〔958〕AcuteEffectsof Alcohol
Assessed

Katsuyuki

by Auditory

Murata,Department

on Cognitive

ShunichiAraki,

Functionand Central

Nervous

Event-Related

Potentials

TakeshiandTanigawa

Eiichi

SystemUchidaof Public Health, Faculty of Medicine, University of Tokyo, Tokyo

Introduction
Alcoholsbepotentarecentralwidelynervousused

as cleaningsystemagents,depressants

andthinners

andirritants

1〜3);

for
for

drinking.
that

They

reason,

it

are
mint

also

known
be

to

difficultto distinguish the influence on the central nervous system function of alcohol from that of other chemical
agents, in particular, among solvent-workers.
International review bodies have recommended that
increased research be directed toward objective evaluation of central nervous system dysfunctions inpersons exposed to organic solvents including alcohols4,5).
The effects of alcohol on latencies of cerebral evoked potentials (EP) originating from the peripherallevel of the sensory system remain less clear, although EP amplitudes tend to be depressed 6,7) Jensen
and Krogh observed a significant prolongation in the P200 latency of visual evoked potentials (VEP)
after alcohol intake while the N75, P100 and N145 latencies of VEP did not change8); in addition, asignificant dose-response relationship between ethanol dose and the P300 component of the event-related
potential (ERP)

has

been

reported

by

some

study

groups9〜12).

On

the

other

hand,

Skalkaetalfailedto find significant
changesin latenciesof the VEP after alcohol
ingestion13). Apart fromelectrophysiologicalstudies, Matsunaga
and Mukasa reported that alcohol affected neuropsychological
functions such as memory and attention
14). On the basis of these findings, the EPs with a long latencyreflecting higher nervous system functions would be expected to be more sensitive for detection of acuteeffects of alcohol than those with a relatively
short latency.

The EP or ERP technique offers a profitable approach for assessing the level of brain functioning
as it permits the concurrent investigation of electrophysiology and cognition. In particular, ERPs canbe obtained in conjunction with behavior, or even when no behavioral response is required; they canbe recorded for both attended and unattended stimuli 15). Thus, the ERP method is considered to bea very sensitive index of the functional integrity of the brain. In the present study, six latencies of theauditory ERP were determined in healthy volunteers to clarify which sites of the central nervous system
are influenced by acute administrationof alcohol at an early stage.
Materials

andMethods

1. Subjects
The subjects consisted of 13 healthy male medical students, aged 20 to 26 (mean 23) years; theyconsented readily to become volunteers for this study. All these subjects had a history of alcohol-induced
facial flushing. They drank alcohol equivalent to 0-450 (mean 100) ml of 100%ethanol per week. They
were not occupationally exposed to neurotoxic substances such as lead or organic solvents, and had
never suffered from neurologic, psychiatric or endocrinological disorders. None of them took drugs,
alcohol, cigarettes or other beverages containing caffeine in the afternoon of the examination day.
2. Study

designERP testing was conducted by ingesting 200ml of Japanese spirits (containing 25%ethanol) at
4:50-5:00p.m.;latencies were measured in the same subject at 4:30-4:45p.m.,
at 6:00-6:15p.m.
and at 7:00-7:15p.m.
(i. e., before and 1-hr and 2-hr after ethanol ingestion), for a total of threetimes on the same day. In addition, the ERP testing was done again in the same manner by ingesting

Vol.

200ml

of wateron anotherday for reference

47,

No.

