Kathrin Finke

Usability of a theory of visual attention (TVA) for parameter-based measurement of attention I: Evidence from normal subjects

The present study investigated the usability of whole and partial report of briefly displayed letter arrays as a diagnostic tool for the assessment of attentional functions. The tool is based on Bundesens (1990, 1998, 2002; Bundesen et al., 2005) theory of visual attention (TVA), which assumes four separable attentional components: processing speed, working memory storage capacity, spatial distribution of attention, and top-down control. A number of studies (Duncan et al., 1999; Habekost & Bundesen, 2003; Peers et al., 2005) have already demonstrated the clinical relevance of these parameters. The present study was designed to examine whether (a) a shortened procedure bears sufficient accuracy and reliability, (b) whether the procedures reveal attentional constructs with clinical relevance, and (c) whether the mathematically independent parameters are also empirically independent. In a sample of 35 young healthy subjects, we found high intraparameter correlations between full- and short-length tests and sufficient internal consistencies as measured via a bootstrapping method. The clinical relevance of the TVA parameters was demonstrated by significant correlations with established clinical tests measuring similar constructs. The empirical independence of the four TVA parameters is suggested by nonsignificant or, in the case of processing speed and working memory storage capacity, only modest correlations between the parameter values.

Staged decline of visual processing capacity in mild cognitive impairment and Alzheimer's disease

Visual information intake was assessed with a whole-report task in patients with probable Alzheimers disease (AD), mild cognitive impairment (MCI), and healthy elderly control subjects. Based on a theory of visual attention (TVA), four parameters were derived characterising different aspects of visual processing capacity: perceptual threshold, iconic memory, processing speed, and visual short-term memory (VSTM) storage capacity. Results indicated increased perceptual thresholds in MCI, and an additional decline in processing speed and VSTM storage capacity in AD. Cholinomimetic medication had beneficial effects on processing speed in AD patients. Perceptual thresholds were associated with disease duration, but not with cognitive measures, while the reverse was true for speed and VSTM measures. These results reveal a staged pattern of deficits affecting pre-attentive visual processing in MCI, and attentive processing in AD. It is compatible with the amyloid cascade hypothesis and suggests that impaired visual processing is a pathological feature present already at the MCI stage and might represent a distinct marker of upcoming AD independently from memory deficits.

Attentional and sensory effects of lowered levels of intrinsic alertness

Low levels of intrinsic alertness are associated with lateralized performance in visual tasks, similar to neglect of the left (ipsilesional) visual hemi-field. However, it is unclear whether reduced alertness produces a specific lateralization of spatial-attentional processes in terms of the prioritization of right- over left-side stimuli, or whether it affects more basic functions of visuo-sensory coding, and/or higher function of the top-down control of selection, of stimuli on the left side. To decide between these alternatives, the present study examined the effects of lowered alertness, induced by a 50-min vigilance task, in a partial-report paradigm of briefly presented letter displays. With only one (unilateral) stimulus in display, no specific hemi-field effects were found under low-alertness conditions, indicating that reduced alertness impairs neither sensory effectiveness nor the top-town control of selection. However, with dual, bilateral stimuli, report accuracy was specifically affected for left-side targets (in subjects who showed comparable performance for both sides under normal-alertness conditions). This pattern can be interpreted in terms of a specific bias in spatial-attentional weighting, where prioritization of stimuli on the right leads to (mild) extinction of targets on the left. Moreover, participants who had a lower general level of alertness also showed a more pronounced re-distribution of weights, evidenced by a more severe imbalance in report accuracy, in a low compared to a normal state of alertness. This suggests that a low general level of intrinsic alertness engenders a specific vulnerability to neglect-like performance with a (mild) left-side extinction.

Preattentive surface and contour grouping in Kanizsa figures: Evidence from parietal extinction

Visual extinction commonly occurs after unilateral, parietal brain damage and manifests in a failure to identify contralesional stimuli when presented simultaneously with other, ipsilesional stimuli - but full awareness for single stimulus presentations. However, extinction can be substantially reduced when preattentive grouping operations link fragmentary items across hemifields into a coherent object. For instance, one study demonstrated preserved access to bilateral stimulus segments when these could be grouped to form a Kanizsa square [Mattingley, J. B., Davis, G., & Driver, J. (1997). Preattentive filling-in of visual surfaces in parietal extinction. Science, 275, 671-674]. Here, we investigated the relative contributions of distinct object attributes to the spared access in Kanizsa figure completion in extinction, by systematically varying the degree to which bilateral surface filling-in and contour interpolations group disparate items. We demonstrate that surface information can substantially reduce extinction, whereas contour completions showed comparably smaller influences. In summary, such graded influences of object attributes support recurrent models of grouping, first, linking fragmentary parts into coherent surfaces and, second, interpolating the precise boundaries.

