| 摘要: | 研究期間：10108~10207;Dissociating functional contributions of brain areas to search performance in natural scenes and in three dimensional stimuli, using brain stimulation and imaging techniques. Search comprises an essential element of our visual behaviour, enabling us to locate objects (targets) against the background of the rest of the environment (distractors). A number of brain areas have been implicated in the success of this, particularly when the target element shares attributes with distracters (i.e. conjunction search performance) in contrast with feature search (e.g. a target defined by one attribute such as colour), by use of correlational imaging techniques (such as fMRI, e.g. Donner et al 2002). Disruptive stimulation techniques, such as transcranial magnetic stimulation (TMS), have illustrated the necessity of a number of these areas (Walsh et al 1998, Muggleton et al 2003, Juan et al 2008). While both posterior parietal cortex, an area implicated in a wide range of attentionally demanding processes, and frontal eye fields, an area traditionally associated with eye movements, have been shown to be important for successful search performance, the contribution of these, and other areas, remains to be clarified in functional terms. Recently the timing of the involvement of these areas in search performance has been compared directly, with that of frontal eye fields (FEF) preceding that of parietal cortex (PPC, Kalla et al 2008, see also O’Shea et al 2004, Ashbridge et al 1997). Additionally, when the presence of a target is indicated with an eye movement, disruption was seen with TMS stimulation of FEF, but not PPC (Muggleton et al, in press). One possibility, therefore, is that FEF is important for the visual processing of the stimuli and that PPC is important for visuomotor transformation specifically when a manual response is required. We propose to start by investigating the relative contributions of areas including FEF and PPC to search in terms of their visual and motor functions using TMS, tDCS, and magnetic resonance imaging. The aims of this series of experiments will be to initially establish the relative functional roles of these areas in visual search performance as well as investigating the effects of learning on the functions of these areas in search performance (TMS delivered over PPC does not affect performance for a learned difficult search, Walsh et al 1998). In addition to this we will further investigate the contribution of these areas to more realistic search, including detecting targets in natural scenes and in three dimensional stimuli, improving the ecological validity of the functional characterization of the areas investigated |
