Parameter-based assessment of visual attention: functional neuroanatomy, timing and interference
Zusammenfassung der Projektergebnisse
The theory of visual attention (TVA, Bundesen 1990) offers both a diagnostic tool and a theoretical frame-work to bridge the gap between clinical examinations and adequate neuro-anatomical models of attentional function or dysfunction. The aim of this proposal was to provide a anatomical allocation of distinct attention parameters by combining fMRI with navigated TMS (NBS) or EEG, thus allowing a functional neuro-anatomical differentiation of distinct attentional parameters. In a series of behavioral, fMRI and TMS experiments, as well as on a patient study anatomical correlates of distinct attentional TVA parameters (visual short term memory storage capacity (VSTM), visual processing speed, spatial weighting and selective control) could be characterized on different levels of the attention network. Behavioral level: In directly comparing the impact of visual hemifields on TVA capacity parameters it became evident that bilateral presentations had a strong importance for visual attention capacity parameters not only on an early level of visual attentional processing, but also on a higher processing stage such as VSTM. Early visual areas: Comparing the fMRI signal at retinotopic positions in early visual areas provided evidence that the bilateral field advantage in parallel attentional processing over separated attended locations can be assigned, at least partly, to differences in distractor position integration in early visual areas. These results provide evidence for a greater integration of locations between two attended locations within one hemifield than across both hemifields. Precuneus: Applying navigated rTMS over the left or right precuneus revealed further evidence that the bilateral field advantage in parallel attentional processing cannot only ascribed to early stages of visual attentional processing. Instead, rTMS over the right precuneus diminished the bilateral field advantage. Thus, the right precuneus seems to play a causal role in VSTM capacity, particularly in bilateral visual displays. Thalamus: According to the neural theory of visual attention (NTVA) besides visual and parietal areas thalamic nuclei are involved in visual attentional processing. Combining TVA-based assessment of visual attention parameters with lesion symptom mapping in stroke patients with very circumscribed lesions in distinct thalamic nuclei provide evidence that specific thalamic nuclei are involved in distinct attentional functions (lateral = processing speed, medial = spatial weighting). Moreover, lesions to lateral thalamic nuclei can lead to fluctuation of sensory symptoms (paresthesia) over time and the thalamus seem to be differentially activated in high and low performers during visual attentional processing. Higher areas: Using fMRI we could show that a network including the cerebellum, the inferior temporal gyrus left, the superior temporal and the precentral gyri, the thalamus, the lingual gyri and precuneus, as well as the medial and superior frontal gyri is involved in TVA-based attentional processing. Besides the thalamus differences between high and low performers were evident in the left precuneus and the medial frontal gyri.
Projektbezogene Publikationen (Auswahl)
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(2011). Hemifield effects of spatial attention in early human visual cortex. Eur J Neurosci 33(12):2349-58
Kraft A, Kehrer S, Hagendorf H, Brandt SA
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(2013). Visual attention capacity parameters covary with hemifield alignment. Neuropsychologia 51(5):876-85
Kraft A, Dyrholm M, Bundesen C, Kyllingsbæk S, Kathmann N, Brandt SA
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(2015). Dissociable spatial and non-spatial attentional deficits after circumscribed thalamic stroke. Cortex. 64:327-42
Kraft A, Irlbacher K, Finke K, Kaufmann C, Kehrer S, Liebermann D, Bundesen C, Brandt SA
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(2015). TMS over the right precuneus reduces the bilateral field advantage in visual short term memory capacity. Brain Stimulation 8(2):216-23
Kraft A, Dyrholm M, Kehrer S, Kaufmann C, Bruening J, Kathmann N, Bundesen C, Irlbacher K, Brandt SA