5, December

to circadian

〔959〕

1992

rhythmwithinthe same

time

period,4:30-7:00

p.m.
3. Electrophysiologicalstudy

The auditory ERP was measured by the use of a Medelec MS-92 two channel electromyograph,Medelec ST-10 stimulator and Apple IIe microcomputer in an electrically shielded room. Measurementof the ERP was conducted using a method with the target-selection(i. e. odd-ball) paradigm 16,17),The subject was presented with a random sequence of two distinguishable stimuli; 80 percent of 300
tone bursts of 20 msec duration (rise/fall time, 6 msec) had a frequency of 1000Hz (non-target tone
stimuli) and 20 percent had a frequency of 2000Hz (target tone stimuli). These stimuli were deliveredbinaurally via earphones at an intensity of 90dB SPL and a rate of 1 tone burst every 2 sec. The subject
was instructed to count only the target tone mentally. In all cases, the reported total of the target
stimuli was correct within 3 stimuli of the actual total presented. Cerebral responses to the two stimuli
were recorded at the vertex (Cz) of a 10-20 system and the linked mastoids, and averaged separately(bandpass, 2-100Hz); then the negative (N100) -positive (P165) -negative (N200) -positive (P300)
complex elicited by the target tone and the negative (N100) -positive (P200) complex by the non-target
tone were recorded as shown in Fig. 1. The daily variations (coefficients of variation) in these latencies
in a 32-year-old male subject for 14 days were between 3.2% and 5.8%.
The ERP components are considered to be as follows 15,16):among components elicited by the target
tone, the N100 is enhanced when attention is directed to the sensory channel in which the stimulus occurs.
The P165 and N200 are associated with processes that underlie signal identification and response selection.
The P300 component is elicited only in circumstances where the subject is required to distinguish one
stimulus (target tone) from a group of other stimuli (non-target tone). The P300 latency corresponds
to the evaluation time of target stimuli; when the task is difficult, the latency becomes longer. Thus,
P300 seems to reflect cognitive function in humans; the functional significance of P300 and other ERP
measures is generally inferred from the behavioral data since the physiological substrate of "cognitive"
potentials is unknown. On the other hand, the response to the non-target tone consists of a series ofwaves (i. e. N100 and P200) that relate to an auditory stimulus.
4. Statistical

Analysis

The Bonferroni multiple comparison method was used to determine the significance levels of repeatedmeasurements in latencies of the ERP on the same day, and of matched differences between tests conductedat the same time on two different days18). The relationships between the change in each latency anddose of ethanol per body weight were tested by Pearson's product moment correlation coefficient. Allanalyses were performed using the Statistical Packages for the Biosciences (SPBS, Uni-Science Co.).

Fig.

1 Waveforms of auditory event-related
potentials recorded
from the vertex following stimulationof ears by target andnon-target
tones

〔960〕

JAPANESEJOURNALOF HYGIENE

Results

Table 1 shows ERP latencies before and after ingestion of alcohol and water in 13 male subjects.
The latency of P300 elicited by the target tone at 1-hr and 2-hr after alcohol ingestion was significantly
longer than that prior to alcohol ingestion, and than the latency measured at the same time on anotherday when water was administered to the subjects. The N200 latency at 2-hr after alcohol ingestion was
also significantly prolonged as compared with that before drinking alcohol. The change in P300 latency
observed between before and 2-hr after alcohol ingestion was significantly correlated with the doseof ethanol per body weight in the 13 subjects (Fig. 2), while no change in other latencies was correlated(p>0.05).
Discussion

The major results in this study were that P300 latency, as well as N200 latency, were significantly
prolonged in subjects with alcohol-induced facial flushing after ethanol ingestion of 0.54-0.74g/kg
body weight (BW); the change in P300 latency was significantly correlated with ethanol dose per BW.
Therefore, it is suggested that P300 latency is the most sensitive indicator for assessing acute ethanol
effects among ERP components with latencies between 100 and 500 msec.
Maximally prolonged latencies of P300 and N200 were found at 2-hr after drinking stopped in thepresent study; while, blood ethanol concentration and the change in heart rate variability have beenreported to reach peaks at 30-60 min8,19)and at 30-90 min20) after intake, respectively. The effect of
ethanol on P300 latency related to cognition of higher nervous functions, agrees with the results of
otherinvestigations8,10〜12),

Acute

Table 1ethanol

Latencies

of

meet)

before

and

in 13

male

intoxication

also

auditory

event‑related

1‑hr

2‑hr

and

after

causesimpairment

potentials
alcoholin(mean±SD,or wateringestionsubjects

a,bp<0 .05 and c,d,ep<0.01(the Bonferroni multiple comparison
method was used to determine the significance levels of repeatedmeasurementson the same day,and of matched differences between
tests conducted at the same time on two different days).

storageofextremely

Vol.

47, No.

5, December

1992

〔961〕

Fig. 2 Relationshipbetween 2-hr alterationin the P300 latency
due to alcohol ingestion and dose of ethanol per body weightin 13 male subjects.
r indicates Pearson's product moment correlation
coefficient

