Scaffolding layered control architectures through constraint closure: insights into brain evolution and development

The functional organization of the mammalian brain can be considered to form a layered control architecture, but how this complex system has emerged through evolution and is constructed during development remains a puzzle. Here we consider brain organization through the framework of constraint closure, viewed as a general characteristic of living systems, that they are composed of multiple sub-systems that constrain each other at different timescales. We do so by developing a new formalism for constraint closure, inspired by a previous model showing how within-lifetime dynamics can constrain between-lifetime dynamics, and we demonstrate how this interaction can be generalized to multi-layered systems. Through this model, we consider brain organization in the context of two major examples of constraint closure—physiological regulation and visual orienting. Our analysis draws attention to the capacity of layered brain architectures to scaffold themselves across multiple timescales, including the ability of cortical processes to constrain the evolution of sub-cortical processes, and of the latter to constrain the space in which cortical systems self-organize and refine themselves. This article is part of the theme issue ‘Systems neuroscience through the lens of evolutionary theory’.

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>

Interference suppression in bilingualism: Stimulus-Stimulus vs. Stimulus-Response conflict

Studies examining the potential effects of bilingualism on interference suppression show inconsistent results. Our study approaches this topic by distinguishing two potential subcomponents within interference suppression (i.e., Stimulus-Stimulus and Stimulus-Response conflict). We investigated the two subcomponents through their operationalisation in different tasks and examined the role of language proficiency in modulating it. A sample of 111 young adult participants performed four non-linguistic cognitive tasks measuring both visual and auditory domains of cognitive control. Bilinguals outperformed monolinguals in tasks involving Stimulus-Stimulus conflict, but showed comparable performance in tasks involving Stimulus-Response conflict. Specific effects of language proficiency on cognitive control were observed: group differences in auditory inhibition and visual orienting were only observed between high-proficient bilinguals and monolinguals. Taken together, types of conflicts involved in interference tasks and language proficiency could differentially affect performance in monolinguals and bilinguals.

The development of foraging organization

In foraging tasks multiple targets must be found within a single display. The targets can be of one or more types, typically surrounded by numerous distractors. Visual attention has traditionally been studied with single target search tasks but adding more targets to the search display results in several additional measures of interest, such as how attention is oriented to different features and locations over time. We measured foraging among five age groups: Children in grades 1, 4, 7, and 10, as well as adults, using both simple feature foraging tasks and more challenging conjunction foraging tasks, with two target types per task. We assessed participants’ foraging organization, or systematicity when selecting all the targets within the foraging display, on four measures: Intertarget distance, number of intersections, best-r, and the percentage above optimal path length (PAO). We found that foraging organization increases with age, in both simple feature-based foraging and more complex foraging for targets defined by feature conjunctions, and that feature foraging was more organized than conjunction foraging. Separate analyses for different target types indicated that children’s, and to some extent adults’, conjunction foraging consisted of two relatively organized foraging paths through the display where one target type is exhaustively selected before the other target type is selected. Lastly, we found that the development of foraging organization is closely related to the development of other foraging measures. Our results suggest that measuring foraging organization is a promising avenue for further research into the development of visual orienting.

Visual Orienting Among Persons with Autism Spectrum Disorders

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