F AA-AM-73-17 

EFFECTS OF SECOBARBITAL AND D-AMPHETAMINE 

ON TRACKING PERFORMANCE DURING 

ANGULAR ACCELERATION 

David J. Schroeder, Ph.D.* 

William E. Collins, Ph.D.':' 

Gary W. Elam, M.D.*':' 

*FAA Civil Aeromedical Institute 

P.O. Box 25082 

Oklahoma City, Oklahoma 73125 

**Department of Otorhinolaryngology 

University of Oklahoma Health Sciences Center 

Oklahoma City, Oklahoma 73104 

December 1973 

Availability is unlimited. Document may be released 

to the National Technical Information Service, 

Springfield, Virginia 22151, for sale to the public. 

Prepared for 

DEPARTMENT OF TRANSPORTATION 

FEDERAL AVIATION ADMINISTRATION 

Office of Aviation Medicine 

Washington, D.C. 20591 
FAA-AM-73-17 

4. Title ana Subtitle 5. Report Dele 

EFFECTS OF SECOBARBITAL AND D-AMPHETAMINE ON December 1973 

TRACKING PERFORMANCE DURING ANGULAR ACCELERATION 6 . Performing Organization Code 

7. Author(s) 8 . Performing Organization Report No. 

David J. Schroeder, Ph.D., William E. Collins, Ph.D., 

and Gary W. Elam M.D. 

9. Performing Organization Name and Address 10. Work Unit No. 

FAA Civil Aeromedical Institute 

P. 0. Box 25082 11. Contract or Grant No . 

Oklahoma City, Oklahoma 73125 

13. Type of Report and Period Covered 

12. Sponsoring Agency Name and Addres• 

Office of Aviation Medicine OAM Report 

Federal Aviation Administration 

800 Independence Avenue, s. w. 14. Sponsoring Age.ncy Code 

Washington, D. c. 20591 

15. Supplementary Notes 

This research was conducted under Tasks No. AM~A-73-PSY-27 and AM-D-74-PSY-27. 

16. Abstract 

Thirty young men were randomly assigned in equal numbers to one .of the following 

groups: placebo (lactose), secobarbital (100 mg), or d-amphetamine (10 mg). The 

drugs or placebo were administered in capsules in a double-blind procedure following practice at a tracking task and baseline determinations of tracking performance 

levels in both static (stationary) and dynamic (angular acceleration) conditions. 

Tests were scheduled 1' 2' and 4 hours after capsule ingestion; all tests were 

conducted inside a Stille-Werner rotator and were in total darkness with the 

exception of the illuminated tracking display. With the rotator stationary, 

d-amphetamine subjects performed significantly better than controls during the 

2-hour and 4-hour post-drug sessions; no other static differences among the groups 

were significant. However, during angular acceleration, secobarbital subjects made 

significant l y more tracking errors and had significantly more vestibular nystagmus 

than both tl-:e control and the d-amphetamine groups for all post-drug sessions. 

These findings agree with our previous studies of alcohol effects: depressant 

drugs may have little or no deleterious influence on tracking performance in 

static environments, but may produce marked performance degradation during angular 

motion. The primary cause of this performance impairment appears to be a vestibulo 

ocular one; =he ability to inhibit vestibular nystagmus by visual fixation is 

impaired. 

17. K!'y Words 18. Di stri butian Statement 

Drugs Angular Acceleration Availability is unlimited. Document may be 

Performance Vestibular released to the National Technical InformaNystagmus tion Service, Springfield, Virginia 22151, 

for sale to the public. 

19. Security Classif. (of this repart) 20 ; Security Classif. (af this page) 21. No. of Pages 22. Price 

Unclassified Unclassified 8 $3.00 

Form DOT F 1700.7 IB-691 
EFFECTS OF SECOBARBITAL AND D-AMPHETAMINE ON TRACKING 

PERFORMANCE DURING ANGULAR ACCELERATION 

I. Introduction. 

Most studies of the eti'ects of drugs on performance have been conducted under stationary 

