Acute Adaptation of Human Cognitive and Motor
Functions to Ethanol
H. M. Franksifb G. A. Starmer and R. K. C. Teo.
INTRODUCTION
It was first noted by M ellanby5 in 1919 that a degree o f adaptation was evident in acute
ethanol intoxication. At any given blood ethanol concentration, im pairm ent was greater when
the ethanol concentration was rising than when it was falling.
Since that time, m any other investigators have also claimed to have shown the phenom ­
enon which is variously referred to as acute tolerance, accom m odation or the ‘Mellanby
effect’. M ethodological deficiencies, however, have precluded absolute proof o f its existence.
Recently, Le Blanc and his co-workers4 dem onstrated unequivocally that adaptation to etha­
nol occurred in rats.
It was considered o f interest, therefore, to attem pt to develop methods o f comparing
the perform ance decrem ents induced by ethanol in tests o f cognitive and m otor functions
and to determ ine the rates o f recovery.
METHOD
Subjects
T he subjects were 100 healthy, paid, male university student volunteers aged between 18
and 25 years. All had mild to m oderate drinking histories (average = 575 m l/day) and were
assigned random ly to one o f five groups (four experim ental and one control). Each group
consisted o f 20 subjects.
Ethanol
Ethanol (800 m g /k g '1) was presented as a 20% v /v solution in lemon squash.
Motor Function Tests
The apparatus used was the M otorische Leistungsserie (Schuhfried, Vienna; Figure 1) and
a num ber o f param eters were measured:
(a) H and steadiness. The subjects were asked to hold a metal stylus (2 mm diameter)
in a 5.8 m m diam eter hole in a vertical workplate w ithout touching the sides. The num ber
o f contacts m ade and the total contact time were recorded.
(b) Re-draw ing lines. The subjects were asked to pass the metal stylus along the track
cut into the w orkplate as quickly as possible but w ithout touching the sides. The num ber
o f contacts m ade, the total contact time and the time taken to complete the task was
recorded.
(c) Plugging. The subjects were required to place twenty-five small brass bolts in holes
in the vertical workplate as quickly as possible. The time taken to complete the task was
recorded.
“Financial support for this project was offered by the Department of Motor Transport, New South
Wales.
bDepartment o f Pharmacology, University o f Sydney, N.S.W.
190
Acute Adaptation o f Human Cognitive and Motor Functions to Ethanol
191
m m m
Figure 1:
Motorische Leistungsserie (Schuhfried, Vienna)
C ognitive Tests
(a) N um erical reasoning (Figure 2). The apparatus used was the A rbeit und K onzentrationtest
G erate (Zak, Simbach am Inn, W est G erm any). The subjects were presented with a series
o f single digit addition and subtraction displays and were required to key in the answers
192
H. M. Franks, G. A. Starmer and R. K. C. Teo
as quickly as possible. A tw o-m inute test period was used and the num ber of correct and
incorrect responses was recorded.
Figure 2:
Work and concentration test apparatus (Zak, Simbach am Inn, West Germany)
(b) Letter sets test (Figure 3). This test was based on the letter grouping test o f Thurstone.6
Each problem in the test has five groups o f four letters. F our o f the groups are alike in
some way and the fifth is different. The subject is asked to find the rule which makes four
o f the groups alike, to strike out the different group and to proceed to the next problem.
A test period o f 2.5 minutes was used and both perform ance and error scores were
recorded.
(c) Inference test. This test was based on the inference test o f G uildford.3 Each problem
in the test (Figure 4) consists o f one or two statem ents which might appear in a newspaper
followed by five possible conclusions which could be drawn from them. The subject is asked,
w ithout assuming any further inform ation, to designate the correct conclusion and to proceed
to the next problem . A three-m inute test period was used and both perform ance and error
scores were recorded.
Blood Ethanol Concentrations
Capillary blood ethanol concentrations were determ ined by gas liquid chrom atography2 and
fingertip blood sam ples were obtained from experim ental subjects when half the tests, which
were adm inistered in random sequence, had been completed.
