Abstract
Attention is the ability to prioritize a set of information at expense of others and can be internally- or externally-oriented. Alpha and theta oscillations have been extensively implicated in attention. However, it is unclear how these oscillations operate when sensory distractors are presented continuously during task-relevant internal processes, in close-to-real-life conditions. Here, EEG signals from healthy participants were obtained at rest and in three attentional conditions, characterized by the execution of a mental math task (internal attention), presentation of pictures on a monitor (external attention), and task execution under the distracting action of picture presentation (internal-external competition). Alpha and theta power were investigated at scalp level and at some cortical regions of interest (ROIs); moreover, functional directed connectivity was estimated via spectral Granger Causality. Results show that frontal midline theta was distinctive of mental task execution and was more prominent during competition compared to internal attention alone, possibly reflecting higher executive control; anterior cingulate cortex appeared as mainly involved and causally connected to distant (temporal/occipital) regions. Alpha power in visual ROIs strongly decreased in external attention alone, while it assumed values close to rest during competition, reflecting reduced visual engagement against distractors; connectivity results suggested that bidirectional alpha influences between frontal and visual regions could contribute to reduce visual interference in internal attention. This study can help to understand how our brain copes with internal-external attention competition, a condition intrinsic in the human sensory-cognitive interplay, and to elucidate the relationships between brain oscillations and attentional functions/dysfunctions in daily tasks.
Highlights
In our daily life, the ability to process relevant information and reduce the interfering effect of distracting information is essential to successfully complete any task at hand
By estimating cortical activity from the EEG signals via eLORETA, we aim to address the following questions: What are the alpha and theta power modulations that play a role in these conditions of external attention and internal attention respectively, and how are some key cortical regions involved? How is the directional flow of information in the two bands modified among these regions by these two states of attention? How do the previous mechanisms of external and internal attention interact when the two forms of attention are in competition?
We considered separately the set of 7 regions of interest (ROIs) selected for the alpha-band analysis and the set of 7 ROIs selected for the theta-band analysis
Summary
The ability to process relevant information and reduce the interfering effect of distracting information is essential to successfully complete any task at hand. This ability is accomplished via attentive processes; attention acts by prioritizing the processing of a subset of information at the expense of others [1, 2]. Externally-oriented attention is directed towards stimuli in the environment. External attention can be voluntarily driven by task demands in a top-down fashion, e.g. when we focus on a specific spatial location or feature of the sensory stimuli, being this location/feature goal-relevant. Examples of internally directed cognition include episodic memory retrieval, working memory, planning, mental imagery, mental calculation [1]
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