Psychopharmacology (2001) 154:61–69DOI 10.1007/s002130000603
Tilman Schulte · Eva M. Müller-Oehring Hans Strasburger · Heinz Warzel · Bernhard A. Sabel
Acute effects of alcohol on divided and covert attention in men
Received: 10 May 2000 / Accepted: 2 October 2000 / Published online: 21 December 2000 Springer-Verlag 2000
Abstract Rationale: While several studies identified
altered visual perceptual performance after alcohol
divided attention to be sensitive to alcohol effects, the
ingestion. Furthermore, differences between the right
impact of alcohol on covert visual attention is still not
and left visual field in the cued target-detection task
clear, despite the latter’s important role in perception.
indicate that alcohol exerts an influence on right-
Objectives: The study tests the effect of acute moderate
doses of alcohol on divided and covert attention in right-handed, male volunteers. Methods: The design of the
Keywords Alcohol · Covert attention ·
study involved a double-blind trial with an alcohol and a
placebo condition; measurements were taken before andafter an oral dose of 0.6 g/kg alcohol versus placebo. Inthe divided-attention task, simultaneous visuo-spatial
and auditory stimulation was applied. In a test of covertattention, subjects had to shift their attentional focus
Even though every-day experience alerts us to the detri-
according to a central cue, from one location in the visual
mental effect of alcohol on attention, the precise effect is
field to another. Results: Under the divided-attention
puzzling. Results from scientific experiments suggest
condition, reaction times were significantly prolonged
different effects depending upon the subtype of attention
after alcohol ingestion compared to placebo. Covert
(Koelega 1995). It is well known that divided-attention
attention pre-post change was also significantly different
tasks are highly sensitive to the effects of alcohol (Landauer
between the alcohol and placebo groups. There is a
and Howat 1983; Moskowitz and Robinson 1987;
reduction of false-cueing disturbance for left-appearing
Roehrs et al. 1994). A deterioration in performance is
stimuli under moderate alcohol but an increase of distur-
seen when two tasks are performed together, compared
bance for rightward stimuli, i.e. we found a lateralised
to when they are performed singly (Perry and Hodges
pattern of reaction for spatial orienting. In the placebo
1999). Road accident data suggest a close relationship
group, no significant differences in right-left perfor-
between alcohol and attention performance (Buser et al.
mance were obtained. Conclusion: The results suggest
1996; Voas et al. 2000). Johnson (1982) proposes a link
that sensory-attentional mechanisms play a key role in
between alcohol-related crashes in curves during auto-mobile driving and divided attention. In contrast, Linnoila(1974) and Fagan et al. (1987) report that alcohol does
T. Schulte · E.M. Müller-Oehring · B.A. Sabel (✉)
not affect vigilance, described as a state of readiness to
detect and respond to unpredictable and rare events
Otto-von-Guericke University of Magdeburg, Medical Faculty,Leipziger Strasse 44, 39120 Magdeburg, Germany
(Broadbent 1971). Similarly, Miles et al. (1986) note that
e-mail: [email protected]
sustained attention tasks, defined as maintaining attention
Tel.: +49-391-6117100, Fax: +49-391-6117103
to a single source of information for an unbroken period
of time (Parasuraman and Davies 1984), have consistently
failed to reveal alcohol-induced impairments, whereas
Otto-von-Guericke University of Magdeburg,
tasks requiring selective attention, defined as attending
Natural Sciences Faculty, Universitätsplatz 2,
to one source of information and excluding another, do
reveal such impairments. It is possible that divided
attention tasks in general are more sensitive than vigilance
tasks, but there may be some types of vigilance task that
Otto-von-Guericke University of Magdeburg, Medical Faculty,Leipziger Strasse 44, 39120 Magdeburg, Germany
do show alcohol effects (Miles et al. 1986; Rohrbaugh et
Fig. 1 The visual task was to detect a square pattern, formed by four out of eight crosses presented on the computer screen (see the four neighboring X in the target trial). All crosses constantly changed their location within a grid of four by four positions
al. 1988; Horne and Gibbons 1991). From these studies
The purpose of the present study was to evaluate the
it seems that for studying the effects of alcohol it is
influence of acute, moderate alcohol consumption on
useful to draw a distinction between (i) global aspects of
attentional performance using tasks of divided attention
attention, such as arousal or vigilance, (ii) sensory attention
and covert shift of attention. From previous work, the
or selective attention and in particular spatial attention
divided-attention task would be expected to be sensitive
(Post et al. 1996), and (iii) the ability to divide attention
to alcohol consumption. Our present interest was therefore
between different sensory modalities (Maylor et al. 1990;
to determine whether this would also be the case with
moderate doses. The effects of alcohol on covert shift of
To emphasise the difference between a shift of spatial
attention have not been previously studied.
