Abstracts

Rationale:
It is a common human experience to enter a room and immediately forget why one entered the room in the first place. This phenomenon, known as the ”doorway effect,” demonstrates the role of environmental context and event segmentation in the formation and recall of human memory. Behavioral studies have shown that subjects are less able to recall items or words after entering a different room in a virtual or real-world environment. Mental context, the representation of stimuli surrounding an event to be remembered, is thought to be changed during the doorway effect. It has been shown that context is reinstated in the temporal lobe during memory recall via traditional electrocorticography (ECoG) studies. We aim to demonstrate the “doorway effect” in the analysis of behavioral data, identify an electrophysiological marker of mental context in the hippocampus, and measure changes in this marker across a free-recall memory task where a doorway is passed.
Method:
We use a free-recall paradigm where subjects are asked to memorize words displayed onscreen in between other visual cues and activities. Subjects were instructed to memorize twelve unique words, six words before (i.e., list A) and six words after (i.e., list B) a possible spatial event-boundary (i.e., crossing a doorway into another room). Images were displayed in between each word only during list A memorization. After list A and list B encoding phases, subjects were told to swipe a magnetometer over their responsive neurostimulators (RNS) both to synchronize the task computer and the RNS clocks and to trigger the RNS to record a 180-second segment of intracranial EEG. Subjects were then asked to complete a math distractor task before recalling any words from either list A or B.
Results:
Thus far, we have enrolled three subjects who have participated in the study, with one subject as of yet having enough trial data for meaningful statistical analysis. A Paired Sample T-Test showed a significant difference in word recall performances between lists A and B during trials with an event-boundary (p< 0.05) and no significant difference in word recall performances during trials without an event-boundary (p >0.05). These results indicate that the context change from crossing a doorway correlates with impaired list A memory and therefore list A recall performance. However, when comparing list A recall performance between the two types of trials, an Independent Sample T-Test yielded no significant difference (p=0.13). While there is no significant difference in recall list B performance between the two types of trials, a Permutation Test did yield an achieved significance level of 0.04.
Conclusion:
From behavioral data analysis, we were able to observe the presence of the “doorway effect.” In addition, this analysis suggests a possible difference in list B recall performance between doorway and non-doorway trials. One possible explanation for this observation is that the presence of a spatial event-boundary disrupts previously observed context-represented words. Thus, the memory of post-event-boundary words is enhanced. As we collect more data, subjects’ neural activity during trials will need to be analyzed to measure the strength of scene representation during recall period and list A memorization and correlated with list A recall performance. Also, with more data, the electrophysiological marker of mental context in the hippocampus will be identified and measured for change across the task.
Funding:
:NSF EPSCoR 1632738Diamond Foundation Research Development Award