REFERENCES

. Benson, A. J., and F. E. Guedry: Comparison of

Tracking Task Performance and Nystagmus During
Sinusoidal Oscillation in Yaw and Pitch, NAMRL~
1123. USAARL Serial No. 71-12. Pensacola, Florida:
Naval Aerospace Medical Research Laboratory, 1970.

. Collins, W. E., R. D. Gilson, D. J. Schroeder, and

F. E. Guedry: Effects of Alcohol Ingestion on Track-
ing Performance During Angular Acceleration.
JOURNAL OF APPLIED PSYCHOLOGY, 55 :559-563,
1971.

. Gilson, R. D., F. E. Guedry, and A. J. Benson: In-

fluence of Vestibular Stimulation and Display Lumi-

nance on the Performance of a Compensatory
Tracking Task. AEROSPACE MEDICINE, 41:1231-
1237, 1970.

. Gilson, R. D., D. J. Schroeder, W. E. Collins, and

F. E. Guedry: Effects of Different Alcohol Dosages
and Display Illumination on Tracking Performance

12

. Guedry, F.

During Vestibular Stimulation. AEROSPACE MED-

ICINE, 43 :656-660, 1972.

. Guedry, F. E., and A. J. Benson: Nystagmus and

Visual Performance During Sinusoidal Stimulation
of the Vertical Semicireular Canals. NAMRL-1181.
USAARL Serial No. 71-16. Pensacola, Florida:
Naval Aerospace Medical Research Laboratory, 1971.
E.: Vision During Angular Acceleration
Considered in Relation to Space Operations, In:
Stahle, J. (Ed.), Vestibular Function on Earth and
in Space, Oxford, Pergamon Press, 1970, pp. 27-34.

. Hixson, W. C., and J. I. Niven: A Bioinstrumentation

Control Center for the Human Disorientation Device.
USNSAM Report No. 79. NASA R-1. Pensacola,
Florida: Naval School of Aviation Medicine, 1963.

. Hixson, W. C., and J. I. Niven: Directional Differ-

ences in Visual Acuity During Vertical Nystagmus.
NAMI—1079. NASA R-93. Pensacola, Florida:
Naval Aerospace Medical Institute, 1969.

28754


ALCOHOL AND DISORIENTATION-RELATED RESPONSES.
VI. EFFECTS OF ALCOHOL ON EYE MOVEMENTS AND TRACKING
PERFORMANCE DURING LABORATORY ANGULAR
ACCELERATIONS ABOUT THE YAW AND PITCH AXES

I, Introduction.

Adequate pilot flight performance, especially
under IFR conditions, requires good visual acuity
and legibility of cockpit instruments. Among
the possible sources of interference with good
vision during flight are nystagmic eye movements
which occur as a result of vestibular stimulation.
Under normal conditions these eye movements
are suppressed by visual fixation, However, two
recent CAMI-USNAMRL studies? * showed that
alcohol ingestion interfered with such fixation
and, concomitantly, degraded performance (com-
pensatory tracking) requiring eye-hand coordi-
nation during angular motion in yaw (Z axis);
interestingly, the aleohol produced no consistent
changes in tracking performance when no angular
motion was involved. These alcohol-induced
changes in eye-hand coordination during motion
lasted for as long as four hours and were evident
at blood alcohol levels as low as .027%.*

However, much of the motion of an aircraft
involves pitch (Y axis) or roll (X axis). Sev-
eral studies'®** have shown that under normal
conditions visual suppression of ocular nystagmus
is not equal for motion about the three axes
(X, Y, and Z). For example, while visual sup-
pression is equally effective during either direc-
tion of motion in Z-axis stimulation, its effect is
asymmetrical during Y-axis stimulation. Spe-
cifically, nystagmic eye movements arising from
“pitch-forward” motion are more frequent and
of greater amplitude than those occurring during
“pitch-backward” motion. These differences in
eye movement patterns results in differences in
tracking performance; tracking error during
“pitch-forward” motion is significantly greater
than during “pitch-backward” motion. Another
difference in response between Y- and Z-axis
stimulation is the greater tendency for Y-axis

motion to produce motion sickness even though
stimulus rates might be identical.*

The present study was designed (a) to examine
some effects of alcohol on performance at an
eye-hand coordination task during angular mo-
tion about the Y axis, (b) to compare those re-
sults with data obtained during Z-axis stimula-
tion, and (c) to compare results from Y- and
Z-axis stimulation with performance in the ab-
sence of motion. In order to reduce the prob-
ability of motion sickness during Y-axis stimu-
lation, the angular stimulus rate (-60°/sec)
used in this investigation was considerably lower
than the rate (+120°/sec) used in our previous
alcohol studies.? *

II. Method.

Subjects. Twenty-four young male volunteers
from the Naval Air Station at Pensacola served
as subjects. All were in good health and without
any history of vestibular disorders. One group
of 12 volunteers was tested under the infiuence
of alcohol; the other group of 12 served as a
control. The latter received a non-alcoholic bev-
erage but were led to believe that it contained
alcohol.

