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3. Neural basis for the joint synthesis
If the goal and means of a goal-directed activity are constructed together then it is of great
importance to understand how this can be implemented in the brain because similar
mechanisms can be used to create artificial goal-directed systems. Undoubtedly, human
goal-directed activity is very complex and a detailed understanding of it is the beyond scope
of this article. Instead, I consider the neural basis of a certain “ideal” goal-directed process
suggesting it includes three obvious stages, i.e. initiation, execution, and termination. My
approach meets most of the contemporary hypotheses, which consider that the prefrontal
cortex (PFC) plays a key role in goal-directed processes (E.K. Miller& Cohen, 2001; Wood&
Grafman, 2003). In accordance with this position, I propose that the prefrontal cortex is
heavily involved in the construction and maintenance of neural patterns representing goals
and means.
It is suggested that the capacity of the PFC to construct and maintain sustainable neural
patterns is based on possible reverberatory characteristics of neurons in this structure
(Fuster 1997). It can be supposed that owing to such reverberatory properties the emergence
of sustainable characteristics of a neural pattern is, to a certain extent, autonomous from the
emergence of its other characteristics. In other words, relatively weak changes in neurons of
the PFC may be sufficient to make a pattern sustainable but more serious alterations are
necessary to form its other characteristics. This underlines a relative autonomy of the
sustainability of goal-directed processes at the cognitive level.
It is suggested that the prefrontal cortex can be considered as blackboard architecture.
Blackboard architecture consists of a set of specialized or stable processors that interact with
each other using a blackboard, consisting of less stable, flexible elements. Some authors (van
der Velde& de Kamps 2003, 2006) have suggested the idea that the prefrontal cortex uses
this sort of architecture. This idea is consistent with the neural data. For example, this means
that most of prefrontal neurons must flexibly adapt its activity to the ongoing task. And 30-
80 percents of prefrontal neurons of the monkey show selective responses to some aspect of
that task's events (Asaad et al 2000). However, it is necessary to emphasize a distinction
between conventional views on blackboard architecture used in AI (Corkill 1991; Craig
1995) and that used in this text. Unlike conventional models, the given model does not
suggest an absolute difference between stable processors and flexible elements, i.e. stable
processors can be converted to flexible elements and vice versa because both groups
comprise of similar neurons and only the level of stability distinguishes them.
It is reasonable to assume that a new goal-directed process emerges from the integration of
various sources of information associated with the ongoing situation. So, it is hypothesized
that prior to the construction of a new goal-directed process the prefrontal cortex can be
considered as a blackboard system in which incoming sensory information and/or ongoing
internal processes (emotions, innate drives, other goal-directed processes, especially those at
higher levels, etc.) presented as spatiotemporal patterns of neural activity in the PFC and
other brain structures are stable processors. Moreover, other ensembles of the PFC comprise
a bulletin board with flexible elements. The construction of a new process started from
interactions between stable processors and flexible elements and owing to such interactions,
the characteristics of flexible elements become similar to some characteristics of stable
processors. At the neural level, this means similar frequency or distribution of firing, etc.