Acute Adaptation o f Human Cognitive and Motor Functions to Ethanol
193
LETTER SETS TEST
EACH PROBLEM IN THIS TEST HAS FIVE GROUPS OF LETTERS
WITH FOUR LETTERS IN EACH GROUP.
LETTERS ARE ALIKE IN SOME WAY.
FOUR OF THE GROUPS OF
YOU ARE TO FIND THE RULE
THAT MAKES THESE FOUR GROUPS A LIK E.
THE FIFTH GROUP IS
DIFFERENT FROM THEM AND WILL NOT F IT THIS RULE.
DRAW AN
X THROUGH THE GROUP OF LETTERS THAT IS DIFFERENT.
NOTE:
THE RULES WILL NQI BE BASED ON THE SOUNDS OF
GROUPS OF LETTERS., THE SHAPES OF LETTERS/ OR WHETHER
LETTER COMBINATIONS FORM WORDS OR PARTS OF WORDS.
E.G .
A.
NOPQ
DEFL
ABCD
H IJK
UVWX
B.
NLIK
P L IK
QLIK
THIK
V L IK
IN EXAMPLE A , FOUR OF THE GROUPS HAVE LETTERS IN
ALPHABETICAL ORDER.
DEFL.
L.
AN X HAS THEREFORE BEEN DRAWN THROUGH
IN EXAMPLE B , FOUR OF THE GROUPS CONTAIN THE LETTER
THEREFORE, AN X HAS BEEN DRAWN THROUGH THIK.
Figure 3:
Letter sets test (Thurstone, 1962)
P rocedure
The test battery was first adm inistered to each subject who then either received an ethanolic
beverage, which he was instructed to consume at a constant rate over a thirty-m inute period,
or, in the case o f controls, no beverage. Each subject was tested only once thereafter (at
50, 90, 110 or 130 minutes after beginning to drink).
A n a lysis o f R esu lts
The results were analysed in two ways:
(a) By analysis o f co-variance based on the m ethod o f Cochran and C ox1, with the scores
o f the predosage trial serving as the co-variate for those at the later time point.
(b) By analysis o f variance to calculate the rates o f recovery which were com pared by
t-test.
194
H. M. Franks, G. A. Starmer and R. K. C. Teo
INFERENCE TEST
IN EACH ITEM ON THIS TEST YOU WILL BE GIVEN ONE OR TWO
STATEMENTS SUCH AS YOU MIGHT SEE IN NEWSPAPERS OR POPULAR
MAGAZINES.
THE STATEMENTS ARE FOLLOWED BY VARIOUS CONCLUSIONS
WHICH SOME PEOPLE MIGHT DRAW FROM THEM.
If! EACH CASE, DECIDE
WHICH CONCLUSION CAN BE DRAWN FROM THE STATEMENT(S) WITHOUT
ASSUMING.ANYTHING IN ADDITION TO THE INFORMATION GIVEN IN THF
STATEMENT(S).
THERE IS ONLY ONE CORRECT CONCLUSION.
MARK YOUR ANSWER BY PUTTING AN X THROUGH THE NUMBER IN
FRONT OF THE CONCLUSION THAT YOU SELECT.
B IL L , A MEMBER OF THE BASKETBALL TEAM, IS 6 FEET, 2
INCHES TALL AND WEIGHS 195 POUNDS.
TO QUALIFY FOR
THE TEAM, A PERSON MUST BE AT LEAST 5 FEET, 10 INCHES
TALL.
1 - THE LARGER A MAN IS , THE BETTER BASKETBALL
PLAYER HE IS.
2 - BASKETBALL PLAYERS ARE OFTEN UNDERWEIGHT.
3 - SOME PLAYERS ON THE TEAM ARE MORE THAN 6
FEET TALL.
i] - B IL L IS LARGER THAN THE AVERAGE MAN.
5 - THE BEST BASKETBALL PLAYERS COME FROM THE
RANKS OF LARGER-THAN-AVERAGE MEN.
