@article{ValsecchiDimigenKliegletal.2009, author = {Valsecchi, Matteo and Dimigen, Olaf and Kliegl, Reinhold and Sommer, Werner and Turatto, Massimo}, title = {Microsaccadic inhibition and P300 enhancement in a visual oddball task}, issn = {0048-5772}, doi = {10.1111/j.1469-8986.2009.00791.x}, year = {2009}, abstract = {It has recently been demonstrated that the presentation of visual oddballs induces a prolonged inhibition of microsaccades. The amplitude of the P300 component in event-related potentials (ERPs) has been shown to be sensitive to the category (target vs. nontarget) of the eliciting stimulus, its overall probability, and the preceding stimulus sequence. In the present study we further specify the functional underpinnings of the prolonged microsaccadic inhibition in the visual oddball task, showing that the stimulus category, the frequency of a stimulus, and the preceding stimulus sequence influence microsaccade rate. Furthermore, by co-recording ERPs and eye movements, we were able to demonstrate that, despite being largely sensitive to the same experimental manipulation, the amplitude of P300 and the microsaccadic inhibition predict each other only weakly.}, language = {en} } @misc{ValsecchiDimigenKliegletal.2009, author = {Valsecchi, Matteo and Dimigen, Olaf and Kliegl, Reinhold and Sommer, Werner and Turatto, Massimo}, title = {Microsaccadic Inhibition and P300 Enhancement in a Visual Oddball Task}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-57170}, year = {2009}, abstract = {It has recently been demonstrated that the presentation of a rare target in a visual oddball paradigm induces a prolonged inhibition of microsaccades. In the field of electrophysiology, the amplitude of the P300 component in event-related potentials (ERP) has been shown to be sensitive to the stimulus category (target vs. non target) of the eliciting stimulus, its overall probability, and the preceding stimulus sequence. In the present study we further specify the functional underpinnings of the prolonged microsaccadic inhibition in the visual oddball task, showing that the stimulus category, the frequency of a stimulus and the preceding stimulus sequence influence microsaccade rate. Furthermore, by co-recording ERPs and eye-movements, we were able to demonstrate that, despite being largely sensitive to the same experimental manipulation, the amplitude of P300 and the microsaccadic inhibition predict each other very weakly, and thus constitute two independent measures of the brain's response to rare targets in the visual oddball paradigm.}, language = {en} } @article{SchinkelMarwanDimigenetal.2009, author = {Schinkel, Stefan and Marwan, Norbert and Dimigen, Olaf and Kurths, J{\"u}rgen}, title = {Confidence bounds of recurrence-based complexity measures}, issn = {0375-9601}, doi = {10.1016/j.physleta.2009.04.045}, year = {2009}, abstract = {In the recent past, recurrence quantification analysis (RQA) has gained an increasing interest in various research areas. The complexity measures the RQA provides have been useful in describing and analysing a broad range of data. It is known to be rather robust to noise and nonstationarities. Yet, one key question in empirical research concerns the confidence bounds of measured data. In the present Letter we suggest a method for estimating the confidence bounds of recurrence-based complexity measures. We study the applicability of the suggested method with model and real- life data.}, language = {en} } @article{KlieglDambacherDimigenetal.2012, author = {Kliegl, Reinhold and Dambacher, Michael and Dimigen, Olaf and Jacobs, Arthur M. and Sommer, Werner}, title = {Eye movements and brain electric potentials during reading}, series = {Psychological research : an international journal of perception, attention, memory, and action}, volume = {76}, journal = {Psychological research : an international journal of perception, attention, memory, and action}, number = {2}, publisher = {Springer}, address = {Heidelberg}, issn = {0340-0727}, doi = {10.1007/s00426-011-0376-x}, pages = {145 -- 158}, year = {2012}, abstract = {The development of theories and computational models of reading requires an understanding of processing constraints, in particular of timelines related to word recognition and oculomotor control. Timelines of word recognition are usually determined with event-related potentials (ERPs) recorded under conditions of serial visual presentation (SVP) of words; timelines of oculomotor control are derived from parameters of eye movements (EMs) during natural reading. We describe two strategies to integrate these approaches. One