Human memory manipulated: dissociating factors contributing to MTL activity, an fMRI study.
Memory processes are mainly studied with subjective rating procedures. We used a morphing procedure to objectively manipulate the similarity of target stimuli. While undergoing functional magnetic resonance imaging, nineteen subjects performed a encoding and recognition task on face and scene stimuli, varying the degree of manipulation of previously studied targets at 0%, 20%, 40% or 60%. Analyses were performed with parametric modulations for objective stimulus status (morphing level), subjective memory (confidence rating), and reaction times (RTs). Results showed that medial temporal lobe (MTL) activity can be best explained by a combination of subjective and objective factors. Memory success is associated with activity modulation in the hippocampus both for faces and for scenes. Memory failures correlated with lower hippocampal activity for scenes, but not for faces. Activity changed during retrieval on similar areas activated during encoding. There was a considerable impact of RTs on memory-related areas. Objective perceptual identity correlated with activity in the left MTL, while subjective memory experience correlated with activity in the right MTL for both types of material. Overall, the results indicate that MTL activity is heterogeneous, showing both linear and non-linear activity, depending on the factor analyzed.
Institute of Cognitive Neuroscience, Dept. of Neuropsychology, Ruhr-University, 150 Universtatstr., 44801 Bochum, Germany. dorian.pustina@rub.de
Dorian
D
Pustina
Elke
E
Gizewski
Michael
M
Forsting
Irene
I
Daum
Boris
B
Suchan
D000328:Adult; D001931:Brain Mapping; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008279:Magnetic Resonance Imaging; D008297:Male; D008568:Memory / Q000502:physiology*; D011939:Mental Recall / Q000502:physiology; D009483:Neuropsychological Tests; D010100:Oxygen / Q000097:blood; D010364:Pattern Recognition, Visual / Q000502:physiology; D010775:Photic Stimulation; D011930:Reaction Time / Q000502:physiology; D021641:Recognition, Psychology; D013702:Temporal Lobe / Q000098:blood supply* / Q000502:physiology*; D055815:Young Adult
D010100:Oxygen