Assessments of Cognitive Function Following Traumatic Brain Injury - Animal Models of Acute Neurological Injuries: Injury and Mechanistic Assessments - page 220

have selected an arm when their hind feet cross into that arm.
No retracing is allowed, and if an animal makes an incorrect choice,
it is confi ned to the arm with no platform for 15 s. If the rat swims
to the correct arm, it is rewarded by fi nding the platform and
removed from the maze to an incubator. Animals learn to select
the arm opposite to the one they are forced to swim to in the sample
phase. All animals are tested in small groups, so that intertribal
intervals during acquisition are approximately 4 min. Right-left
order for the fi fteen trials is assigned randomly to each animal, with
a limit of three consecutive left or right trials.
Following acquisition, animals can be tested on subsequent
days using variable delays between the sample and choice phases.
15, 30, and 120 s delays have been used previously. On these days,
each animal received 15 trials at each delay. Delays are tested on
separate days (e.g., Day 16: 15 s, Day 17: 30 s, and Day 18: 120 s).
At the beginning of each day of delayed testing, animals are given
fi ve reminder trials with an approximate 10 s delay. This is done to
ensure the animal has retained the non-matching rule. The total
percentage of choices made on each day in both acquisition and
delayed testing are reported.
Previous results using this protocol following moderate lateral-
FPI indicate that injured animals do not differ in rates of acquisi-
tion, or during reminder trials; however, there is a delay-dependent
impairment in memory performance when delays of 30 and 120 s
are used.

The novel object recognition (NOR) test has been used to study
recognition memory in animals ( 21, 22 ). The NOR test is a relatively
simple procedure that takes advantage of the rat's natural preference
for novelty. The NOR test has been used following FPI to investigate
post-injury defi cits at two post-injury time intervals: 2-6 and
14-18 days post-injury (Whiting MD and Hamm RJ, unpublished
data). In this study, the authors found that the NOR test detects
memory defi cits following injury at early time points (2-6 days)
post-injury, but not at later time points (14-18) post-injury. Another
study, with a similar protocol found signifi cant defi cits between
sham and contusive-injured 7-day-old rat pups at 15 days post-
injury ( 23 ). The task has also been used following injury to inves-
tigate the effects of therapies ( 24, 25 ). Although protocols vary
from study to study, a standard protocol is presented below.

2.4. Novel Object
Recognition Tests

A simple open fi eld is used consisting of a white square open fi eld.
Various dimensions have been used ranging from 50 cm × 50 cm ×
35 cm to 95 cm × 95 cm × 40 cm. The open fi eld is constructed of
Plexiglass walls and a plywood fl oor painted white, located in a
dimly lit room. Several stimulus objects are needed for testing, and
are fi xed in place by Velcro. Objects can range in height and width.
A video camera is placed above the fi eld and each trial is recorded
for scoring purposes.

2.4.1. Open Field and
Novel Object Apparatus