Related Experiment Video
Updated: Apr 17, 2026
Novel Object Recognition Test for the Investigation of Learning and Memory in Mice
Published on: August 30, 2017
NMDA Receptor Antagonist Ketamine Distorts Object Recognition by Reducing Feedback to Early Visual Cortex
Anouk M van Loon1, Johannes J Fahrenfort2, Bauke van der Velde3
1Department of Brain and Cognition, University of Amsterdam, Amsterdam 1018 XA, The Netherlands Amsterdam Brain and Cognition, University of Amsterdam, Amsterdam 1018 WS, The Netherlands Department of Cognitive Psychology, VU University, Amsterdam 1081 BT, The Netherlands.
Top-down brain processes shape visual perception. This study shows that recognizing images alters neural patterns, an effect dependent on NMDA receptor function, particularly in early visual cortex.
Area of Science:
- Neuroscience
- Cognitive Science
- Visual Perception
Background:
- Top-down processing influences neural activity in lower visual areas.
- NMDA receptor function is implicated in these top-down processes, based on animal studies and models.
- Human evidence for this mechanism was previously lacking.
Purpose of the Study:
- To investigate the role of NMDA receptor functioning in human top-down visual processing.
- To compare neural representations of ambiguous images before and after recognition.
- To assess the impact of ketamine, an NMDA receptor antagonist, on these processes.
Main Methods:
- Functional magnetic resonance imaging (fMRI) multivoxel pattern analysis.
- Comparison of brain activation patterns for Mooney images before and after recognition.
- Administration of ketamine (NMDA receptor antagonist) to participants.
Main Results:
- Image recognition led to neural representations becoming more similar to unambiguous versions.
- Unrecognized images showed similar neural patterns, while recognized images showed distinct patterns.
- Ketamine disrupted these recognition effects in early visual cortex, but not in the lateral occipital cortex.
Conclusions:
- Human top-down visual processing, particularly in early visual cortex, appears to rely on NMDA receptor pathways.
- Recognition transforms neural representations, making them more distinct.
- These findings provide crucial human evidence for NMDA receptor involvement in top-down visual modulation.