Event-related potentials dissociate perceptual from response-related age effects in visual search.

Attentional decline plays a major role in cognitive changes with aging. However, which specific aspects of attention contribute to this decline is as yet little understood. To identify the contributions of various potential sources of age decrements in visual search, we combined response time measures with lateralized event-related potentials of younger and older adults performing a compound-search task, in which the target-defining dimension of a pop-out target (color/shape) and the response-critical target feature (vertical/horizontal stripes) varied independently across trials. Slower responses in older participants were associated with age differences in all analyzed event-related potentials from perception to response, indicating that behavioral slowing originates from multiple stages within the information-processing stream. Furthermore, analyses of carry-over effects from one trial to the next revealed repetition facilitation of the target-defining dimension and of the motor response-originating from preattentive perceptual and motor execution stages, respectively-to be independent of age. Critically, we demonstrated specific age deficits on intermediate processing stages when intertrial changes required more executively controlled processes, such as flexible stimulus-response (re-)mapping across trials.

Distinct Neural Markers of TVA-Based Visual Processing Speed and Short-Term Storage Capacity Parameters

An individuals visual attentional capacity is characterized by 2 central processing resources, visual perceptual processing speed and visual short-term memory (vSTM) storage capacity. Based on Bundesens theory of visual attention (TVA), independent estimates of these parameters can be obtained from mathematical modeling of performance in a whole report task. The frameworks neural interpretation (NTVA) further suggests distinct brain mechanisms underlying these 2 functions. Using an interindividual difference approach, the present study was designed to establish the respective ERP correlates of both parameters. Participants with higher compared to participants with lower processing speed were found to show significantly reduced visual N1 responses, indicative of higher efficiency in early visual processing. By contrast, for participants with higher relative to lower vSTM storage capacity, contralateral delay activity over visual areas was enhanced while overall nonlateralized delay activity was reduced, indicating that holding (the maximum number of) items in vSTM relies on topographically specific sustained activation within the visual system. Taken together, our findings show that the 2 main aspects of visual attentional capacity are reflected in separable neurophysiological markers, validating a central assumption of NTVA.

The capacity of attention and simultaneous perception of objects: A group study of Huntington's disease patients

Using a whole report-paradigm based on [Bundesen, C. (1990). A theory of visual attention. Psychological Review, 97, 523-547; Bundesen, C. (1998). A computational theory of visual attention. Philosophical Transactions of the Royal Society of London B, Biological Sciences, 353, 1271-1281] theory of visual attention (TVA), [Finke, K., Bublak, P., Dose, M., Müller, H. J., & Schneider, W. X. (2006). Parameter-based assessment of spatial and non-spatial attentional deficits in Huntingtons disease. Brain, 129, 1137-1151] demonstrated profound reductions in perceptual processing speed and visual working memory (WM) storage capacity in Huntingtons disease (HD) patients. A comparably severe impairment of visual processing capacity has previously been reported for two simultanagnosia patients [Duncan, J., Bundesen, C., Olson, A., Humphreys, G., Ward, R., Kyllingsbaek, S., van Raamsdonk, M., Rorden, C., & Chavda, S. (2003). Attentional functions in dorsal and ventral simultanagnosia. Cognitive Neuropsychology, 20, 675-702]. To investigate whether such a deficit does also prevail in HD, the simultaneous perception of visual objects was tested in 10 HD patients under free viewing conditions and without time constraints. Objects were presented under four different conditions: (i) single, (ii) multiple adjacent, (iii) multiple embedded, and (iv) multiple overlapping. The dependent measure was the percentage of identification failures. Performance was compared to that of 15 healthy subjects matched for age, education, gender and general mental ability. For HD patients, the percentage of errors in the various testing conditions was examined for correlations with the TVA parameters of visuo-perceptual processing speed and WM storage capacity. These parameters were estimated using verbal whole report of briefly presented letters. TVA permits the two parameters to be estimated mathematically independently and relatively unaffected by any motor deficits present in HD. The identification error rate was substantially increased in HD patients, compared to control subjects, in the overlapping-figures subtest. This deficit was significantly and negatively correlated with processing speed, whereas there was no correlation with WM storage capacity. These results demonstrate the presence of deficits in simultaneous perception in HD, related to a severe reduction in perceptual processing speed. The results are discussed with respect to a dopamine mediated decline of cortical cholinergic activation, diminishing the number of visual objects that can be simultaneously represented within the visual processing system.

