Task and Spatial Frequency Modulations of Object Processing: An EEG Study

Abstract

Visual object processing may follow a coarse-to-fine sequence imposed by fast processing of low spatial frequencies (LSF) and slow processing of high spatial frequencies (HSF). Objects can be categorized at varying levels of specificity: the superordinate (e.g. animal), the basic (e.g. dog), or the subordinate (e.g. Border Collie). We tested whether superordinate and more specific categorization depend on different spatial frequency ranges, and whether any such dependencies might be revealed by or influence signals recorded using EEG. We used event-related potentials (ERPs) and time-frequency (TF) analysis to examine the time course of object processing while participants performed either a grammatical gender-classification task (which generally forces basic-level categorization) or a living/non-living judgement (superordinate categorization) on everyday, real-life objects. Objects were filtered to contain only HSF or LSF. We found a greater positivity and greater negativity for HSF than for LSF pictures in the P1 and N1 respectively, but no effects of task on either component. A later, fronto-central negativity (N350) was more negative in the gender-classification task than the superordinate categorization task, which may indicate that this component relates to semantic or syntactic processing. We found no significant effects of task or spatial frequency on evoked or total gamma band responses. Our results demonstrate early differences in processing of HSF and LSF content that were not modulated by categorization task, with later responses reflecting such higher-level cognitive factors.

A Rapid Subcortical Amygdala Route for Faces Irrespective of Spatial Frequency and Emotion

“…Previous studies have also reported greater neural activity for Low than High spatial frequency images at approximately 160ms 31,34,36 . Moreover, similar findings have been reported for overall greater amplitude for High compared with Low spatial frequency faces 35,37,38 , with some studies reporting an earlier modulation than presented here (i.e. the M100 compared with the M170) 37,38 .…”

“…Moreover, similar findings have been reported for overall greater amplitude for High compared with Low spatial frequency faces 35,37,38 , with some studies reporting an earlier modulation than presented here (i.e. the M100 compared with the M170) 37,38 . This discrepancy may be due to differences in analysis technique, such that statistics on specific electrodes and time-windows are more specific (but also biased) compared with our more conservative and unbiased spatiotemporal analysis, where corrections for multiple comparisons are made across the entire sensor space and all time-points.…”

A Rapid Subcortical Amygdala Route for Faces Irrespective of Spatial Frequency and Emotion

“…Thus, we found distinct early (160 ms) and late (460 ms) components of LSF processing despite overwhelmingly greater activity for HSF overall (170 -585 ms). Some studies have reported earlier effects of LSF (i.e., within the M100 component) than our relatively later effect (Craddock et al, 2013;Mu and Li, 2013). This may be due to differences in analysis technique, such that statistics on specific electrodes and time windows are more specific (but also more biased) compared with our more conservative and unbiased spatiotemporal analysis, where corrections for multiple comparisons are made across the entire sensor space and all time-points.…”

Tracking changes in spatial frequency sensitivity during natural image processing in school age: an event-related potential study

“…In particular, the P1 component (a positive peak arising between 80 and 140 ms) is evoked both by LSF and HSF stimuli, and can be either enhanced or reduced to HSF (relative to LSF) stimuli, depending on several factors, including contrast, structural complexity and possibly also task requirements (Baseler & Sutter, 1997;Boeschoten, Kemner, Kenemans, & Engeland, 2005;Craddock, Martinovic, & Müller, 2013;Ellemberg, Hammarrenger, Lepore, Roy, & Guillemot, 2001;Hansen, Jacques, Johnson, & Ellemberg, 2011;Rokszin, Győri-Dani, Nyúl, & Csifcsák, 2016). Similarly, the subsequent N1 component (with a negative peak between 140-220 ms) reflects the cortical analysis of both LSF and HSF images, but its amplitude is modulated by the spectral content of stimuli in an inconsistent way, an effect that is probably paradigm-specific (Boeschoten et al, 2005;Craddock et al 2013;Rokszin et al, 2016). Since the posterior P1 and N1 components reflect continuously unfolding, temporally overlapping processes of visual analysis such as feature detection, figure-ground segregation and structural encoding, and as outlined above, they are both influenced by SFs, these ERPs provide a unique measure for tracking the time course of SF processing in various groups of participants.…”