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A simple method for measuring spontaneous motor activity in squirrel monkeys during chair restraint
Physiology nnd Behavior, Vol 10, pp. 1115-l 117. Brain Research Publications Inc., 1973. Prmted m the U.S.A
BRIEF COMMUNICATION A Simple Method for Measuring Spontaneous Motor Activity in Squirrel Monkeys During Chair Restraint ’ WILLIAM S. LOVE AND VINCENT P. HOUSER Veterans Administration Hospital, Perry Point, Maryland 21902
(Received 3 January
1973)
LOVE, W. S. AND V. P. HOUSER. A sunple method for measuring spontaneous motor activrty m squvrel monkeys during chair restraint. PI-IYSIOL. BEHAV. lO(6) 1115-1117, 1973.- A simple, reliable and sensitive method for measuring spontaneous motor activity in squirrel monkeys during chair restraint is described. In this method the restraint chair is suspended from a wooden enclosure in a way that allows the chair to swing m any lateral direction. This movement is recorded by two brass rings which are connected to the chair and the fixed wooden enclosure, respectively. These brass rings act as electrical contacts which serve to trigger an electronic recording device. This method is extremely sensitive to even slight movements made by the animal while m the restraint chair and should provide a reliable means of obtaimng consistent data under a variety of conditions. Spontaneous motor activity
Restraint chair
Squirrel monkeys
IT IS OFTEN advisable to obtain a measure of spontaneous motor activity from animals who are undergomg some type of experimental procedure. Some investigators have attempted to measure changes m activity level by means of a response lever located in the test chamber [l] but this method has been criticized as lacking sufficient sensitivity [2]. Other methods include the use of photocells or microswitches to sense lateral movement m a confined area. It is difficult to apply either of these two methods to the measurement of spontaneous motor activity in the restrained squirrel monkey. The sensitivity of the photocell method depends upon the location of the photobeams m reference to the animal. Since mdividual animals sit in different positions in the same chair, and many different types of chairs are used in various laboratories, it is difficult to replicate this measurement procedure with any degree of accuracy The same problems are encountered if the restraint chair is pivoted and microswitches are used at the four corners of the restramt chair to act as movement sensors. In this method the placement of the pivot becomes critical to msure a balanced system. Since the weight of the individual animal and restraint chair is variable, replication
is difficult both within and between laboratories. The present report describes a method for measuring spontaneous motor activity in restrained squirrel monkeys which is both simple and reliable. More importantly, the data that are generated from this method should be easily rephcable since it is not affected by variability m the position or weight of the individual animal. Furthermore, differences m the weight or balance of a particular restraint chair should not substantially affect this measure. Thus, various laboratories could use this method and be reasonably sure of obtaining similar results. Figure 1 is a photograph of the apparatus used to obtam a measure of spontaneous motor activity in restrained squirrel monkeys. The particular restraint chair depicted m Fig. 1 is manufactured by Plas Labs., 917 E Chilson Street, Lansing, Michigan, 48906. The choice of restraint chair is not critical, however, and a similar unit has been constructed at our laboratories using a small primate cockpit (Model 142-10) supplied by Lehigh Valley Electronics, Box 125, Fogelsvllle, Pennsylvania, 1805 1. In order to fit the Plas Labs chair m Fig. 1 mto a sound-attenuated chamber we
‘The authors wish to express therr appreciation to Mr. Luther R. Gilltam of the Medrcal Illustration Servrce, VA Hospital, Perry Point, Maryland, for hrs assistance m performing the photographic work and to Mrs Joan Van Dyke for typing the manuscript 1115
1116
FIG. 1. Photograph of apparatus used to measure spontaneous motor actlvlty m sqmrrel monkeys during chau restraint The two Inserts m the right-hand portlon of the photograph depict the ring assembly that detects movement and the bracket assembly which 1s uced to suspend the restraint chair m a manner that allows It to swing in any lateral directlon
were forced to shorten the herght of this commercrally produced apparatus by 3-5116 in. The basic design of thus unit consists of suspending the restraint chair by means of four aluminum strips that are loosely bolted to metal angle brackets which are, m turn, attached to a wooden enclosure This method of suspensron insures that the chair IS firmly balanced but IS allowed to swing m any lateral directron The bolts which connect both ends of the alummum strrps are not screwed trghtly so that the charr can swing m all directions. The presence of any lateral movement of the chair is detected by the rmg mechanism located on the bottom left hand portron of the restraint chair As the close-up in Fig. 1 indicates, two brass rings are placed m a concentric arrangement. The top ring 1s connected to the chair while the bottom nng IS firmly bolted to the bottom of the fixed wooden enclosure Whenever the chair moves srgnlficantly the outer rmg IS moved, thus touching the inner brass rmg This contact can
then act to conduct an electrical impulse which can be fed through an electromecharucal pulse former and then mto an electronic counting device In order to insure a certam amount of adjustment capablhty in the sensitrvrty of thus measurement two machine screws can be placed m the outer ring through threaded openings as seen m the close-up of the ring mechanism m Fig. 1. These two screws can then be adjusted so that each screw normally lies l/64 m from the mner ring. A lock nut on the outside of the rmg insures that these adjustments remain fixed over repeated trials Thus, the chair need move only l/64 m. to trrgger the movement sensmg device Thus fact makes this partrcular system extremely sensitive to even the slightest movement from an animal. To insure that the electrical contacts (1 e., metal rings) do not produce current arcs, It IS advisable to place a capacitor m parallel wrth these contacts Although the various measurements to follow are not critical they are supplied as general references for those
MEASUREMENT
OF MOTOR ACTIVITY IN SQUIRREL
1117
MONKEYS
TABLE 1 MEAN ACTIVITY COUNTS PER MIN AND STANDARD ERROR OF THE MEANS (S.E.M.) FOR FIVE SQUIRREL MONKEYS DURING THE VARIOUS SEGMENTS OF TWENTY DAILY SIDMAN AVOIDANCE SESSIONS
S.E M.
