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Early and late effects of objecthood and spatial frequency on event-related potentials and gamma band activity.

Craddock M, Martinovic J, Müller MM - BMC Neurosci (2015)

Bottom Line: The peak-to-peak N1 showed that the N1 was much reduced for BB non-objects relative to all other images, while HSF and LSF non-objects still elicited as negative an N1 as objects.Different pathways are involved in the processing of low and high spatial frequencies during object recognition, as reflected in interactions between objecthood and spatial frequency in the visual N1 component.Total gamma band seems to be related to a late, probably high-level representational process.

View Article: PubMed Central - PubMed

Affiliation: Institute of Psychology, University of Leipzig, 04109, Leipzig, Germany. m.p.craddock@leeds.ac.uk.

ABSTRACT

Background: The visual system may process spatial frequency information in a low-to-high, coarse-to-fine sequence. In particular, low and high spatial frequency information may be processed via different pathways during object recognition, with LSF information projected rapidly to frontal areas and HSF processed later in visual ventral areas. In an electroencephalographic study, we examined the time course of information processing for images filtered to contain different ranges of spatial frequencies. Participants viewed either high spatial frequency (HSF), low spatial frequency (LSF), or unfiltered, broadband (BB) images of objects or non-object textures, classifying them as showing either man-made or natural objects, or non-objects. Event-related potentials (ERPs) and evoked and total gamma band activity (eGBA and tGBA) recorded using the electroencephalogram were compared for object and non-object images across the different spatial frequency ranges.

Results: The visual P1 showed independent modulations by object and spatial frequency, while for the N1 these factors interacted. The P1 showed more positive amplitudes for objects than non-objects, and more positive amplitudes for BB than for HSF images, which in turn evoked more positive amplitudes than LSF images. The peak-to-peak N1 showed that the N1 was much reduced for BB non-objects relative to all other images, while HSF and LSF non-objects still elicited as negative an N1 as objects. In contrast, eGBA was influenced by spatial frequency and not objecthood, while tGBA showed a stronger response to objects than non-objects.

Conclusions: Different pathways are involved in the processing of low and high spatial frequencies during object recognition, as reflected in interactions between objecthood and spatial frequency in the visual N1 component. Total gamma band seems to be related to a late, probably high-level representational process.

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N1 mean amplitudes for the interaction between object and spatial frequency at left and right hemisphere electrode clusters. Error bars depict bootstrapped 95% confidence intervals.
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Fig5: N1 mean amplitudes for the interaction between object and spatial frequency at left and right hemisphere electrode clusters. Error bars depict bootstrapped 95% confidence intervals.

Mentions: In our analysis of N1 mean amplitudes, there was a significant main effect of Object [F(1,14) = 5.07, p = .04, ƞ2g. = .03], with a more negative N1 amplitude for objects (2.1 μV) than for non-objects (3.22 μV). There was also a significant main effect of Spatial Frequency [F(2,28) = 33.71, p < .001 ƞ2g. = .08], with more a negative N1 amplitude for HSF images (1.70 μV) than for BB (3.91 μV; p < .001) and LSF (2.36 μV; p = .01) images. LSF images were also more negative than BB images (p < .001). However, there was a significant interaction between Object and Spatial Frequency [F(2,28) = 6.08, p < .001, ƞ2g. = .02], see Figures 3 and 5. The N1 was significantly more negative for BB objects than for BB non-objects (p < .001), and more negative for LSF objects than for LSF non-objects (p = .03). However, there was no significant difference between HSF objects and HSF non-objects (p = 1). Thus, the N1 was sensitive to objecthood for BB and LSF but not HSF images. The N1 was also significantly more negative for HSF (p = .003) and LSF objects (p = .02) than for BB objects. Indeed, BB non-objects elicited significantly more positive amplitudes than any other combination of object and spatial frequency (all ps < .001). Neither the main effect of Hemsiphere nor any of the interactions involving Hemisphere were significant (all ps > .2).Figure 5


Early and late effects of objecthood and spatial frequency on event-related potentials and gamma band activity.