short-term memory process in Benton's visual retention test 14). On the other hand, Genkina observedthat the amplitude of the P300 wave decreased significantly after ingestion of an ethanol dose of 0.82
g/kg BW despite the absence of any significant change in an ethanol concentration of 0.41g/kg BW
by means of the visual ERP9). Also, Teo and Ferguson indicated that prolongation of P300 latency
with increased ethanol doses was in a dose-dependent manner10, as shown in Fig. 2. Thus, it is concluded
that ethanol, in proportion to its dose, affects the higher nervous functions, including cognition, at
a relatively early stage.
No ethanol-induced prolongation in latencies of less than 200 msec was seen in the current study.
A similar finding has been reported by three previous studies8,13,21), in which VEP latencies of morethan 180 msec were significantly prolonged but no slowing of latencies below 180 msec could be found(the ethanol doses were between 0.7 and 1.2g/kg BW). The VEP latencies, elicited by flash stimuli,of 140 msec and above increased after ethanol administration of 1g/kg BW level22). On the other hand,the brainstem auditory evoked potential (BAEP) with a latency of less than only 10 msec is well-known
to be resistant to changes in attention or consciousness and to pharmacologic insults 23); whereas, some"peak" latencies of the BAEP were significantly prolonged after ethanol intake of 1g/kg BW (the authors
did not test the statistical significance of the changes in their "interpeak" latencies)24). In this way,
the relatively short-latency EPs appear to be less affected by ethanol; such EPs might also respondto higher doses as it is likely that all brain loci are ultimately affected by ethanol.
Teo and Ferguson, however, found a significant prolongation in the N100, P165, N200 and P300
latencies of ERP after ethanol intake of 0.54 g/kg BW 10), which is not consistent with our results inregard to the dose and influenced peaks. Two explanations are possible for this disagreement: (1) Whenethanol was administered to the subjects, Teo and Ferguson adulterated it with orange juice and we
did so only with water. For that reason, the absorption rate of ethanol in the stomach and small intestine
might have been different between these two groups. (2) About 50-60%of Orientals exhibit ethanol-induced
facial flushing, but only a few percent do so among Caucasians 25). It has also been reported that f lushers
are deficient in aldehyde dehydrogenase I, which has a low Km value for acetaldehyde26); nevertheless,the alteration of blood ethanol concentrationin flushers was similar to that in non-flushers19).
Accordingly, the above discord may be attributable to the difference in race and genetic predisposition
between Japanese and Australian subjects.
Cellulotoxic studies do not yet offer a comprehensive and consistent interpretation of the effectsof ethanol on electrophysiological processes in single neurons or integrated circuits. There have been
two hypotheses concerning ethanol toxicity: (1) the major effects of ethanol are on synaptic transmission

JAPANESE〔962〕

JOURNALOF HYGIENE

and are cumulative in polysynaptic paths3,27) and (2) the mechanism of action probably involves
interference with ion transport at the cell membrane rather than at synapses 1). The VEP latency has
been considered to be a sensitive indicator of both long- and short-term exposure such as visual fatigue
induced by visual display terminal work28).Thus, latencies of VEP or P300 may be easily affected bychanges in the arousal or cognitive function of the cortex due to visual fatigue or ethanol, inasmuch
as these latencies have many synaptic circuits in the long pathway between the periphery and cortex.
In contrast, latencies of the short-latency somatosensory evoked potentials or BAEP may be resistantto acute effects of ethanol, since they have at most a few synapses. Further study will be required toestablish the cellulo-physiologicalmechanism in alcoholic neurotoxicity.
Finally, long-term brain impairment in chronic alcoholics also has been observed by Ciesielski
et al29), who suggested that cognitive brain potentials (N200 and P300) were more sensitive indicatorsof cerebral impairment than psychometric data. Thus, alcohol is considered to be one of the mostimportant confounders for ERP testing. When long-latency EPs, including ERPs, are measured toevaluate subclinical effects of environmental neurotoxins such as organic solvents, particular attention
should be paid to not only the degree of the daily drinking habit (i. e., its dose, frequency and duration)
but also the interval between the measurement and alcohol intake, together with other confounders(e. g., age) 16), to preserve the comparability of the ERP data between exposed and unexposed groups.
Summary

To clarify which sites of the central nervous system are influenced by acute administration of alcoholat an early stage, auditory event-related potentials (ERP) using a target-selection
paradigm were
measured in 13 healthy volunteers. In the recorded waveforms of ERPs, the N100, P165, N200 and P300
latencies for the target tone and the N100 and P200 latencies for the non-target tone were determinedin each subject before and 1- and 2-hr after ingestion of 200ml of alcohol (containing 25%ethanol)
or of 200ml of water, for a total of six times on two different days. The P300 latency was significantly
prolonged at 1- and 2-hr after alcohol ingestion; and, the N200 latency was significantly prolonged
at 2-hr after alcohol ingestion. The 2-hr alteration in the P300 latency after alcohol ingestion was
positively correlated with the ethanol dose per body weight. These data suggest that ethanol, in proportion
to its dose, affects cognitive function estimated by the P300 latency earlier than other lower central
nervous system functions. Evaluating subclinical effects on central nervous function, using the ERPs,
of environmental neurotoxins such as organic solvents, researchers should pay particular attention
not only to the degree of the drinking habit but also to the interval between the measurement and alcohol
intake.
Requests
University

for reprintsof Tokyo,should7-3-1

be sent to:
Hongo,Prof.

