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Projection neurons throughout the mature mammalian neocortex extend efferent axons either through the ventrolaterally positioned internal capsule to subcortical targets or through the dorsally located midline corpus callosum to the contralateral cortex. In rats, the internal capsule is pioneered on E14, but the corpus callosum is not pioneered until E17,(More)
To understand how the skeletal muscle lineage is induced during vertebrate embryogenesis, we have sought to identify the regulatory molecules that mediate induction of the myogenic regulatory factors MyoD and Myf-5. In this work, we demonstrate that either signals from the overlying ectoderm or Wnt and Sonic hedgehog signals can induce somitic expression of(More)
Approximately one half-century ago several classes of medications, discovered by serendipity, were introduced for the treatment of depression and bipolar disorder. These highly effective medications revolutionized our approach to mood disorders and helped launch the modern era of psychiatry. Yet our progress since those serendipitous discoveries has been(More)
We have described our studies of the development of projections from layer 5 of the rat neocortex to subcortical targets in the midbrain and hindbrain. The major points are briefly summarized here. 1. Layer-5 neurons extend a primary axon out of cortex and along a spinally directed trajectory, bypassing all of their targets in the midbrain and hindbrain.(More)
In adult rats, layer 5 cortical neurons send axons through the corpus callosum to contralateral cortex or through the internal capsule to subcortical targets, but individual neurons reportedly do not have both connections. Here we confirm this adult separation and address whether it develops by extension of axon collaterals to both sets of targets with(More)
We demonstrate in rat neocortex that the distinct laminar arrangements of the apical dendrites of two classes of layer 5 projection neurons, callosal and corticotectal, do not arise de novo, but are generated later in development from a common tall pyramidal morphology. Neurons of each class initially elaborate an apical dendrite in layer 1. Layer 5(More)
The internal capsule and corpus callosum are the two major efferent axonal pathways of the mammalian neocortex. Previous studies have shown that the first cortical axons to grow through the internal capsule, the pathway from cortex to its subcortical targets, are extended by subplate neurons, which are the earliest generated neurons in the neocortex. Here,(More)