2012 台灣心理學年會 MS035

fMRI Repetition Effects in Priming and Recognition Memory Tasks Chi-Lan Yang, Han-Yuan Lai, Yu-Yun Hsu, Yun-Shin Wen, Yu-Yi Cheng, Yuong-Hsuen Ni, & Chun-Yu Lin Department of Psychology, National Cheng Kung University, Taiwan

fMRI RESULTS

INTRODUCTION  When visual stimuli are presented repeatedly, fMRI activations may increase or decrease in various brain regions.

RS: New > Repeated, RE: New < Repeated

Perceptual priming : RS: bilateral fusiform gyri, occipital cortices

 Repetition suppression (RS): Reduced activations for repeated stimuli.  Repetition enhancement (RE): Increased activations for repeated stimuli.

RE: bilateral middle/superior temporal gyri, middle frontal gyrus, ACC, precuneus, lateral parietal areas

 Repetition priming task (measuring implicit memory):  Study phase: a series of stimuli.

Recognition (perceptual):

 Test phase (e.g., object classification): repeated stimuli intermixed with new stimuli.

RS: caudate nucleus RE: precuneus, lateral parietal cortex, left inferior frontal gyrus, precentral

 Behavioral priming effect: repeated better/faster than new.  Neural priming effect: Priming is often found to be accompanied with RS in fusiform or prefrontal regions (Henson, 2003).

 It is thought to be an automatic, low-level, perceptual process: Whenever a stimulus is repeated, RS should be seen (Wiggs & Martin, 1998).  Therefore, RS should also appear in recognition tasks. However, it is often not the case (Henson et. al., 2002).

Common regions : RS: perceptual priming & recognition

RE: perceptual priming & recognition

No common regions were found.  Recognition task (measuring explicit memory):  Study phase: a series of stimuli. Precuneus, left middle temporal gyrus

 Test phase (“Have you seen this?”): repeated stimuli intermixed with new stimuli.  Correctly identified repeated stimuli often show increased neural activations (ie. RE) compared to new stimuli in medial temporal lobe, etc. (Vannini et. al., 2012).

Conceptual priming : RS: Fusiform gyrus, inferior frontal gyrus, prefrontal cortex

 Implicit & explicit memories are thought to be rely on dissociable neural systems, but when stimuli are repeated in a similar manner in both types of tasks, are there common neural activation patterns?

RE: Precuneus, bilateral temporal lobe, lateral prefrontal cortex, middle frontal gyrus, ACC

 Two types of stimuli and priming tasks were used:  Perceptual priming: symmetry judgment on meaningless silhouettes

Recognition (conceptual):

 Conceptual priming: natural/man-made judgment on meaningful silhouettes

RS: fusiform gyrus, prefrontal cortex

 Followed by recognition tasks on these stimuli.

RE: Middle frontal gyrus, superior temporal gyrus

 Main question: Can similar fMRI repetition effects (RS or RE) be found in both priming and recognition tasks?

METHODS Participants : 25 healthy young adults. 9 were excluded for not having enough trials for all the conditions.

Common regions : RS: conceptual priming & recognition

RE: conceptual priming & recognition

Image Acquisition and Analysis: •

Event-related fMRI. 3T GE scanner. Spiral-in-and-out sequence.

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32 slices, 4 mm, no skip, TE=30ms, TR=2.227s, FOV=22, AC-PC plane.

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Analyzed by SPM8

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Events modeled as 0 duration.

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All voxels thresholded at p < 0.005, uncorrected.

Left frontal gyrus, left occipital lobe, bilateral prefrontal cortex

Right middle frontal gyrus, superior temporal gyrus

SUMMARY  Repetition suppression (RS):

 RE regions in both perceptual & conceptual conditions are similar to the default mode network (Vannini et al., 2012).

 Perceptual:  Priming: ventral visual stream  Recognition: caudate

 First encounters may produce deactivations in the default network. With repetitions, deactivations may reduce (hence, RE).  Collaborative brain system works together => successful information processing

 No overlap  Conceptual:  Similar pattern in priming & recognition: ventral visual stream, IFG  Overlap found only in conceptual condition: automatic processes? Top-down modulation?  Repetition enhancement (RE):  Perceptual:  Similar pattern in priming & recognition: STG/MTG, MFG, LPC, precuneus, (ACC)  Conceptual:  Similar pattern in priming & recognition: STG/MTG, MFG, (LPC, precuneus, ACC)

References Henson, R. N. A. (2003). Neuroimaging studies of priming. Progress in Neurobiology, 70(1), 53–81. doi:10.1016/S0301-0082(03)00086-8

Henson, R. N. A., T. Shallice, et al. (2002). Face Repetition Effects in Implicit and Explicit Memory Tests as Measured by fMRI. Cerebral Cortex, 12, 178-186. Vannini, P., Hedden, T., Sullivan, C., & Sperling, R. A. (2012). Differential functional response in the posteromedial cortices and hippocampus to stimulus repetition during successful memory encoding. Human Brain Mapping. doi:10.1002/hbm.22011 Wiggs, C. L., & Martin, A. (1998). Properties and mechanisms of perceptual priming. Current opinion in neurobiology, 8(2), 227-233.

Questions, comments or reprint requests please contact: Dr. Chun-Yu Lin ([email protected])