|PubMed:15525788, ECO:0000269|PubMed:18464934, ECO:0000269|PubMed:19710327, ECO:0000269|PubMed:29992740, ECO:0000269|PubMed:30765606, ECO:0000269|PubMed:36696443, ECO:0000269|PubMed:8125980, ECO:0000269|PubMed:8394762}. [Isoform 2]: Cell adhesion molecule that plays a critical role in neuronal migration and pathfinding during brain development. Stimulates neurite outgrowth (PubMed:21994374). Has no regulatory function on the SCN2A sodium channel complex (PubMed:14622265). .