conditions. In an aviation environment, however, 

an important aspect of drugs concerns their effects 

on performance during motion. Recent joint 

studies by CAMI and USNAMRV 612 have 

shown that the deleterious effects of alcohol on 

psychomotor performance in the laboratory are 

more pronounced during angular motion than 

under stationary conditions. This difference may 

be attributed to the interfering effects of alcohol 

on the ability of the subject to reduce with visual 

cues the nystagmic eye mo,·ements which occur 

as a result of angular stimulation of the vestibular system. Since alcohol acts primarily as a 

central nervous system depressant, it seems likely 

that other drugs which have depressive effects 

may similarly affect an individual's visual fixation ability and, consequently, his psychomotor 

performance during vestibular stimulation. Moreover, there is no information presently available 

concerning the effects of an analeptic, as opposed 

to a depressant, on eye-hand coordination during 

concomitant vestibular stimulation. Consequently, 

the purpose of this study was to extend our 

knowledge of the interaction of tracking performance, angular acceleration, and drugs to 

include the effects of both a commonly used depressant other than alcohol (secobarbital) and a 

commonly used analeptic ( d-amphetamine). 

II. Method. 

Sttbjects. Thirty male college students ranging 

in age from 20 to 30 years · served as subjects. 

Before any testing, 10 subjects each were randomly assigned by a double-blind procedure to 

one of three groups: a placebo, secobarital, or 

We gratefull~· acknowledge assistance in data collection and scoring hy Carolyn Eubanks, l\Iartha Manley, 

and Cynthia l\Iitchell. 

The sturl~· was supported in part by NIH Grant Numher TOl KR 05418-00 from KINDS. 

1 

d-amphetamine group. None had any previous 

laboratory experience involving vestibular stimulation. Subjects were not allowed to smoke or 

drink be,·erages containing cafl:'ine, except during 

the 2-hour lunch period which preceded the final 

test session. 

ApparatUii. The angular stimulation was pro-

,·ided by a modified Stille-Werner rotation de-

,·ice. The subject was seated in an upright 

position directly over the center of rotation, with 

his head fixed in a. headrest so that the lateral 

semicircular canals were approximately in the 

plane of rotation. The device was programmed, 

using a "\Vavetek signal generator, to provide a 

triangular w:weform stimulus of 10° /sec2 with a 

period of 48 seconds and a peak velocity of 

120° / sec in both clockwise and counterclockwise 

directions. 

A one-degree-of-freedom compensatory tracking task consisting of an aircraft localizer/glideslope indicator (attached to the front of the 

rotation device and a joy stick (mounted directly in front of the subject) was used as a 

measure of psychomotor (eye-hand) coordination. 

The vertical needle on the instrument was deflected to the left and right of center by a sinusoidal forcing function with a 14-second period. 

The needle movemenf was thus in the same approximate plane as the eye movements arising 

from the vestibular stimulation. The subject's 

task was one of keeping the needle in the center 

or null position by compensatory movements of 

the joy stick. Deviations from the null position 

were considered as errors and a voltage proportional to these deviations was electronically integrated over 1-second intervals and recorded. 

Further details concerning the operation of the 

tracking task are presented elsewhere.5 

Light was projected through a tube to illuminate the display. A card, coated with the same 

white paint as the needle, was placed in front 

of the instrument for luminance calibrations. 
illuminometer and set at one ft.L. The test room 

was otherwise in total darkness. 

Electrodes were taped beside the outer canthus 

of each eye to record horizontal eye moYements. 

Calibration: of the horizontal eye moYements was 

accomplished by having the subject sweep his 

eyes between hYo small flashing lights on the 

front of the rotator; the I ights subtended a visual 

angle of 15°. Eye mo,·ements and tracking 

errors were recorded on a Beckman Type T 

electroencephalograph. 

Procedure. Following instructions, each subject \Yas giYen two minutes of static tracking 

practice, i.e., ''it h the rotator stationary. This 

''as follO\Yed by a practice session comprising one 

minute of static tracking, 2.5 minutes of dynamic 

tracking (during fiye complete cycles of rotation), 

and three minutes of rotation in the dark (the 

latter was conducted for purposes other than those 

of the presently reported experiment). A predrug session and three post -drug sessions ''ere 

identica I to the practice session. 

consumed their respective capsules on an empty 

stomach: either 10 mg of d-amphetamine, 100 mg 

of secobarbital, or a placebo containing lactose. 

