Biomedical Engineering Reference
In-Depth Information
Action potential
Presynaptic
Na+ conductance
30
K+ conductance
Neurotransmitter
Na+
Na+
Refractory period
-65
K+
Time (ms)
K+
K+
Synapse
Postsynaptic
Soma
Dendrites
Axon
Synapse
FIGURE 2.3 Mechanism of spike generation and signal propagation through synapses and neurons. (Images from
Wikipedia.)
the discriminatory information present in the
input spike trains while inhibiting the rest. This
not only reduces the rate of spike generation at
the higher layer of the receptive field (leading to
improved energy efficiency), but it also opti-
mizes the information transfer that facilitates
real-time recognition and motor operation.
Indeed, later inhibition and synaptic adaptation
are related to the concept of noise shaping. Before
we discuss the role of noise in neurobiological
sensory systems, let us introduce some mathe-
matical models that are commonly used to cap-
ture the dynamics of spike generation and
spike-based information encoding.
is referred as the presynaptic neuron , whereas
the neuron receiving the spike from the syn-
apse is referred as the postsynaptic neuron (see
Figure 2.3 ). Also, there are two types of synapses
typically encountered in neurobiology: excita-
tory synapses and inhibitory synapses. For
excitatory synapses, the membrane potential of
the postsynaptic neuron (referred to as the excita-
tory postsynaptic potential , or EPSP) increases,
whereas for inhibitory synapses, the membrane
potential of the post-synaptic neuron (referred
to as the inhibitory postsynaptic potential , or IPSP)
decreases.
It is important to note that the underlying
dynamics of EPSP, IPSP, and the action potential
are complex and several texts have been dedi-
cated to discuss the underlying mathematics
[12] . Therefore, for the sake of brevity, we only
describe a simple integrate-and-fire neuron
model that has been extensively used for the
2.2.1 Spiking Models of Neuron and
Neural Coding
As a convention, the neuron transmitting or
generating a spike and incident onto a synapse
Search WWH ::




Custom Search