Induced gamma-band response to fragmented images: An intracranial EEG study

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Induced gamma-band response (iGBR) has been linked to coherent perception of images and is thought to represent the synchronisation of neuronal populations mediating binding of elements composing the image and the comparisons with memory for proper recognition. This study uses fragmented images with intracranial electroencephalography to investigate the precise spatio-temporal dynamic of iGBR elicited by the recognition of objects presented for the first time and 24 h later. Results show an increased iGBR at recognition in regions involved in bottom-up processes such as the cuneus and the lateral occipital complex. Top-down facilitation involved the lingual gyrus, the precuneus and the superior parietal lobule when images were presented for the first time. Twenty-four hours later, top-down facilitation was mediated by frontal areas involved in retrieval from episodic memory. This study showed that the classically reported iGBR is related to object recognition and that top-down processes vary according to task demand.


★ To examine the spatio-temporal dynamics of gamma-band binding using fragmented images. ★ Intracranial electroencephalography is performed in six epileptic patients. ★ Bottom-up processes recruit mainly occipital and temporal cortical areas. ★ Top-down processes involve occipital and parietal areas. ★ Subsequent recognition of images involves frontal areas for retrieval from memory.

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