node through the transmitter mechanism. The role of the node responsible for the processing
of internal signals includes the representation of internal signals, the combination of internal
and external signals, and the competitive processes among motivationally incompatible
behaviours. This produces the observed final external behaviour to be strongly dependent on
the internal states. All the internal states registered by the interoceptors compete among them
to determine which external behaviour will be executed. This competition is of the type winner-
take-all.
The blackboard of this node organizes the signals in four levels of abstraction: Internal
Perceptions, External Perceptions, Intero/Extero/Drive Congruents, and Drive. The signals
recorded at Internal Perceptions correspond to the current values of the internal states, sensed
and preprocessed by the interoceptors mechanism, multiplied by a coupling strength. At the
External Perceptions level the values of the external signals, still represented at the Perceptual
Persistents level of the node related with the external signals, are recorded (these signals are
transmitted and received by the communication mechanisms). The signals placed at the
Intero/Extero/Drive level are derived from a combination of signals at the Internal Perceptions,
External Perceptions and Drive levels. The signals created at the Drive level represent the
strongest internal needs that should be satisfied.
The signals at both the Internal Perceptions and External Perceptions levels are
combined by the intero/extero/drive congruence internal behaviour. This combination may be
increased if a corresponding signal has been created at the Drive level. The model for the
combination of internal and external signals is given by expression (7).
4c = 2y,√qz(ff+ rT,⅛∕cfj+ FaPoP (7)
where AC is the intensity of the signal to be created at the Intero/Extero/Drive Congruents level
of the motivational node; OE is the signal from the Internal Perceptions level and FaE its
coupling strength; O S is the signal from the External Perceptions level and Fa S its coupling
strength; O D is the signal from the Drive level and Fa D its coupling strength; J is a lesion factor;
and " regulates the combination of the internal and external signals. This combination model
is discussed in detail in (Gonzalez et. al., 2000).
For a value of " equal to zero, the internal signal and external signals interact in a
multiplicative way. If one of the signals (internal or external) is very small, it decreases the
importance of the other signal. In this way, external signals that contribute to weak motivations,
will make the corresponding external behaviour to have little chance of being selected. The
same occurs with small external signals for strong motivations. If we consider a value of "
greater than zero, then the internal state will have more importance than the external signal.
In this way, external signals that contribute to strong motivations, will make the corresponding
external behaviour to have a strong chance of being selected, even in the total absence of
external signals. This results in the external behaviour being a motivated one.
Once the external and internal signals are combined by the intero/extero/drive congruence
internal behaviour and the resulting signals are placed on the Intero/Extero/Drive Congruents
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