Video game experience and its influence on visual attention parameters: An investigation using the framework of the Theory of Visual Attention (TVA)

Experts with video game experience, in contrast to non-experienced persons, are superior in multiple domains of visual attention. However, it is an open question which basic aspects of attention underlie this superiority. We approached this question using the framework of Theory of Visual Attention (TVA) with tools that allowed us to assess various parameters that are related to different visual attention aspects (e.g., perception threshold, processing speed, visual short-term memory storage capacity, top-down control, spatial distribution of attention) and that are measurable on the same experimental basis. In Experiment 1, we found advantages of video game experts in perception threshold and visual processing speed; the latter being restricted to the lower positions of the used computer display. The observed advantages were not significantly moderated by general person-related characteristics such as personality traits, sensation seeking, intelligence, social anxiety, or health status. Experiment 2 tested a potential causal link between the expert advantages and video game practice with an intervention protocol. It found no effects of action video gaming on perception threshold, visual short-term memory storage capacity, iconic memory storage, top-down control, and spatial distribution of attention after 15 days of training. However, observations of a selected improvement of processing speed at the lower positions of the computer screen after video game training and of retest effects are suggestive for limited possibilities to improve basic aspects of visual attention (TVA) with practice.

Systematic biases in the tactile perception of the subjective vertical in patients with unilateral neglect and the influence of upright vs. supine posture

Patients with right hemisphere lesions often show contralesional neglect. Recent research focused on deficits beyond the typical neglect symptoms observed in the horizontal plane. Studies investigating deficits in the frontal and sagittal plane revealed impairments in the judgment of the subjective vertical. Systematic deviations in the subjective vertical have been demonstrated in the visual and tactile modality, indicating a supramodal spatial orientation deficit. Further, the magnitude of deviations appears to be manipulable by modulations of body posture. The present study investigated the subjective tactile vertical (STV) in neglect patients in the frontal and sagittal plane and its dependence on posture. Neglect patients and healthy controls performed tactile-spatial judgments of axis orientations in supine and upright posture. Neglect patients displayed a marked variability as well as a systematic tilt in their STV judgments. The STV was tilted counterclockwise in the frontal and backward in the sagittal plane. This tilt was larger in severe compared to moderate neglect patients, while it was not evident in healthy subjects. Our results support previous evidence and indicate a multisensory spatial orientation deficit in neglect patients which is related to neglect severity. Further, we found that performance of neglect patients deteriorated in supine compared to upright posture. This finding conflicts with the suggestion of a performance benefit in supine posture due to reduced (asymmetric) gravitational input. The negative effect of supine posture on the spatial bias in neglect is discussed with respect to a presumably further reduced intrinsic alertness state in the typically hypo-aroused neglect patients.

Hemispheric dominance in the processing of J. S. Bach fugues: a transcranial Doppler sonography (TCD) study with musicians

Although the majority of studies on musical processing in musicians observed a left hemisphere dominance which has usually been explained by a proficient analytical strategy used by these subjects, the findings are still inconsistent. Changes in hemispheric activity induced by listening to music (J. S. Bach fugues) and by recognizing the repetitions of the fugue theme were examined, using the technique of bilateral transcranial Doppler sonography (TCD) of the left and right middle cerebral artery (MCA). Subjects were 32 right-handed musicians, half of whom were members of an orchestra or members of a choir. The fugues were presented in two versions: a-cappella and instrumental. During passive listening to the a-cappella version, a weak left-dominant asymmetry of blood flow acceleration was observed, while there was no hemispheric asymmetry during listening to the instrumental version. During the task of fugue theme recognition, a highly significant asymmetry in favour of the right MCA was observed with both versions. It is concluded that when the processing of complex musical material has to be based on the analysis of melodic contour features and calls for working memory capacities a right hemisphere dominance is observed even in musically sophisticated subjects.