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It is a common "folk-practice" within the animal research community to establish a regiment of scheduled deprivation (typically 22-23 hours) of any stimulus (e.g., food or water) to be used as reinforcement, and to do so for several days or weeks prior to actual conduct of experiments. This assures a relatively stable "deprivation" establishing operation effect vis a vis the animal's bar pressing for that reinforcer within subsequent experimental sessions. In pursuit of making CyberRat accurately reflect such establishing operations (manipulable within the "Set Experimental Parameters" section), we investigated whether there might in fact be a cumulative change in the effectiveness of deprivation across successive days as reflected in bar press rates during those sessions. We also wished to establish the parameters of a subject's developing "satiety" state within a prolonged session in order to accurately reflect "across-session" dynamics within the CyberRat model.
To accomplish a reasonable measure of time-to-satiety, we first conducted one "satiation test" session of 60 minutes duration to establish the expected bar press rate during sessions where no pre-session deprivation (i.e., home-cage ad libitum water availability) of the reinforcer had been applied. Three subjects who had prior CRF and some VR training were taken off of deprivation for several weeks before running this "satiation test" session. The session thus gave us a "satiety" bar press rate for each well-trained, but not recently practiced, subject which could then be applied as a criterion for reaching an equivalent rate in subsequent "deprived" sessions. A detailed report of the satiation test session outcomes is available for inspection in the Satiation Bar Pressing section.
The actual criterion for satiation was "a continuous 5 minute period where the average bar press rate within that 5 minute window was at or below the average bar press rate for that subject established from the satiation test session." The time of onset for this 5 minute period was then used as the time at which "satiety" had been reached for that animal, regardless of subsequent bar press rates. However, because we had some subjects who met this criteria before any sustained rates of bar pressing had been established (see discussion below concerning session "warm-up/habituation" phenomena and measures), we specifically excluded this period by imposing a "prerequisite" criterion that the "average rate of bar pressing for the entire session had to be reached and/or exceeded prior to application of the satiation criterion."
We subsequently imposed 22.5 hour water deprivation "establishing operations" and evaluated their effects on pre-trained bar pressing animals via a series of 1-hour sessions involving continuous reinforcement (CRF) for bar presses conducted on each of 5 successive days following this satiation "base-line" session. Three rats were evaluated, and their records for each of the 5 "deprivation-CRF" sessions are reported, along with various group summary statistics.
The data collected from subject A2 are shown in Column 1 of the above 5 rows of graphs. The average time it took for the rat to become satiated is 21.4 minutes (standard deviation of 5.3 minutes). The average number of bar presses that it took the rat to become satiated was 135.2 (standard deviation of 69.6). The average maximum sustained bar press rate after the 20th bar press (see "Warm-up/Habituation Discussion below) and continuing until the satiation criterion was met was 7.4 bpm.
The data collected from subject A3 are shown in Column 2 of the above 5 rows of graphs. The average time it took for the rat to become satiated is 21 minutes (standard deviation of 7.4 minutes). The average number of bar presses that it took the rat to become satiated was 222 (standard deviation of 99.5). The average maximum sustained bar press rate after the 20th bar press (see "Warm-up/Habituation Discussion below) and continuing until the satiation criterion was met was 10.7 bpm.
The data collected from subject A4 are shown in Column 3 of the above 5 rows of graphs. The average time it took for the rat to become satiated is 8.4 minutes (standard deviation of 1.1 minutes). The average number of bar presses that it took the rat to become satiated was 104 (standard deviation of 30). The average maximum sustained bar press rate after the 20th bar press (see "Warm-up/Habituation Discussion below) and continuing until the satiation criterion was met was 14.1 bpm.
All of the subjects considered as a group across all sessions averaged 16.93 minutes to satiation (standard deviation of 7.96 minutes). The group also averaged 153.73 bar presses to satation (standard deviation of 84.5). The average maximum sustained bar press rate after the 20th bar press (see "Warm-up/Habituation Discussion below) and continuing until the satiation criterion was met for the group was 10.7 bpm.
