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Recognition memory for studied words is determined by cortical activation differences at encoding but not during
Michael W L Chee1, Joshua O S Goh, Yanhong Lim
1Cognitive Neuroscience Laboratory, SingHealth Research Laboratories, Singapore, Singapore. mchee@pacific.net.sg
Neuroimage
|July 28, 2004
Summary
Encoding processes, not retrieval, determined word recognition accuracy for some studied words. Word frequency influenced brain activity differently for correctly identified targets versus rejected foils, supporting a dual process memory model.
Area of Science:
- Cognitive Neuroscience
- Neuroimaging
Background:
- Prior research links left prefrontal BOLD signal to memory success and word frequency.
- Left prefrontal activation is greater for subsequently remembered words and low-frequency words.
Purpose of the Study:
- To investigate the distinct roles of encoding and retrieval in recognizing target words.
- To determine if word frequency affects brain activity during encoding versus retrieval.
Main Methods:
- Incidental encoding of high- and low-frequency words with simultaneous fMRI scanning.
- fMRI data collected during both encoding and recognition phases.
- Replication with varied test item numbers and encoding strengths.
Main Results:
- During encoding, increased left prefrontal and anterior cingulate activation predicted more hits for low-frequency words.
- During recognition, word frequency did not alter activation for correctly recognized words.
- Activation for correctly rejected foils was higher for high-frequency words in left parietal and prefrontal regions.
Conclusions:
- Word recognition can be solely dependent on encoding processes under certain conditions.
- Word frequency differentially modulates brain activity for targets versus foils.
- Findings support a dual process theory of episodic memory.