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Neural networks in relay nuclei integrate sensory information from multiple receptors. A. Sensory information is transmitted in the central nervous system
through hierarchical processing networks. A stimulus to the skin is registered by a large group of postsynaptic neurons in relay nuclei in the brain stem and
thalamus, but most strongly by neurons in the center of the array (red neuron). The receptive field of an individual relay neuron is larger than that of any of
the presynaptic sensory neurons because of the convergent connections. (Adapted, with permission, from Dudel 1983.)
B. Inhibition (gray areas) mediated by local interneurons confines excitation (orange area) to the central zone where stimulation is strongest, enhancing
the contrast between
strongly and
weakly
stimulated
relay neurons.
Source: Sensory
Coding,
Principles
of Neural
Science, Fifth Editon
C. InhibitoryCitation:
interneurons
in
a
relay
nucleus
are
activated
three distinct
Feed-forward
is produced
the afferent
fibers
Kandel ER, Schwartz JH, Jessell TM,by
Siegelbaum
SA,excitatory
Hudspethpathways.
AJ, Mack S.
Principles ofinhibition
Neural Science,
Fifth by
Editon;
2012 Available
of receptors that terminate
on
the
inhibitory
interneurons.
Feedback
inhibition
is
produced
by
recurrent
collateral
axons
of
neurons
in
the
output
pathway
at: http://mhmedical.com/ Accessed: May 13, 2017
from the nucleus.
The interneurons
in turn inhibit
nearby
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Education.
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rights neurons,
reserved creating sharply defined zones of excitatory and inhibitory activity in the nucleus.
In this way the most active relay neurons reduce the output of adjacent, less active neurons, permitting a winner-take-all strategy that ensures that only