Mean Counts per Mm During the 3-mm Before CS Onset
S.E.M.
Min During the cs
S E.M.
Mean Counts per
Mm for Entire Animal
2-hr Sessron
Mean Counts per
Abby
55.15
2 66
51.05
2.59
55.70
2.34
Jerry
26.15
1.63
14 14
2 19
108.00
4.16
Chuck
25 90
1.65
20 65
1 76
42 20
188
Francrs
128 55
3.81
125.20
3 49
156.05
6.39
48.15
2.24
47.25
2.44
55.05
3.26
Gary
wishmg to construct similar devices to that shown in Fig. 1. The outside dimensions of the wooden enclosure m Fig. 1 are 21 in. high, 26 in. wide and 14 in. deep. The aluminum strips used as supports for the chair were 6-3/8 m. long, 3/4 in. wide and l/16 m. thick. The machine screws used to bolt both ends of these aluminum strips were 8-32. The brackets that were bolted to the chair were 4-l/ 18 in. from the top of the restraint chair. The ring assembly consisted of a top ring that had an outside dia. of l-114 in. and an inside dia. of 15/16 in. Thus, the thickness of the ring was S/32 m. while the height of the top ring was 9/16 m. The bottom ring was 314 in. in dia. with a height of 9/ 16 m. The machme screws used m the outer ring to adjust the sensitivity of this device were 6-32 The clear plastic support that held the top ring to the restraint chair measured 2-l/2 m. wide, 4 m. long, and l/4 m. thick. This support was fastened to the chair through two slots drilled at one end of the support. These slots insured that the top brass ring could be adjusted to fit exactly over the bottom ring. The Plexiglas square that held the bottom ring to the wooden enclosure measured 4 m. wide, 3-l/2 in. long and l/4 in. thick. Finally, the space between the bottom of the restraint chair and the bottom of the wooden enclosure m which the ring assembly was housed was exactly l-3/16 in. This method has allowed us to collect extremely reliable and sensitive measures of activity in restrained squirrel monkeys Table 1 summarizes activity data gathered from
~
five squirrel monkeys while they were subjected to a modified Sidman avoidance schedule (R-S, S-S 20 set). These data demonstrate that although individual animals had different activity rates during these twenty, two-hour sessions, there was little variability within animals as indicated by the low S.E.M. session values. An analysis of variance for repeated measures performed on these data revealed no significant session effects (p>O.O5, 19/76 dfl. Thus, the data within animals was extremely stable across 20 sessions suggesting that the present measure was a reliable index of general motor activity In order to see d the measure was sensitive to changes in the external environment separate activity measures were taken three minutes before, as well as during, the mtroduction of a 3 min conditioned stimulus (CS) whose offset was paired with an unavoidable shock. As Table 1 indicates, all five monkeys demonstrated higher mean activity rates during the CS than during the nonCS segments of the Sidman avoidance schedule. T-tests for related samples (two-tailed) were performed on these data which indicated significant increments (p
REFERENCES
1.
Carlton,
P.
Brain-acetylcholine and mhrbrtion. In: edited by Jack T. Tapp. New York: Academic Press, 1969, pp. 286-327.
Reinforcement
and Behavior,
2.
