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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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Grand mean total gamma band activity. (a) Mean percent change from baseline in tGBA for each individual condition. Left column shows activity on object trials, right column shows activity on non-object trials. (b) topography of tGBA averaged across all conditions, 40–90 Hz, and 200-500 ms. Black ovals indicate the electrode clusters used for analysis. (c) Bar graph showing mean percent change in tGBA for each condition. Red bars show tGBA on object trials, blue on non-object trials. Error bars depict 95% confidence intervals.
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Fig8: Grand mean total gamma band activity. (a) Mean percent change from baseline in tGBA for each individual condition. Left column shows activity on object trials, right column shows activity on non-object trials. (b) topography of tGBA averaged across all conditions, 40–90 Hz, and 200-500 ms. Black ovals indicate the electrode clusters used for analysis. (c) Bar graph showing mean percent change in tGBA for each condition. Red bars show tGBA on object trials, blue on non-object trials. Error bars depict 95% confidence intervals.

Mentions: Total gamma band activity showed a significantly greater increase [F(1,14) = 28.3, p < .001, ƞ2g. = .14] relative to baseline for objects (18.1%) than for non-objects (7.6%). Neither the main effects of Spatial Frequency [F(2,28) = 2.44, p = .1, ƞ2g. = .008] nor Hemisphere [F(1,14) = .03, p = .9, ƞ2g. < .001] were significant. Importantly, the two-way interaction between Object and Spatial Frequency was not significant [F(2,28) = 1.36, p = .3, ƞ2g. = .008], see Figure 8. However, there was a significant interaction between Spatial Frequency and Hemisphere [F(2,28) = 5.86, p = .007, ƞ2g. = .01]. Although no comparisons were significant in post-hoc follow-up tests (all ps > .1), this interaction was likely driven by smaller gamma band responses to HSF images in the left hemisphere than the right hemisphere. Note that, although Figure 8 shows the three-way interaction between Object, Spatial Frequency, and Hemisphere, this interaction was not significant [F(2,28) = 0.17, p = .8, ƞ2g. < .001]. No other interactions were significant (all ps > .3).Figure 8


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)

Grand mean total gamma band activity. (a) Mean percent change from baseline in tGBA for each individual condition. Left column shows activity on object trials, right column shows activity on non-object trials. (b) topography of tGBA averaged across all conditions, 40–90 Hz, and 200-500 ms. Black ovals indicate the electrode clusters used for analysis. (c) Bar graph showing mean percent change in tGBA for each condition. Red bars show tGBA on object trials, blue on non-object trials. Error bars depict 95% confidence intervals.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Fig8: Grand mean total gamma band activity. (a) Mean percent change from baseline in tGBA for each individual condition. Left column shows activity on object trials, right column shows activity on non-object trials. (b) topography of tGBA averaged across all conditions, 40–90 Hz, and 200-500 ms. Black ovals indicate the electrode clusters used for analysis. (c) Bar graph showing mean percent change in tGBA for each condition. Red bars show tGBA on object trials, blue on non-object trials. Error bars depict 95% confidence intervals.
Mentions: Total gamma band activity showed a significantly greater increase [F(1,14) = 28.3, p < .001, ƞ2g. = .14] relative to baseline for objects (18.1%) than for non-objects (7.6%). Neither the main effects of Spatial Frequency [F(2,28) = 2.44, p = .1, ƞ2g. = .008] nor Hemisphere [F(1,14) = .03, p = .9, ƞ2g. < .001] were significant. Importantly, the two-way interaction between Object and Spatial Frequency was not significant [F(2,28) = 1.36, p = .3, ƞ2g. = .008], see Figure 8. However, there was a significant interaction between Spatial Frequency and Hemisphere [F(2,28) = 5.86, p = .007, ƞ2g. = .01]. Although no comparisons were significant in post-hoc follow-up tests (all ps > .1), this interaction was likely driven by smaller gamma band responses to HSF images in the left hemisphere than the right hemisphere. Note that, although Figure 8 shows the three-way interaction between Object, Spatial Frequency, and Hemisphere, this interaction was not significant [F(2,28) = 0.17, p = .8, ƞ2g. < .001]. No other interactions were significant (all ps > .3).Figure 8

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