Temporal order memory impairments in individuals with moderate-severe traumatic brain injury

ABSTRACT

Introduction

Temporal order memory is a core cognitive function that underlies much of our behavior. The ability to bind together information within and across events, and to reconstruct that sequence of information, critically relies upon the hippocampal relational memory system. Recent work has suggested traumatic brain injury (TBI) may particularly impact hippocampally mediated relational memory. However, it is currently unclear whether such deficits extend to temporal order memory, and whether deficits only arise at large memory loads. The present study assessed temporal order memory in individuals with chronic, moderate-severe TBI across multiple set sizes.

Method

Individuals with TBI and Neurotypical Comparison participants studied sequences of three to nine objects, one a time. At test, all items were re-presented in pseudorandom order, and participants indicated the temporal position (i.e., first, second, etc.) in which each object had appeared. Critically, we assessed both the frequency and the magnitude of errors (i.e., how far from its studied position was an item remembered).

Results

Individuals with TBI were not impaired for the smallest set size, but showed significant impairments at 5+ items. Group differences in the error frequency did not increase further with larger set sizes, but group differences in error magnitude did increase with larger memory loads. Individuals with TBI showed spared performance for the first object of each list (primacy) but were impaired on the last object (recency), though error frequency was better for last compared to middle items.

Conclusions

Our findings demonstrate that TBI results in impaired temporal order memory for lists as small as five items, and that impairments are exacerbated with increasing memory loads. Assessments that test only small set sizes may be insufficient to detect these deficits. Further, these data highlight the importance of additional, sensitive measures in the assessment of cognitive impairments in TBI.

KEYWORDS:

• Traumatic brain injury
• relational memory
• hippocampus
• temporal memory
• assessment

Acknowledgments

We thank Nirav Patel for his help with data collection and all of the individuals who participated in this study. Portions of this work were previously presented at the International Brain Injury Association’s 13^th Annual World Congress on Brain Injury in Toronto, ON, Canada in March 2019.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Notes

1. These values were collapsed as there were not enough trials to have sufficient power to assess each value. However, it should be noted that the ANOVAs for Primacy and Recency with factors of Set Size and Group showed no significant Set Size by Group interactions [F’s < 1.80, p’s > 0.17], suggesting collapsing in this way did not mask group differences across Set Sizes.

2. This subset of participants still had no significant group differences in age, education, or sex [p’s > 0.28]. The previous analyses of the Temporal Order Task were conducted again with only this subset of participants; all statistical results were the same with regards to significance, confirming that this subset of participants performed in line with reported results.

Additional information

Funding

This work was supported by NINDS grant [R01 NS110661] to MCD and NJ.