Figure 4:
The inference test (Guildford, 1962)
Acute Adaptation o f Human Cognitive and Motor Functions to Ethanol
195
RESU LTS
B lo o d E th a n o l C oncentration
TABLE I
Mean blood ethanol concentrations (m g /100 m l l) ± s.e.m. attained by male subjects
who received ethanol (800 m g /k g ~!) where (a) a single sample was taken from each
subject and (b) serial samples were taken.
Mean blood ethanol
concentration (m g/100 ml~')
± s.e.m.
50
(a): Only one blood sample
taken (n = 20 at each time
point)
91.5
±
3.5
(b) Serial samples
taken (n = 5)
85.0
±
4.0
Time after beginning to drink (min)
60
70
80
-
-
-
89.9
±
4.0
92.0
±
5.0
90.0
±
4.0
90
110
91.9
±
2.1
74.1
±
2.0
85.0
±
7.0
130
74.0
±
3.0
-
-
-
-
From the data obtained when only one blood sample was taken from each subject, it appeared
that a peak blood ethanol concentration was attained between 50 and 90 minutes after begin­
ning to drink (see Table I). F urther investigations on five o f the same subjects with repeated
sampling located the peak at around 70 minutes. On both occasions, the blood ethanol concen­
trations were essentially similar 50 and 90 m inutes after ethanol adm inistration. It is im portant
to note in all o f these tests that practice and fatigue effects have been elim inated by having
only one pre- and one post-ethanol trial.
M o to r F unction Tests
Table II shows the results o f t-tests carried out to assess the difference in perform ance at
each o f the post-ethanol trials from control values. It can be seen that all the m otor function
tests were very sensitive to ethanol. Calculation o f the rates o f recovery showed that rapid
im provem ent occurred in both measures o f the hand steadiness test (e.g. the rate o f recovery
for the num ber o f contacts, as illustrated in Figure 5). The re-drawing o f lines test, although
very sensitive, was difficult to evaluate in that the faster the subject attem pted to complete
the task, the greater was the num ber o f contacts made. Perhaps it might have been more
appropriate to derive a single score from the product o f all three param eters. The plugging
test was too sensitive for the ethanol dose used and no dem onstrable recovery occurred.
C ognitive F unctio n Tests
Table III has the same form at as Table II and again illustrates the fact that cognitive perform ­
ance is much more resistant to ethanol than m otor perform ance. Significant decrem ents were
only found in the scores for the num erical reasoning test (correct answers) and the letter
sets test (errors). It was only possible to show significant im provem ent with time in the letter
sets (errors) test.
Com parisons o f the rates o f recovery for those tests where significant recovery did occur
indicated that im provem ent in both measures o f the hand steadiness test was significantly
slower (t-test o f the difference between regression slopes, p < 0.01) than in the letter sets
(errors) test.
Table IV shows com parisons o f perform ance at each re-test time for the m otor function
tests. The com parisons at 50 and 90 minutes are the most im portant since the m ean blood
196
H. M. Franks, G. A. Starmer and R. K. C. Teo
ethanol concentrations were virtually identical (Figure 5). It can be seen that a degree of
acute adaptation occurred in both measures o f the hand steadiness test since performance
at 90 m inutes was significantly better than at 50 minutes.
t/>
G
C
o
o
CU
.o
E
D
Time after ethanol (mini
Figure 5:
Hand steadiness test: Comparison o f performance at 50 and 90 minutes in relation to the
blood ethanol concentration
Acute Adaptation o f Human Cognitive and Motor Functions to Ethanol
197
COMPARISON
TEST
'130
vs.
vs.
(B) CONTROL
CONTROL
CONTROL
y • ••
( I I ) TOTAL CONTACT TIME
RE-DRAWING OF LIN ES :
( I ) NUMBER OF CONTACTS
•••
( I I ) TOTAL CONTACT TIME
( I I I ) TASK COMPLETION TIME
PLUGGING:
( I ) COMPLETION TIME
TABLE II:
'90
vs.
t~
t~
•
t***
HAND STEADINESS:
( I ) NUMBER OF CONTACTS
* P < 0.1;
(A) T50
P < 0 .0 5;
t"
Iw««
f
t-
P < 0 .0 1
M otorfunction tests: Results o f t-tests carried out to assess the differences in perform­
ance at each o f the post-ethanol trials from control values.
