Visual Attention and Cortical Circuits (Bradford Books (Hardcover))

Rating:
Summary: Looking and seeing with the mind's I, and its brain
Review: Aimed principally at the student and researcher working in cognitive neuroscience, this book reports the findings of the "Visual attention and cortical circuits" workshop held on Catalina Island, USA, in 1999. Its primary focus was to bring together a variety of interdisciplinary approaches to inform a better understanding of visual attention processing in the cerebral cortex. Some fourteen contributions are collected here, addessing the long standing implications of dorsal versus ventral stream visual processing, and, of more recent interest, the functional significance of the (often reciprocal) connections now known to exist between temporal, parietal and frontal cortical neurones. Appropriately illustrated throughout with task paradigms and experimental data presentations, it is perhaps surprising that this volume contains only one putative cortical circuit diagram [Tsotsos et al.] in an attempt to show the ways in which variously proposed cortical areas might be critically connected in support of their role in visual attention and/or its modulation.

Although it has been clear since the demonstration of Yarbus (1967) that we employ quite different brain circuitry when ?looking for?, as opposed to ?looking at? something in our visual field, I have never felt that the physiological significance of this observation has really been considered prior to single-cell recording from the awake, behaving monkey. At least nine of the contributions to this volume (both imagers and electrophysiologists, from human and monkey labs) explicitly argue for the existence of top-down, context-dependant, task effects of attention. One way or another, this amounts to claiming that at least some ?late? (typically frontal cortex) visual processing activity can be shown to be affecting the response properties of ?early? visual processing neurons, including primary visual cortex (V1), V2-V4, and extrastriate areas MT & MST. One clearly emerging story to be taken away from this book, is that traditional claims for the visuomotor system operating largely via unidirectional, monolithic ?Retina > RGN > V1 > V2... > frontal cortex? pathway models must be discarded. Recurrent, massively parallel cortical circuits are the order of the day here.

Throughout its middle six chapters, the results of visual attention experiments using monkey single-cell recording is variously interpreted as providing evidence for the biasing of response competition amongst early visual input neurons [Duncan; Reynolds & Desimone], their possible gating [Heeger et al; Tsotsos et al] and other modulations of their activity [Ito et al; Maunsell & MacAdams]. Several authors have now expressed support for Schall?s notion of the frontal eye-field area potentially serving as a task-based "saliency map" for the purpose of supporting both the selection and preparation of visually-guided action [Thompson et al] and a similar model is proposed to underlay visually-guided search [Sperling et al]. Others rightly encourage our caution lest we forget the necessarily constraining architectures of bottom-up processing, upon top-down operating pathways [Braun et al; Pouget et al].

The problem space for attentional research has always been one largely concerned with determining how the cortex selects and locates targets from a potentially infinite candidate array of such targets for focused consideration. Furthermore, attention experiments must be conducted in the face of limited processing capacity and with reference to one?s ontogenetic life-history of experience and learning with any number and variety of tasks. There are no surprises amongst the results presented in this book emerging from the studies of (visual) attention as reported, but it does provide for a useful review as to some of the current thinking ?outside the box? of the old monolithic pathways. However, and more importantly, it also warns that we must continue to explore the neural bases of behaviour bearing in mind that the subject?s task understanding, and the context(s) in which their tasks are presented, will necessarily affect the very cortical circuitries we are attempting to characterise. Fortunately, this holds true as much for the researcher?s brains, as it does for the brains of their research subjects, and for the fine details and anatomy of the neural circuits themselves, we must be content to await the reports of future workshops.

Rating:
Summary: Looking and seeing with the mind's I, and its brain
Review: Aimed principally at the student and researcher working in cognitive neuroscience, this book reports the findings of the "Visual attention and cortical circuits" workshop held on Catalina Island, USA, in 1999. Its primary focus was to bring together a variety of interdisciplinary approaches to inform a better understanding of visual attention processing in the cerebral cortex. Some fourteen contributions are collected here, addessing the long standing implications of dorsal versus ventral stream visual processing, and, of more recent interest, the functional significance of the (often reciprocal) connections now known to exist between temporal, parietal and frontal cortical neurones. Appropriately illustrated throughout with task paradigms and experimental data presentations, it is perhaps surprising that this volume contains only one putative cortical circuit diagram [Tsotsos et al.] in an attempt to show the ways in which variously proposed cortical areas might be critically connected in support of their role in visual attention and/or its modulation.

