Straight Alley Behavioral Task

 

 

In the straight alley, a rat can be trained to approach a goal box in order to obtain a liquidor food reward. The rat will usually be placed on a food or water restricted schedule in order to motivate it to approach the reward. The straight alley is divided into three main parts: 1) The startbox, 2) the runway, and 3) the goalbox. The startbox is divided from the runway by a sliding door. At the beginning of each session the rat is placed in the startbox facing away from the sliding door; once the rat has turned towards the door it is opened and three timers are started. When the rat enters the runway a light beam connected to one of the timers is broken. This gives a time measurement of the time elapsed between the opening of the startbox door and the rats entrance into the runway. Within the runway itself there are two small hurdles that the rat must negotiate. Within the middle of the runway a second light sensor measures the time it took the rat to reach the middle of the runway since the opening of the startbox door. At the end of the straight alley lies the goalbox. Within the goalbox rests a small cup that usually contains the food reward (sugar or grain pellets). A light beam between the runway and the goalbox is broken when the rat passes by and gives a measurement of how long it took the rat to reach the goalbox. A fourth measurement is often taken of how long it takes the rat to consume its reward.

Various behavioral manipulations can be employed with this procedure. Many studies have found that when an animal is trained to expect a reward of a certain kind or quantity, changing the magnitude of the reward (e.g. reducing the amount) or changing the reward (e.g. replacing a banana with lettuce) results in alterations in behavior. This effect has often been termed “learned frustration.”
For example, when rats trained to approach the goal end of a straight alley are shifted from a large reward (10 food pellets) to a smaller reward (1 pellet) a significant decrease in running speed is observed. An increase in reward magnitude (1 pellet to 10 pellets) will also produce an increase in running speed.
The learning of this kind of shift has been found to be dependent upon the integrity of the amygdala, hippocampus, and nucleus accumbens. Current research in our lab examines hemispheric differences in amygdala norepinephrine response to shifts in reward magnitude as well as the effects of lesions and reversible inactivation of regions within the frontal cortex.

 

 

Cedric Williams
The University of Virginia
Psychology Department

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