Semantic Influences on Overt and Covert Visual Attention

<p>People are constantly confronted by a barrage of visual information. Visual attention is the crucial mechanism which selects for further processing, subsets of information which are most behaviourally relevant, allowing us to function effectively within our everyday environment. This thesis explored how semantic information (i.e., information which has meaning) encountered within the environment influences the selective orienting of visual attention. Past research has shown semantic information does affect the orienting of attention, but the processes by which it does so remain unclear. The extent of semantic influence on the visual attention system was determined by parsing visual orienting into the tractable components of covert and overt orienting, and capture and hold process stages therein. This thesis consisted of a series of experiments which were designed, utilising well- established paradigms and semantic manipulations in concert with eye-tracking techniques, to test whether the capture and hold of either overt or covert forms of visual attention were influenced by semantic information. Taking together the main findings across all experiments, the following conclusions were drawn. 1) Semantic information differentially influences covert and overt attentional orienting processes. 2) The capture and hold of covert attention is generally uninfluenced by semantic information. 3) Semantic information briefly encountered in the environment can facilitate or prime action independent of covert attentional orienting.4) Overt attention can be both preferentially captured and held by semantically salient information encountered in visual environments. The visual attentional system thus appears to have a complex relationship with semantic information encountered in the visual environment. Semantic information has a differential influence on selective orienting processes that depends on the form of orienting employed and a range of circumstances under which attentional selection takes place.</p>

Semantic Influences on Overt and Covert Visual Attention

<p>People are constantly confronted by a barrage of visual information. Visual attention is the crucial mechanism which selects for further processing, subsets of information which are most behaviourally relevant, allowing us to function effectively within our everyday environment. This thesis explored how semantic information (i.e., information which has meaning) encountered within the environment influences the selective orienting of visual attention. Past research has shown semantic information does affect the orienting of attention, but the processes by which it does so remain unclear. The extent of semantic influence on the visual attention system was determined by parsing visual orienting into the tractable components of covert and overt orienting, and capture and hold process stages therein. This thesis consisted of a series of experiments which were designed, utilising well- established paradigms and semantic manipulations in concert with eye-tracking techniques, to test whether the capture and hold of either overt or covert forms of visual attention were influenced by semantic information. Taking together the main findings across all experiments, the following conclusions were drawn. 1) Semantic information differentially influences covert and overt attentional orienting processes. 2) The capture and hold of covert attention is generally uninfluenced by semantic information. 3) Semantic information briefly encountered in the environment can facilitate or prime action independent of covert attentional orienting.4) Overt attention can be both preferentially captured and held by semantically salient information encountered in visual environments. The visual attentional system thus appears to have a complex relationship with semantic information encountered in the visual environment. Semantic information has a differential influence on selective orienting processes that depends on the form of orienting employed and a range of circumstances under which attentional selection takes place.</p>

A Bridge between the Breath and the Brain: Synchronization of Respiration, a Pupillometric Marker of the Locus Coeruleus, and an EEG Marker of Attentional Control State

Yogic and meditative traditions have long held that the fluctuations of the breath and the mind are intimately related. While respiratory modulation of cortical activity and attentional switching are established, the extent to which electrophysiological markers of attention exhibit synchronization with respiration is unknown. To this end, we examined (1) frontal midline theta-beta ratio (TBR), an indicator of attentional control state known to correlate with mind wandering episodes and functional connectivity of the executive control network; (2) pupil diameter (PD), a known proxy measure of locus coeruleus (LC) noradrenergic activity; and (3) respiration for evidence of phase synchronization and information transfer (multivariate Granger causality) during quiet restful breathing. Our results indicate that both TBR and PD are simultaneously synchronized with the breath, suggesting an underlying oscillation of an attentionally relevant electrophysiological index that is phase-locked to the respiratory cycle which could have the potential to bias the attentional system into switching states. We highlight the LC’s pivotal role as a coupling mechanism between respiration and TBR, and elaborate on its dual functions as both a chemosensitive respiratory nucleus and a pacemaker of the attentional system. We further suggest that an appreciation of the dynamics of this weakly coupled oscillatory system could help deepen our understanding of the traditional claim of a relationship between breathing and attention.

Positive emotion enhances conflict processing in preschoolers

The rapid detection and resolution of conflict between opposing action tendencies is crucial for our ability to engage in goal-directed behavior. Research in adults suggests that emotions might serve as a ‘relevance detector’ that alarms attentional and sensory systems, thereby leading to more efficient conflict processing. In contrast, previous research in children has almost exclusively stressed the impeding influence of emotion on the attentional system, as suggested by the protracted development of performance in ‘hot’ executive function tasks. How does emotion modulate conflict processing in development? We addressed this question applying a modified version of a color flanker task that either involved or did not involve emotional stimuli in preschool children (N = 43, with preregistered Bayesian sequential design, aged 2.8 – 7.0 years). Our results show a robust conflict effect with higher error rates in incongruent compared to congruent trials. Crucially, conflict resolution was faster in emotional compared to neutral conditions. Furthermore, while efficient conflict processing increases with age, we find evidence against an age-related change in the influence of emotion on conflict processing. Taken together, these findings provide first indication that emotion can trigger efficient control processes already from early on in life. In contrast to previous findings and theories in developmental psychology, this indicates that, depending on the role that emotion has in conflict processing, emotion may show a facilitative or impeding effect.

