The neural factors that account for the visual processing-speed reduction in aging are incompletely understood. Based on previous reports of age-related decreases in the intrinsic functional connectivity (iFC) within the cingulo-opercular network and its relevance for processing speed, we hypothesized that these decreases are associated with age-related reductions in visual processing speed. We used a whole-report task and modeling based on Bundesen's 'theory of visual attention' to parameterize visual processing speed in 91 healthy participants from 20 to 77 years old. iFC was estimated using independent-component analysis of resting-state fMRI data. From the clusters within the cingulo-opercular network exhibiting age-related decreased iFC, we found a cluster in the left insula to be particularly associated with visual processing speed and to mediate the age effect on visual speed. This mediation was not observed for age-related decreased iFC in other networks or for other attentional parameters. Our results point to the iFC in the cingulo-opercular network, represented by the left insula, as being a relevant marker for visual processing-speed changes in aging.Next, we performed two lines of control analysis. First, we checked whether the association between the cingulo-opercular network and visual processing speed is a specific one, as hypothesized, rather than being part of a more global relationship between changes in iFC and visual attention functions in general. That is, given the well-documented age-related decreases in iFC in the default-mode and dorsal-attention networks (see, e.g., Andrews-Hanna et al., 2007;Damoiseaux et al., 2008;Ferreira and Busatto, 2013), age-related reductions in visual processing speed might conceivably be associated with a general age-related decrease of iFC, rather than with that of the cingulo-opercular network exclusively. To check for this, (a) we examined whether visual processing speed C also relates to the iFC in other networks; and (b) we assessed whether the iFC in the cingulo-opercular network relates to other visual attention functions previously reported to change with aging, such as the visual perceptual threshold and VSTM storage capacity (see, e.g., McAvinue et al., 2012).Second, we controlled for potentially relevant confounds in the association between iFC in the cingulo-opercular network and visual processing speed. In particular, given that iFC in the cinguloopercular network has previously been found to be related to anxiety (see, e.g., Seeley et al., 2007) and anxiety level might in turn affect processing speed, we controlled for anxiety using the state-trait anxiety inventory (STAI;Laux et al., 1981;Spielberger et al., 1970). Two other potential confounds

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Attentional deficits are considered key cognitive symptoms in major depressive disorder (MDD) arising from abnormal activation patterns within dorsolateral prefrontal cortex (dlPFC) alertness networks. Altering these activity patterns with transcranial direct current stimulation (tDCS) might thus ameliorate alertness-dependent cognitive deficits in MDD patients. In a double-blind, randomized, sham-controlled study, we investigated the effect of a single session of anodal tDCS (2 mA) applied to the left dlPFC on different parameters of visual attention based on Bundesen's theory of visual attention (Psychol Rev 97(4):523-547, 1990) in a group of 20 patients with MDD and a control group of 20 healthy participants. The parametric attention assessment took place before, immediately after and 24 h after tDCS intervention. It revealed a selective impairment in visual processing speed as a primary functional deficit in MDD at baseline assessment. Furthermore, a significant stimulation condition × time point interaction showed that verum tDCS over the left dlPFC resulted in a processing speed enhancement 24 h post-stimulation in MDD patients. In healthy control participants, we did not find similar tDCS-induced effects. Our results suggest that even a single session of tDCS over the dlPFC can induce enduring neurocognitive benefits that indicate an amelioration of cortical under-arousal in MDD patients in a time frame beyond that of immediate, excitability increases that are directly induced by the current.

Patients with asymptomatic, high-grade internal carotid artery stenosis often suffer from subtle cognitive impairments with unclear underlying neuro-cognitive mechanisms. Thus, we hypothesized that stenosis-related unilateral cerebral hypoperfusion leads to an ipsilateral attentional bias; 22 patients with asymptomatic, one-sided high-grade carotid stenosis and 24 age-matched healthy controls underwent pseudo-continuous arterial spin labeling to assess brain perfusion in the territory of the carotid arteries. Furthermore, a parametric assessment of attention functions was carried out on the basis of the computational Theory of Visual Attention. Both patients' perfusion and spatial attention were significantly more lateralized than those of healthy controls. Critically, both asymmetry indices were significantly correlated in patients, i.e. the stronger one-sided relative hypoperfusion, the stronger ipsilateral bias of attention. This association was specifically pronounced in parietal cortices and independent of white matter hyperintensities as a surrogate for cerebrovascular brain damage. Results provide evidence for a link between lateralized hypoperfusion and lateralized attentional weighting in asymptomatic, high-grade carotid stenosis. Data suggest that lateralized hypoperfusion with simultaneous spatial attentional bias might serve as a potential therapeutic target in one-sided carotid stenosis.

Older adults show higher dual task performance decrements than younger adults. While this is assumed to be related to attentional capacity reductions, the precise affected functions are not specified. Such specification is, however, possible based on the “theory of visual attention” (TVA) which allows for modeling of distinct attentional capacity parameters. Furthermore, it is unclear whether older adults show qualitatively different attentional effects or whether they show the same effects as younger adults experience under more challenging conditions. By varying the complexity of the secondary task, it is possible to address this question. In our study, participants performed a verbal whole report of briefly presented letter arrays. TVA-based fitting of report performance delivered parameters of visual threshold t0, processing speed C, and visual short-term memory (VSTM) storage capacity K. Furthermore, participants performed a concurrent motor task consisting of continuous tapping of a (simple or complex) sequence. Both TVA and tapping tasks were performed under single and dual task conditions. Two groups of 30 younger adults each performed either the simple or complex tapping, and a group of 30 older adults performed the simple tapping condition. In older participants, VSTM storage capacity declined under dual task conditions. While no such effect was found in younger subjects performing the simple tapping sequence under dual task conditions, the younger group performing the complex tapping task under dual task conditions also showed a significant VSTM capacity reduction. Generally, no significant effect on other TVA parameters or on tapping accuracy was found. Comparable goodness-of-fit measures were obtained for the TVA modeling data in single and dual tasks, indicating that tasks were executed in a qualitatively similar, continuous manner, although quantitatively less efficiently under dual- compared to single-task conditions. Taken together, our results show that the age-specific effects of motor-cognitive dual task interference are reflected by a stronger decline of VSTM storage capacity. They support an interpretation of VSTM as central attentional capacity, which is shared across visual uptake and concurrent motor performance. Capacity limits are reached earlier, and already under lower motor task complexity, in older compared to younger adults.