S. Araki,

Bunkyo-ku,

Department

Tokyoof Public

Health,Facultyof Medicine,

113.

References

1) Ellenhorn, M. J. and Barceloux, D. G.: Medical Toxicology, pp.782-797, Elsevier, New York(1988).
2) LaDou, J.: Occupational Medicine, Aplleton & Lange, Norwalk (1990).
3) Rall, T. W.: Hypnotics and sedatives: ethanol, in "Goodman and Gilman's The Pharmacological
Basis of Therapeutics, 8th Edn"(eds.:
A. G. Gilman, T. W. Rail, A. S. Nies and P. Taylor),
pp.1345-1385, Pergamon Press, New York (1990).
4) NIOSH.: Organic Solvent Neurotoxicity (Current Intelligence Bulletin 48), U. S. Department of
Health and Human Services, Cincinnati (1987).
5) Agency for Toxic Substances and Disease Registry: Toxicological Profile for Toluene, U. S.
Department of Health and Human Services, Atlanta (1989).
6) Porjesz, B. and Begleiter, H.: Human evoked potentials and alcohol, Alcoholism Clin. Exp. Res.,5, 304-317 (1981).

Vol.

47, No.

5, December

1992

〔963〕

7 ) Campbell, K. B. and Lowick, B. M.: Ethanol and event-related potentials: the influence of distractor
stimuli, Alcohol, 4, 257-263 (1987).
8 ) Jensen, O. L. and Krogh, E.: Visual evoked response and alcohol intoxication, Acta Ophthalmol.,62, 651-657 (1984).
9 ) Genkina, O. A.: Effect of alcohol on evoked electrical activity in healthy man, Hum. Physiol.,
10, 189-192 (1984).
10) Teo, R. K. C. and Ferguson, D. A.: The acute effects of ethanol on auditory event-related potentials,
Psychopharmacology,
90, 179-184 (1986).
11) Oscar-Berman,
M.: Alcohol-related ERP changes in cognition, Alcohol, 4, 289-292 (1987).
12) Rohrbaugh, J. W., Stapleton, J. M., Parasuraman,R., Zubovic, E.A., Frowein, H. W.,
Varner, J. L., Adinof,f, B., Lane, E. A., Eckardt, M. J. and Linnoila, M.: Dose-related effectsof ethanol on visual sustained attention and event-related potentials, Alcohol, 4, 293-300 (1987).
13) Skalka, H. W., Helms, H. and Holman, J.: Effects of ethyl alcohol on VECP, Doc. Ophthalmol.,62, 47-51 (1986).
14) Matsunaga, K. and Mukasa, H.: The effect of alcohol on the human memory, Jpn. J. Alcohol
Drug Depend., 21, 64-73 (1986). (in Japanese with English abstract)
15) Picton, T. W. and Stuss, D. T.: The component structure of the human event-related potentials,
in "Motivation, Motor and Sensory Processes of the Brain: Electrical Potentials, Behaviour andClinical Use (Prog. Brain Res. Vol. 54)" (eds.: H. H. Kornhuber and L. Deecke), pp.17-49, Elsevier,
Amsterdam (1980).
16) Goodin, D. S.: Event-related (endogenous) potentials, in "Electrodiagnosis in Clinical Neurology,
2nd Edn" (ed.: M. J. Aminoff), pp.575-595, Churchill Livingstone, New York (1986).
17) Araki, S., Murata, K., Yokoyama, K. and Uchida, E.: Auditory event-related potential (P300)
in relation to peripheral nerve conduction in workers exposed to lead, zinc, and copper: effectsof lead on cognitive function and central nervous system, Am. J. Ind. Med., 21, 539-547 (1992).
18) Morrison, D. F.: Multivariate Statistical Methods, pp. 128-169, McGraw-Hill, New York (1976).
19) Tanaka, T. and Mukasa, H.: The individual differences in responses after alcohol ingestion, Jpn.
J. Alcohol Drug Depend., 20, 375-387 (1985). (in Japanese with English abstract)20) Weise, F., Krell, D. and Brinkhoff, N.: Acute alcohol ingestion reduces heart rate variability,
Drug Alcohol Depend., 17, 89-91 (1986).
21) Erwin, C. W. and Linnoila, M.: Effect of ethyl alcohol on visual evoked potentials, Alcoholism
Clin. Exp. Res., 5, 49-55 (1981).
22) Zuzewicz, W.: Ethyl alcohol effect on the visual evoked potential, Acta Physiol. Pol., 32, 93-98(1981).
23) Stockard, J. J., Stockard, J. E. and Sharbrough, F. W.: Brainstem auditory evoked potentials
in neurology: methodology, interpretation, and clinical application, in "Electrodiagnosis in Clinical
Neurology, 2nd Edn" (ed.: M. J. Aminoff), pp.467-503, Churchill Livingstone, New York (1986).
24) Church, M. W. and Williams, H. L.: Dose- and time-dependent effects of ethanol on brain stem
auditory evoked responses in young adult males, Electroencephalogr.
Clin. Neurophysiol.,54,
161-174 (1982).
25) Kubouchi, H., Suwaki, H. and Ohara, H.: The relationship of the intensity of alcohol-induced
flushing to drinking patterns in Japanese students, Jpn. J. Alcohol Drug Depend., 22, 352-365(1987). (in Japanese with English abstract)
26) Harada, S., Agarwal, D. P., Goedde, H. W., Takagi, S. and Ishikawa, B.: Possible protectiverole against alcoholism for aldehyde dehydrogenase isozyme deficiency in Japan, Lancet, II, 827(1982).
27) Kalant, H. and Woo, N.: Electrophysiological effects of ethanol on the nervous system, Pharmacol.
Ther., 14, 431-457 (1981).
28) Murata, K., Araki, S., Kawakami, N., Saito, Y. and Hino, E.: Central nervous system effects
and visual fatigue in VDT workers, Int. Arch. Occup. Environ. Health, 63, 109-113 (1991).

