A Metric Test for Assessing Spatial Working Memory in Adult Rats Following Traumatic Brain Injury

Summary

Traumatic brain injury (TBI) is commonly associated with memory impairment. Here, we present a protocol to assess spatial working memory after TBI via a metric task. A metric test is a useful tool to study spatial working memory impairment after TBI.

Abstract

Impairments to sensory, short-term, and long-term memory are common side effects after traumatic brain injury (TBI). Due to the ethical limitations of human studies, animal models provide suitable alternatives to test treatment methods, and to study the mechanisms and related complications of the condition. Experimental rodent models have historically been the most widely used due to their accessibility, low cost, reproducibility, and validated approaches. A metric test, which tests the ability to recall the placement of two objects at various distances and angles from one another, is a technique to study impairment in spatial working memory (SWM) after TBI. The significant advantages of metric tasks include the possibility of dynamic observation, low cost, reproducibility, relative ease of implementation, and low stress environment. Here, we present a metric test protocol to measure impairment of SWM in adult rats after TBI. This test provides a feasible way to evaluate physiology and pathophysiology of brain function more effectively.

Introduction

The prevalence of neurological deficits such as attention, executive function, and certain memory deficits after moderate traumatic brain injury (TBI) is more than 50 percent^{1,2,3,4,5,6,7,8}. TBI can lead to severe impairments in spatial short-term, long-term, and working memory⁹. These memory impairments have been observed in rodent models of TBI. Rodent models have enabled the de....

Protocol

The experiments were performed following the recommendations of the Declarations of Helsinki and Tokyo and the Guidelines for the Use of Experimental Animals of the European Community. The experiments were approved by the Animal Care Committee of Ben-Gurion University of the Negev. A protocol timeline is illustrated in Figure 1.

1. Surgical procedures and fluid percussion TBI

1. Select male and female adult Sprague-Dawley rats, housed at a room temperature of 22 ± 1 °C, and humidity of 40%-60%, with 12-12 h light-dark cycles.
2. Provide food as chow and water ad libitum. Perfo....

Results

The significance of comparisons between groups was determined using the Mann-Whitney test. Statistical significance of results was considered at P < 0.05, while statistically high relevance was measured at P < 0.01.

The results showed no differences in NSS between all groups before intervention and 28 days after TBI. Each group consisted of 12 female or 12 male rats. The NSS scores obtained 48 h after TBI are presented in Table 1. Rats from the TBI group that showed si.......

Discussion

By specifically targeting the metric spatial information process, this metric test provides a necessary tool toward understanding memory deficiency after TBI. The protocol presented in this paper is a modification of previously described behavioral tasks¹¹. One previously described metric task used two different paradigms, each consisting of three habituation sessions and one testing session. The first paradigm consisted of moving the familiar objects closer together after habituation and the seco.......

Materials

Name	Company	Catalog Number	Comments
2% chlorhexidine in 70% alcohol solution	SIGMA - ALDRICH	500 cc	For general antisepsis of the skin in the operatory field
Bupivacaine 0.1 %
4 boards of different thicknesses (1.5cm, 2.5cm, 5cm and 8.5cm)			This is to evaluate neurological defect
4-0 Nylon suture	4-00
Bottles	Techniplast	ACBT0262SU	150 ml bottles filled with 100 ml of water and 100 ml 1%(w/v) sucrose solution
Bottlses (four) for topological an metric tasks			For objects used two little bottles, first round (height 13.5 cm) and second faceted (height 20 cm) shape and two big faceted bottles, first 9x6 cm (height 21 cm) and second 7x7 cm (height 21 cm).
Diamond Hole Saw Drill 3mm diameter		Glass Hole Saw Kit	Optional.
Digital Weighing Scale	SIGMA - ALDRICH	Rs 4,000
Dissecting scissors	SIGMA - ALDRICH	Z265969
Ethanol 99.9 %	Pharmacy		5%-10% solution used to clean equipment and remove odors
EthoVision XT (Video software)	Noldus, Wageningen, Netherlands		Optional
Fluid-percussion device	custom-made at the university workshop		No specific brand is recommended.
Gauze Sponges	Fisher	22-362-178
Gloves (thin laboratory gloves)			Optional.
Heater with thermometer	Heatingpad-1	Model: HEATINGPAD-1/2	No specific brand is recommended.
Horizon-XL	Mennen Medical Ltd
Isofluran, USP 100%	Piramamal Critical Care, Inc	NDC 66794-017	Anesthetic liquid for inhalation
Office 365 ProPlus	Microsoft	-	Microsoft Office Excel
Olympus BX 40 microscope	Olympus
Operating  forceps	SIGMA - ALDRICH
Operating  Scissors	SIGMA - ALDRICH
PC Computer for USV recording and data analyses	Intel		Intel® core i5-6500 CPU @ 3.2GHz, 16 GB RAM, 64-bit operating system
Plexiglass boxes linked by a narrow passage			Two transparent 30 cm × 20 cm × 20 cm plexiglass boxes linked by a narrow 15 cm × 15 cm × 60 cm passage
Purina Chow	Purina	5001	Rodent laboratory chow given to rats, mice and hamster is a life-cycle nutrition that has been used in biomedical researc for over 5
Rat cages  (rat home cage or another enclosure)	Techniplast	2000P	No specific brand is recommended
Scalpel blades 11	SIGMA - ALDRICH	S2771
SPSS	SPSS Inc., Chicago, IL, USA	20 package
Stereotaxic Instrument	custom-made at the university workshop		No specific brand is recommended
Timing device	Interval Timer:Timing for recording USV's		Optional. Any timer will do, although it is convenient to use an interval timer if you are tickling multiple rats
Topological and metric tasks device	Self made in Ben Gurion University of Negev		White circular platform 200 cm in diameter and 1 cm thick on table
Video camera	Logitech	C920 HD PRO WEBCAM	Digital video camera for high definition recording of rat behavior under plus maze test
Windows 10	Microsoft