Decomposing the neural mechanisms of visual search through model-based analysis of fMRI: Top-down excitation, active ignoring and the use of saliency by the right TPJ

Mavritsaki, Eirini; Allen, Harriet A.; Humphreys, Glyn W.

doi:10.1016/j.neuroimage.2010.03.044

Cited by 26 publications

(36 citation statements)

References 72 publications

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“…In a previous study, right TPJ activity correlated with the relative saliency of a target compared to other elements in the visual field (Mavritsaki et al, 2010). Activity levels of right TPJ are also increased during oddball trials (Braver et al, 2001;Bledowski et al, 2004;Downar et al, 2000).…”

Section: Discussionmentioning

confidence: 64%

Attentional priorities and access to short-term memory: Parietal interactions

et al. 2012

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The intraparietal sulcus (IPS) has been implicated in selective attention as well as visual short-term memory (VSTM). To contrast mechanisms of target selection, distracter filtering, and access to VSTM, we combined behavioral testing, computational modeling and functional magnetic resonance imaging. Sixteen healthy subjects participated in a change detection task in which we manipulated both target and distracter set sizes. We directly compared the IPS response as a function of the number of targets and distracters in the display and in VSTM. When distracters were not present, the posterior and middle segments of IPS showed the predicted asymptotic activity increase with an increasing target set size. When distracters were added to a single target, activity also increased as predicted. However, the addition of distracters to multiple targets suppressed both middle and posterior IPS activities, thereby displaying a significant interaction between the two factors. The interaction between target and distracter set size in IPS could not be accounted for by a simple explanation in terms of number of items accessing VSTM. Instead, it led us to a model where items accessing VSTM receive differential weights depending on their behavioral relevance, and secondly, a suppressive effect originates during the selection phase when multiple targets and multiple distracters are simultaneously present. The reverse interaction between target and distracter set size was significant in the right temporoparietal junction (TPJ), where activity was highest for a single target compared to any other condition. Our study reconciles the role of middle IPS in attentional selection and biased competition with its role in VSTM access.

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Section: Discussionmentioning

confidence: 64%

Attentional priorities and access to short-term memory: Parietal interactions

et al. 2012

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“…It follows that these brain regions may provide a source of the activation profiles evident in the feature maps in the model. Mavritsaki et al (2010) also carried out a more direct analysis of topological parallels between sSoTS and brain activity. To do this, activity within the location map was summed and convolved with the assumed HDR and then correlated with the brain activation recorded in an fMRI study of single-feature, conjunction, and preview search conducted by Allen et al (2008).…”

Section: Study 4: Simulating Fmri Datamentioning

confidence: 99%

Bridging the gap between physiology and behavior: Evidence from the sSoTS model of human visual attention.

Mavritsaki¹,

Heinke²,

Allen³

et al. 2011

Psychological Review

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We present the case for a role of biologically plausible neural network modeling in bridging the gap between physiology and behavior. We argue that spiking-level networks can allow "vertical" translation between physiological properties of neural systems and emergent "whole-system" performanceenabling psychological results to be simulated from implemented networks and also inferences to be made from simulations concerning processing at a neural level. These models also emphasize particular factors (e.g., the dynamics of performance in relation to real-time neuronal processing) that are not highlighted in other approaches and that can be tested empirically. We illustrate our argument from neural-level models that select stimuli by biased competition. We show that a model with biased competition dynamics can simulate data ranging from physiological studies of single-cell activity (Study 1) to whole-system behavior in human visual search (Study 2), while also capturing effects at an intermediate level, including performance breakdown after neural lesion (Study 3) and data from brain imaging (Study 4). We also show that, at each level of analysis, novel predictions can be derived from the biologically plausible parameters adopted, which we proceed to test (Study 5). We argue that, at least for studying the dynamics of visual attention, the approach productively links single-cell to psychological data. Keywords: visual search, integrate-and-fire neurons, computational model, fMRI, neuropsychologyUnderstanding human cognition is difficult. One of the difficulties is that cognition can be described at many different levelsfrom the high-level computational principles that may shape the landscape within which processes must function, through to the physiological principles by which neurons operate. How can these different levels best be related? Marr (1982) provided an influential framework in which different levels of analysis were described. This framework separated out, on the one hand, theories dealing with the computational principles and the neural hardware, from, on the other, "midlevel" theories that deal with abstract algorithms, which could operate on a variety of platforms (computers as well as human brains). However, what was not specified in this framework was how we move between the different levels; indeed, the levels were described as operating in a quasi-independent manner. This means that, within the framework, it is possible to have an algorithmic account of cognition that is separated from constraints based on neural-level functions, as well as neural-level accounts unconstrained by data derived from the operation of component cognitive processes. This leaves unspecified how we may link theories dealing with abstract psychological mechanisms (attention, memory, decision making) to theories that are concerned with how neurons communicate. It also means that the benefits that might be gained from this linkage are unexploited; theoretical insights at one level do not infiltrate other levels. The aim of t...

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“…The net result is no effect on the TPJ in search in the temporal segmentation condition. The TPJ does show activity in relation to successful preview search, when brain activity is probed with more fine-tuned regressors derived from computational models of search (Mavritsaki, Allen, & Humphreys, 2010).…”

Section: Search Activationmentioning

confidence: 99%

Comparing Segmentation by Time and by Motion in Visual Search: An fMRI Investigation

Dent¹,

Allen²,

Humphreys³

2011

Journal of Cognitive Neuroscience

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Abstract■ Brain activity was recorded while participants engaged in a difficult visual search task for a target defined by the spatial configuration of its component elements. The search displays were segmented by time (a preview then a search display), by motion, or were unsegmented. A preparatory network showed activity to the preview display, in the time but not in the motion segmentation condition. A region of the precuneus showed (i) higher activation when displays were segmented by time or by motion, and (ii) correlated activity with larger segmentation benefits behaviorally, regardless of the cue. Additionally, the results revealed that success in temporal segmentation was correlated with reduced activation in early visual areas, including V1. The results depict partially overlapping brain networks for segmentation in search by time and motion, with both cue-independent and cue-specific mechanisms. ■

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Decomposing the neural mechanisms of visual search through model-based analysis of fMRI: Top-down excitation, active ignoring and the use of saliency by the right TPJ

Cited by 26 publications

References 72 publications

Attentional priorities and access to short-term memory: Parietal interactions

Attentional priorities and access to short-term memory: Parietal interactions

Bridging the gap between physiology and behavior: Evidence from the sSoTS model of human visual attention.

Comparing Segmentation by Time and by Motion in Visual Search: An fMRI Investigation

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