Home cage testing of delay discounting in rats

Abstract

Testing rodents in their home cages has become increasingly popular. Since human intervention, handling, and transport are minimized, behavior can be recorded undisturbed and continuously. Currently existing home cage systems are too complex if only relatively simple operant-learning tests are to be carried out in rats. For that purpose, a new low-cost computer-controlled operant panel was designed, which can be placed inside the home cage. A pilot study was carried out, using an intolerance-to-delay protocol, classically developed for testing behavioral impulsivity. Male adult rats were tested in their home cages, containing the operant panel provided with nose-poking holes. Nose poking in one hole resulted in the immediate delivery of one food pellet (small-soon, SS), whereas nose poking in the other hole delivered five food pellets after a delay (large-late), which was increased progressively each day (0-150 sec). The two daily sessions, spaced 8 h apart, lasted 1 h each, and the time-out after food delivery was 90 sec. A clear-cut shift toward preference for SS, which is considered a classical index of cognitive impulsivity, was shown at the longest delay. It is noteworthy that rats shifted when the delay interval was longer than the mean intertrial interval-that is, when they experienced more than one delay-equivalent odds against discounting (see Adriani & Laviola, 2006). The shortened training (2 days) and testing (5 days) phases, as allowed by prolonged and multiple daily sessions, can be advantageous in testing rodents during selected short phases of development. Current research is focusing on further validation of this and similar protocols

Cognitive impulsivity in animal models: Role of response time and reinforcing rate in delay intolerance with two-choice operant tasks

“…a low odds value) if subjects are paced to very long mITI (e.g. Koot et al, 2009), while it would be perceived as much more frustrating (i.e. equivalent to higher odds values) if subjects are paced to quite a shorter mITI, as in the present study.…”

“…Koot et al, 2009). In summary, even though a further and deeper validation should be carried out, we propose that the concept of delay-equivalent odds values may allow to compare ID task results across various studies, differing for objective (e.g.…”

“…delay) elapsed for any LL event. The formulas are: mITI ¼ timeoutðTOÞ þ spontaneous waitingðRTÞ Odds ¼ delay=mITI (1) As such, the mITI represents a "crucial interval" within the task (Koot et al, 2009;Laviola, 2006, 2009). For instance, if we assume that animals have a spontaneous waiting (RT) as low as 15 s in average, within a protocol where the timeout is set at 20 s, then the mITI can be as low as 35 s (see indeed Table 2).…”

Females in the forefront: time-based intervention effects on impulsive choice and interval timing in female rats

“…Previous work has demonstrated that male and female rats and humans often differ in their performance on tasks measuring impulsivity (e.g., Anker et al 2008; Bayless et al 2012; Bayless et al 2015; Koot et al 2009a; Marsh et al 2002). Despite our knowledge that impulsive choice contributes to maladaptive behaviors, current understanding of female rodent choice behavior is sparse, as most work investigating the mechanisms of various behaviors has been conducted in male rats.…”

Early life stress in fathers improves behavioural flexibility in their offspring

“…Females that did not adapt to the IntelliCage (no drinking for at least 36 h during habituation) were removed from the cage and excluded from testing. For training on the DDT 47 , all doors were opened and females had free access to water and saccharine in each corner (0 s delay). DDT started when preference to saccharine was established (450% saccharine licks over all licks).…”