Limits...
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.

Show MeSH
ERP time course at the left and right parieto-occipital clusters. Solid lines show responses to objects, dashed lines responses to non-objects. Red lines indicate responses to HSF images; blue lines indicate responses to BB images; green lines indicate responses to LSF images. Shaded grey area indicates P1 time window; shaded pink area indicates N1 time window.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Fig3: ERP time course at the left and right parieto-occipital clusters. Solid lines show responses to objects, dashed lines responses to non-objects. Red lines indicate responses to HSF images; blue lines indicate responses to BB images; green lines indicate responses to LSF images. Shaded grey area indicates P1 time window; shaded pink area indicates N1 time window.

Mentions: In our analysis of P1 mean amplitudes, there was a significant main effect of Object [F(1,14) = 14.59, p = .002, ƞ2g. = .02], with more positive amplitudes on object (3.67 μV) relative to non-object (3.05 μV) trials. Furthermore, there was a significant main effect of Spatial Frequency [F(2,28) = 17.95, p < .001, ƞ2g. = .04]. Pairwise comparisons between each level of Spatial Frequency revealed that amplitudes were more positive for BB images (3.91 μV) than for HSF (3.26 μV; p < .001) and LSF images (2.93 μV; p < .001). Responses to HSF images were also significantly higher than to LSF images, despite the noticeably smaller difference (p = .01). Finally, there was a significant main effect of Hemisphere [F(1,14) = 6.54, p = .02, ƞ2g. = .04], with significantly more positive amplitudes in the right hemisphere (3.80 μV) than the left hemisphere (2.93 μV). No interactions were significant (all ps > .08). See Figures 3 and 4 for an overview. For P1 peak latency, no effects were significant (all ps > .08).Figure 3


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)

ERP time course at the left and right parieto-occipital clusters. Solid lines show responses to objects, dashed lines responses to non-objects. Red lines indicate responses to HSF images; blue lines indicate responses to BB images; green lines indicate responses to LSF images. Shaded grey area indicates P1 time window; shaded pink area indicates N1 time window.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Fig3: ERP time course at the left and right parieto-occipital clusters. Solid lines show responses to objects, dashed lines responses to non-objects. Red lines indicate responses to HSF images; blue lines indicate responses to BB images; green lines indicate responses to LSF images. Shaded grey area indicates P1 time window; shaded pink area indicates N1 time window.
Mentions: In our analysis of P1 mean amplitudes, there was a significant main effect of Object [F(1,14) = 14.59, p = .002, ƞ2g. = .02], with more positive amplitudes on object (3.67 μV) relative to non-object (3.05 μV) trials. Furthermore, there was a significant main effect of Spatial Frequency [F(2,28) = 17.95, p < .001, ƞ2g. = .04]. Pairwise comparisons between each level of Spatial Frequency revealed that amplitudes were more positive for BB images (3.91 μV) than for HSF (3.26 μV; p < .001) and LSF images (2.93 μV; p < .001). Responses to HSF images were also significantly higher than to LSF images, despite the noticeably smaller difference (p = .01). Finally, there was a significant main effect of Hemisphere [F(1,14) = 6.54, p = .02, ƞ2g. = .04], with significantly more positive amplitudes in the right hemisphere (3.80 μV) than the left hemisphere (2.93 μV). No interactions were significant (all ps > .08). See Figures 3 and 4 for an overview. For P1 peak latency, no effects were significant (all ps > .08).Figure 3

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