A Bridge Between the Breath and the Brain: Synchronization of Respiration, a Pupillometric Marker of the Locus Coeruleus, and an EEG Marker of Attentional Control State

Yogic and meditative traditions have long held that the fluctuations of the breath and the mind are intimately related. While respiratory modulation of cortical activity and attentional switching are established, the extent to which electrophysiological markers of attention exhibit synchronization with respiration is unknown. To this end, we examined 1) frontal midline theta-beta ratio, an indicator of attentional control state known to correlate with mind wandering episodes and functional connectivity of the executive control network; 2) pupil diameter (PD), a known proxy measure of locus coeruleus (LC) noradrenergic activity; and 3) respiration for evidence of phase synchronization and information transfer (multivariate Granger causality) during quiet restful breathing. Our results indicate that both TBR and PD are simultaneously synchronized with the breath, suggesting an underlying oscillation of an attentionally relevant electrophysiological index that is phase-locked to the respiratory cycle which could have the potential to bias the attentional system into switching states. We highlight the LC&rsquo;s pivotal role as a coupling mechanism between respiration and TBR, and elaborate on its dual functions as both a chemosensitive respiratory nucleus and a pacemaker of the attentional system. We further suggest that an appreciation of the dynamics of this weakly coupled oscillatory system could help deepen our understanding of the traditional claim of a relationship between breathing and attention.

Distinct Neural Substrates Support Phonological and Orthographic Working Memory: Implications for Theories of Working Memory

Prior behavioral and neuroimaging evidence supports a separation between working memory capacities in the phonological and orthographic domains. Although these data indicate distinct buffers for orthographic and phonological information, prior neural evidence does indicate that nearby left inferior parietal regions support both of these working memory capacities. Given that no study has directly compared their neural substrates based on data from the same individuals, it is possible that there is a common left inferior parietal region shared by both working memory capacities. In fact, those endorsing an embedded processes account of working memory might suggest that parietal involvement reflects a domain-general attentional system that directs attention to long-term memory representations in the two domains, implying that the same neural region supports the two capacities. Thus, in this work, a multivariate lesion-symptom mapping approach was used to assess the neural basis of phonological and orthographic working memory using behavioral and lesion data from the same set of 37 individuals. The results showed a separation of the neural substrates, with regions in the angular gyrus supporting orthographic working memory and with regions primarily in the supramarginal gyrus supporting phonological working memory. The results thus argue against the parietal involvement as supporting a domain-general attentional mechanism and support a domain-specific buffer account of working memory.

Across-trial spatial suppression in visual search

In order to focus on objects of interest, humans must be able to avoid distraction by salient stimuli that are not relevant to the task at hand. Many recent studies have shown that through statistical learning we are able to suppress the location that is most likely to contain a salient distractor. Here we demonstrate a remarkable flexibility in attentional suppression. Participants had to search for a shape singleton while a color distractor singleton was present. Unbeknown to the participant, the color distractor was presented according to a consistent pattern across trials. Our findings show that participants learn this distractor sequence as they proactively suppressed the anticipated location of the distractor on the next trial. Critically, none of the participants were aware of these hidden sequences. We conclude that the spatial priority map is highly flexible, operating at a subconscious level preparing the attentional system for what will happen next.

Semantic and syntactic information for neural machine translation

Introducing factors such as linguistic features has long been proposed in machine translation to improve the quality of translations. More recently, factored machine translation has proven to still be useful in the case of sequence-to-sequence systems. In this work, we investigate whether this gains hold in the case of the state-of-the-art architecture in neural machine translation, the Transformer, instead of recurrent architectures. We propose a new model, the Factored Transformer, to introduce an arbitrary number of word features in the source sequence in an attentional system. Specifically, we suggest two variants depending on the level at which the features are injected. Moreover, we suggest two combination mechanisms for the word features and words themselves. We experiment both with classical linguistic features and semantic features extracted from a linked data database, and with two low-resource datasets. With the best-found configuration, we show improvements of 0.8 BLEU over the baseline Transformer in the IWSLT German-to-English task. Moreover, we experiment with the more challenging FLoRes English-to-Nepali benchmark, which includes both low-resource and very distant languages, and obtain an improvement of 1.2 BLEU. These improvements are achieved with linguistic and not with semantic information.

Pupil size in the evaluation of static and dynamic stimuli in peripheral vision

It has been evidenced that in attention-window tasks, the participants fixate on the center of a screen while inspecting two stimuli that appear at the same time in parafoveal vision. Such tasks have successfully been used to estimate a person’s breadth of attention under various conditions. While behavioral investigations of visual attention have often made use of response accuracy, recent research has shown that the pupil size can also be used to track shifts of attention to the periphery. The main finding of previous studies is that the harder the evaluation of the stimuli becomes, e.g., because they appear farther away from the central fixation point, the stronger the pupils dilate. In this paper, we present experimental data suggesting that in an attention-window task, the pupil size can also be used to assess whether the participants attend to static, non-moving, or dynamic, moving stimuli. That is, regression models containing information on presentation mode (static vs. dynamic) and the visual angle between spatially separated stimuli better predict accuracy of perception and pupil dilation than model without these sources of information. This finding is useful for researchers who aim at understanding the human attentional system, including potential differences in its sensitivity to static and dynamic objects.