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JAPANESEJOURNALOF

HYGIENE

29) Ciesielski, K. T., Madden, J. S., Bligh, J. G. and Schopflocher, D.: Long-term brain impairment
in chronic alcoholics: N2-P3 cognitive potentials in a template-matchingmemory task, Alcohol
Alcoholism, 20, 403-408 (1985).
;(Received May 11, 1992/Accepted

September3, 1992)

認知 お よび中枢神経機能 に及 ぼす急性 アル コール摂取 の影響‑聴 性事象 関連電位を用 いた検討‑

村

田

勝

敬,荒

記

俊

一,谷

田

栄

一

内

川

武,

東京大学医学部公衆衛生学教室

急 性 アル コール 摂 取 に よ り中 枢 神経 の どの 部位 が早 期 に影 響 され る かを 明 らか にす るた め,健 常 対 象 者13名 の 目標‑
選 択 課題 を用 い た聴 性事 象 関連 電 位 を測 定 した。 事 象 関連 電位 の記 録 波形 の うち,目 標刺 激 音 に よ って誘 発 され るN100,
P165,N200,P300潜
取 前,摂 取 後1お時 お よび 非 目標刺 激 音 に よるN100,P200潜

時 が,200mlのよび2時 間 に測 定 され た 。 さ らに,こ れ らの潜 時 は200mlのアル コー ル(エ タ ノ ール を25%含 有)の 摂
水 摂 取 前後 で も 同様 に 測 定 され た(各 被検 者 と も2日 間計6回 測定)。
主 な結 果 は 以下 の 通 りで あ った 。
1.P300潜時 は 飲 酒 後1お よ び2時 間 で 有 意 に 延 長 した。N200潜 時 も飲 酒 後2時 間 で 有 意 に延 長 した 。 そ の 他 の潜 時には 有 意 な変 化 が 見 られ な か った 。
2.飲酒後2時 間 のP300潜 時 の 変化 は体 重 当 りの エ タ ノ ール 量 と有意 な正 の 相 関 が あ った 。

3.水

摂 取 に よる事 象 関連 電 位 潜 時 の変 化 は 認 め られ なか った 。

P300潜 時 は 認 知 機 能 を反 映 す る と考 え られ て い る。 従 って,エ タ ノ ール は,そ の 摂 取 量 に 比 例 して,下 位 中枢 神 経系機 能 よ りも早 期 に高 次 中枢 神 経(認 知)機 能 に 影 響 を及 ぼ す こ とが示 唆 され た 。有 機 溶 剤 の よ うな環 境 中 の神 経 毒 性物
質 の中 枢 神経 系 機 能 に 及 ぼす 影 響 を 評価 す る場 合,飲 酒 習 慣 の 程度 だけ で な く測 定 前 の 飲 酒 時刻 に対 して も特 別 の 注意
が払 わ れ るべ きで あ る。

Key words:

Event-related
Cognitive

potentials

function,事 象 関 連 電 位(P300),急(P300),

Confounder,

Acute effectsof ethanol,

Centralnervous

枢 神 経 系,認知 機 能,交

system,Humans性 ア ル コ ー ル 影 響,中絡 因 子,ヒト