Overt Visual Attention as a Causal Factor of Perceptual Awareness

Our everyday conscious experience of the visual world is fundamentally shaped by the interaction of overt visual attention and object awareness. Although the principal impact of both components is undisputed, it is still unclear how they interact. Here we recorded eye-movements preceding and following conscious object recognition, collected during the free inspection of ambiguous and corresponding unambiguous stimuli. Using this paradigm, we demonstrate that fixations recorded prior to object awareness predict the later recognized object identity, and that subjects accumulate more evidence that is consistent with their later percept than for the alternative. The timing of reached awareness was verified by a reaction-time based correction method and also based on changes in pupil dilation. Control experiments, in which we manipulated the initial locus of visual attention, confirm a causal influence of overt attention on the subsequent result of object perception. The current study thus demonstrates that distinct patterns of overt attentional selection precede object awareness and thereby directly builds on recent electrophysiological findings suggesting two distinct neuronal mechanisms underlying the two phenomena. Our results emphasize the crucial importance of overt visual attention in the formation of our conscious experience of the visual world

Enhancing organisational competitiveness via social media - a strategy as practice perspective

The affordances, popularity and pervasive use of social media platforms such as Facebook, Twitter and Instagram have made these platforms attractive to organisations for enhancing their competitiveness and creating business value. Despite this apparent significance of social media for businesses, they are struggling with the development of a social media strategy as well as understanding the implications of social media on practice within their organisations. This paper explores how social media has become a tool for competitiveness and its influence on organisational strategy and practice. Using the 'strategy as practice' lens and guided by the interpretivist philosophy, this paper uses the empirical case of a telecom organisation in Tanzania. The findings show that social media is influencing competitiveness through imitation and product development. Also, the findings indicate how social media affects the practices within an organisation, consequently making the social media strategy an emergent phenomenon

Self-reported sleep relates to microstructural hippocampal decline decline in β-amyloid positive adults beyond genetic risk

Study Objectives: A critical role linking sleep with memory decay and β-amyloid (Aβ) accumulation, two markers of Alzheimer’s disease (AD) pathology, may be played by hippocampal integrity. We tested the hypotheses that worse self-reported sleep relates to decline in memory and intra-hippocampal microstructure, including in the presence of Aβ. Methods: Two-hundred and forty-three cognitively healthy participants, aged 19-81 years, completed the Pittsburgh Sleep Quality Index once, and 2 diffusion tensor imaging sessions, on average 3 years apart, allowing measures of decline in intrahippocampal microstructure as indexed by increased mean diffusivity. We measured memory decay at each imaging session using verbal delayed recall. One session of positron emission tomography, in 108 participants above 44 years of age, yielded 23 Aβ positive. Genotyping enabled control for APOE ε4 status, and polygenic scores for sleep and AD, respectively. Results: Worse global sleep quality and sleep efficiency related to more rapid reduction of hippocampal microstructure over time. Focusing on efficiency (the percentage of time in bed at night spent asleep), the relation was stronger in presence of Aβ accumulation, and hippocampal integrity decline mediated the relation with memory decay. The results were not explained by genetic risk for sleep efficiency or AD. Conclusions: Worse sleep efficiency related to decline in hippocampal microstructure, especially in the presence of Aβ accumulation, and A β might link poor sleep and memory decay. As genetic risk did not account for the associations, poor sleep efficiency might constitute a risk marker for AD, although the driving causal mechanisms remain unknown.</p

Self-reported sleep relates to hippocampal atrophy over the adult lifespan – results from the Lifebrain consortium

Objectives Poor sleep is associated with multiple age-related neurodegenerative and neuropsychiatric conditions. The hippocampus plays a special role in sleep and sleep-dependent cognition, and accelerated hippocampal atrophy is typically seen with higher age. Hence, it is critical to establish how the relationship between sleep and hippocampal volume loss unfolds across the adult lifespan. Methods Self-reported sleep measures and MRI-derived hippocampal volumes were obtained from 3105 cognitively normal participants (18–90 years) from major European brain studies in the Lifebrain consortium. Hippocampal volume change was estimated from 5116 MRIs from 1299 participants for whom longitudinal MRIs were available, followed up to 11 years with a mean interval of 3.3 years. Cross-sectional analyses were repeated in a sample of 21,390 participants from the UK Biobank. Results No cross-sectional sleep—hippocampal volume relationships were found. However, worse sleep quality, efficiency, problems, and daytime tiredness were related to greater hippocampal volume loss over time, with high scorers showing 0.22% greater annual loss than low scorers. The relationship between sleep and hippocampal atrophy did not vary across age. Simulations showed that the observed longitudinal effects were too small to be detected as age-interactions in the cross-sectional analyses. Conclusions Worse self-reported sleep is associated with higher rates of hippocampal volume decline across the adult lifespan. This suggests that sleep is relevant to understand individual differences in hippocampal atrophy, but limited effect sizes call for cautious interpretation

Poor self-reported sleep is related to regional cortical thinning in aging but not memory decline – results from the Lifebrain consortium

We examined whether sleep quality and quantity are associated with cortical and memory changes in cognitively healthy participants across the adult lifespan. Associations between self-reported sleep parameters (Pittsburgh Sleep Quality Index, PSQI) and longitudinal cortical change were tested using five samples from the Lifebrain consortium (n = 2205, 4363 MRIs, 18–92 years). In additional analyses, we tested coherence with cell-specific gene expression maps from the Allen Human Brain Atlas, and relations to changes in memory performance. “PSQI # 1 Subjective sleep quality” and “PSQI #5 Sleep disturbances” were related to thinning of the right lateral temporal cortex, with lower quality and more disturbances being associated with faster thinning. The association with “PSQI #5 Sleep disturbances” emerged after 60 years, especially in regions with high expression of genes related to oligodendrocytes and S1 pyramidal neurons. None of the sleep scales were related to a longitudinal change in episodic memory function, suggesting that sleep-related cortical changes were independent of cognitive decline. The relationship to cortical brain change suggests that self-reported sleep parameters are relevant in lifespan studies, but small effect sizes indicate that self-reported sleep is not a good biomarker of general cortical degeneration in healthy older adults

Local feature suppression effect in face and non-face stimuli

There is evidence that the cognitive system processes human faces faster and more precisely than other stimuli. Also, faces summon visual attention in an automatic manner, as evidenced by efficient, ‘pop-out’ search for face targets amongst homogeneous non-face distractors. Pop-out for faces implies that faces are processed as a basic visual ‘feature’ by specialized face-tuned detectors, similar to the coding of other features (e.g., color, orientation, motion, etc.). However, it is unclear whether such face detectors encode only the global face configuration or both global and local face features. If the former were correct, the face detectors should be unable to support search for a local face feature, rendering search slower relative to non-face stimuli; that is, there would be local feature suppression (LFS) for faces. If the latter was the case, there should be no difference in the processing of local and, respectively, global face features. In two experiments, participants discerned the presence (vs. absence) of a local target defined as a part of either a normal or a scrambled (schematic or realistic) face or of a non-face (Kanizsa diamond or realistic house) configuration. The results consistently showed a robust LFS effect in both reaction times and error rates for face stimuli, and either no difference or even a local feature enhancement effect for the control stimuli. Taken together, these findings indicate that faces are encoded as a basic visual feature by means of globally tuned face detectors