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Report

Teaser, summary, work performed and final results

Periodic Reporting for period 1 - DynamAtt (Dynamics of Attentional Networks in the Human Brain in Health and Disease:Evidence from Intracerebral and MEG Recordings)

Teaser

Summary

Attention allows us to explore the environment and to effectively respond to external events. Attention sets priorities on the basis of our goals and of the salience of external stimuli. Human visual attention relies on distinct dorsal and ventral fronto-parietal cortical networks, but little is known about their dynamics, because hitherto our knowledge mostly depends on functional Magnetic Resonance Imaging, which has limited temporal resolution. Lesions to these networks result in hemispatial neglect, a common disabling condition affecting attention functions, and a common sequel of stroke. This project uses high-resolution intracerebral recordings during attention task execution in epileptic patients, exhibiting normal attention, implanted with depth electrodes in preparation for surgery. The data collected will serve to find the neural basis supporting different aspects of attention within each network; discern their temporal behavior; and analyze their interaction dynamics. Next, the results can aid in mapping the pathological changes in patients with neglect, a common disabling disorder affecting attention. This study will extend our knowledge of attention in health and disease, potentially improving rehabilitation.

Work performed

First, we developed a theoretical model, FORTIOR, describing the cortical processes leading to two well documented behavioral phenomena related to attention: facilitation and inhibition of return (IOR). Facilitation refers to the accelerated response to a visual stimulus when it is preceded by a stimulus appearing at the same peripheral location, relative to when it is preceded by a stimulus appearing at a different location. IOR is an opposite phenomena, whereby the same set of two stimuli appearing one after the other at the same peripheral location but with a longer delay between them, elicits a slower response compared to when they appear at different locations. The model is based on known facts about the anatomical and functional organization of fronto-parietal attention networks, and accounts for a broad range of behavioral findings in healthy participants and brain-damaged patients. FORTIOR does that by combining four principles of asymmetry: FORTIOR accounts for spatial asymmetries in the occurrence of IOR after brain damage and after non-invasive transcranial magnetic stimulation on parietal and frontal regions. It also provides a framework to understand dissociations between manual and saccadic IOR, and makes testable predictions for future experiments to assess its validity.
Additionally, high resolution brain activity was collected from 27 epileptic patients implanted with depth electrodes while they performed the Posner cueing task, testing their exogenous attention. The data obtained was used to test some of FORTIOR predictions, and to map the spatiotemporal dynamics of the responses across the brain to exogenous cues and targets. This studies were presented in seven international conferences and seminars, and resulted in three publications in international peer reviewed journals.

Final results

This project will explore the spatiotemporal dynamics of visual attention in better resolution than previously done. Its results will shed light on normal and pathological attention brain mechanisms.
Better understanding attention mechanisms is highly relevant for everyday attention-critical tasks, such as operating heavy machinery, conducting medical procedures and driving. In the European Union, about 50,000 individuals are killed in transport accidents every year, the majority in road traffic accidents (http://ec.europa.eu/transport/infrastructure/doc/crash-cost.pdf). One of the main causes for accidents is human error, which often results from failures in attention processes (for example a failure to detect a pedestrian or to simultaneously monitor approaching vehicles in dense traffic). Using cell phones or texting while driving increases attentional load and thus result in a greater risk. Better understanding of the neural basis of attention and its constraints may aid in developing solutions to deal with this tragic problem. Indeed, any field in which distraction can have detrimental results may benefit from this research.
Additionally, this project will promote our knowledge of abnormal attention processing in hemispatial neglect. Worldwide, 15 million people suffer a stroke each year. Forty percent of right hemisphere stroke survivors will suffer from neglect, which is one of the most negative prognostic signs for rehabilitation success. The estimated economic burden of stroke is vast (e.g. in Europe the cost was approximately â‚¬ 64.1 billion in 2010), so expanding the knowledge of normal and pathological attention mechanism underlying neglect and consequentially developing better rehabilitation strategies will have a direct impact on European society.