The question of how the neural tube is patterned along the dorsoventral axis continues to exercise the minds of developmental neuroscientists. The floor plate — a specialized population of ventral midline cells that provides crucial signals for both cell subtype specification and axon guidance — has received particular attention in this regard, and the development of the floor plate itself has also become the subject of intense debate. Two models for floor plate development have been put forward, one based on induction from pre-existing neuroectoderm by signals from the underlying notochord, and the other based on insertion of node-derived cells into the ventral midline. Previous attempts to reconcile these models have focused on the idea that different species might use different mechanisms for floor plate generation, but on page 230 of this issue, Placzek and Briscoe offer an alternative explanation. They cite recent evidence for heterogeneity in floor plate characteristics along the anteroposterior axis, and they suggest that this heterogeneity might be an indication of anteroposterior differences in floor plate induction.

The specification of neurons and glia in the spinal cord is also a prominent theme in this month's Research Highlights. 'Striking the right balance' (page 170) describes intriguing new insights into the molecular mechanisms that regulate the sequential generation of motor neurons and oligodendrocytes in the pMN progenitor domain of the spinal cord. 'Oligodendrogenesis on a higher plane' (page 172) highlights two recent studies that identify an additional dorsal domain of oligodendrocyte precursor cell production that could be responsible for a second wave of oligodendrogenesis in the spinal cord.