Network Properties Of Axons

Long axons form connections between structures. Connections are often schematized by arrows (e.g., 'area A —area B'), but this is really a shorthand notation for complex processes, such as convergence (how many axons converge on a given postsynaptic target), divergence (how many postsynaptic neurons are contacted by a single axon), and combinations and integration of multiple inputs.

Network properties are difficult to investigate, even in animal models. To some extent, we know what is connected to what, but only partial and incomplete data exist concerning biophysical parameters and dynamic properties. A recent, powerful approach is the combination of intracellular labeling and EM analyses with dual or triple intracellular recordings in vitro. This combined anatomical-physiological approach provides highly precise data regarding the number and location of synapses between interconnected neurons and also regarding the functional dynamics of the identified synapses. For example, in pyramidal-to-interneuron but not pyramidalto-pyramidal connections, higher presynaptic firing rates result in frequency-dependent, incremental facilitation.

For long-distance connections, network properties have been more difficult to address. This is partially because of their spatial dispersion. It is difficult to trace a single axon along its complete trajectory and through multiple spatially separate arbors. Moreover, there is only a relatively small EM database, especially for human and subhuman primates, and this leaves many unanswered questions: Are there changes in caliber along the course of an axon? What are the postsynaptic targets? How do multiple inputs interact at a given postsynaptic target?

Understanding And Treating Autism

Understanding And Treating Autism

Whenever a doctor informs the parents that their child is suffering with Autism, the first & foremost question that is thrown over him is - How did it happen? How did my child get this disease? Well, there is no definite answer to what are the exact causes of Autism.

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