Evaluation of Metric, Topological, and Temporal Ordering Memory Tasks after Lateral Fluid Percussion Injury

Abstract

Impairments in learning and memory occur in as many as 50% of patients following traumatic brain injury (TBI). Similar impairments occur in rodent models of TBI, and the development of new memory testing procedures provides an opportunity to examine how TBI affects memory processing in specific neural memory systems. Specifically, metric, topological, and temporal ordering tasks are object-based tests for memory of spatial orientation and temporal sequencing working memory developed for use in rodents. Previous studies demonstrated that specific lesions of the dentate gyrus/CA3 of the hippocampus and the parietal cortex resulted in deficits in the metric and topological spatial orientation tasks, respectively. Lesions of the CA1 impaired a rat's ability to recall the temporal order of odors. The purpose of the following study was to determine whether moderate lateral fluid percussion TBI would generate deficits in these working memory tasks, and whether observed deficits were associated with cell loss in the CA2/3 and/or CA1 of the hippocampus. Two weeks following a moderate lateral fluid percussion TBI, adult rats demonstrated significant deficits in both the metric and temporal ordering tasks (p<0.05) but not in the topological task. Stereological analysis identified a significant reduction in neurons in the CA2/3 (p<0.05) but not the CA1 of the hippocampus. These data demonstrate the utility of three object-based tasks to expand our understanding of how different neural memory systems are affected by TBI.

Diffusion tensor imaging detects chronic microstructural changes in white and gray matter after traumatic brain injury in rat

“…LFP injury is an established animal model of TBI (McIntosh et al, 1989 ) that mimics many of the features of human TBI, regarding both tissue damage and outcome (Graham et al, 2000 ; D'Ambrosio et al, 2004 ; Kharatishvili et al, 2007 ; Flygt et al, 2013 ; Gurkoff et al, 2013 ). The primary injury provokes a cortical lesion that, over time, progresses to distal areas in the brain.…”

Pathophysiology and Treatment of Memory Dysfunction After Traumatic Brain Injury

“…In order to test the time (or “when”) component of episodic memory, Gurkoff and colleagues used a temporal order task [60•]. Specifically, these animals were exposed to an odor sequence and after an hour delay or longer, were tested for their ability to discriminate the initial odor sequence versus a new sequence.…”

“…Here, animals are tested for their ability to distinguish when two objects have their locations transposed in space. Mild and moderate LFPI demonstrated no significant impairments when a short delay time window is used between familiarization and test phase [60•]. However, at a longer time window (1 hour), TBI animals were unable to discriminate that the object’s new location from the old location (unpublished data).…”

Making Waves in the Brain: What Are Oscillations, and Why Modulating Them Makes Sense for Brain Injury

“…Not surprisingly, for a prolonged period after the initial injury, neurons in the corrupted neural network can have impaired neurophysiological responses (Reeves et al, 1997 ; Golarai et al, 2001 ; Santhakumar et al, 2001 ; Kao et al, 2004 ; Goforth et al, 2011 ) including long-term potentiation (LTP; Miyazaki et al, 1992 ; Reeves et al, 1995 ; D’Ambrosio et al, 1998 ; Sick et al, 1998 ; Sanders et al, 2000 ; Schwarzbach et al, 2006 ; Li et al, 2014 ). In addition, TBI results in deficits impacting certain forms of behavioral plasticity (Ip et al, 2002 ; Griesbach et al, 2004 ) and formation of long term memories (Rimel et al, 1981 ; Leininger et al, 1990 ; Fedor et al, 2010 ; Gurkoff et al, 2013 ; Zhang et al, 2015 ). Disruption to cognition and plasticity following TBI is of particular relevance to our research interests and will be the focus of this review.…”