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Temporal brain dynamics of multiple object processing: the flexibility of individuation.

Mazza V, Caramazza A - PLoS ONE (2011)

Bottom Line: In three ERP experiments, participants saw a variable number of target elements among homogenous distracters and performed either an enumeration task (Experiment 1) or a detection task, reporting whether at least one (Experiment 2) or a specified number of target elements (Experiment 3) was present.While in the enumeration task the N2pc response increased as a function of the number of targets, no such modulation was found in Experiment 2, indicating that individuation of multiple targets is not mandatory.However, a modulation of the N2pc similar to the enumeration task was visible in Experiment 3, further highlighting that object individuation is a flexible mechanism that binds indexes to object properties and locations as needed for further object processing.

View Article: PubMed Central - PubMed

Affiliation: Center for Mind/Brain Sciences (CIMeC), University of Trento, Trento, Italy. veronica.mazza@unitn.it

ABSTRACT
The ability to process concurrently multiple visual objects is fundamental for a coherent perception of the world. A core component of this ability is the simultaneous individuation of multiple objects. Many studies have addressed the mechanism of object individuation but it remains unknown whether the visual system mandatorily individuates all relevant elements in the visual field, or whether object indexing depends on task demands. We used a neural measure of visual selection, the N2pc component, to evaluate the flexibility of multiple object individuation. In three ERP experiments, participants saw a variable number of target elements among homogenous distracters and performed either an enumeration task (Experiment 1) or a detection task, reporting whether at least one (Experiment 2) or a specified number of target elements (Experiment 3) was present. While in the enumeration task the N2pc response increased as a function of the number of targets, no such modulation was found in Experiment 2, indicating that individuation of multiple targets is not mandatory. However, a modulation of the N2pc similar to the enumeration task was visible in Experiment 3, further highlighting that object individuation is a flexible mechanism that binds indexes to object properties and locations as needed for further object processing.

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Stimuli and behavioral results.(A) Example of trials with one (left), two (middle) and three (right) targets. (B) Response times (milliseconds) of all the experiments show an anchoring effect for the extreme target numerosities in Experiment 1 (enumeration) and in the match condition of Experiment 3.
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pone-0017453-g001: Stimuli and behavioral results.(A) Example of trials with one (left), two (middle) and three (right) targets. (B) Response times (milliseconds) of all the experiments show an anchoring effect for the extreme target numerosities in Experiment 1 (enumeration) and in the match condition of Experiment 3.

Mentions: In the first two ERP experiments of the present study participants saw a variable number (zero, one, two or three) of uniquely colored elements presented together with various distracters (see example displays in Figure 1a). The use of distracters served two purposes. First, by creating a cluttered scene it can help accentuate the role of individuation processes in distinguishing and selecting the task-relevant objects. Second, we wanted to have a context similar to the one used in Drew and Vogel's [26] study, as well as in most of the previous studies on the N2pc component (e.g., [23]).


Temporal brain dynamics of multiple object processing: the flexibility of individuation.

Mazza V, Caramazza A - PLoS ONE (2011)

Stimuli and behavioral results.(A) Example of trials with one (left), two (middle) and three (right) targets. (B) Response times (milliseconds) of all the experiments show an anchoring effect for the extreme target numerosities in Experiment 1 (enumeration) and in the match condition of Experiment 3.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3046149&req=5

pone-0017453-g001: Stimuli and behavioral results.(A) Example of trials with one (left), two (middle) and three (right) targets. (B) Response times (milliseconds) of all the experiments show an anchoring effect for the extreme target numerosities in Experiment 1 (enumeration) and in the match condition of Experiment 3.
Mentions: In the first two ERP experiments of the present study participants saw a variable number (zero, one, two or three) of uniquely colored elements presented together with various distracters (see example displays in Figure 1a). The use of distracters served two purposes. First, by creating a cluttered scene it can help accentuate the role of individuation processes in distinguishing and selecting the task-relevant objects. Second, we wanted to have a context similar to the one used in Drew and Vogel's [26] study, as well as in most of the previous studies on the N2pc component (e.g., [23]).

Bottom Line: In three ERP experiments, participants saw a variable number of target elements among homogenous distracters and performed either an enumeration task (Experiment 1) or a detection task, reporting whether at least one (Experiment 2) or a specified number of target elements (Experiment 3) was present.While in the enumeration task the N2pc response increased as a function of the number of targets, no such modulation was found in Experiment 2, indicating that individuation of multiple targets is not mandatory.However, a modulation of the N2pc similar to the enumeration task was visible in Experiment 3, further highlighting that object individuation is a flexible mechanism that binds indexes to object properties and locations as needed for further object processing.

View Article: PubMed Central - PubMed

Affiliation: Center for Mind/Brain Sciences (CIMeC), University of Trento, Trento, Italy. veronica.mazza@unitn.it

ABSTRACT
The ability to process concurrently multiple visual objects is fundamental for a coherent perception of the world. A core component of this ability is the simultaneous individuation of multiple objects. Many studies have addressed the mechanism of object individuation but it remains unknown whether the visual system mandatorily individuates all relevant elements in the visual field, or whether object indexing depends on task demands. We used a neural measure of visual selection, the N2pc component, to evaluate the flexibility of multiple object individuation. In three ERP experiments, participants saw a variable number of target elements among homogenous distracters and performed either an enumeration task (Experiment 1) or a detection task, reporting whether at least one (Experiment 2) or a specified number of target elements (Experiment 3) was present. While in the enumeration task the N2pc response increased as a function of the number of targets, no such modulation was found in Experiment 2, indicating that individuation of multiple targets is not mandatory. However, a modulation of the N2pc similar to the enumeration task was visible in Experiment 3, further highlighting that object individuation is a flexible mechanism that binds indexes to object properties and locations as needed for further object processing.

Show MeSH