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>

Neuronal modulation in the mouse superior colliculus during covert visual selective attention

Covert visual attention is accomplished by a cascade of mechanisms distributed across multiple brain regions. Recent studies in primates suggest a parcellation in which visual cortex is associated with enhanced representations of relevant stimuli, whereas subcortical circuits are associated with selection of visual targets and suppression of distractors. Here we identified how neuronal activity in the superior colliculus (SC) of head-fixed mice is modulated during covert visual attention. We found that spatial cues modulated both firing rate and spike-count correlations, and that the cue-related modulation in firing rate was due to enhancement of activity at the cued spatial location rather than suppression at the uncued location. This modulation improved the neuronal discriminability of visual-change-evoked activity between contralateral and ipsilateral SC neurons. Together, our findings indicate that neurons in the mouse SC contribute to covert visual selective attention by biasing processing in favor of locations expected to contain relevant information.

Sign language experience redistributes attentional resources to the inferior visual field

While a substantial body of work has suggested that deafness brings about an increased allocation of visual attention to the periphery there has been much less work on how using a signed language may also influence this attentional allocation. Signed languages are visual-gestural and produced using the body and perceived via the human visual system. Signers fixate upon the face of interlocutors and do not directly look at the hands moving in the inferior visual field. It is therefore reasonable to predict that signed languages require a redistribution of covert visual attention to the inferior visual field. Here we report a prospective and statistically powered assessment of the spatial distribution of attention to inferior and superior visual fields in signers – both deaf and hearing – in a visual search task. Using a Bayesian Hierarchical Drift Diffusion Model, we estimated decision making parameters for the superior and inferior visual field in deaf signers, hearing signers and hearing non-signers. Results indicated a greater attentional redistribution toward the inferior visual field in adult signers (both deaf and hearing) than in hearing sign-naïve adults. The effect was smaller for hearing signers than for deaf signers, suggestive of either a role for extent of exposure or greater plasticity of the visual system in the deaf. The data provide support for a process by which the demands of linguistic processing can influence the human attentional system.