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How the Camel Lost its Hump: The impact of object typicality on ERP signals in object decision
| CBU number: | 6304 |
| Authors: | HAUK, O., PATTERSON, K., WOOLLAMS, A., COOPER-PYE, E., PULVERMULLER, F. & Rogers, T.T. |
| Reference: | Journal of Cognitive Neuroscience, 19(8), 1338-1353 |
| Year of publication: | 2007 |
| Abstract text: | Using an object decision task, event-related potentials (ERP) and minimum norm current source estimates, we investigated early spatio-temporal aspects of cortical activation elicited by line drawings which were manipulated on two dimensions: ìAuthenticityî and ìTypicalityî. Authentic objects were those that match real-world experience, while non-authentic objects were ëdoctoredí by deletion or addition of features (e.g., a camel with its hump removed, a hammer with two handles). The main manipulation of interest for both authentic and non-authentic objects was the degree of typicality in the objectís structure: typical items are composed of parts that have tended to co-occur across many different objects in the perceiverís experience. The ERP pattern revealed a significant typicality effect at 116ms after stimulus onset. Both atypical authentic objects (e.g. a camel with its hump) and atypical non-authentic objects (e.g., a jackal with a hump) elicited stronger brain activation than objects with typical structure. A significant effect of authenticity was observed at 480 ms, with stronger activation for the non-authentic objects. The factors of typicality and authenticity interacted at 160 ms and 330 ms. The most prominent source of the typicality effect was bilateral occipito-temporal cortex, whereas the interaction and the authenticity effects were mainly observed in more anterior bilateral temporal cortex. These findings support the hypothesis that within the first few hundred milliseconds after stimulus presentation onset, visual-form-related perceptual and conceptual processes represent distinct but interacting stages in object recognition. |
| First CBU author: | Hauk, O. |
| Annual report number: | CBUAR 52 |
| Keywords: | object recognition, semantic dementia, semantics, source estimation |