Signatures of top-down and bottom-up effects on visual perception measured intracranially from human visual cortex
-
1
Max Planck Institute for Brain Research, Germany
-
2
University of Bonn, Germany
Visual perception is not only determined by the sensory input but also by context, expectations and prior knowledge about the world. It is at present unknown how and through which mechanisms previous experience affects visual perception and how this is different from the effects of simply providing more sensory information. We investigated these questions by manipulating the amount of bottom-up sensory evidence and top-down prior knowledge while recording intracranial EEG. We presented natural images, where sensory evidence was manipulated by degrading them with different levels of noise. Previous experience was manipulated by presenting half of these images without any noise in a preceding familiarization phase. Behavioral results showed that recognition was similarly enhanced for familiarized images and for pictures containing more sensory evidence. To understand the neural mechanisms behind these behavioral and perceptual effects, we recorded the electrocorticogram from the surface of occipital and temporal cortex of 6 epilepsy patients. We focused on the gamma band response (GBR, 80-150 Hz) and on the event related potentials (ERPs). The GBR was spatially confined to the lateral occipital cortex and fusiform gyrus and was reliably modulated by the amount of sensory evidence but not by prior knowledge. ERPs were spatially more distributed and reflected the amount of sensory evidence but also the effect of prior knowledge. Interestingly, these ERP-effects of sensory evidence and prior knowledge were mostly non-overlapping in space and time. We conclude that although manipulating the degree of top-down prior knowledge has the same effect on perception as changing the amount of bottom-up sensory information, the neural mechanisms underlying these effects are different. Funding: Supported by the Max Planck Society.
Keywords:
Intra-cranial Electrophysiology,
Visual Perception
Conference:
XI International Conference on Cognitive Neuroscience (ICON XI), Palma, Mallorca, Spain, 25 Sep - 29 Sep, 2011.
Presentation Type:
Poster Presentation
Topic:
Abstracts
Citation:
Aru
J,
Axmacher
N,
TA Do Lam
A,
Fell
J,
Singer
W and
Melloni
L
(2011). Signatures of top-down and bottom-up effects on visual perception measured intracranially from human visual cortex.
Conference Abstract:
XI International Conference on Cognitive Neuroscience (ICON XI).
doi: 10.3389/conf.fnhum.2011.207.00073
Copyright:
The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers.
They are made available through the Frontiers publishing platform as a service to conference organizers and presenters.
The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated.
Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed.
For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions.
Received:
16 Nov 2011;
Published Online:
25 Nov 2011.
*
Correspondence:
Dr. Jaan Aru, Max Planck Institute for Brain Research, Frankfurt, Germany, jaan.aru@gmail.com