The dmgs ''ere administered using a double-blind 

procedure. Post-drug sessions were conducted 

1, 2, and 4 hours after administration of the drugs 

with blood pressure and heart rate monitored 

immediately prior to each of the test sessions. 

S coring. One-second intervals of tracking 

error were measured, summed, and averages obtained for both the static and dynamic conditions. 

The amount of slow-phase eye displacement was 

measured and the number of nystagmic eye 

mo,·ements was counted across the last two cycles 

of rotation dnring dynamic tracking. Mean 

Yalues in degrees per second and beats per second 

were calculated and used as measures of nystagmic output. Scoring was accomplished without knowledge of the group (drugs or placebo) 

to which any subject belonged, and these absolute 

ya lues were used in the statistical analyses. 

Table 1 

Mean pulse rates and blood pressure measures (systolic/diastolic) 

obtained during each pre- and post-drug session for subjects in 

the secobarbital, d-amphetamine, and placebo groups. 

Post-Drug Sessions 

Group Pre-Drug 1-hr. 2-hr. 4-hr. 

Pulse Rate 

secobarbital 65.1 65.2 65.5 70.0 

d-amphetamine 66.7 66.0 70.9 78.2 

placebo 72.2 65.8 67.2 72.6 

Blood Pressure 

secobarbital 115/73 114/73 112/73 117/72 

d-amphetamine 116/73 122/75 126/76 111/73 

placebo 116/77 120/79 117/79 121/77 

2 
Levels of statistical significance (Not Significant;~~ .05; ~< .01; 

~~ .001) obtained within groups by~ tests~ Comparisons were made 

between tracking scores and measures of nystagmus from the predrug session and each post-drug session for the s~cobarbital 

d-amphetamine, and placebo groups separately. 

Measure 

Static 

Tracking 

Error 

Dynamic 

Tracking 

Error 

Slow-Phase 

Nystagmus 

Group 

secobarbital 

d-amphetamine 

placebo 

secobarbital 

d-amphetamine 

placebo 

secobarbital 

d-amphetamine 

placebo 

Pre-Drug 

1-hr. 

N.S. 

N.S. 

N .S. 

. 01** 

N.S. 

N.S. 

.01** 

N.S. 

. OS* 

Nystagmic 

Beats 

secobarbital .001** 

d-amphetamine N.S. 

placebo N.S. 

* indicates significantly less of the measure 

** indicates significantly more of the measure 

Session 

2-hr. 

N.S. 

.05* 

N .S. 

.001** 

.001* 

N.S. 

.01** 

.01* 

N.S. 

.001** 

.OS* 

N .S. 

vs. 

4-hr. 

N .S. 

.01* 

N .S • 

N.S. 

.05* 

.01* 

.01** 

.001* 

N .S . 

.01** 

N.S. 

N.S. 

For graphic presentation, however, "change" 

scores were computed. For each group and each 

measure, the mean score for the pre-drug session 

was plotted as a zero base and the percentage of 

increase or decrease in subsequent scores for a 

gi,·en measure (i.e., in sessions which followed 

administration of a drug or placebo) was plotted 

as· "per cent increase" or "per cent decrease" 

from the pre-drug level. 

3 
(!) 

z 

~ 

.., 

U) 

0 c 

C( .., 

a:: a:: 70 u .... ~ 

11.1 lit 60 

.J 

% ~0 

~ 

U) 40 

:::) 

~ 30 

(!) 

C( 

.... 20 

U) 

> 

z 10 

0 

.., 

U) -10 

c 

- Secobarbital 

- d- Amphetamine 

o--o Placebo 

SLOW PHASE 

-

130 

120 

100 

90 

80 

70 

60 

!50 

40 

30 

20 

10 

0 

-10 

NUMBER OF BEATS 

......... 0_- -----o 

.., 

~ -20 ~- - - - - - 0 -20 .., 

0 -30 lit 

-30 

-40 

PRE 2 4 

HOURS AFTER 

PRE 

INGESTION 

2 4 

FIGURE 1. Changes in tracking performance under static (stationary) and dynamic (angular acceleration) conditions. Error scores for the pre-trial (before ingestion of the drug or placebo capsule) were set at 0. Error 

scores for the post-ingestion sessions were converted to percentages of increase or decrease from the pre-ingestion baseline. 

