Book contents
- Frontmatter
- Contents
- Preface
- 1 Anatomy of the cerebral cortex
- 2 The probability for synaptic contact between neurons in the cortex
- 3 Processing of spikes by neural networks
- 4 Relations between membrane potential and the synaptic response curve
- 5 Models of neural networks
- 6 Transmission through chains of neurons
- 7 Synchronous transmission
- Appendix Answers and hints
- Index
6 - Transmission through chains of neurons
Published online by Cambridge University Press: 03 May 2011
- Frontmatter
- Contents
- Preface
- 1 Anatomy of the cerebral cortex
- 2 The probability for synaptic contact between neurons in the cortex
- 3 Processing of spikes by neural networks
- 4 Relations between membrane potential and the synaptic response curve
- 5 Models of neural networks
- 6 Transmission through chains of neurons
- 7 Synchronous transmission
- Appendix Answers and hints
- Index
Summary
The necessity of diverging/converging connections
The execution of brain processes often requires hundreds of milliseconds. Even a simple reaction-time exercise (in which the subject is required to press a button each time a sound is heard) has a central delay of about 100 ms. As the task becomes more complex (e.g., by requesting the subject to respond only to one of several possible sounds), the central delay becomes longer. The long central delay is accounted for by assuming that information processing is done through neuronal activity that must traverse through many stations in tandem. This type of processing often is visualized as being carried through a chain of serially connected neurons, such as that shown in Figure 6.1.1A. However, this arrangement is faulty, because if one of the neurons in the chain is damaged, the entire chain (composed of n cells) will become inoperative. The cortex is subject to a process by which its neuronal population is continually thinned out. Comparisons of neuronal densities in the brains of people who died at different ages (from causes not associated with brain damage) indicate that about a third of the cortical cells die between the ages of twenty and eighty years [Gerald, Tomlinson, and Gibson, 1980]. Adults can no longer generate new neurons, and therefore those neurons that die are never replaced.
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- Information
- CorticonicsNeural Circuits of the Cerebral Cortex, pp. 208 - 226Publisher: Cambridge University PressPrint publication year: 1991
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