is to collect ERPs and EMs in separate SVP and natural reading experiments for the same experimental material (but different subjects). The other strategy is to co-register EMs and ERPs during natural reading from the same subjects. Both strategies yield data that allow us to determine how lexical properties influence ERPs (e.g., the N400 component) and EMs (e.g., fixation durations) across neighboring words. We review our recent research on the effects of frequency and predictability of words on both EM and ERP measures with reference to current models of eye-movement control during reading. Results are in support of the proposition that lexical access is distributed across several fixations and across brain-electric potentials measured on neighboring words.}, language = {en} } @article{FroemerDimigenNiefindetal.2015, author = {Fr{\"o}mer, Romy and Dimigen, Olaf and Niefind, Florian and Krause, Niels and Kliegl, Reinhold and Sommer, Werner}, title = {Are Individual Differences in Reading Speed Related to Extrafoveal Visual Acuity and Crowding?}, series = {PLoS one}, volume = {10}, journal = {PLoS one}, number = {3}, publisher = {PLoS}, address = {San Fransisco}, issn = {1932-6203}, doi = {10.1371/journal.pone.0121986}, pages = {18}, year = {2015}, abstract = {Readers differ considerably in their speed of self-paced reading. One factor known to influence fixation durations in reading is the preprocessing of words in parafoveal vision. Here we investigated whether individual differences in reading speed or the amount of information extracted from upcoming words (the preview benefit) can be explained by basic differences in extrafoveal vision-i.e., the ability to recognize peripheral letters with or without the presence of flanking letters. Forty participants were given an adaptive test to determine their eccentricity thresholds for the identification of letters presented either in isolation (extrafoveal acuity) or flanked by other letters (crowded letter recognition). In a separate eye-tracking experiment, the same participants read lists of words from left to right, while the preview of the upcoming words was manipulated with the gaze-contingent moving window technique. Relationships between dependent measures were analyzed on the observational level and with linear mixed models. We obtained highly reliable estimates both for extrafoveal letter identification (acuity and crowding) and measures of reading speed (overall reading speed, size of preview benefit). Reading speed was higher in participants with larger uncrowded windows. However, the strength of this relationship was moderate and it was only observed if other sources of variance in reading speed (e.g., the occurrence of regressive saccades) were eliminated. Moreover, the size of the preview benefit-an important factor in normal reading-was larger in participants with better extrafoveal acuity. Together, these results indicate a significant albeit moderate contribution of extrafoveal vision to individual differences in reading speed.}, language = {en} } @misc{FroemerDimigenNiefindetal.2015, author = {Fr{\"o}mer, Romy and Dimigen, Olaf and Niefind, Florian and Kliegl, Reinhold and Sommer, Werner}, title = {Are individual differences in reading speed related to extrafoveal visual acuity and crowding?}, series = {Postprints der Universit{\"a}t Potsdam : Humanwissenschaftliche Reihe}, journal = {Postprints der Universit{\"a}t Potsdam : Humanwissenschaftliche Reihe}, number = {494}, issn = {1866-8364}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-408003}, pages = {18}, year = {2015}, abstract = {Readers differ considerably in their speed of self-paced reading. One factor known to influence fixation durations in reading is the preprocessing of words in parafoveal vision. Here we investigated whether individual differences in reading speed or the amount of information extracted from upcoming words (the preview benefit) can be explained by basic differences in extrafoveal vision-i.e., the ability to recognize peripheral letters with or without the presence of flanking letters. Forty participants were given an adaptive test to determine their eccentricity thresholds for the identification of letters presented either in isolation (extrafoveal acuity) or flanked by other letters (crowded letter recognition). In a separate eye-tracking experiment, the same participants read lists of words from left to right, while the preview of the upcoming words was manipulated with the gaze-contingent moving window technique. Relationships between dependent measures were analyzed on the observational level and