Data Archive of the Animal Cognition Lab

University of Georgia

 

Catalog Number:  0001

 

Title:  Representation of Time in Time-Place Learning 1

 

Reference:  Pizzo, M.J. & Crystal, J.D. (2002).  Representation of time in time-place learning. Animal Learning & Behavior, 30, 387-393.

 

Note:  These data were reported as Experiment 1 by Pizzo & Crystal (2002).  Training was conducted in sessions 1-76.  Randomized blocks of testing mixed with training were conducted in sessions 77-92 (probe tests were conducted on sessions 77, 86, and 92).

 

METHOD

 

Subjects

Ten male Long Evans rats were obtained from Harlan (Madison, WI).  The rats were experimentally naive and 93 days old at the beginning of the experiment.  The rats were given 5001 Rodent Diet (Lab Diet, Brentwood, MO) ad lib for one week, followed by 20 g for 1 day, and 15 g per day thereafter.  They were given free access to water except during brief experimental sessions.  The average rat weight was 284 g at the beginning of the experiment.  The rats were individually housed in clear plastic cages lined with bedding (Andersons, Bed’o cobs, Maumee, OH).  The colony was subjected to a 12:12 h LD cycle with light onset and offset at 0700 and 1900, respectively.

 

Apparatus

An open-field box (43.2 x 43.2 cm PVC base) with clear acrylic walls (30.5 cm high, MED Associates, ENV-515, Georgia, VT) was covered with clear acrylic.  A food trough (MED Associates, ENV- 200R2M) was positioned in the center of each wall, 7 cm above the floor, which consisted of a 1.27 x 1.27 cm metal grid.  A photobeam (MED Associates, ENV-254), situated 1 cm inside the trough (1 cm from the bottom of the trough) detected head entries in each food trough.  A response was recorded at the time that the photobeam was first interrupted; the interruption was required to terminate before the occurrence of another response.  A food dispenser (MED Associates, ENV-203IR) was connected to each food trough outside of the box.  The open field was placed on a table (74 cm above the floor) centered in a 3.7 x 4.0 m room.  There were several objects in the room (i.e., desk, chair, sink, shelves) that remained in fixed locations throughout the experiment.  In an adjacent room, a Celeron 500 MHz computer running MED-PC for Windows (Version 1.15) controlled experimental events and recorded events with 10 msec resolution. 

 

Procedure

The rats were individually placed in the box three times per day (shifts A, B, and C), at approximately the same times each day.  For each rat, three locations were active and one was inactive.  Food (45-mg pellets, Improved Formula A/I; P.J. Noyes Co., Lancaster, NH) was available at one active location for each shift.  The active locations were randomly assigned to shift times for each rat prior to the start of the experiment.  The rats were randomly assigned to groups with the constraint that each group had five rats.  All rats were tested in the morning and the afternoon (shifts A and C, respectively).  The time at which shift B occurred varied across groups.  In group AB-C, shift B occurred immediately after shift A (i.e., in the morning).  In group A-BC, shift B occurred immediately before shift C (i.e., in the afternoon).  The apparatus was cleaned once per day.

 

Daily testing began at 0900.  Group A-BC’s shift A occurred first.  This was immediately followed by group AB-C’s shifts A and B.  Testing resumed in the afternoon at approximately 1520, at which time group A-BC’s shifts B and C were tested.  Finally, group AB-C’s shift C was tested.  This testing arrangement equated short and long intervals between the shifts for each group.  The mean short and long intervals were 0.55 (SE = 0.02) and 6.21 (SE = 0.03) h, respectively.

 

In the initial day of training, 10 pellets were dispensed at the scheduled active location with a 60-sec interfood interval during each shift.  On this day only, a head-entry response had no effect on the delivery of food.  On the second day of training, the rats received a 1-sec fixed interval (FI) schedule; the first reward was delivered after the first response (i.e., head entry) after 1 sec at the active location.  The session ended when 25 reinforcements were obtained or 10 min had elapsed.  In the third session, the FI was replaced by two fixed ratio (FR) schedules.  The first pellet was earned on a FR1 schedule; the remaining pellets in the session were earned on a FR5 schedule.  The shift ended after 26 reinforcements or 10 min had elapsed.  An important factor in development of time-place discrimination is the effect of response cost.  Widman et al., (2000) found that high response costs promoted time-place discrimination.  Therefore, schedules were gradually increased until each rat earned the first and subsequent pellets on a FR70 and FR10 schedule, respectively.  All rats reached these criteria within 42 days.  The data consist of the number of photobeam interruptions at each location during the initial FR (i.e., prior to the first pellet).  After each shift, the rat was returned to the colony, and the next rat was tested.  The rats received 15 g of food at the end of the day, approximately 20-30 min after shift C.  This meal occurred at approximately 1700. The daily testing was conducted at a fixed time and fixed sequence each day, 6-7 days per week.  Acquisition consisted of 76 sessions.

 

On occasional non-rewarded probes, the B shift for group AB-C was conducted unusually late in the day; the B shift for group A-BC was conducted unusually early in the day.  During these probe shifts, responses were recorded until any single location registered 70 responses, and pellets were not delivered; therefore, probe shifts were identical to the initial portion of training shifts (i.e., both types of shift had a location with 70 nonreinforced responses).  The rats were tested during shifts A and C as in training.  Three probe shifts were conducted.  Intermixed with these probe days were training days that were identical to acquisition described above.  Each probe was randomized within a seven-day block with the restriction that probes were separated by at least three consecutive training days.

 

FILE NAME CONVENTION AND FORMAT

 

File names:  Each file name contains the experiment, shift number, rat number, and session with ‘TEF’ in the file name to indicate time-event format.  The following values were used for naming the files:

 

Experiment:               GV

Shifts:                         1-3

Rat numbers:              01-10

Sessions:                     001 – 092

 

For example, Rat #7 in shift 3 of session 26 would have the file name: GV307TEF.026

 

File format:  Each text file contains three tab-delimited columns.  Column 1 contains the time stamp (in seconds).  Column 2 contains an event code (a number that represents a stimulus, response, or stage of the procedure).  Column 3 contains an event name (a label for the event code number).  The list of event code numbers and event names appear in a file labeled GV.DAT (which is included in the files that appears in the download).  The time stamps are cumulative times since the start of each session (the start is issues just after placing the animal in the box, so it is possible to have an event that precedes the start of the session).  For example, a row in the file might contain the following: 

120.39 <tab> 8 <tab> HeadEntry4

This indicates that at 120.39 seconds after the start of the session a head entry was detected at food trough 4.

 

EVENT CODES

 

Available Responses:

2

HeadEntry1

4

HeadEntry2

6

HeadEntry3

8

HeadEntry4

1

FoodReportOK1

3

FoodReportOK2

5

FoodReportOK3

7

FoodReportOK4

 

Available Stimuli:

21

OnFood1

22

OnFood2

25

OnFood3

26

OnFood4

28

OnSpeaker

31

OffFood1

32

OffFood2

35

OffFood3

36

OffFood4

38

OffSpeaker

 

Other Events:

50

StatePrime

51

StateActiveLocation1

52

StateActiveLocation2

53

StateActiveLocation3

54

StateActiveLocation4

55

StateFR_X_Trial

56

StateFR_Y_Trial

 

 

Click here for a picture of the apparatus

 

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Last updated 16 January 2003