Apparatus. The USNAMI Human Disorien-
tation Device (HDD),’ a multi-axis rotator, was
programmed to provide sinusoidal oscillation
with a peak velocity of ++60°/sec and a period
of 25 sec. Motion about the Z axis (stimulation
of the horizontal semicircular canals) was ac-
complished with the subject seated upright, over
the center of rotation. For Y-axis stimulation
(ie, of the vertical semicircular canals), the
capsule was rotated 90° about the horizontal axis
so that, with the subject’s right side down, a line
drawn between the two ears was co-linear with



N ol & a (2) N
T T T T T 1

SLOW PHASE EYE VELOCITY (DEG/SEC)
T

i. |

NYSTAGMUS
(y AXIS) VERTICAL @——®
(Z AXIS) HORIZONTAL 0---O

CIN LIGHT)

PRE I

2 3 4

HOURS AFTER DRINKING

Ficure 5. Comparison by sessions of slow-phase eye velocity in the light obtained during Y- and Z-axis stimulation
of the alcohol subjects.

pare Figures 6 and 7). While slow-phase eye
velocity was nearly symmetrical for the clock-
wise and counterclockwise directions of Z-axis
oscillation, the eye velocity during the “pitch-
forward” period of Y-axis oscillation was sig-
nificantly higher (p<.001) than during the
“pitch-backward” segment of the cycle. This
differential suppression of nystagmic eye move-
ments during Y-axis oscillation with vision
permitted supports findings in previous stud-
ies? **® and has been attributed to an asymmetri-
cal habituation of the eye movements.*

The results of alcohol ingestion were par-
ticularly evident in the large and statistically
significant (p<.001) increases in mean slow-
phase eye velocity one hour after drinking for

both Y- and Z-axis oscillation. During subse-
quent post-drinking sessions, mean slow-phase
eye velocity returned toward the pre-drinking
level such that, four hours after drinking, the
velocity measure for motion about the Y axis
was 21% below the pre-drinking level whereas,
for Z-axis motion, the values were still slightly
above (11%) the pre-drinking level. However,
it should be noted that the mean eye velocity for
Y-axis stimulation was still significantly higher
than that for Z-axis stimulation (compare Fig-
ures 6 and 7).

Tracking Error. The absolute tracking error
was integrated and then recorded in digital and
graphic form. Means for both static and dy-
namic tracking error are plotted in Figure 8.


of oscillation (five cycles) followed, during which
the localizer/glide-slope instrument was illumi-
nated and the subject tracked (dynamic track-
ing). The same procedure was then repeated for
the other axis. The order of stimulus presenta-
tion of the Y and Z axes was counterbalanced
among subjects.

Following the pre-drinking session, the sub-
jects were taken to a nearby room where they
consumed either orange juice (control group) or
a mixture of orange juice and vodka (alcohol
group). The alcoholic mixture contained 2 ml of
100-proof Smirnoff vodka per kg of body weight.
All subjects were allowed 30 min to drink their
respective beverages.

Three post-drinking sessions were spaced at 1,
2, and 4 hours after drinking was completed.

Each session involved: (a) one min of static
tracking, (b) one min of oscillation in the dark,
and (c) 2.5 min of dynamic tracking each for
the Y and the Z axes,

A venous blood sample was drawn from those
in the alcohol group prior to each of the experi-
mental sessions. Only a pre-drinking blood
sample was drawn from the control subjects.
Blood ethanol levels were determined by use of
gas chromatography.

IH. Results and Discussion.
Blood Ethanol Levels
There was no evidence of any ethanol in the
pre-drinking blood samples for either group.
The mean blood ethanol levels for the alcohol

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x
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3 4
) |_a | | | |
PRE I 2 3 4

HOURS AFTER DRINKING

Freurr 2. Comparison by sessions of mean slow-phase eye velocity in the dark obtained during Y- and Z-axis
stimulation of the alcohol subjects.

3



OSCILLATION ABOUT
Z AXIS — (YAW)

Lv ——¢

TD

fies

OSCILLATION ABOUT
Y AXIS — (PITCH)

Favre 1, Illustration of how subjects were positioned in the Human Disorientation Device for Y- and Z-axis
stimulation.

the axis of rotation. An illustration of the two
positions is presented in Figure 1.