III. Results. 

Oardiova8cular J,f ea8ures 

Means and standard deviations for heart rate 

and blood pressure are presented in Table 1. 

A rise in both measures occurred for the d-amphetamine group after administration of the drug, 

but these changes were not statistically significant 

at the .05 level. Moreover, none of the measures 

of heart rate or blood pressure for either the secobarbital or . control group changed significantly 

(p>.05) across sessions. (Goldstein, Searle, and 

Schimke7 also failed to find any effect of 10 mg 

4 

of d-amphetamine or of 200 mg of secobarital on 

blood pressure and heart rate, although Collins 

and Poe4 reported statistically reliable increases 

in these measures following 12 mg doses of amphetamine administered subcutaneously.) Thus, 

the presence or absence of the drugs could not be 

ascertained by these cardiovascular measures. 

Static Tracking 

Within-Group Comparisons of Tracking Performance. Subjects in the placebo and the secobarbital groups evidenced little . change in static 

tracking error from the pre-drug through the 
Levels of statistical significance (Not Significant; 2 < .05; 

~ < .01) obtained between groups with analyses of covariance 

of tracking and nystagmus scores. .. Duncan s New Multiple Range 

Test was then used to determine which of the secobarbital (S), 

d-amphetamine (D), and placebo (P) groups differed(<;>) in 

scores during the sessions following drug administration. 

Measure 

Static 

Tracking 

Error 

Dynamic 

Tracking 

Error 

Slow-Phase 

Nystagmus 

Nystagmic 

Beats 

1-hr. 

N.S. 

.01 

S > D 

s > p 

.01 

S > D 

s > p 

.01 

S > D 

s > p 

post-drug sessions (Figure 1) ; all of the postdrug static tracking error means were within 

± 11% of their respective pre-drug levels and 

none of these differences was statistically significant at the .05 leYel by t test (Table 2). In contrast, subjects in the d-amphetamine group evidenced a steady decrease in tracking error from 

5 

Post-Drug Sessions 

2-hr. 4-hr. 

---

.05 .05 

D < p D < p 

.01 .01 

S > D S > D 

s > p s > p 

.01 .01 

S > D S > D 

s > p s > p 

.01 .01 

S > D S > D 

S>P s > p 

the pre-drug session through the 4-hour post-dru

tests. Some improvement with practice in stat

tracking performance at this task is not an u

usual finding · even for non-drugged subjects. 

However, while most of the improvement 

tracking performance for the d-amphetami

group occurred during the session conducted 
statistically lower than the pre-drug level (p<.05 

and .01, respectively). 

Between-Group Comparisons of Tracking Performance. Comparisons of static tracking performance among the three groups were made 

using analysis of covariance and Duncan's New 

Multiple Range Test; results are presented in 

Table 3. During static tracking, the only statistically significant differences (p<.05 in both 

cases) occurred betw~en the placebo and d-amphetamine groups for the 2-hour and 4-hour 

post-drug sessions; the d-amphetamine group performed with less error during these sessions. 

Thus, d-amphetamine had some positive effect on 

static tracking performance; a stronger conclu·-

sion does not seem warranted since (a) the 

placebo group in this study showed little performance improvement while in two previous 

studies3 6 control groups decreased tracking errors by approximately 15% over similar time and 

test periods, and (b) there were no significant 

differences in performance between the group receiving d-amphetamine and the secobarbital 

group. 

Dynamic Tracking 

Within-Group Comparisons of Tracking Performance. Both the d-amphetamine and control 

groups exhibited steady improvement in dynamic 

tracking performance across sessions. This predrug to post-drug improvement for the two 

groups (which must be considered largely as a 

practice effecV 6 12 ) ranged from 3% to 28% 

across sessions (see Figure 1) and was statistically 

significant by t tests two hours and four hours 

after administration of the capsules (p<.001 and 

.05, respectively) for the d-amphetamine group, 

and four hours post-administration (p<.01) for 

the placebo group (Table 2). Although there 

was an initial tendency for the subjects receiving 

the d-amphetamine to show slightly greater performance improYement than the control subjects, 

none of the differences between the two groups 

was statistically significant. On the other hand, 

subjects in the secobarbital group evidenced a 

dramatic increase in tracking error (66%) one 

hour after receiving the drug; during subsequent sessions their tracking error was reduced, 

but the error scores four hours after administra6 

in tracking performance for the secobarital group 

was statistically significant for the 1- and 2-hour 

post-drug sessions (p<.01 and .001, respectively). 

