Does coarse-to-fine spatial frequency processing depend on object categorization task? M Craddock1, J Martinovic2, M Müller1 |
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1Institute of Psychology, University of Leipzig, Germany |
| Visual object processing follows a coarse-to-fine sequence imposed by fast processing of low spatial frequencies (LSF) and slow processing of high spatial frequencies (HSF). We tested how these different spatial frequency ranges may support categorization at superordinate (e.g. "animal") and more specific levels (e.g. basic-level, "dog"), and whether any such dependencies are reflected in signals recorded using EEG. We used event-related potentials and time-frequency analysis to examine the time course of object processing while participants performed a grammatical gender-classification task (which generally forces basic-level categorization) or a living/non-living judgement (superordinate categorization) on every day, familiar objects. The objects were filtered to contain only LSF or HSF. 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 enhanced during gender-classification relative to superordinate categorization, indicating that this component relates to semantic or syntactic processing. Induced gamma-band activity was not influenced by task or spatial frequency. Our results indicate early differences in processing of HSF and LSF content which did not interact with categorization task, while later responses reflected higher-level cognitive factors. |
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