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Usually, attention is divided onto the involuntary one caused by ascending (bottom-up)
excitation of visual cortical areas, and voluntary one (top-down), which source is descending
excitation of visual areas by voluntary activated PfC (Naatanen, 1992). Remarkably, that
dopamine modulates both types of attention (Kahkonen et al., 2001). In our model, diverse
pathways for dopaminergic cell excitation contribute to mentioned types of attention.
Involuntary attention is triggered by dopamine release in response to visual stimulus, whereas
voluntary attention is initiated by dopamine release in response to voluntary activation of the
PfC before appearance of a real stimulus (Fig. 3). In parallel, the PfC excites neurons in
different visual cortical areas via feedback projections.
Figure 3. A model of contribution of cortico-basal ganglia-thalamocortical loop and dopamine to
involuntary and voluntary visual attention. Processes in hatched part of the basal ganglia (BG) are
dopamine-dependent; Thal, thalamus; OS, oculomotor structures. APia and DPia, ascending and
descending pathways for initiating involuntary attention, respectively; DPva, descending pathways for
initiating voluntary attention, are marked by broken lines; a star - modifiable inputs. Other
abbreviations as in Figures 1 and 2.
It is possible that PFC represents relatively coarse visual information that can mediate
between-category decisions (Bar, 2003). In spite of prefrontal representations of objects are
not detailed, they are sufficient to activate anticipated activity in specific visual areas based
on coarse information (Bar, 2003). During the expectation period preceding the attended
presentations, regions within visual areas with a representation of the attended location are
activated (Kastner et al., 1999). This activity is related to directing attention to the target
location in the absence of visual stimulation, and the increase in activity during expectation is
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