Full-length reviewA neuronal model of attentional spotlight: parietal guiding the temporal
Introduction
Over the last 40 years, we have made considerable progress in our knowledge of the visual pathways, in particular through electrophysiological investigations regarding the trigger features of cells at various levels of the visual system and also from psychophysical studies in humans and other primates. However, the natural world differs substantially from the visual stimuli used in these studies in many ways. One important respect in which it differs is that stimuli in real life rarely occur in isolation and the visual system is often confronted with a multitude of stimuli of different shapes, sizes, colours, depths and speeds of movement. Nevertheless, we are able to focus attention on one object and process just the relevant information, sometimes even doing this covertly while foveating elsewhere. We are also able to employ visual search over a large scene and find, for example, a known face in a crowd fairly rapidly. While doing all this, we can also quite effortlessly bind different features of an object together, so that we can attribute correctly say, the yellow colour to the banana and the red to the apple. One puzzling aspect of this capability is a large body of evidence (see later) which suggests that different stimulus attributes like colour, form and motion may be processed in different areas of the brain. Given this, how is the binding of features made possible? A neuronal model that provides a framework for visual attention should be able to address these questions satisfactorily.
This paper will briefly review some of the psychophysical and neurophysiological studies that are relevant to this problem and propose a neuronal scheme that can explain these data and make testable predictions.
Section snippets
A model of attention that incorporates a novel view of convergence of parallel pathways in vision
In proposing a neurophysiological basis for attention, this paper builds upon concepts that have been derived largely from psychophysical experiments over the last 20 years. These ideas and the relevant literature on parallel pathways in vision will be reviewed first.
Psychophysical consequences
This neural account of selective attention explains a number of psychophysical observations that have been difficult to reconcile fully with Treisman's original Feature Integration Theory and seem to fit better with its modified version, namely the guided search model [100]. Treisman's early examples [83]of conjunctions that required serial search were features that would be largely processed by the parvocellular pathways and the ventral stream. They in fact showed the typical dependence on
Relation to other models
The scheme outlined here stresses the importance of spatial selection in visual attention as have some others 19, 83, 86. It seems to contradict the alternative idea that attentional selection could be the result of competition between objects for dominance over neural resources rather than due to an early spatial filter 27, 28, 29. This latter model has gained considerable currency in recent years with the finding of within-modality competition in attentional tasks and single unit studies
Conclusions
In the present scheme, the following factors determine the time taken for visual search.
(1) Which of the features defining the target can be processed by the magnocellular dominated dorsal stream. To the extent that one or more defining features can be processed by the dorsal stream, the search would be parallel and therefore faster.
(2) The sizes and spatial separation of the targets that need to be processed by the ventral stream. When objects are crowded together in the visual world, the
Acknowledgements
I wish to thank M.B. Calford, M. Cook, B. Dreher and G.H. Henry for helpful criticism and J. Cappello for technical assistance. The work is supported by a grant from the National Health and Medical Research Council of Australia.
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2022, Schizophrenia ResearchCitation Excerpt :The visual detection task deficits described above are consistent with a model of selective deficits in magnocellular over parvocellular visual processing pathways (Butler et al., 2001, 2005). Magnocellular pathways carry low-resolution visual feature information quickly and primarily drive attention capture and salience in downstream higher-level cortical areas, whereas parvocellular streams are thought to be slower and comprise more high-resolution featural information such as fine-grained stimulus configurations that enables operations including object identification in higher-level visual processing cortical areas (Norman, 2002; Steinman et al., 1997; Vidyasagar, 1999; Merigan and Maunsell, 2003). In a seminal series of studies, steady-state visual evoked potentials were measured from patients with schizophrenia in response to stimuli varying in luminance contrast, chromatic contrast, and spatial frequency (Butler and Javitt, 2005).
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2021, NeuropsychologiaCitation Excerpt :The tenets of the visuo-attentional (VA) theory of impaired reading performance argue that a subset of dyslexic children are unable to process as many letters as normal reading children and therefore cannot develop any reading expertise. This VA impairment has been associated with SPL dysfunction (Lobier et al, 2012a, 2012b, 2014; Peyrin et al, 2011, 2012; Reilhac et al., 2013) and is viewed in the literature as a consequence of either a reduced VA span (Lobier and Valdois, 2015; Valdois et al., 2019) or a reduced “spotlight” (Khan et al., 2016; Vidyasagar, 1999; Vidyasagar and Pammer, 2010). LP, AZK and AV designed the study, analyzed the data and wrote the manuscript.