Sutterer, J. and P. A. Obrrst. Heart rate and general actrvrty alterations of dogs durmg several aversive condrtiomng procedures. J camp physlol. Psycho1 80: 314-326, 1972
BRIEF COMMUNICATION A Simple Method for Measuring Spontaneous Motor Activity in Squirrel Monkeys During Chair Restraint ’ WILLIAM S. LOVE AND VINCENT P. HOUSER Veterans Administration Hospital, Perry Point, Maryland 21902
(Received 3 January
1973)
LOVE, W. S. AND V. P. HOUSER. A sunple method for measuring spontaneous motor activrty m squvrel monkeys during chair restraint. PI-IYSIOL. BEHAV. lO(6) 1115-1117, 1973.- A simple, reliable and sensitive method for measuring spontaneous motor activity in squirrel monkeys during chair restraint is described. In this method the restraint chair is suspended from a wooden enclosure in a way that allows the chair to swing m any lateral direction. This movement is recorded by two brass rings which are connected to the chair and the fixed wooden enclosure, respectively. These brass rings act as electrical contacts which serve to trigger an electronic recording device. This method is extremely sensitive to even slight movements made by the animal while m the restraint chair and should provide a reliable means of obtaimng consistent data under a variety of conditions. Spontaneous motor activity
Restraint chair
Squirrel monkeys
IT IS OFTEN advisable to obtain a measure of spontaneous motor activity from animals who are undergomg some type of experimental procedure. Some investigators have attempted to measure changes m activity level by means of a response lever located in the test chamber [l] but this method has been criticized as lacking sufficient sensitivity [2]. Other methods include the use of photocells or microswitches to sense lateral movement m a confined area. It is difficult to apply either of these two methods to the measurement of spontaneous motor activity in the restrained squirrel monkey. The sensitivity of the photocell method depends upon the location of the photobeams m reference to the animal. Since mdividual animals sit in different positions in the same chair, and many different types of chairs are used in various laboratories, it is difficult to replicate this measurement procedure with any degree of accuracy The same problems are encountered if the restraint chair is pivoted and microswitches are used at the four corners of the restramt chair to act as movement sensors. In this method the placement of the pivot becomes critical to msure a balanced system. Since the weight of the individual animal and restraint chair is variable, replication
is difficult both within and between laboratories. The present report describes a method for measuring spontaneous motor activity in restrained squirrel monkeys which is both simple and reliable. More importantly, the data that are generated from this method should be easily rephcable since it is not affected by variability m the position or weight of the individual animal. Furthermore, differences m the weight or balance of a particular restraint chair should not substantially affect this measure. Thus, various laboratories could use this method and be reasonably sure of obtaining similar results. Figure 1 is a photograph of the apparatus used to obtam a measure of spontaneous motor activity in restrained squirrel monkeys. The particular restraint chair depicted m Fig. 1 is manufactured by Plas Labs., 917 E Chilson Street, Lansing, Michigan, 48906. The choice of restraint chair is not critical, however, and a similar unit has been constructed at our laboratories using a small primate cockpit (Model 142-10) supplied by Lehigh Valley Electronics, Box 125, Fogelsvllle, Pennsylvania, 1805 1. In order to fit the Plas Labs chair m Fig. 1 mto a sound-attenuated chamber we
‘The authors wish to express therr appreciation to Mr. Luther R. Gilltam of the Medrcal Illustration Servrce, VA Hospital, Perry Point, Maryland, for hrs assistance m performing the photographic work and to Mrs Joan Van Dyke for typing the manuscript 1115
1116
FIG. 1. Photograph of apparatus used to measure spontaneous motor actlvlty m sqmrrel monkeys during chau restraint The two Inserts m the right-hand portlon of the photograph depict the ring assembly that detects movement and the bracket assembly which 1s uced to suspend the restraint chair m a manner that allows It to swing in any lateral directlon
were forced to shorten the herght of this commercrally produced apparatus by 3-5116 in. The basic design of thus unit consists of suspending the restraint chair by means of four aluminum strips that are loosely bolted to metal angle brackets which are, m turn, attached to a wooden enclosure This method of suspensron insures that the chair IS firmly balanced but IS allowed to swing m any lateral directron The bolts which connect both ends of the alummum strrps are not screwed trghtly so that the charr can swing m all directions. The presence of any lateral movement of the chair is detected by the rmg mechanism located on the bottom left hand portron of the restraint chair As the close-up in Fig. 1 indicates, two brass rings are placed m a concentric arrangement. The top ring 1s connected to the chair while the bottom nng IS firmly bolted to the bottom of the fixed wooden enclosure Whenever the chair moves srgnlficantly the outer rmg IS moved, thus touching the inner brass rmg This contact can
then act to conduct an electrical impulse which can be fed through an electromecharucal pulse former and then mto an electronic counting device In order to insure a certam amount of adjustment capablhty in the sensitrvrty of thus measurement two machine screws can be placed m the outer ring through threaded openings as seen m the close-up of the ring mechanism m Fig. 1. These two screws can then be adjusted so that each screw normally lies l/64 m from the mner ring. A lock nut on the outside of the rmg insures that these adjustments remain fixed over repeated trials Thus, the chair need move only l/64 m. to trrgger the movement sensmg device Thus fact makes this partrcular system extremely sensitive to even the slightest movement from an animal. To insure that the electrical contacts (1 e., metal rings) do not produce current arcs, It IS advisable to place a capacitor m parallel wrth these contacts Although the various measurements to follow are not critical they are supplied as general references for those
MEASUREMENT
OF MOTOR ACTIVITY IN SQUIRREL
1117
MONKEYS
TABLE 1 MEAN ACTIVITY COUNTS PER MIN AND STANDARD ERROR OF THE MEANS (S.E.M.) FOR FIVE SQUIRREL MONKEYS DURING THE VARIOUS SEGMENTS OF TWENTY DAILY SIDMAN AVOIDANCE SESSIONS
S.E M.
