4. Target Detection
Studies (for example [1] and [7]) have shown that there is a distinction
between an alert state where we are not actually attending to any target
at some location and the state where some target has been "detected" and
we are attending to it and processing information related to it at some
location. In the alert state, since our "attentional resources" are
not in place. it is easy to detect some target and then focus our attention
on it. By detecting a target, it allows us to respond to the target
in many different ways depending on the situation. For example, consider
crossing the street with some vehicle approaching quickly. Once we
detect this (e.g. realize that the car is fast approaching towards us)
we can increase our pace (possibly run) to the other side of the street
or we can go back to where we started from. According to the author,
the fact that we can respond to some event in many ways, is evidence that
we are aware of the signal (event) and processing information related to
it in order to react in some way.
Studies indicate that the anterior cyngulate gyrus is involved in target
detection. During target detection experiments (various other target
detection experiments as well, but as an example, consider figure 4 where
the task is to locate the red triangle in the presence of other distracters),
it has been observed that increasing the number of targets increases the
blood flow to the cingulate gyrus,
Finally, target detection experiments also suggest that the attention
system is not a single unified system, but rather a hierarchy of systems.