with linear mixed models. We obtained highly reliable estimates both for extrafoveal letter identification (acuity and crowding) and measures of reading speed (overall reading speed, size of preview benefit). Reading speed was higher in participants with larger uncrowded windows. However, the strength of this relationship was moderate and it was only observed if other sources of variance in reading speed (e.g., the occurrence of regressive saccades) were eliminated. Moreover, the size of the preview benefit-an important factor in normal reading-was larger in participants with better extrafoveal acuity. Together, these results indicate a significant albeit moderate contribution of extrafoveal vision to individual differences in reading speed.}, language = {en} } @article{DimigenValsecchieSommeretal.2009, author = {Dimigen, Olaf and Valsecchie, Matteo and Sommer, Werner and Kliegl, Reinhold}, title = {Human microsaccade-related visual brain responses}, issn = {0270-6474}, doi = {10.1523/JNEUROSCI.0911-09.2009}, year = {2009}, language = {en} } @misc{DimigenValsecchiSommeretal.2009, author = {Dimigen, Olaf and Valsecchi, Matteo and Sommer, Werner and Kliegl, Reinhold}, title = {Human Microsaccade-Related Visual Brain Responses}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-56923}, year = {2009}, abstract = {Microsaccades are very small, involuntary flicks in eye position that occur on average once or twice per second during attempted visual fixation. Microsaccades give rise to EMG eye muscle spikes that can distort the spectrum of the scalp EEG and mimic increases in gamma band power. Here we demonstrate that microsaccades are also accompanied by genuine and sizeable cortical activity, manifested in the EEG. In three experiments, high-resolution eye movements were corecorded with the EEG: during sustained fixation of checkerboard and face stimuli and in a standard visual oddball task that required the counting of target stimuli. Results show that microsaccades as small as 0.15° generate a field potential over occipital cortex and midcentral scalp sites 100 -140 ms after movement onset, which resembles the visual lambda response evoked by larger voluntary saccades. This challenges the standard assumption of human brain imaging studies that saccade-related brain activity is precluded by fixation, even when fully complied with. Instead, additional cortical potentials from microsaccades were present in 86\% of the oddball task trials and of similar amplitude as the visual response to stimulus onset. Furthermore, microsaccade probability varied systematically according to the proportion of target stimuli in the oddball task, causing modulations of late stimulus-locked event-related potential (ERP) components. Microsaccades present an unrecognized source of visual brain signal that is of interest for vision research and may have influenced the data of many ERP and neuroimaging studies.}, language = {en} } @misc{DimigenSommerHohlfeldetal.2011, author = {Dimigen, Olaf and Sommer, Werner and Hohlfeld, Annette and Jacobs, Arthur M. and Kliegl, Reinhold}, title = {Coregistration of eye movements and EEG in natural reading analyses and review}, series = {Journal of experimental psychology : General}, volume = {140}, journal = {Journal of experimental psychology : General}, number = {4}, publisher = {American Psychological Association}, address = {Washington}, issn = {0096-3445}, doi = {10.1037/a0023885}, pages = {552 -- 572}, year = {2011}, abstract = {Brain-electric correlates of reading have traditionally been studied with word-by-word presentation, a condition that eliminates important aspects of the normal reading process and precludes direct comparisons between neural activity and oculomotor behavior. In the present study, we investigated effects of word predictability on eye movements (EM) and fixation-related brain potentials (FRPs) during natural sentence reading. Electroencephalogram (EEG) and EM (via video-based eye tracking) were recorded simultaneously while subjects read heterogeneous German sentences, moving their eyes freely over the text. FRPs were time-locked to first-pass reading fixations and analyzed according to the cloze probability of the currently fixated word. We replicated robust effects of word predictability on EMs and the N400 component in FRPs. The data were then used to model the relation among fixation duration, gaze duration, and N400 amplitude, and to trace the time course of EEG effects relative to effects in EM behavior. In an extended Methodological Discussion section, we review 4 technical and data-analytical problems that need to be addressed when FRPs are recorded in free-viewing situations (such as reading, visual search, or scene perception) and propose solutions. Results suggest that EEG recordings during normal vision are feasible and useful to consolidate findings from EEG and eye-tracking studies.