Mean Counts per Mm During the 3-mm Before CS Onset
S.E.M.
Min During the cs
S E.M.
Mean Counts per
Mm for Entire Animal
2-hr Sessron
Mean Counts per
Abby
55.15
2 66
51.05
2.59
55.70
2.34
Jerry
26.15
1.63
14 14
2 19
108.00
4.16
Chuck
25 90
1.65
20 65
1 76
42 20
188
Francrs
128 55
3.81
125.20
3 49
156.05
6.39
48.15
2.24
47.25
2.44
55.05
3.26
Gary
wishmg to construct similar devices to that shown in Fig. 1. The outside dimensions of the wooden enclosure m Fig. 1 are 21 in. high, 26 in. wide and 14 in. deep. The aluminum strips used as supports for the chair were 6-3/8 m. long, 3/4 in. wide and l/16 m. thick. The machine screws used to bolt both ends of these aluminum strips were 8-32. The brackets that were bolted to the chair were 4-l/ 18 in. from the top of the restraint chair. The ring assembly consisted of a top ring that had an outside dia. of l-114 in. and an inside dia. of 15/16 in. Thus, the thickness of the ring was S/32 m. while the height of the top ring was 9/16 m. The bottom ring was 314 in. in dia. with a height of 9/ 16 m. The machme screws used m the outer ring to adjust the sensitivity of this device were 6-32 The clear plastic support that held the top ring to the restraint chair measured 2-l/2 m. wide, 4 m. long, and l/4 m. thick. This support was fastened to the chair through two slots drilled at one end of the support. These slots insured that the top brass ring could be adjusted to fit exactly over the bottom ring. The Plexiglas square that held the bottom ring to the wooden enclosure measured 4 m. wide, 3-l/2 in. long and l/4 in. thick. Finally, the space between the bottom of the restraint chair and the bottom of the wooden enclosure m which the ring assembly was housed was exactly l-3/16 in. This method has allowed us to collect extremely reliable and sensitive measures of activity in restrained squirrel monkeys Table 1 summarizes activity data gathered from
~
five squirrel monkeys while they were subjected to a modified Sidman avoidance schedule (R-S, S-S 20 set). These data demonstrate that although individual animals had different activity rates during these twenty, two-hour sessions, there was little variability within animals as indicated by the low S.E.M. session values. An analysis of variance for repeated measures performed on these data revealed no significant session effects (p>O.O5, 19/76 dfl. Thus, the data within animals was extremely stable across 20 sessions suggesting that the present measure was a reliable index of general motor activity In order to see d the measure was sensitive to changes in the external environment separate activity measures were taken three minutes before, as well as during, the mtroduction of a 3 min conditioned stimulus (CS) whose offset was paired with an unavoidable shock. As Table 1 indicates, all five monkeys demonstrated higher mean activity rates during the CS than during the nonCS segments of the Sidman avoidance schedule. T-tests for related samples (two-tailed) were performed on these data which indicated significant increments (p
REFERENCES
1.
Carlton,
P.
Brain-acetylcholine and mhrbrtion. In: edited by Jack T. Tapp. New York: Academic Press, 1969, pp. 286-327.
Reinforcement
and Behavior,
2.
Sutterer, J. and P. A. Obrrst. Heart rate and general actrvrty alterations of dogs durmg several aversive condrtiomng procedures. J camp physlol. Psycho1 80: 314-326, 1972