The individual session data illustrated above clearly show that each rat takes varying amounts of time to "warm up" (habituate to being placed into the operant chamber) at the beginning of each session before a steady and sustained rate of bar pressing occurrs. We calculated the amount of time it took to reach the 5th, 10th, 15th, and finally the 20th bar press to determine the character of this warm-up/habituation period. The time it took for each rat in each session to get to 20 bar presses is shown in the graph above. Descriptive statistics for these data reveal a mean of 2.5 minutes for all animals to press the bar 5 times, a mean of 3.7 to press 10 times, a mean of 4.5 minutes to press 15 times, and finally a mean of 5.3 minutes (standard deviation of 4.3 minutes) to reach their 20th press. Inspection of the individual plots above clearly reveal that two or three "outliers" at the 20th press tend to inflate the "average time to-reach 20 presses" -- especially during the 15-20 period, so the median is probably a better representative of the true 20-second warm-up time (3.65 minutes). Detailed statistics for each of these four 5-minute "bins" is given in corresponding "Columns" of data in the Table below (Column 1 = Time to First 5 Presses, Column 2 = Time to 10th press, etc.):
As noted in the introduction at the top of this page, common practices often dictate that animals be placed on a deprivation schedule for some time prior to initiating research. The idea is to "get subjects used to the deprivation schedule" or to "stabilize deprivation scheduling effects." We wished to document whether this is a true concern, and thus immediately transferred from "ad-lib water availability" in the home cages (see previous page discussion of bar pressing during "satiation" setting conditions) to a 22.5 hour schedule of deprivation. Detailed analysis of these effects are summarized in the Table and discussion below:
When this schedule was first initiated, bar pressing was considerably elevated above the previous day's "satiation" test session, where average bar press rates for the entire session ranged from 1.1 to 1.5 bpm. First sessions under deprivation conditions range from 6.9 (A2) to 9.6 (A4) bpm. By the 5th day of CRF testing, they were up even more. As the Summary Table above reveals, rates of bar pressing for A2 went from approximately 7 bpm to 9 bpm between session 1 and 5; A3 went from 8.8 to 11.4 bpm; and A4 went from 9.56 to nearly 17 bpm.
Likewise, the total minutes of bar pressing until the animal showed clear signs of within-session satiety was increased for two of the three subjects: A2 went from 17 minutes (session 1) to 30 minutes of bar pressing (session 5), (A3 went from 15 to 34, but A4 remained about the same (10 to 9).
However, the actual NUMBER OF BAR PRESSES during this period really reflects an increasing effect of the deprivation schedule. Thus A2 went from 69 bar presses to satiation criteria in session 1 to 253 bar presses to the same criteria in session 5; A3 went from 128 (session 1) to 380 (session 5); and A4 went from 67 to 134 bar presses between session 1 and 5 before reaching satiation criteria.
In a follow-up study we subsequently imposed 22.5 hour water deprivation "establishing operations" and evaluated these effects on pre-trained bar pressing animals via a series of 30 min. sessions involving continuous reinforcement (CRF) for bar pressing conducted across a total of 10 sessions. Three rats were evaluated, and their records for each of the "deprivation-CRF" sessions are reported, along with various group summary statistics.
Individual Session Data for Each of the Three Subjects for 10 Sessions:
All of the subjects considered as a group across all sessions averaged 14.12 minutes to satiation (standard deviation of 5.29 minutes). The group also averaged 161.81 bar presses to satation (standard deviation of 103.56).
Detailed analysis of the effects of a 22.5 hour deprevation schedule for Study 2 are summarized in the Table and discussion below:
The total minutes of bar pressing until the animal showed clear signs of within-session satiety was sporadic and the current data are unclear as to an imerging pattern.
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