The idea of two separate attention networks in the human brain for the voluntary deployment of attention and the reorientation to unexpected events, respectively, has inspired an enormous amount of research over the past years. In this review, we will reconcile these theoretical ideas on the dorsal and ventral attentional system with recent empirical findings from human neuroimaging experiments and studies in stroke patients. We will highlight how novel methods—such as the analysis of effective connectivity or the combination of neurostimulation with functional magnetic resonance imaging—have contributed to our understanding of the functionality and interaction of the two systems. We conclude that neither of the two networks controls attentional processes in isolation and that the flexible interaction between both systems enables the dynamic control of attention in relation to top-down goals and bottom-up sensory stimulation. We discuss which brain regions potentially govern this interaction according to current task demands.

It is hypothesized that eye movements are used to coordinate elements of a mental model with elements of the visual field. In two experiments, eye movements were recorded while observers imagined or recalled objects that were not present in the visual display. In both cases, observers spontaneously looked at particular blank regions of space in a systematic fashion, to manipulate and organize spatial relationships between mental and/or retinal images. These results contribute to evidence that interpreting a linguistic description of a visual scene requires a spatial (mental model) representation, and they support claims regarding the allocation of position markers in visual space for the manipulation of visual attention. More broadly, our results point to a concrete embodiment of cognition, in that a construction of a mental image is almost "acted out" by the eye movements, and a mental search of internal memory is accompanied by an ocolumotor search of external space.

The parietal lobe forms about 20% of the human cerebral cortex and is divided into two major regions, the somatosensory cortex and the posterior parietal cortex. Posterior parietal cortex, located at the junction of multiple sensory regions, projects to several cortical and subcortical areas and is engaged in a host of cognitive operations. One such operation is selective attention, the process where by the input is filtered and a subset of the information is selected for preferential processing. Recent neuroimaging and neuropsychological studies have provided a more fine-grained understanding of the relationship between brain and behavior in the domain of selective attention. anterior intraparietal sulcus CVA cerebrovascular accident DMS delayed match-to-sample fMRI functional magnetic resonance imaging IPL inferior parietal lobule SPL superior parietal lobule TPJ temporoparietal junction IntroductionParietal cortex, situated at the intersection of visual, auditory, and tactile cortices at the 'crossroads of the brain' [1], is 'association' or tertiary cortex. With its requisite connectivity to cortical and subcortical regions associated with motor responses, parietal cortex serves a crucial role in transforming sensory input into motor output. In the course of doing so, a host of cognitive computations are engaged including spatial representation and updating, attention, coordinate transformation, as well as abstract motor planning [2]. Although much progress has been made in demarcating fine-grained anatomical distinctions in parietal cortex and their functional correlates in nonhuman primates [2,3], this has not been possible in humans. In the past, neuropsychological studies in individuals with lesions have been somewhat helpful in this regard; however, in most cases, the lesions are diffuse, precluding definitive conclusions about the structural and functional aspects of human parietal cortex.With the advent of high-resolution functional neuroimaging, this mapping of anatomical areas is now possible. In addition, the development and accessibility of methods for detailed structural analysis of lesions has enabled a more fine-grained demarcation of the lesion site in braindamaged individuals, and, consequently, a more precise brain-behavior correlation. Here, we review the recent advances that suggest that the role of posterior parietal cortex in selective attention is more specific than was previously assumed. Parietal cortex and attentionSelective attention is the process whereby a subset of the input is selected preferentially for further processing. A primary focus of several recent neuroimaging investigations of attention has been to determine the anatomical locus within the parietal lobe that gives rise to the attentional biasing signal (i.e. the source) that ultimately initiates the sensory enhancement of the selected stimulus (i.e. the effect). The attentional biasing signal could potentially be generated in one of two ways: first, in a bottom-up or stimulus-driven manner (also referred to as 'attent...

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Much is known about the mechanisms by which attention is focused to facilitate perception, but little is known about what happens to attention after perception of the attended object is complete. One possibility is that the focus of attention passively fades. A second possibility is that attention is actively terminated after the completion of perception so that the brain can be prepared for the next target. The present study investigated this issue with event-related potentials (ERPs) in humans, focusing on the N2pc component (a neural measure of attentional deployment) and the Pd component (a neural measure of attentional suppression). We found that active suppression occurred both to prevent the allocation of attention to known distractors and to terminate attention after the perception of an attended object was complete. In addition, the neural measure of active suppression was correlated with a behavioral measure of trial-to-trial variations in the allocation of attention. Active suppression therefore appears to be a general-purpose mechanism that both prevents and terminates the allocation of attention.

HighlightsWe examine the function of the temporo-parietal junction (TJP) in the human brain.The function of TPJ is critically evaluated using data from cognitive neuroscience.We conclude TPJ function in many domains is well described by contextual updating.

We explored how variability in the probability of target locations affects visual search in normal individuals and in patients with hemispatial neglect, a deficit in attending to the contralesional side of space. Young and elderly normal participants responded faster when targets appeared in the more probable region than when targets appeared in the less probable region. Similarly, patients were sensitive to the distribution of targets, even in the neglected field. Although the attentional gradient that characterizes neglect was not eliminated, the response facilitation due to the probability distribution was proportionate to that of control participants and equal in magnitude across the neglected field. All participants exploited the uneven distribution of targets to enhance task performance without explicit instructions to do so or awareness of biases in their behavior. These results suggest that attentional orientation and sensitivity to external probabilities are possibly dissociable. An early sensory and a late motor mechanism are postulated as possibly being involved in the observed probability-matching behavior of participants.

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