}, language = {en} } @article{DimigenKlieglSommer2012, author = {Dimigen, Olaf and Kliegl, Reinhold and Sommer, Werner}, title = {Trans-saccadic parafoveal preview benefits in fluent reading: A study with fixation-related brain potentials}, series = {NeuroImage : a journal of brain function}, volume = {62}, journal = {NeuroImage : a journal of brain function}, number = {1}, publisher = {Elsevier}, address = {San Diego}, issn = {1053-8119}, doi = {10.1016/j.neuroimage.2012.04.006}, pages = {381 -- 393}, year = {2012}, abstract = {During natural reading, a parafoveal preview of the upcoming word facilitates its subsequent recognition (e.g., shorter fixation durations compared to masked preview) but nothing is known about the neural correlates of this so-called preview benefit. Furthermore, while the evidence is strong that readers preprocess orthographic features of upcoming words, it is controversial whether word meaning can also be accessed parafoveally. We investigated the timing, scope, and electrophysiological correlates of parafoveal information use in reading by simultaneously recording eye movements and fixation-related brain potentials (FRPs) while participants read word lists fluently from left to right. For one word the target (e.g., "blade") parafoveal information was manipulated by showing an identical ("blade"), semantically related ("knife"), or unrelated ("sugar") word as preview. In boundary trials, the preview was shown parafoveally but changed to the correct target word during the incoming saccade. Replicating classic findings, target words were fixated shorter after identical previews. In the EEG, this benefit was reflected in an occipitotemporal preview positivity between 200 and 280 ms. In contrast, there was no facilitation from related previews. In parafoveal-on-foveal trials, preview and target were embedded at neighboring list positions without a display change. Consecutive fixation of two related words produced N400 priming effects, but only shortly (160 ms) after the second word was directly fixated. Results demonstrate that neural responses to words are substantially altered by parafoveal preprocessing under normal reading conditions. We found no evidence that word meaning contributes to these effects. Saccade-contingent display manipulations can be combined with EEG recordings to study extrafoveal perception in vision.}, language = {en} } @article{DambacherDimigenBraunetal.2012, author = {Dambacher, Michael and Dimigen, Olaf and Braun, Mario and Wille, Kristin and Jacobs, Arthur M. and Kliegl, Reinhold}, title = {Stimulus onset asynchrony and the timeline of word recognition: Event-related potentials during sentence reading}, series = {Neuropsychologia : an international journal in behavioural and cognitive neuroscience}, volume = {50}, journal = {Neuropsychologia : an international journal in behavioural and cognitive neuroscience}, number = {8}, publisher = {Elsevier}, address = {Oxford}, issn = {0028-3932}, doi = {10.1016/j.neuropsychologia.2012.04.011}, pages = {1852 -- 1870}, year = {2012}, abstract = {Three ERP experiments examined the effect of word presentation rate (i.e., stimulus onset asynchrony, SOA) on the time course of word frequency and predictability effects in sentence reading. In Experiments 1 and 2, sentences were presented word-by-word in the screen center at an SOA of 700 and 490 ms, respectively. While these rates are typical for psycholinguistic ERP research, natural reading happens at a considerably faster pace. Accordingly. Experiment 3 employed a near-normal SOA of 280 ms, which approximated the rate of normal reading. Main results can be summarized as follows: (1) The onset latency of early frequency effects decreases gradually with increasing presentation rates. (2) An early interaction between top-down and bottom-up processing is observed only under a near-normal SOA. (3) N400 predictability effects occur later and are smaller at a near-normal (i.e., high) presentation rate than at the lower rates commonly used in ERP experiments. (4) ERP morphology is different at the shortest compared to longer SOAs. Together, the results point to a special role of a near-normal presentation rate for visual word recognition and therefore suggest that SOA should be taken into account in research of natural reading.}, language = {en} }