Does brain stimulation help to increase selection performance in visual attention?

• Applicant: Sandra Utz, Ph.D.
• Subject Area: General, Cognitive and Mathematical Psychology
• Term: from 2014 to 2016
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 264603963

Due to the fact that our processing resources are limited to a certain amount of information and are not able to process all information around us, it is very important that only the relevant information is processed to control our thinking and behavior. The basic cognitive ability underlying selection is referred to as attention. One experimental paradigm for investigating selection processes in the visual domain is visual search. In visual search experiments, participants have to indicate as fast and as accurately as possible if a predefined target stimulus (e.g., a red apple) surrounded by a certain number of distractor stimuli (e.g., green apples) is present or absent. In varying the search displays (e.g., number, complexity, and location of items) measured reaction times and accuracy indicate how good an observer is able to select the relevant information and ignore irrelevant information dependent on the variation. Research by Müller and his colleagues (Müller, Heller & Ziegler, 1995; Found & Müller, 1996) argued in favour of a memory-based guidance of visual search behaviour. They could show that the detection of targets is facilitated when the target-defining dimension (e.g., dimension colour: red apple followed by a red apple) remains the same compared to when it changes across trials (e.g., red apple [relevant dimension: colour] followed by an inverted apple [relevant dimension: orientation]). A previous study investigated the brain regions necessary for these dimensional carry-over effects with brain lesioned patients (Utz, Humphreys, & Chechlacz, 2013). The data suggest that some regions of the parietal cortex are necessary to implement attention shifting in the context of visual dimensional change and lesions in these regions lead to a loss of dimensional effects. The transcranial direct-current stimulation (tDCS) is a widely used non-invasive method of neuromodulation having- dependent on the type of stimulation - excitatory or inhibitory effects (Nitsche and Paulus, 2000; 2001). In the initial phase of the present project I will receive extensive training with tDCS to enable me to conduct my own study in the second part of the project. The basic idea of the study is to use tDCS to either enhance or inhibit the dimensional effects (reaction time benefits in dimensional repetitions, reaction time costs in dimensional changes) by applying either stimulation to right or left parietal cortex. Previous work indicated that excitatory stimulation of the parietal cortex facilitates and inhibitory stimulation suppresses detection of targets in a visual search task (Sparing et al., 2009). I anticipate that excitatory stimulation will increase selection performance by increasing benefits and decreasing costs. The study will enable us to investigate structural and functional substrates of dimensional carry-over effects, i.e., if the parietal cortex actually plays a necessary role in generating memory-based guidance of search.

• DFG Programme: Research Fellowships
• International Connection: United Kingdom
• Host: Professor Dr. Glyn Humphreys