Electrophysiological and behavioral evidence for attentional up-regulation, but not down-regulation, when encoding pictures into long-term memory

Abstract

Visual long-term memory allows us to store a virtually infinite amount of visual information (Brady, Konkle, Alvarez, & Oliva in Proceedings of the National Academy of Sciences of the United States of America, 105(38), 14325-14329, 2008; Standing in Quarterly Journal of Experimental Psychology, 25(2), 207-222, 1973). However, our ability to encode new visual information fluctuates from moment to moment. In Experiment 1, we tested the hypothesis that we have voluntary control over these periodic fluctuations in our ability to encode representations into visual long-term memory using a precueing paradigm combined with behavioral and electrophysiological indices of memory encoding. We found that visual memory encoding can be up-regulated, but it was much more difficult, if not impossible, to down-regulate encoding on a trial-by-trial basis. In Experiment 2, we tested the hypothesis that voluntary up-regulation of visual memory encoding for an item incurs a cost to memory encoding of other items by manipulating the cueing probability. Here, we found that, although the cueing benefit was constant for both low (20%) and high (50%) cueing probabilities, the benefit in the high cueing probability condition came with the overall impairment of memory encoding. Taken together, our findings demonstrate that top-down control of visual long-term memory encoding may be primarily to prioritize certain memories, but this prioritization has a cost and should not be overused to avoid its negative consequences.

Keywords: EEG; Visual long-term memory encoding; Voluntary control.

Fig. 1

a Schematic of encoding task in Experiment 1. b Schematic of recognition task in Experiment 1. (Color figure online)

Fig. 2

Behavioral results of Experiment 1. Left panel shows the ROC curves for each cue condition. Right panel shows the area under the ROC curves. Error bars indicate within-subject 95% confidence intervals

Fig. 3

EEG results of Experiment 1. Column shows frontal positivity (top) and occipital alpha power (bottom) recorded during encoding task for high-confidence hit items (recognized with high confidence, or HC) and for missed items (not recognized). Error region represents within-subject standard error of the mean. Gray bars indicate the a priori defined measurement windows for each EEG correlate of memory encoding. Middle column shows topographical distribution of the subsequent memory effect (i.e., amplitude difference between HC hit and miss) for frontal positivity (top) and occipital alpha power (bottom). Green dots represent a priori determined channels of measurement. Right column shows result of nonparametric permutation-based statistical analysis for subsequent memory effect for frontal positivity (top) and occipital alpha power (bottom). Histogram represents null distribution derived from permutation procedure. Black line and p value indicate observed effect. (Color figure online)

Fig. 4

EEG Results of Experiment 1. Left column shows frontal positivity (top), occipital alpha power (middle), and visual N1 (bottom) recorded during encoding task for up-regulation (UP), down-regulation (Down), and neutral (Neutral) conditions. Error region represents within-subject standard error of the mean. Gray bars indicate the a priori defined measurement windows for each EEG correlate of memory encoding. Histograms show result of the nonparametric permutation-based statistical analysis for effect of voluntary control effect for frontal positivity (top), occipital alpha power (middle), and visual N1 (bottom). Green histograms represent null distribution derived from permutation procedure for effect of voluntary up-regulation, and the ed histograms show same for voluntary down-regulation. Black lines and p values indicate observed effects. Of note, observed effect of voluntary down-regulation is opposite in direction to what would be expected if voluntary down-regulation was possible. (Color figure online)

Fig. 5

Behavioral results of Experiment 2. a Result for 0% and 100% cue probability conditions. b Result for 20% and 50% cue probability conditions. Left column shows ROC curves for each condition. Right panel shows corresponding area under ROC curve for each condition. Error bars indicate within-subject 95% confidence intervals