Craddock M, Martinovic J, Müller MM - BMC Neurosci (2015)

N1 mean amplitudes for the interaction between object and spatial frequency at left and right hemisphere electrode clusters. Error bars depict bootstrapped 95% confidence intervals.
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC4352290&req=5

Fig5: N1 mean amplitudes for the interaction between object and spatial frequency at left and right hemisphere electrode clusters. Error bars depict bootstrapped 95% confidence intervals.
Mentions: In our analysis of N1 mean amplitudes, there was a significant main effect of Object [F(1,14) = 5.07, p = .04, ƞ2g. = .03], with a more negative N1 amplitude for objects (2.1 μV) than for non-objects (3.22 μV). There was also a significant main effect of Spatial Frequency [F(2,28) = 33.71, p < .001 ƞ2g. = .08], with more a negative N1 amplitude for HSF images (1.70 μV) than for BB (3.91 μV; p < .001) and LSF (2.36 μV; p = .01) images. LSF images were also more negative than BB images (p < .001). However, there was a significant interaction between Object and Spatial Frequency [F(2,28) = 6.08, p < .001, ƞ2g. = .02], see Figures 3 and 5. The N1 was significantly more negative for BB objects than for BB non-objects (p < .001), and more negative for LSF objects than for LSF non-objects (p = .03). However, there was no significant difference between HSF objects and HSF non-objects (p = 1). Thus, the N1 was sensitive to objecthood for BB and LSF but not HSF images. The N1 was also significantly more negative for HSF (p = .003) and LSF objects (p = .02) than for BB objects. Indeed, BB non-objects elicited significantly more positive amplitudes than any other combination of object and spatial frequency (all ps < .001). Neither the main effect of Hemsiphere nor any of the interactions involving Hemisphere were significant (all ps > .2).Figure 5

Bottom Line: The peak-to-peak N1 showed that the N1 was much reduced for BB non-objects relative to all other images, while HSF and LSF non-objects still elicited as negative an N1 as objects.Different pathways are involved in the processing of low and high spatial frequencies during object recognition, as reflected in interactions between objecthood and spatial frequency in the visual N1 component.Total gamma band seems to be related to a late, probably high-level representational process.

View Article: PubMed Central - PubMed

Affiliation: Institute of Psychology, University of Leipzig, 04109, Leipzig, Germany. m.p.craddock@leeds.ac.uk.

ABSTRACT

Background: The visual system may process spatial frequency information in a low-to-high, coarse-to-fine sequence. In particular, low and high spatial frequency information may be processed via different pathways during object recognition, with LSF information projected rapidly to frontal areas and HSF processed later in visual ventral areas. In an electroencephalographic study, we examined the time course of information processing for images filtered to contain different ranges of spatial frequencies. Participants viewed either high spatial frequency (HSF), low spatial frequency (LSF), or unfiltered, broadband (BB) images of objects or non-object textures, classifying them as showing either man-made or natural objects, or non-objects. Event-related potentials (ERPs) and evoked and total gamma band activity (eGBA and tGBA) recorded using the electroencephalogram were compared for object and non-object images across the different spatial frequency ranges.

Results: The visual P1 showed independent modulations by object and spatial frequency, while for the N1 these factors interacted. The P1 showed more positive amplitudes for objects than non-objects, and more positive amplitudes for BB than for HSF images, which in turn evoked more positive amplitudes than LSF images. The peak-to-peak N1 showed that the N1 was much reduced for BB non-objects relative to all other images, while HSF and LSF non-objects still elicited as negative an N1 as objects. In contrast, eGBA was influenced by spatial frequency and not objecthood, while tGBA showed a stronger response to objects than non-objects.

Conclusions: Different pathways are involved in the processing of low and high spatial frequencies during object recognition, as reflected in interactions between objecthood and spatial frequency in the visual N1 component. Total gamma band seems to be related to a late, probably high-level representational process.

Show MeSH