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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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Grand-average ERP waveforms and topographical scalp distribution maps (amplitude scale: ±3 µV) of Experiment 2, obtained as in Experiment 1, showed no modulation of the N2pc and CDA as function of target numerosity.
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pone-0017453-g003: Grand-average ERP waveforms and topographical scalp distribution maps (amplitude scale: ±3 µV) of Experiment 2, obtained as in Experiment 1, showed no modulation of the N2pc and CDA as function of target numerosity.

Mentions: Two aspects of the present results differed markedly from those of Experiment 1 (see Figure 3). First, an N2pc was clearly elicited in all three conditions, but was not modulated by the number of targets presented in the visual display. No significant main effect of target numerosity or interaction emerged, both ps>.2. In addition, no CDA emerged from the analysis in the subsequent time range (350–600 ms), all ps>.12.


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

Mazza V, Caramazza A - PLoS ONE (2011)

Grand-average ERP waveforms and topographical scalp distribution maps (amplitude scale: ±3 µV) of Experiment 2, obtained as in Experiment 1, showed no modulation of the N2pc and CDA as function of target numerosity.
© Copyright Policy
Related In: Results  -  Collection

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

pone-0017453-g003: Grand-average ERP waveforms and topographical scalp distribution maps (amplitude scale: ±3 µV) of Experiment 2, obtained as in Experiment 1, showed no modulation of the N2pc and CDA as function of target numerosity.
Mentions: Two aspects of the present results differed markedly from those of Experiment 1 (see Figure 3). First, an N2pc was clearly elicited in all three conditions, but was not modulated by the number of targets presented in the visual display. No significant main effect of target numerosity or interaction emerged, both ps>.2. In addition, no CDA emerged from the analysis in the subsequent time range (350–600 ms), all ps>.12.

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