COMPARISON
TEST
(A) Tso
'90
'130
vs.
vs.
vs.
(B) CONTROL
CONTROL
CONTROL
NUMERICAL REASONING:
(I)
(II)
(
CORRECT ANSWERS
ERRORS
t*
I*
f
LETTER SET TEST:
(I)
(II)
t-
CORRECT ANSWERS
ERRORS
t-
INFERENCE TEST:
(I)
(II)
CORRECT ANSWERS
ERRORS
P < 0.1;
TABLE III:
P < 0 .0 5 ;
P < 0 .0 1
Cognitive function tests: Results o f t-tests carried out to assess the significance
o f differences in performance at each o f the post-ethanol trials from control
values.
198
H. M. Franks, G. A. Starmer and R. K. C. Teo
TABLE IV:
M otor function tests: Results o f t-tests carried out to assess the significance o f
differences M
n p r f n r m n n r p at
nt all
nil re-test
ro-iaei times.
in performance
COMPARISON
TEST
T90
T110
vs .
T130
vs.
T110
T130
V S.
VS.
VS.
t 130
vs.
T50
T50
T50
T90
T90
T110
HAND STEADINESS:
( I ) NUMBER OF CONTACTS
( I I ) TOTAL CONTACT TIME
i ...
j**
|
j ...
j ..
RE-DRAWING OF LIN ES :
( I ) NUMBER OF CONTACTS
( I I ) TOTAL CONTACT TIME
|
( I I I ) TASK COMPLETION TIME
PLUGGING:
(COMPLETION TIM E)
* P < 0 .1 ;
j "
* * P < 0 .0 5 ;
|« *
• * * P < 0. 01
DISCUSSION
The research reported in this paper has illustrated greater ethanol effects on motor than
cognitive functions. As cognitive functions are less likely to be im paired than motor, and
recovery from the effects o f ethanol earlier, drink-drivers are likely to have a false sense
o f security and place themselves at risk o f crash involvement.
O ur results have supported the findings o f M ellanby.5 Performance by subjects with
equivalent blood ethanol concentrations was affected differently according to whether the
level was rising or falling. This raises several interesting legal and practical issues.
It may well be that a driver who drinks after work or recreation is more at risk driving
im m ediately after a few drinks than an hour later with the same blood ethanol concentration
but on a descending blood ethanol curve. Similarly, a driver is more at risk driving im m edi­
ately after a drinking session than the following morning when he may drive to work with
the same blood ethanol concentration but on a descending blood ethanol curve.
Thus, in this pilot study, it was established that:
(a) M otor functions are m ore susceptible to ethanol than intellectual functions.
(b) Even with a peak blood ethanol concentration o f below 100 m g /100 ml 1 the plugging
test was too sensitive to show recovery after 130 minutes.
(c) Intellectual functions recover from ethanol im pairm ent more rapidly than m otor func­
tions.
(d) Acute adaptation between 50 and 90 m inutes was shown in both measures o f the hand
steadiness test.
A more realistic approach, which will be adopted in the future, although it poses severe
logistic difficulties, is to plot perform ance decrem ent against capillary blood ethanol concen­
tration for several doses o f ethanol at a given time point. If this procedure is repeated at
several time points and a shift o f the im pairm ent-blood ethanol concentration curve to the
right occurs, then acute adaptation will have been dem onstrated.
Acute Adaptation o f Human Cognitive and Motor Functions to Ethanol
199
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2.
3.
4.
5.
6.
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between alcohol dosage and performance decrement in human volunteers, Journal o f Studies on
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Guildford, J. P., Inference Test. Educational Testing Service, Australian Council for Educational
Research, Melbourne, 1962.
Le Blanc, A. E., Kalant, H., Gibbins, R. J., Acute tolerance to ethanol in the rat. Psychopharmacologia (Berl.), 41, 43-47, 1975.
Mellanby, E., A Icohol: its absorption into and disappearance from the blood under different conditions.
Special Report Series No. 31 Medical Research Committee, London, 1919.
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