Although it has been clear since the demonstration of Yarbus (1967) that we employ quite different brain circuitry when ?looking for?, as opposed to ?looking at? something in our visual field, I have never felt that the physiological significance of this observation has really been considered prior to single-cell recording from the awake, behaving monkey. At least nine of the contributions to this volume (both imagers and electrophysiologists, from human and monkey labs) explicitly argue for the existence of top-down, context-dependant, task effects of attention. One way or another, this amounts to claiming that at least some ?late? (typically frontal cortex) visual processing activity can be shown to be affecting the response properties of ?early? visual processing neurons, including primary visual cortex (V1), V2-V4, and extrastriate areas MT & MST. One clearly emerging story to be taken away from this book, is that traditional claims for the visuomotor system operating largely via unidirectional, monolithic ?Retina > RGN > V1 > V2... > frontal cortex? pathway models must be discarded. Recurrent, massively parallel cortical circuits are the order of the day here.

Throughout its middle six chapters, the results of visual attention experiments using monkey single-cell recording is variously interpreted as providing evidence for the biasing of response competition amongst early visual input neurons [Duncan; Reynolds & Desimone], their possible gating [Heeger et al; Tsotsos et al] and other modulations of their activity [Ito et al; Maunsell & MacAdams]. Several authors have now expressed support for Schall?s notion of the frontal eye-field area potentially serving as a task-based "saliency map" for the purpose of supporting both the selection and preparation of visually-guided action [Thompson et al] and a similar model is proposed to underlay visually-guided search [Sperling et al]. Others rightly encourage our caution lest we forget the necessarily constraining architectures of bottom-up processing, upon top-down operating pathways [Braun et al; Pouget et al].

The problem space for attentional research has always been one largely concerned with determining how the cortex selects and locates targets from a potentially infinite candidate array of such targets for focused consideration. Furthermore, attention experiments must be conducted in the face of limited processing capacity and with reference to one?s ontogenetic life-history of experience and learning with any number and variety of tasks. There are no surprises amongst the results presented in this book emerging from the studies of (visual) attention as reported, but it does provide for a useful review as to some of the current thinking ?outside the box? of the old monolithic pathways. However, and more importantly, it also warns that we must continue to explore the neural bases of behaviour bearing in mind that the subject?s task understanding, and the context(s) in which their tasks are presented, will necessarily affect the very cortical circuitries we are attempting to characterise. Fortunately, this holds true as much for the researcher?s brains, as it does for the brains of their research subjects, and for the fine details and anatomy of the neural circuits themselves, we must be content to await the reports of future workshops.

Rating:
Summary: great colection
Review: Attention is a hot topic in the cognitive neurosciences, and although there are many other much more comprehensive collections (The Attentive Brain), this book adequately illustrates the level of specificity aquired in the field of the neural bases of attention. The topic concentrates on visual attention, for the now commonlly expressed reason that the primate visual sistem is the best understood neural sistem in perception. This makes the probing of attention easier, for its effects on the visual sistem can be generalized to the mechanisms of attention in general.

The articles are all good, and many general issues arise. Attention depends on distribuited neural sistems, it can exert strong effects on the firings of neurons in many levels of the proccesing hierarchy, attention both increases firing of attended stimulus responsive neurons and decreases activity of the surround, or unattended receptive fields.
These general observations, among others, point towards where the researchers are starting to converge theoretically. Practically, however, one still finds the common inconsistencies. For example, in chapter 1 the author finds parietal activity in the selection of attention, but no frontal activity, while in chapter 4 the author finds frontal activity but no parietal activity. One could reconcile this observations by postulating that both parietal and frontal areas can select for attention (the view I prefer), but still these discrepancies say something about the field at large.

The papers deal with common issues from different prespectives, and use various methods. There are chapters on cognitive aspects, neural aspects, perceptual aspects, theorethical and even a computer neural network simulation. That one can find any agreement at all tells us that progress is being made.