The compensatory tracking device, which is
described in more detail elsewhere,? consisted of
a joy stick and an aircraft localizer/glide-slope
instrument. The subject was instructed to keep
the instrument’s needle display in the center or
null position by compensatory movements of the
joy stick located between his legs. A sinusoidal
forcing function with a period of .071 Hz was
used to deflect the needle; all deflections were
recorded. The needle’s null position was always
aligned with true vertical and was parallel to
the axis of rotation; thus, the needle movement
was approximately in the same plane as the
subject’s oscillation-induced eye movements. The
interior of the HDD was in total darkness with
the exception of 0.1 ft. L. of illumination on the
tracking instrument.

Procedure. The subject was seated and
strapped in the HDD after electrodes had been
attached beside the outer canthus of each eye to
record horizontal eye movements. Another pair
of electrodes was located above and below the
left eye to record vertical eye movements. Fol-
lowing an instruction period, the subjects were
given 2.5 min of tracking practice in each of the
two body positions while the HDD was stationary
(static tracking). The pre-drinking session was
then begun. Static tracking performance was
first recorded for one min with the subject either
upright or in the right-side-down position. The
subject. was then oscillated in the HDD. For
the first min of the oscillation, involving two
cycles, the subject’s eye movements were re-
corded in total darkness with alertness being
maintained by a mental multiplication task; this
assured adequate recording. A 2.5 min period


n
a
1

Le)
fo)
T
y
>

Z AXIS (IN DARK)
HORIZONTAL NYSTAGMUS

@—e PRE
O--O | — HOUR
4—A 2- HOUR

4— HOUR

SLOW PHASE VELOCITY OF NYSTAGMUS
~

is) °

T

TIME

IN SECONDS

Ficure 4. Second-by-second plots of slow-phase eye velocity in the dark for Z-axis stimulation of the alcohol
subjects.

Y-axis stimulation were 5-10% below their pre-
drinking level. However, none of these pre- to
post-drinking changes was statistically signifi-
cant.

Nystagmus in the Light, As noted above, dur-
ing oscillation about both the Y and Z axes,
nystagmus in the dark was nearly symmetrical
for both halves of the oscillation cycles. There
was, however, considerable visual suppression of
these eye movements during angular stimulation

with the tracking task illuminated. Mean slow-
phase eye velocities during tracking for each axis
of stimulation appear in Figure 5. Mean values
for Y-axis stimulation were nearly double those
for Z-axis stimulation for all sessions; these dif-
ferences were statistically significant (p<.05-
001). The higher values for the Y axis were
due primarily to the velocity of the nystagmic
eye movements occurring during the “pitch-
forward” period of the Y-axis stimulation (com-



TECHNICAL REPORT STANDARD TITLE PAGE

1. Report No. 2. Government Accession No. 3. Recipient's Catalog No.
FAA~AM-72 -34

4, Title ond Subtitle ALCOHOL AND DISORIENTATION- RELATED 3. Report Date
RESPONSES. VI. EFFECTS OF ALCOHOL ON EYE MOVEMENTS December 1972

AND TRACKING PERFORMANCE DURING LABORATORY ANGULAR 6. Performing Organization Code
ACCELERATIONS ABOUT THE YAW AND PITCH AXES
7. Author(s) 8. Performing Organization Report No.
D. J. Schroeder, Ph.D., R. D. Gilson, Ph.D.,
F. E. Guedry, Ph.D., W. E. Collins, Ph.D.

9. Performing Orgonization Name and Address 10, Work Unit No.
FAA Civil Aeromedical Institute
P. 0. Box 25082 V1. 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
Federal Aviation Administration OAM Report
800 Independence Avenue, S. W. 14. Sponsoring Agency Code
Washington, D. C. 20591

15. Supplementary Notes

This research was performed under Tasks AM-A-72-PSY-27 and AM-A-73-PSY-27.

