Auditory Working Memory Load Impairs Visual Ventral Stream Processing: Toward a Unified Model of Attentional Load

Attentional interference between tasks performed in parallel is known to have strong and often undesired effects. As yet, however, the mechanisms by which interference operates remain elusive. A better knowledge of these processes may facilitate our understanding of the effects of attention on human performance and the debilitating consequences that disruptions to attention can have. According to the load theory of cognitive control, processing of task-irrelevant stimuli is increased by attending in parallel to a relevant task with high cognitive demands. This is due to the relevant task engaging cognitive control resources that are, hence, unavailable to inhibit the processing of task-irrelevant stimuli. However, it has also been demonstrated that a variety of types of load (perceptual and emotional) can result in a reduction of the processing of task-irrelevant stimuli, suggesting a uniform effect of increased load irrespective of the type of load. In the present study, we concurrently presented a relevant auditory matching task [n-back working memory (WM)] of low or high cognitive load (1-back or 2-back WM) and task-irrelevant images at one of three object visibility levels (0%, 50%, or 100%). fMRI activation during the processing of the task-irrelevant visual stimuli was measured in the lateral occipital cortex and found to be reduced under high, compared to low, WM load. In combination with previous findings, this result is suggestive of a more generalized load theory, whereby cognitive load, as well as other types of load (e.g., perceptual), can result in a reduction of the processing of task-irrelevant stimuli, in line with a uniform effect of increased load irrespective of the type of load

Neural dynamics of learning sound-action associations

A motor component is pre-requisite to any communicative act as one must inherently move to communicate. To learn to make a communicative act, the brain must be able to dynamically associate arbitrary percepts to the neural substrate underlying the pre-requisite motor activity. We aimed to investigate whether brain regions involved in complex gestures (ventral pre-motor cortex, Brodmann Area 44) were involved in mediating association between novel abstract auditory stimuli and novel gestural movements. In a functional resonance imaging (fMRI) study we asked participants to learn associations between previously unrelated novel sounds and meaningless gestures inside the scanner. We use functional connectivity analysis to eliminate the often present confound of ‘strategic covert naming’ when dealing with BA44 and to rule out effects of non-specific reductions in signal. Brodmann Area 44, a region incorporating Broca's region showed strong, bilateral, negative correlation of BOLD (blood oxygen level dependent) response with learning of sound-action associations during data acquisition. Left-inferior-parietal-lobule (l-IPL) and bilateral loci in and around visual area V5, right-orbital-frontal-gyrus, right-hippocampus, left-para-hippocampus, right-head-of-caudate, right-insula and left-lingual-gyrus also showed decreases in BOLD response with learning. Concurrent with these decreases in BOLD response, an increasing connectivity between areas of the imaged network as well as the right-middle-frontal-gyrus with rising learning performance was revealed by a psychophysiological interaction (PPI) analysis. The increasing connectivity therefore occurs within an increasingly energy efficient network as learning proceeds. Strongest learning related connectivity between regions was found when analysing BA44 and l-IPL seeds. The results clearly show that BA44 and l-IPL is dynamically involved in linking gesture and sound and therefore provides evidence that one of the mechanisms required for the evolution of human communication is found within these motor regions

St. John's Daily Star, 1920-09-13

The St. John's Daily Star was published daily except Sunday between 17 April 1915 - 23 July 1921

Dissociating networks of imitation

Abstract: The investigation of imitation, which consists of observation and later reproduction of voluntary actions, promises insights into the complex processes of human actions. Although several aspects concerning the component neural processes necessary for action execution are known, our current understanding of the neural networks underlying these remains sparse. The present study applies independent component analysis (ICA) to functional magnetic resonance imaging (fMRI) data acquired during imitation of abstract gestures and object-related actions. This enables identification of neural networks underlying the production of these imitations. The explorative approach of ICA is complemented by an analysis of time courses from the maxima of each component. Four independent networks were active during delayed imitation. These can be assigned to the aspects of (1) action perception, (2) motor preparation and action execution, (3) encoding and retrieval into and from working memory, as well as (4) the dynamic integration of object affordances into the action. At least two of these networks participate in action preparation, one contains areas involved with motor working memory and one includes areas which are connected to the true action execution. The fourth network only shows activity shortly before an object-related action is imitated. This indicates a late integration of object affordances into the movement as the time course of activity in this network pertains to action rather than perception of the object. Hum Brain Mapp 30:3339-3350

Grasping language

The new concept of embodied cognition theories has been enthusiastically studied by the cognitive sciences, by as well as such disparate disciplines as philosophy, anthropology, neuroscience, and robotics. Embodiment theory provides the framework for ongoing discussions on the linkage between ―low‖ cognitive processes as perception and ―high‖ cognition as language processing and comprehension, respectively. This review gives an overview along the lines of argumentation in the ongoing debate on the embodiment of language and employs an ALE meta-analysis to illustrate and weigh previous findings. The collected evidence on the somatotopic activation of motor areas, abstract and concrete word processing, as well as from reported patient and timing studies emphasizes the important role of sensorimotor areas in language processing and supports the hypothesis that the motor system is activated during language comprehension

Sleep Deprivation Selectively Upregulates an Amygdala-Hypothalamic Circuit Involved in Food Reward

Sleep loss is associated with increased obesity risk, as demonstrated by correlations between sleep duration and change in body mass index or body fat percentage. Whereas previous studies linked this weight gain to disturbed endocrine parameters after sleep deprivation or restriction, neuroimaging studies revealed upregulated neural processing of food rewards after sleep loss in reward-processing areas such as the anterior cingulate cortex, ventral striatum, and insula. To address this ongoing debate between hormonal versus hedonic factors underlying sleep-loss-associated weight gain, we rigorously tested the association between sleep deprivation and food cue processing using high-resolution fMRI and assessment of hormones. After taking blood samples from 32 lean, healthy, human male participants, they underwent fMRI while performing a neuroeconomic, value-based decision-making task with snack food and trinket rewards following a full night of habitual sleep and a night of sleep deprivation in a repeated-measures crossover design. We found that des-acyl ghrelin concentrations were increased after sleep deprivation compared with habitual sleep. Despite similar hunger ratings due to fasting in both conditions, participants were willing to spend more money on food items only after sleep deprivation. Furthermore, fMRI data paralleled this behavioral finding, revealing a food-reward-specific upregulation of hypothalamic valuation signals and amygdala-hypothalamic coupling after a single night of sleep deprivation. Behavioral and fMRI results were not significantly correlated with changes in acyl, des-acyl, or total ghrelin concentrations. Our results suggest that increased food valuation after sleep loss might be due to hedonic rather than hormonal mechanisms