We review evidence for partially segregated networks of brain areas that carry out different attentional functions. One system, which includes parts of the intraparietal cortex and superior frontal cortex, is involved in preparing and applying goal-directed (top-down) selection for stimuli and responses. This system is also modulated by the detection of stimuli. The other system, which includes the temporoparietal cortex and inferior frontal cortex, and is largely lateralized to the right hemisphere, is not involved in top-down selection. Instead, this system is specialized for the detection of behaviourally relevant stimuli, particularly when they are salient or unexpected. This ventral frontoparietal network works as a 'circuit breaker' for the dorsal system, directing attention to salient events. Both attentional systems interact during normal vision, and both are disrupted in unilateral spatial neglect.

Control of goal-directed and stimulus-driven attention in the brain

Despite the concern that has been expressed about potential method biases, and the pervasiveness of research settings with the potential to produce them, there is disagreement about whether they really are a problem for researchers in the behavioral sciences. Therefore, the purpose of this review is to explore the current state of knowledge about method biases. First, we explore the meaning of the terms “method” and “method bias” and then we examine whether method biases influence all measures equally. Next, we review the evidence of the effects that method biases have on individual measures and on the covariation between different constructs. Following this, we evaluate the procedural and statistical remedies that have been used to control method biases and provide recommendations for minimizing method bias.

Sources of Method Bias in Social Science Research and Recommendations on How to Control It

In recent years, many new cortical areas have been identified in the macaque monkey. The number of identified connections between areas has increased even more dramatically. We report here on (1) a summary of the layout of cortical areas associated with vision and with other modalities, (2) a computerized database for storing and representing large amounts of information on connectivity patterns, and (3) the application of these data to the analysis of hierarchical organization of the cerebral cortex. Our analysis concentrates on the visual system, which includes 25 neocortical areas that are predominantly or exclusively visual in function, plus an additional 7 areas that we regard as visual-association areas on the basis of their extensive visual inputs. A total of 305 connections among these 32 visual and visual-association areas have been reported. This represents 31% of the possible number of pathways if each area were connected with all others. The actual degree of connectivity is likely to be closer to 40%. The great majority of pathways involve reciprocal connections between areas. There are also extensive connections with cortical areas outside the visual system proper, including the somatosensory cortex, as well as neocortical, transitional, and archicortical regions in the temporal and frontal lobes. In the somatosensory/motor system, there are 62 identified pathways linking 13 cortical areas, suggesting an overall connectivity of about 40%. Based on the laminar patterns of connections between areas, we propose a hierarchy of visual areas and of somatosensory/motor areas that is more comprehensive than those suggested in other recent studies. The current version of the visual hierarchy includes 10 levels of cortical processing. Altogether, it contains 14 levels if one includes the retina and lateral geniculate nucleus at the bottom as well as the entorhinal cortex and hippocampus at the top. Within this hierarchy, there are multiple, intertwined processing streams, which, at a low level, are related to the compartmental organization of areas V1 and V2 and, at a high level, are related to the distinction between processing centers in the temporal and parietal lobes. However, there are some pathways and relationships (about 10% of the total) whose descriptions do not fit cleanly into this hierarchical scheme for one reason or another. In most instances, though, it is unclear whether these represent genuine exceptions to a strict hierarchy rather than inaccuracies or uncertainities in the reported assignment.

/pdf/distributed-hierarchical-processing-in-the-primate-cerebral-1dvblm6d82.pdf

Distributed Hierarchical Processing in the Primate Cerebral Cortex

The two basic phenomena that define the problem of visual attention can be illustrated in a simple example. Consider the arrays shown in each panel of Figure 1. In a typical experiment, before the arrays were presented, subjects would be asked to report letters appearing in one color (targets, here black letters), and to disregard letters in the other color (nontargets, here white letters). The array would then be briefly flashed, and the subjects, without any opportunity for eye movements, would give their report. The display mimics our. usual cluttered visual environment: It contains one or more objects that are relevant to current behavior, along with others that are irrelevant. The first basic phenomenon is limited capacity for processing information. At any given time, only a small amount of the information available on the retina can be processed and used in the control of behavior. Subjectively, giving attention to any one target leaves less available for others. In Figure 1, the probability of reporting the target letter N is much lower with two accompa­ nying targets (Figure la) than with none (Figure Ib). The second basic phenomenon is selectivity-the ability to filter out un­ wanted information. Subjectively, one is aware of attended stimuli and largely unaware of unattended ones. Correspondingly, accuracy in identifying an attended stimulus may be independent of the number of nontargets in a display (Figure la vs Ie) (see Bundesen 1990, Duncan 1980).

Neural Mechanisms of Selective Visual Attention

I have developed "tennis elbow" from lugging this book around the past four weeks, but it is worth the pain, the effort, and the aspirin. It is also worth the (relatively speaking) bargain price. Including appendixes, this book contains 894 pages of text. The entire panorama of the neural sciences is surveyed and examined, and it is comprehensive in its scope, from genomes to social behaviors. The editors explicitly state that the book is designed as "an introductory text for students of biology, behavior, and medicine," but it is hard to imagine any audience, interested in any fragment of neuroscience at any level of sophistication, that would not enjoy this book. The editors have done a masterful job of weaving together the biologic, the behavioral, and the clinical sciences into a single tapestry in which everyone from the molecular biologist to the practicing psychiatrist can find and appreciate his or

