Any dendrite in a dendritic tree that emerges near the basal pole of a neuron (e.g. in bipolar neurons, basal dendrites are either on the same side of the soma as the axon, or project toward the axon), and which is the closest to the cell body of the neuron (the soma).
Source:
GOC:bc,
PMID:16899232,
PMID:22683681,
PMID:17046728,
GOC:aruk,
PMID:9214543,
PMID:1720142