How does working memory enable number-induced spatial biases?

Number-space associations are a robust observation, but their underlying mechanisms remain debated. Two major accounts have been identified. First, spatial codes may constitute an intrinsic part of number representations stored in the brain – a perspective most commonly referred to as the Mental Number Line account. Second, spatial codes may be generated at the level of working memory when number (or other) representations are coordinated in function of a specific task. The aim of the current paper is twofold. First, whereas a pure Mental Number Line account cannot capture the complexity of observations reported in the literature, we here explore if and how a pure working memory account can suffice. Second, we make explicit (more than in our earlier work) the potential building blocks of such a working memory account, thereby providing clear and concrete foci for empirical efforts to test the feasibility of the account

Normal and impaired reflexive orienting of attention after central nonpredictive cues

Recent studies suggest that stimuli with directional meaning can trigger lateral shifts of visuospatial attention when centrally presented as noninformative cues. We investigated covert orienting in healthy participants and in a group of 17 right braindamaged patients (9 with hemispatial neglect) comparing arrows, eye gaze, and digits as central nonpredictive cues in a detection task. Orienting effects elicited by arrows and eye gaze were overall consistent in healthy participants and in right brain-damaged patients, whereas digit cues were ineffective. Moreover, patients with neglect showed, at the shortest delay between cue and target, a disengage deficit for arrow cueing whose magnitude was predicted by neglect severity. We conclude that the peculiar form of attentional orienting triggered by the directional meaning of arrow cues presents some features previously thought to characterize only the stimulus-driven (exogenous) orienting to noninformative peripheral cues

Extra-powerful on the visuo-perceptual space, but variable on the number space: Different effects of optokinetic stimulation in neglect patients

We studied the effects of optokinetic stimulation (OKS; leftward, rightward, control) on the visuo-perceptual and number space, in the same sample, during line bisection and mental number interval bisection tasks. To this end, we tested six patients with right-hemisphere damage and neglect, six patients with right-hemisphere damage but without neglect, and six neurologically healthy participants. In patients with neglect, we found a strong effect of leftward OKS on line bisection, but not on mental number interval bisection. We suggest that OKS influences the number space only under specific conditions

Contingent attentional engagement: stimulus- and goal-driven capture have qualitatively different consequences

We examined whether shifting attention to a location necessarily entails extracting the features at that location, a process referred to as attentional engagement. In three spatial-cuing experiments ( N = 60), we found that an onset cue captured attention both when it shared the target's color and when it did not. Yet the effects of the match between the response associated with the cued object's identity and the response associated with the target (compatibility effects), which are diagnostic of attentional engagement, were observed only with relevant-color onset cues. These findings demonstrate that stimulus- and goal-driven capture have qualitatively different consequences: Before attention is reoriented to the target, it is engaged to the location of the critical distractor following goal-driven capture but not stimulus-driven capture. The reported dissociation between attentional shifts and attentional engagement suggests that attention is best described as a camera: One can align its zoom lens without pressing the shutter button

Dissociating between the N2pc and attentional shifting: an attentional blink study

The N2pc is routinely used as an electrophysiological index of attentional shifting. Its absence is thus taken as evidence that no shift of attention occurred. We provide evidence in contrast to this notion using a variant of the attentional blink (AB) paradigm. Two target letters, embedded in two streams of distractor letters and defined by their color, were separated by either 300 or 800 ms. The second target was preceded by a distractor frame of the same color (cue). As expected, identification of the second target was poorer at the short than at the long lag (the AB effect). The AB did not affect attentional capture by the cue, but suppressed and delayed the N2pc associated with it. This result suggests that the N2pc does not reflect attentional shifting. Instead, we conclude that the N2pc indexes the transient enhancement that occurs at the spatial focus of attention and promotes high-level processing such as identification. This conclusion calls for a reinterpretation of findings from the attentional capture literature that relied on the N2pc as an index of attentional shifting. Our results also inform contemporary models of the AB

Working Memory Deficits in Children: Contributions of Executive Control Processes and Symptoms of ADHD

The most empirically supported model of working memory contains four components: (a) the phonological loop, (b) the visuospatial sketchpad, (c) the episodic buffer, and (d) the central executive (Baddeley and Hitch, 1974; Baddeley, 2003). The central executive has been fractionated into four subprocesses: (a) sustained attention, (b) selective attention/inhibition (c) shifting attention, and (d) control of retrieval from long-term memory (Baddeley, 2003; Mirsky et al., 1991; Zoelch et al., 2005). Children with ADHD are known to have working memory deficits, though the role of each component of the working memory system in these deficits is not known. The purpose of the current study is to examine the relationships between (a) symptoms of ADHD and working memory performance, (b) central executive processes and working memory performance, and (c) the unique contributions of each fractionated central executive component to the relationship between symptoms of ADHD and working memory performance. 85 children ages 8 to 16 from an outpatient clinical database were included in the study sample. Sustained attention was found to contribute unique variance to working memory performance after controlling for short-term memory. Selective attention/inhibition, shifting attention, and control of retrieval from long-term memory did not contribute unique variance to working memory, though limited power may have affected results. ADHD symptoms did not correlate with working memory, but they did correlate with short-term memory. Sustained attention was then examined as a mediator between ADHD hyperactivity symptoms and short-term memory. Though not a significant mediator, results of mediation procedures appear to indicate partial mediation. Results indicate that sustained attention may be a fractionated process of the central executive. They also suggest that ADHD symptoms may interfere with working memory at the short-term memory and executive levels. Further investigation is suggested to explain relationships between executive processes and working memory performance and between symptoms of ADHD and all components of the working memory system

Predictive Coding as a Model of Biased Competition in Visual Attention

Attention acts, through cortical feedback pathways, to enhance the response of cells encoding expected or predicted information. Such observations are inconsistent with the predictive coding theory of cortical function which proposes that feedback acts to suppress information predicted by higher-level cortical regions. Despite this discrepancy, this article demonstrates that the predictive coding model can be used to simulate a number of the effects of attention. This is achieved via a simple mathematical rearrangement of the predictive coding model, which allows it to be interpreted as a form of biased competition model. Nonlinear extensions to the model are proposed that enable it to explain a wider range of data

Dynamics of the Central Bottleneck: Dual-Task and Task Uncertainty

Why is the human brain fundamentally limited when attempting to execute two tasks at the same time or in close succession? Two classical paradigms, psychological refractory period (PRP) and task switching, have independently approached this issue, making significant advances in our understanding of the architecture of cognition. Yet, there is an apparent contradiction between the conclusions derived from these two paradigms. The PRP paradigm, on the one hand, suggests that the simultaneous execution of two tasks is limited solely by a passive structural bottleneck in which the tasks are executed on a first-come, first-served basis. The task-switching paradigm, on the other hand, argues that switching back and forth between task configurations must be actively controlled by a central executive system (the system controlling voluntary, planned, and flexible action). Here we have explicitly designed an experiment mixing the essential ingredients of both paradigms: task uncertainty and task simultaneity. In addition to a central bottleneck, we obtain evidence for active processes of task setting (planning of the appropriate sequence of actions) and task disengaging (suppression of the plan set for the first task in order to proceed with the next one). Our results clarify the chronometric relations between these central components of dual-task processing, and in particular whether they operate serially or in parallel. On this basis, we propose a hierarchical model of cognitive architecture that provides a synthesis of task-switching and PRP paradigms