Working Memory Deficits following Traumatic Brain Injury in the Rat

Abstract

This study was designed to examine working memory following fluid-percussion traumatic brain injury (TBI) using the Morris water maze (MWM). Rats were injured (n = 9) at a moderate level of central fluid percussion injury (2.1 atm) or were prepared for injury but did not receive a fluid pulse (sham injury) (n = 10). On days 11-15 postinjury, working memory was assessed using the MWM. Each animal received 8 pairs of trials per day. For each pair of trials, animals were randomly assigned to one of four possible starting points and one of four possible escape platform positions. On the first trial of each pair, rats were placed in the maze facing the wall and were given 120 sec to locate the hidden escape platform. After remaining on the goal platform for 10 sec, they were placed back into the maze for the second trial of the pair. The platform position and the start position remained unchanged on this trial. After the second trial, the animal was given a 4 min intertrial rest. Between pairs of trials, both the start position and the goal location were changed. Analyses of the latency to reach the goal platform indicated that sham-injured animals performed significantly better on the second trial than on the first trial of each pair. However, injured animals did not significantly differ between first and second trial goal latencies on any day. These results indicate that injured animals have a profound and enduring deficit in spatial working memory function on days 11-15 after TBI.

Reversal of Brain Injury-Induced Prefrontal Glutamic Acid Decarboxylase Expression and Working Memory Deficits by D1Receptor Antagonism

“…All behavioral tests were performed by an experimenter blind to the treatment groups. Spatial working memory was assessed as described previously (Hamm et al, 1996;Steele and Morris, 1999;Kline et al, 2002). Briefly, 24 h before testing, animals were given five training trials in a working memory version of the Morris water maze task (delay match-to-place task) to familiarize them with the task (Dash et al, 2004).…”

“…The delay match-to-place task has been extensively used to study working memory and its dysfunction in pathological conditions (Hamm et al, 1996;Steele and Morris, 1999;Dash et al, 2004). In this task, animals are required to locate a hidden escape platform (location trial), removed from the maze, and then, after a few second delay, placed back into the training context and allowed to relocate the platform (match trial).…”

Long-Lasting Suppression of Acoustic Startle Response after Mild Traumatic Brain Injury

“…41 Using a similar behavior paradigm as the present study, moderate TBI after midline fluid percussion slowed the latency to find the platform on both sample and choice phases to a similar degree. 42 Uninjured rats are more efficient in finding the platform during the choice phase because of information gained on the sample phase. In contrast, injured rats had similar escape latencies on sample and choice phases, suggesting a working memory impairment.…”

Midbrain Raphe Stimulation Improves Behavioral and Anatomical Recovery from Fluid-Percussion Brain Injury

“…This protocol differs from commonly used tests for working memory that do not initially reveal the location. 29 The rats were given 60 s to find the submerged platform and were placed on it if they failed. After 10 s on the platform, they were released for the second of each pair of trials with the platform and release point unchanged.…”