At any given moment, we are confronted with an overwhelming amount of information, far more than our sensory systems can fully process at once. How does the human mind deal with this surplus of information and forms coherent representations from the constant stream of multi-sensory inputs? Our research aims at understanding how attention allows us to selectively process information, what the abilities and capacity limits of this selection process are, how attention can change our experience with the visual world, and how attention integrates sensory processing across different modalities. SOME CURRENT RESEARCH QUESTIONS How does hearing a sound influence visual processing? Hearing a sound can influence visual processing of a co-localized visual object: it can make it appear higher contrast, or make it appear earlier in time, than it is actually is. These sound-induced changes in visual perception are accompanied by modulations of the neural processing strength of the visual object in the early visual processing pathways. What are the neural mechanisms of these cross-modal interactions? We have found that a task-irrelevant, salient sound activates visual cortex automatically - even in the absence of any visual inputs. Interestingly, these sound-induced changes in visual-cortical processing are spatially specific and occur in the region of the visual cortex that represents that location. In other words, when hearing a sound on the left side of the visual field, processing in the right visual cortex is enhanced, and vice versa. This line of work shows that our senses are inextricably connected - and perceptual processing in one modality influences perceptual processing in another modality, at least for audition and vision. Sounds activate visual cortex and improve visual discrimination. Feng, W., Störmer, V.S., Martinez, A., McDonald, J.J.,& Hillyard, S.A. (2014). The Journal of Neuroscience, 34(29), 9817-9824. Cross-modal orienting of visual attention. Hillyard, S.A., Störmer, V.S., Feng, W., Martinez, A., & McDonald, J.J. (2015). Neuropsychologia. 83, 170-178. Salient, irrelevant sounds reflexively induce alpha rhythm desynchronization in parallel with slow potential shifts in visual cortex. Störmer, V.S., Feng, W., Martinez, A., McDonald, J.J.,& Hillyard, S.A. (2016). Journal of Cognitive Neuroscience, 28(3), 433-445. In what ways does attention alter our perception? Attention is well-known to increase the speed and accuracy by which we process a stimulus. But does attention change the way we see an object? Involuntary (exogenous) cueing of attention can enhance the perceived contrast of a simple object (Gabor patch), by increasing the signal strength of that object at the location of the attentional cue in early visual cortex. More recently we explored whether attention can also increase the contrast of more complex, real-world stimuli like faces, and found that attention increases the perceived contrast of face parts, in particular the region of the eyes. Furthermore, attended faces were judged to be more attractive than unattended faces - possibly because higher contrast faces tend to be judged as more attractive. These studies show that attention not only helps us by facilitating processing of an attended stimulus, but it fundamentally changes the way we perceive the world - for example, how attractive we find the people around us. Attention alters perceived attractiveness. Störmer, V.S., & Alvarez, G.A. (2016). Psychological Science., 27(4), 563-571. What are the fundamental mechanisms of selection? We can select a stimulus based on its location in the visual field, or based on its feature, for example its color. What happens to stimuli inside and outside the focus of attention? We found that when attending to a particular color, for example red, processing of items in that color is enhanced throughout the visual field (global excitation), and at the same time processing of colors perceptually similar to the attended color is inhibited. Thus, feature-based selection elicits an excitatory peak at the attended feature with a narrow inhibitory surround in feature space to suppress potentially confusable stimuli during visual perception. This center-surround profile is similar to what other research has reported for spatial attention, and thus suggests that surround-suppression is a canonical principle of attentional selection that can operate based on location or based on features, depending on the task and visual environment. What are the limits of selection? Attentional selection is inherently limited and we can only select small subsets of objects at once. But why are there these limits? For effective stimulus selection, attention often modulates target representations at the earliest stages of processing - for example, in low-level visual cortex. However, low-level visual cortex is anatomically divided at the hemifield, with left visual cortex processing the right half-field, and the right visual cortex processing the left half-field. We found that attention effectively enhances target representations for objects presented in separate visual fields (left, right), but not when objects are presented in the same visual field (e.g., only left). These results indicate that attention - a system usually considered high-level - is constrained by the neural architecture of the perceptual systems, in this case the anatomy of the visual cortex. Thus, attention limits appear not to be fixed - but rather depend on the nature and content of the neural representations over which it operates. Sustained multifocal attentional enhancement of stimulus processing in early visual areas predicts tracking performance. Störmer, V.S., Winther, G.N., Li, S.-C., & Andersen, S.K. (2013).The Journal of Neuroscience, 33(12), 5346-5351. How does attentional selection change in the course of healthy aging? With advancing age, many cognitive abilities decline. The mechanisms underlying these age-related differences are yet not well understood. In a series of studies, we investigated in what ways older adults differ from younger adult in their ability to select multiple target objects from nontargt objects . Using EEG, we found that the age-related decline is - at least in part - driven by differences at early processing stages, namely during stimulation processing itself. We found these age-related deficits at early processing stages across different types of tasks, in particular an attentive tracking task and a visual-spatial working memory task. Importantly, we also found that many of the older adults performed at the same level as many of the younger adults. This subgroup of high-performing older adults nonetheless showed differences in the underlying neural responses, suggesting that selection mechanisms change throughout the lifespan. Normative shifts of cortical mechanisms of encoding contribute to adult age differences in visual-spatial working memory. Störmer, V.S., Li, S.-C., Heekeren, H.R., Lindenberger, U. (2013). NeuroImage, 73, 167-175. Normal aging delays and compromises early multifocal visual attention during object tracking. Störmer, V.S., Li, S.-C., Heekeren, H.R., Lindenberger, U., (2013). Journal of Cognitive Neuroscience, 25(2), 188-202. Feature-based interference from unattended visual field during attentional tracking in younger and older adults. Störmer, V.S., Li, S.-C., Heekeren, H.R., Lindenberger, U., (2011).Journal of Vision, 11, 1-12. Dopaminergic and cholinergic modulation of working memory and attention: insights from genetic research and implications for cognitive aging. Störmer, V.S., Passow, S., Biesenack, J., Li, S.-C. (2012). Developmental Psychology, 48, 875-889. |      |
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