Between-Group Comparisons of Tracking Performance. Results of an analysis of covariance 

and Duncan's New Multiple Range Test indicated that the dynamic tracking performance of 

subjects in the secobarbital group was significantly poorer than that of subjects in both the 

placebo and d-amphetamine groups for all of the 

post-drug sessions (p<.01 in each case). Although the d-amphetamine group had less tracking error than placebo subjects during the 1-hour 

and 2-hour post-drug sessions (and ·particularly 

during the latter when a maximal effect of the 

drug might be expected; see Figure 2), none of 

these differences was statistically significant. 

Nystagmus During Tracking 

Within-Group Comparisons of Nystagmic Output. With regard to both the slow-phase velocity 

and the number of nystagmic eye movements, 

subjects in the placebo and d-amphetamine groups 

exhibited a steady decline from the pre-dnig 

through the post-drug sessions (Figure 2) ; several of these differences were statistically significant (Table 2). In contrast, for subjects in 

the secobarbital group, both slow-phase nystagmus and number of nystagmic beats increased 

significantly during the 1-hour post-drug session 

(p<.Ol and .001, respectively) and, although 

there was a gradual return toward the pre-drug 

leYel, both measures of nystagmus for this group 

remained significantly above the pre-drug levels 

through the 4-hour post-drug session (p<.01). 

Between-Group Comparisons of Nystagmic 

Ontpnt. The slow-phase velocity measures and 

the number of nystagmic beats recorded for subjects in each group were submitted to analyses 

of co,·ariance and Duncan's New Multiple Range 

Test. Scores for both measures were significantly 

higher (p<.Ol in eYery case) for secobarbital subjects than scores for the placebo and d-amphetamine groups during each of the post-drug testing 

sessions (Table 3). Only one appreciable difference occurred between the placebo and d-amphetamine groups (at the 2-hour post-drug sessions; 

see Figure 2) but that difference was not statistically reliable. 
60 60 

50 w 

(/) 

- Secobarbital 

- d -Amphetamine 

50 

ct 40 0:: w 

0 0:: 

0:: (.) 

30 

0:: ~ 

o-- o Placebo 40 

30 

IJJ ~ 

20 20 

C) 

z 10 10 ~ 

0 

<l 0 0 

0:: 

t- ~ -10 -10 

ct 

w 

~ -20 - 20 w 

0 

~ -30 - 30 

- 40 

PRE 2 4 

HOURS AFTER 

PRE 

INGESTION 

2 

FIGURE 2. Slow-phase displacement of nystagmus and the numher of nystagmic beats obtained while subjects we

tracking in the dynamic condition. Measures for the pre-trial (before ingestion of the drug or placebo capsul

wer e set at 0. Measures for the post-ingestion sessions were converted to percentages of increase or decrea

from the pre-ingestion baseline. 

Conclusion 

The obtained decrement in tracking performance for the secobarbital subjects during angular 

stimulation is correlated with a considerable increase in the number and velocity of nystagmic 

eye movements with attendant visual blurring. 

Thus, these deleterious effects of secobarbital appear to be similar to those produced by alcohol; 

both apparently interfere with the ability of the 

visual system to suppress nystagmic eye movements which result from angular stimulation of 

the vestibular system. Further support of such 

an effect of barbiturates appears in an ~arlier 

study of optokinetic and caloric nystagmus by 

Rashbass and Russell10 where the authors found 

that the barbiturate sodium amytal " ... abolished 

the inhibiting effect of visual fixation" (p. 355). 

Barbiturates apparently suppress optokinetic nystagmus1 2 and iuterfere with smooth tracking 

movement9 10 and visual fixation ability10 in much 

the same fashion as does alcohol. 3 6 11 12 

The present data support our previous findings3 6 12 with alcohol, i.e., the effect of at least 

7 

some depressant drugs on performance may n

be evident in a stationary environment, but ma

be substantial during angular stimulation of th

,·estibular system. Such degradation in perform

ance appears primarily attributable to impaire

visual acuity resulting from the inability to sup

press vestibular nystagmus by visual means.