Principles of Neural Science

The visual system, like all sensory systems, contains parallel pathways (see Stone 1 983). Recently, m uch emphasis has been placed on the relationship between two subcortical and two cortical pathways. It has been suggested that the cortical and subcortical pathways are continuous, so that distinct channels of information that arise in the retina remain segregated up to the highest levels of visual cortex. According to this view, the visual system comprises two largely independent subsystems that mediate different classes of visual behaviors. In this paper, we evaluate this proposal, which has far-reaching implications for our understanding of the functional organization of the visual system. The subcortical projection from the retina to cerebral cortex is strongly dominated by the two pathways (M and P pathways) that are relayed by the magnocellular and parvocellular subdivisions of the lateral geniculate nucleus (LGN) (see Shapley & Perry 1 986). The importance of these pathways is demonstrated by the fact that they include about 90% of the axons that leave the retinas (Silveira & Perry 1 99 1 ) and that little vision survives when both pathways are destroyed (Schiller et al 1 990a). The P and M pathways maintain their sharp anatomical segregation through the termination of the LGN projection in layer 4C of VI (striate cortex). The complex network of connections in primate extrastriate visual cor-

How parallel are the primate visual pathways

1. Recordings were made from single units in the middle temporal visual area (MT) of anesthetized, paralyzed macaque monkeys. A computer-driven stimulator was used to make quantitative tests of sel...

Functional properties of neurons in middle temporal visual area of the macaque monkey. I. Selectivity for stimulus direction, speed, and orientation

The cortical and subcortical connections of the middle temporal visual area (MT) of the macaque monkey were investigated using combined injections of [3H]proline and horseradish peroxidase within MT. Cortical connections were assigned to specific visual areas on the basis of their relationship to the pattern of interhemispheric connections, revealed by staining for degeneration following callosal transection. MT was shown to be reciprocally connected with many topographically organized cortical visual areas, including V1, V2, V3, and V4. These pathways link regions representing corresponding portions of the visual field in the different areas. In addition, MT has reciprocal connections with two previously unidentified cortical areas, which we have designated the medial superior temporal area (MST) and the ventral intraparietal area (VIP). The laminar distribution of terminals and cell bodies in cortical areas connected with MT follows a consistent pattern. In areas V1, V2, and V3, the projections to MT arise largely or exclusively from cells in supragranular layers, and the reciprocal connections from MT terminate mainly in supragranular and infragranular layers. In contrast, the projections to MST and VIP terminate mainly in layer IV, and the reciprocal pathways originate from cells in both superficial and deep layers. On the basis of this pattern, each connection can be designated as forward or feedback in nature, and a hierarchical arrangement of visual areas can be determined. In this hierarchy, MT is at a higher level than V1, V2, and V3, and at a lower level than MST and VIP. Subcortical projections were seen from MT to the claustrum, the putamen, the caudate nucleus, the inferior and lateral subdivisions of the pulvinar complex, the ventral lateral geniculate nucleus, the reticular nucleus of the thalamus, the superior colliculus, and the pontine nuclei.

https://www.jneurosci.org/content/jneuro/3/12/2563.full.pdf

The connections of the middle temporal visual area (MT) and their relationship to a cortical hierarchy in the macaque monkey

The neuronal processes that lead to visual perception have attracted intense interest since Kuffier's studies of receptive field organization in cat retinal ganglion cells over three decades ago (Kuffier 1953). A variety of ana­ tomical and physiological approaches have been employed to analyze the organization of thc visual pathway between the retina and striate cortex (VI ) and the transformations of visual information that occur at each stage (see Hubel & Wiesel 1977, Stone 1 983, Shapley & Lennie 1985). The growth in understanding of the retinostriate pathway has been accompanied by increasing interest in visual processing in the expanse of extrastriate cortex beyond V I . Studies of extrastriate cortex in many spec­ ies showed that it comprises a mosaic of visual areas that can be dis­ tinguished by several anatomical and physiological criteria (reviewed by Kaas 1 978, Zeki 1 978, Cowey 1979, Van Essen 1 979, 1985, Wagor et al 1980, Tusa et al 1 98 1) . The literature in this field is large, and we do not attempt to review all relevant studies. Rather, we concern ourselves with three recent devel­ opments that have yielded insight into information processing and flow within extrastriate cortex. The first of these is the convergence of ana tom-

Visual Processing in Monkey Extrastriate Cortex

We examined how attention affected the orientation tuning of 262 isolated neurons in extrastriate area V4 and 135 neurons in area V1 of two rhesus monkeys. The animals were trained to perform a delayed match-to-sample task in which oriented stimuli were presented in the receptive field of the neuron being recorded. On some trials the animals were instructed to pay attention to those stimuli, and on other trials they were instructed to pay attention to other stimuli outside the receptive field. In this way, orientation-tuning curves could be constructed from neuronal responses collected in two behavioral states: one in which those stimuli were attended by the animal and one in which those stimuli were ignored by the animal. We fit Gaussians to the neuronal responses to twelve different orientations for each behavioral state. Although attention enhanced the responses of V4 neurons (median 26% increase) and V1 neurons (median 8% increase), selectivity, as measured by the width of its orientation-tuning curve, was not systematically altered by attention. The effects of attention were consistent with a multiplicative scaling of the driven response to all orientations. We also found that attention did not cause systematic changes in the undriven activity of the neurons.

https://www.jneurosci.org/content/jneuro/19/1/431.full.pdf

John H. R. Maunsell

Papers

How parallel are the primate visual pathways

Functional properties of neurons in middle temporal visual area of the macaque monkey. I. Selectivity for stimulus direction, speed, and orientation

The connections of the middle temporal visual area (MT) and their relationship to a cortical hierarchy in the macaque monkey

Visual Processing in Monkey Extrastriate Cortex

Effects of Attention on Orientation-Tuning Functions of Single Neurons in Macaque Cortical Area V4