since the single neuron will furnish mostly a response to the area activated early.
However, the inhibitory regulation of these mechanisms can produce several
different levels of single-neuron response to the two different stimuli. In other
words, the mechanisms of regulation of the synaptic information transfer based on
the variation of the membrane potential regulate also the competition and/or the
level of integration of the information arriving from different areas of the brain on
close areas of the dendritic tree of the same neuron.
A last comment on the nature of the codification of the synaptic information and
on the computational ability of the dendrites is necessary. While one can discuss on
the digital or analogical nature of the neural code which is based on stereotyped
spike (bit) sequence, the same does not hold for the transformation of the neural
code into the synaptic code at the dendritic level. EPSPs are not stereotyped (all or
none) systems, and, as shown before, their representation of the presynaptic
“words” change the number of bits, shape, and amplitude. By looking this type of
synaptic codification, we would exclude a “dendritic computation” based on
algebraic-like or Boolean-type computation (see, e.g., [31]). Most probably, dendritic computation has to be a sort of analog computation which still remains to be
understood.
4. Conclusion
In this chapter we have given a non-exhaustive light overview on how the synaptic response is modulated by several intrinsic and extrinsic factors acting at different stages of the process of the information processing and transfer among neurons.
A first important point that should emerge from what exposed is that the problem, also at the level of the single synapse, is extremely complicated by the different
effects produced by the many systems of modulation of the information.
A second, but not less, important point is that our knowledge of the information
transfer by synaptic transmission is still very poor although a great effort is spent in
this direction.
The different levels, at which the regulation of the information processing
mediated by synapse occurs, require the cooperativeness of different scientific
approaches. The experimental methodologies and paradigms of investigations,
although improving day by day, cannot answer alone all the questions still open
because of the experimental technique limitations. A good synergy between
experimental, theoretical, and computational modeling approaches is needed.
The possibility to use big computational facility becomes a limiting factor for the
success.
The unveiling of the synaptic mechanisms of information processing and transfer is of great importance because information processing is the key ability of the
living systems to survive in the environment and, for the humans, is also the key
ability for high-level cognitive performance. As stressed in the introduction, the loss
of cognitive performance, like in the Alzheimer and in the Parkinson diseases, is
strongly associated to the synaptic malfunctioning. Memory and learning are
essentially synaptic functions.
In addition, the investigation on synaptic information processing and in the
synaptic functionality also support the researches in other fields as, for example, in
projecting and realizing artificial computational systems which, by using the powerful mechanism of synaptic information processing, tray to produce highperformance artificial system (see, e.g., [74]).
Some important challenges for the future studies of the information processing
mediated by synapses can be summarized as follows:
103
Information Processing and Synaptic Transmission
DOI: http://dx.doi.org/10.5772/intechopen.88405
However, the inhibitory regulation of these mechanisms can produce several
different levels of single-neuron response to the two different stimuli. In other
words, the mechanisms of regulation of the synaptic information transfer based on
the variation of the membrane potential regulate also the competition and/or the
level of integration of the information arriving from different areas of the brain on
close areas of the dendritic tree of the same neuron.
A last comment on the nature of the codification of the synaptic information and
on the computational ability of the dendrites is necessary. While one can discuss on
the digital or analogical nature of the neural code which is based on stereotyped
spike (bit) sequence, the same does not hold for the transformation of the neural
code into the synaptic code at the dendritic level. EPSPs are not stereotyped (all or
none) systems, and, as shown before, their representation of the presynaptic
“words” change the number of bits, shape, and amplitude. By looking this type of
synaptic codification, we would exclude a “dendritic computation” based on
algebraic-like or Boolean-type computation (see, e.g., [31]). Most probably, dendritic computation has to be a sort of analog computation which still remains to be
understood.
4. Conclusion
In this chapter we have given a non-exhaustive light overview on how the synaptic response is modulated by several intrinsic and extrinsic factors acting at different stages of the process of the information processing and transfer among neurons.
A first important point that should emerge from what exposed is that the problem, also at the level of the single synapse, is extremely complicated by the different
effects produced by the many systems of modulation of the information.
A second, but not less, important point is that our knowledge of the information
transfer by synaptic transmission is still very poor although a great effort is spent in
this direction.
The different levels, at which the regulation of the information processing
mediated by synapse occurs, require the cooperativeness of different scientific
approaches. The experimental methodologies and paradigms of investigations,
although improving day by day, cannot answer alone all the questions still open
because of the experimental technique limitations. A good synergy between
experimental, theoretical, and computational modeling approaches is needed.
The possibility to use big computational facility becomes a limiting factor for the
success.
The unveiling of the synaptic mechanisms of information processing and transfer is of great importance because information processing is the key ability of the
living systems to survive in the environment and, for the humans, is also the key
ability for high-level cognitive performance. As stressed in the introduction, the loss
of cognitive performance, like in the Alzheimer and in the Parkinson diseases, is
strongly associated to the synaptic malfunctioning. Memory and learning are
essentially synaptic functions.
In addition, the investigation on synaptic information processing and in the
synaptic functionality also support the researches in other fields as, for example, in
projecting and realizing artificial computational systems which, by using the powerful mechanism of synaptic information processing, tray to produce highperformance artificial system (see, e.g., [74]).
Some important challenges for the future studies of the information processing
mediated by synapses can be summarized as follows:
103
Information Processing and Synaptic Transmission
DOI: http://dx.doi.org/10.5772/intechopen.88405