Ketamine changes the neural representation of object recognition A M van Loon1, H Scholte1, J J Fahrenfort2, B van der Velde3, P B Lirk4, N C Vulink5, M W Hollmann4, V Lamme1 |
|---|
1Cognitive Neuroscience Group, University of Amsterdam, Netherlands |
| What does recognition of an object do to its representation in the brain? Previous research demonstrated that recognition alters the spatial patterns of fMRI activation even in early visual cortex (Hsieh et al. 2009). This process is thought to depend on feedback from higher-level areas to early visual areas. In turn, feedback activity is suggested to rely on the NMDA-receptor. To investigate the role of feedback in the effect of recognition, we administered either Ketamine, an NMDA-receptor antagonist, or a placebo to participants. Participants viewed Mooney images that were initially unrecognizable and later recognizable and grayscale photo versions of the same images. We used representational dissimilarity matrixes (RDM) to investigate how the spatial patterns of fMRI activation changed with recognition. Preliminary data suggests that the neural patterns of recognized Mooney images more strongly resemble neural patterns of the photographic images than of same Mooney images when not recognized. This effect was observed both in early visual areas and in object related areas. Ketamine reduced these effects of recognition in early visual areas. This suggests that reduction of feedback by Ketamine counteracts the effect of object recognition in early visual areas, or even that feedback is necessary for recognition to occur. |
| Up Home |
|---|