16. Abstract
Recent CAMI-USNAMRL studies have shown that alcohol ingestion interferes with visual]
control of vestibular eye movements and thereby produces significant decrements in
performance at a compensatory tracking task during oscillation about the yaw axis;
significant or consistent decrements in performance in the absence of motion were
not obtained. The present study was designed to extend knowledge about these
effects to pitch-plane stimulation. ‘Twenty-four young men, equally divided into
alcohol and control (no alcohol) groups, performed a compensatory tracking task
while stationary and while oscillating about their pitch and their yaw axes in

the USN Human Disorientation Device. Alcohol doses were 2.0 ml of Smirnoff vodka
per kg of body weight and tests were conducted before drinking and 1, 2, and 4
hours after drinking. In the absence of motion, there was no difference between
the groups in tracking error while subjects were in the pitch position; signifi-
cantly more errors occurred for alcohol subjects in the yaw position one and four
hours (but not two hours) after drinking. During motion, one and two hours after
drinking, alcohol subjects performed significantly poorer than the non-drinkers

and had significantly less control of their eye movements for both axes of stimu-
lation. Absolute error was greater during all sessions for pitch-plane stimulation
as compared with yaw-plane stimulation. These degrading effects of alcohol on
performance, particularly evident during motion, are discussed from the viewpoint
of aviation safety.

17. Key Words 78. Distribution Statement
Alcohol Availability is unlimited. Document may
Performance be released to the National Technical
Nystagmus - Information Service, Springfield, Virginia
Angular Acceleration 22151, for sale to the public.
Vestibular
19. Security Classif. (of this report) 20. Security Clessif, (of this page) DI. No. of Pages | 22. Price

12
Unclassified Unclassified $3.00

Form DOT F 1700.7 (8-69)



20F

Z AXIS (IN LIGHT)
HORIZONTAL NYSTAGMUS

@—e PRE
O--O |— HOUR
4—A& 2- HOUR

A--S 4— HOUR

SLOW PHASE VELOCITY OF NYSTAGMUS

-254

TIME

COUNTERCLOCKWISE

CLOCKWISE

IN SECONDS

Figure 7. Second-by-second plots of slow-phase eye velocity in the light for Z-axis stimulation of the alcohol
subjects.

tracking errors for the 2-hour and 4-hour post-
drinking sessions gradually returned to the pre-
drinking level for both axes of stimulation, with
the 4-hour post-drinking error for the Z axis
dropping slightly below the pre-drinking level.
These apparent differences between axes of stim-
ulation were due primarily to the tracking error
incurred during the equivalent of “pitch-forward”
motion. Mean tracking error, across time, for
the Y and Z axes are plotted in Figures 9 and
10. In agreement with previous findings,'***

while tracking error for the two half-cycles was
approximately symmetrical for Z-axis stimula-
tion, the error during Y-axis stimulation was
significantly greater during “pitch-forward” mo-
tion as opposed to “pitch-backward” motion.

Comparison of the Alcohol and Control Groups

For ease of comparing the differences between
the alcohol and control groups in nystagmic ac-
tivity and tracking performance, “change” scores
were computed across sessions. ‘The derived
values represent the percentages of increase or


25

"“PITCH-FORWARD"

“PITCH- BACKWARD"

SLOW PHASE VELOCITY OF NYSTAGMUS
°

TIME

AXIS (IN LIGHT)
VERTICAL NYSTAGMUS

@—e PRE

O--O | — HOUR
4—4A 2-— HOUR
4--4 4— HOUR

IN SECONDS

Fievre 6. Second-by-second plots of slow-phase eye velocity in the light for Y-axis stimulation of the alcohol
subjects.

Post-drinking means for static tracking were
5-15% above their pre-drinking levels for both
the upright and the right-side-down position.
However, only one static tracking score, that for
the right-side-down position two hours after
drinking, was significantly above the pre-drink-
ing level (p<.05).

Dynamic tracking errors for Y-axis oscillation
were significantly greater than for Z-axis oscil-
lation during all sessions (p<.001). Mean dy-

namic tracking errors one hour after drinking
were 32% (Y axis) and 20% (Z axis) above
pre-drinking levels (significant at p<.01 and
p<.05, respectively). Although the increase in
error during Y-axis oscillation was 12% greater
than: that for the Z axis one hour after drinking,
and errors during Y-axis stimulation remained
proportionately greater during the two remain-
ing post-drinking sessions, these differences were
not statistically significant. However, mean



20F

SLOW PHASE VELOCITY OF NYSTAGMUS
°

TIME

Y AXIS (IN DARK)
VERTICAL NYSTAGMUS

@—e PRE

O--O |— HOUR
&—A 2-— HOUR
4--4 4—- HOUR

IN SECONDS

Fieure 8. Second-by-second plots of slow-phase eye velocity in the dark for Y-axis stimulation of the alcohol
subjects.

subjects at the 1-, 2-, and 4-hour testing sessions
were: .081%, .075%, and .047%, respectively.

