The hypothalamus is the higher neuroendocrine center of the brain and therefore possesses numerous intrinsic axonal connections and is connected by afferent and efferent fiber systems with other brain structures. These projection systems have been described in detail in the adult but data on their early development is sparse. Here I review studies of the time schedule and features of the develo...

While transplantation represents a key tool for assessing in vivo functionality of neural stem cells and their suitability for neural repair, little is known about the integration of grafted neurons into the host brain circuitry. Rabies virus-based retrograde tracing has developed into a powerful approach for visualizing synaptically connected neurons. Here, we combine this technique with light...

The avian caudolateral neostriatum (NCL) was first identified on the basis of its dense dopaminergic innervation. This fact and data from lesion studies have led to the notion that NCL might be the avian equivalent of prefrontal cortex (PFC). A key feature of the PFC is the ability to integrate information from all modalities needed for the generation of motor plans. By using antero- and retrog...

A neural connection between the trigeminal ganglion and the auditory brainstem was investigated by using retrograde and anterograde tract tracing methods: iontophoretic injections of biocytin or biotinylated dextran-amine (BDA) were made into the guinea pig trigeminal ganglion, and anterograde labeling was examined in the cochlear nucleus and superior olivary complex. Terminal labeling after bi...

Virally based transsynaptic tracing technologies are powerful experimental tools for neuronal circuit mapping. The glycoprotein-deletion variant of the SAD-B19 vaccine strain rabies virus (RABV) has been the reagent of choice in monosynaptic tracing, since it permits the mapping of synaptic inputs to genetically marked neurons. Since its introduction, new helper viruses and reagents that facili...

Primary sensory neurons convey information from the external world to relay circuits within the CNS, but the identity and organization of the neurons that process incoming sensory information remains sketchy. Within the CNS, viral tracing techniques that rely on retrograde transsynaptic transfer provide a powerful tool for delineating circuit organization. Viral tracing of the circuits engaged ...

Because neurotropic viruses naturally traverse neural pathways, they are extremely valuable for elucidating neural circuits. Naturally occurring herpes and rabies viruses have been used for transneuronal circuit tracing for decades. Depending on the type of virus and strain, virus can travel preferentially in the anterograde or the retrograde direction. More recently, genetic modifications have...

A major challenge in systems neuroscience is to unravel the complex matrix of connections that characterize functional circuits within the central nervous system. Retrograde transneuronal transport of rabies virus has proven to be especially useful for this purpose. Here we provide specific examples in which transneuronal transport of rabies virus has been used to unravel multi-synaptic pathway...

Anatomical path tracing is of pivotal importance to decipher the relationship between brain and behavior. Unraveling the formation of neural circuits during embryonic maturation of the brain however is technically challenging because most transsynaptic tracing methods developed to date depend on stereotaxic tracer injection. To overcome this problem, we developed a binary genetic strategy for c...

Neural circuits are organized into functional topographic maps. In order to visualize complex circuit architecture we developed an approach to reliably label the global patterning of multiple topographic projections. The cerebellum is an ideal model to study the orderly arrangement of neural circuits. For example, the compartmental organization of spinocerebellar mossy fibers has proven to be a...