EEG alpha oscillations in the preparation for global and local processing predict behavioral performance

Abstract

Visual attention can be directed either to the global features of a display or to the local elements that make up the display. We investigated whether oscillatory brain responses to globally or locally directed cue stimuli predict behavioral performance in subsequent target processing. Induced alpha band (8-12 Hz) amplitudes in the pre-stimulus interval were measured separately for the global and the local level, where individual trials were assigned to one of three groups according to the response speed towards incongruent stimuli. Fast responses to local features were associated with high alpha amplitudes in the right centro-parietal cortex, whereas fast responses to global forms were associated with high alpha in left centro-parietal cortex. For trials with slower responses, the pattern of hemispheric differences was diminished or even reversed. It is interpreted that the left and the right parietal cortex exert top-down control over hierarchical processing by inhibiting stimulus representations in one hemisphere.

Neural correlates of after-effects caused by adaptation to multiple face displays

“…3c) revealed a non-significant tendency for longer reaction times in the global than in the focal condition (main effect of condition (F(1,10) = 3.45, p = 0.09), while the effect of different female/male ratios and interactions were nonsignificant. This finding suggests that only by manipulating the experimental task (focal vs. global attention), we are able to manipulate the subjects' decision, similarly to previous studies (Navon 1977;Romei et al 2012;Sasaki et al 2001;Volberg et al 2009), using textures or letters. Altogether, the results of Experiment 1 support that the observers are able to process MFS globally by extracting the statistical average of the presented gender composition.…”

“…Previous experiments, using simple geometrical patterns or letters, arranged in a way that they form another, global pattern or letter (Navon 1977;Romei et al 2012;Sasaki et al 2001;Scherf et al 2009;Volberg et al 2009) suggest that separate systems control attention at the local and global levels (for a review see Sasaki 2007). Our current results are not excluding this possibility: the relatively longer reaction times, observed for the global when compared to local condition suggest different neural mechanisms.…”

“…This desensitization could be the result of a shift from a noise-driven modus to an adaptation-driven modus of the neurons due to after-hyperpolarization currents (Theodoni et al 2011). However, previous studies of global/local attention suggested the existence of separate neural mechanisms of the processing of global and local aspects of a complex stimulus (Lamb et al 1990;Volberg et al 2009;Weissman and Woldorff 2005). Thus, it is possible that the neural correlates of global MFS representations are also distinct from those of single isolated elements.…”

“…Previous adaptation studies with single high-level stimuli showed that occipitotemporal category-selective areas (fusiform face area and occipital face area) are responsible for hand-and facerelated after-effects (Kovács et al 2008;Cziraki et al 2010). However, studies of global/local attention indicate that distinct neural mechanisms underlie global versus local processing of composite objects shapes (Hübner and Volberg 2005;Lamb et al 1990;Volberg and Hübner 2004;Volberg et al 2009;Weissman and Woldorff 2005). Thus, it is possible that the neural correlates of global MFS representations are distinct from those of single-isolated elements.…”

“…Second, they could attend to the global aspects of a scene and integrate the relevant pieces of information (Liechty et al 2003). In the relevant literature, the manipulation of attention is reached via different instructions: subjects are either asked to attend the global or local properties of a given stimulus (Navon 1977;Romei et al 2012;Sasaki et al 2001;Volberg et al 2009). In the present set of experiments, we were interested in participants' ability to process a MFS globally, as a whole.…”