Alcohol Group

Nystagmus in the Dark, Average slow-phase
eye velocities for the pre- and post-drinking ses-
sions are plotted in Figure 2. Although the
mean values for Y-axis stimulation were always
above the values for Z-axis stimulation, the dif-
ference was significant (p<.05) only during the
pre-drinking session. Since the direction of the

eye movement is dependent upon the direction
of the oscillation, average slow-phase velocities
of the nystagmic eye movements were plotted for
each sec of an oscillation cycle (Figures 3 and
4). These plots show that nystagmus was nearly
symmetrical for both halves of the cycle, for both
Y and Z axes.

While there was a general pre- to post-drink-
ing increase (7-11%) in slow-phase eye velocity
for Z-axis stimulation, post-drinking values for




ACKNOWLEDGMENTS

This study was conducted at the Naval Aerospace Medical Research
Laboratory and was co-sponsored by the Federal Aviation Administration,
the Army Medical Research and Development Command, and the Naval
Aerospace Medical Research Laboratory.

Drs. Schroeder and Collins are from the FAA’s Civil Aeromedical Insti-
tute, Oklahoma City, Oklahoma; Dr. Gilson, formerly with the Naval Aero-
space Medical Research Laboratory, is now with the Departments of Aviation
and Psychology, The Ohio State University, Columbus, Ohio; and Dr. Guedry
is from the Naval Aerospace Medical Research Laboratory, Pensacola,
Florida.

The assistance of Gene Turnipseed and Joel Norman in the conduct of
the study; of Dr. Delbert Lacefield, Rob Holmes, Pat Roberts, and Curtis
Blossom in the collection and analysis of the blood samples; and of Edna
Highsmith, Dave Gripka, Carlyn Conrad, and RuthAnn Parvin in the scor-
ing of the tracings is gratefully acknowledged.





907 STATIC TRACKING

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PRE 1 2 3 4

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sot
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eo
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ae ae
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40r
(Y AXIS) VERTICAL @——#
30f- (2 AXIS) HORIZONTAL 0-~0
4, L i 1 4
PRE ! 2 3 4

HOURS AFTER ORINKING

Figure 8. Static and dynamic tracking error by alcohol subjects during each session of Y- and Z-axis stimulation.

decrease in nystagmic activity and in tracking
error for each post-drinking session based on the
pre-drinking level for each group and each con-
dition.

Nystagmus. There was little evidence of any
alcohol effect under “dark” conditions. Nystag-
mus changed very little under either Y- or Z-axis
stimulation and no difference between the two
groups in ocular output was statistically signifi-
cant at any session for corresponding axes of
oscillation (see Figure 11). However, under the
“light” (tracking) condition there was a general
pre- to post-drinking decline in nystagmic activ-
ity for the control group while the alcohol sub-
jects evidenced sharp increases in eye velocity
(Figure 11). The changes in eye velocity (trom
the pre-drinking level) which were obtained
during the “light” sessions conducted one and
two hours after drinking were significantly
higher for the alcohol group (p<.001 and
p<.05, respectively) than those noted for the
control group, for both axes of stimulation.

Tracking Error. Pre- to post-drinking changes
in static and dynamic tracking error, expressed
in percentages for both the alcohol and control
groups, are presented in Figure 12, While the
alcohol group evidenced slight post-drinking in-
creases in static tracking error for both the Y
and Z axes, the control group generally evidenced
slight declines. None of these pre- to post-
drinking changes in static performance between
the two groups was significant for the right-side-
down position; however, similar comparisons for

the upright position were significant one and
four hours after drinking (p<.05).

Changes in dynamic tracking error (Figure
12) generally reflect changes observed in the
slow-phase velocity of the eye movements (Figure
11). While the alcohol group evidenced pre- to
post-drinking increases in dynamic tracking error
for both axes of oscillation, the control group
evidenced declines. Statistical comparisons of
the differences in dynamic tracking performance
between the alcohol and control groups were sig-
nificant, for both the Y and Z axes, at the testing
sessions conducted one (p<.001 and p<.01, re-
spectively) and two (p<.01 and p<.05, respec-
tively) hours after alcohol ingestion.

General Comment

Evidence from this study concerning alcohol
effects on eye-hand coordination in the absence
of whole-body motion was inconclusive. Only
in the upright position, one and four hours after
drinking (but not two hours after drinking),
was the increase in tracking error for the alcohol
group significantly greater than that of the con-
trol group. These findings of minimal, incon-
sistent or nonsignificant effects of alcohol on
static tracking error agree with earlier findings.* *

The consistent differences obtained in this and
our previous studies?+ regarding dynamic track-
ing performance following drinking can be at-
tributed to an impairment in vision. Since
alcohol ingestion apparently interferes with the