5 8 I

addition to nystagmus, however, motion may co

tribute to performance declines by producin

other effects, such as distraction, which esse

tially make the tracking task more complex an

more susceptible to the influence of depressa

drugs. d-Amphetamine, an alerting drug, ap

peared not to affept dynamic tracking althoug

it had some facilitory effect on static trackin

In any event, future evaluations of effects o

drugs on performance should take into accou

the influence of motion. Any drug which inte

feres with the ability of a pilot to fixate and rea

cockpit instruments during flight would severe

compromise his ability to react properly durin

maneuvers, especially under IFR conditions. 
REFERENCES 

1. Bender, M. B., and F . H . O'Brien: The Jnfluenee of 

Barbiturate on Various Forms of Nystagmus, Al\U;RICAN JOURNAL OF OP'l'HALl\IOLOGY, 29 :J541-

1552, 1946. 

2. Bergman, P. S., 1\I. Nathanson, a·nd M. B. Bender: 

Electrical Recordings of Normal and Abnormal Eye 

Movements Modified hy Drugs, ARCHIVE:"; 01<' 

NEUROLOGY AND PSYCHIATRY, 67 :R57-374, J952. 

3. Collins, W. E., R. D. Gilson, D .. T. Schroeder, and 

F. E. Guedry : Effects of Alcohol Ingestion on Tracking Performance During Angular . Acceleration, 

JOURNAL OF APPLIED PSYCHOLOGY, 55 :!559-

563, 1971. 

4. Collins, W. E., ann R. H. Poe: Amphetamine, Arousal, 

and Human Vestibular Nystagmus, .TOURNAL 01<' 

PHARMACOLOGY AND J~XPERil\fEN'l'AL 'l'HERAPEUTICS, i38 :12Q-125, 1962. 

5. Gilson, R. ·D., F. E. Guedry, and A. J. Henson : Influence of Vestibular Stimulation and Display 

Luminance on the Performance of a <'ompensaton· 

Tracking Task, AEROSPACE l\IEDI< 'INE, 41 :1231-

1237, 1970. 

6. Gilson, R. D., D. J. Schroeder, W. E. Collins, anrl 

F. E. Guedry: Effects of Different Alcohol Dosages 

and Display Illumination on Tracking Performance 

During Vestibular Stimulation, AEROSPACE 1\IEDICINE, 43 :65G-6GO, 1972. 

8 

7. Goldstein, A., B. W. Searle, and R. T. Schimke: 

Effects of Secobarbital and d-Amphetamine on Psrchomotor Performance of Xormal Subjects, .JOURNAL OF PHARMACOLOGY AND EXPERIMENTAL 

THERAPEUTICS, 180 :55-58, 1900. 

R Guedry, F. E.: Relations Between Vestibular Nys-

. tagmus and Visual Performan<·e, AEROSPACE 1\IEDICINE, 39 :57Q-579, 1968. 

D. Norris, H.: The Time <'ourse of Barbiturate Action 

in Man Investigaterl hr Measurement of Smooth 

Tracking Ere 1\Iovement, BRITISH JOURNAL OF 

CHEMOTHERAPY, 33:117-128, 1968. 

10. Rashbass, C., and G. F. l\1. Russell: Action of a 

Barbiturate Drug (Amrloharhitone Sodium) on the 

Vestibulo-Ocular Reflex, BRAIN, 84 :329-335, 19Gl. 

11. Schroeder, D. J. : Some Effects of Alcohol on Nystagmus and Vertigo During Caloric and Optoklnetie 

Stimulation, A 'NALS OF OTOLOGY, RHINOLOGY, 

AND LARYNGOLOGY, 81:218-229, 1972. 

12. Schroeder, D .. T., R. D. Gilson, F . E. Guedry, and 

w: E. Collins: Effects of Alcohol on Nystagmus and 

Tracking Performance During Laboratory Angular 

Accelerations About theY and Z Axes, AEROSPACE 

1\IEDIC'INE, 44 :477-483, 1973.