attention by eye movements versus internal movement ofa focus of attention (the so-called spotlight of attention),Posner (1980) has coined the distinction between overt
and covert attention. Covert attention has been mostlyinvestigated using location-cueing tasks, in which a spatial
We studied 46 right-handed male volunteers (mean age 28.5±3.94
cue presented in advance of the target directs the partici-
years). Subjects were recruited via newspaper advertisements and
pant’s attention to a location while fixation remains
were paid for their participation. All were healthy as shown byphysical examination and none had a history of alcohol or drug
steady at another location. The impact of alcohol on
abuse. Prior to being accepted, potential volunteers completed a
covert attention has still not been studied, despite the
questionnaire on their habits of alcohol consumption and biological
concept’s important role in visual perception (Heinze et
markers of consumption were measured. Written informed consent
al. 1994; Desimone and Duncan 1995; Woldorff et al. 1999).
was obtained from all participants and the study was approved bythe local ethics committee. Subjects were instructed to stay abstinent
To understand how alcohol influences attentional pro-
from alcohol for 1 day before testing. The experiment was
cesses, it is of interest to determine the brain structures
performed at the same time of day for each subject and at least 2 h
involved in this process. Ethanol may potentiate the
after the last meal, to minimise the effect of circadian cycle on
action of endogenous GABA by increasing the sensitivity
cognitive performance (Babkoff et al. 1991).
of a specific GABA receptor subunit. Frye and Breese
(1982) demonstrated that GABA agonists can enhance
ethanol-induced sedation. Robinson and Petersen (1992)showed effects of chemically induced unilateral deacti-
Two different types of attention were measured with computerised
vation of the pulvinar dorsomedial region (PDM) on
standardised attention tasks (TAP, Test battery of attention;Zimmermann and Fimm 1994). Subjects were seated in a darkened
spatial cueing task in monkeys. When muscimol, a GABA
room in front of a 14” computer screen at a viewing distance of
agonist, was injected in that region of the thalamus, the
monkey had difficulties shifting its attention to the
The divided attention task measures the ability to divide attention
contralateral visual field. In contrast, when bicuculine, a
between two sensory modalities (dual task performance), herevisuo-spatial and auditory stimulation. The visual task was to
GABA antagonist, was injected, the monkey could shift
detect a square pattern, consisting of four out of eight crosses
its attention more easily to the contralateral visual field.
presented on the computer screen. All crosses constantly changed
The allocation of spatial attention is further controlled by
their location within a grid of four by four positions (see Fig. 1).
parietal brain structures (Posner et al. 1984; Rafal and
In the auditory task, two tones alternated, and the subject had todetect irregularities in this two-tone sequence. To ensure correct
Posner 1987; Cohen et al. 1994). Specifically, there is
single task performance, subjects had to perform a probe trial for
considerable evidence for a predominance of the right
each task. In the following test, 100 visual and 200 auditory stimuli
hemisphere for this attentional shift (Ladavas et al.
were presented simultaneously. Reaction times, misses, anticipations
1989). In an fMRI study, Levin et al. (1998) showed that
the right hemispheric predominance of activation in
In the covert shift of attention task (Posner 1980), subjects had
to shift their attentional focus according to a cue that appeared
response to visual stimulation by a diffuse flash was
before each stimulus presentation. Maintaining fixation to a central
fixation cross was controlled visually by the experimenter who,
Table 1 Baseline characteristics of the subject groups. BMI Body-
(normal range in parentheses): CDT carbohydrate-deficient trans-
mass index; the d2 (Brickenkamp 1994) was used to assess the
ferrin; MCV mean corpuscular volume; GGT gamma glutamyl
capacity for concentration and the number of correctly identified
transferase. Significance level is at P<0.05
elements (GZ-F); Drinks/w drinks per week; biological markers
Table 2 Results of divided-attention task (error rate and reaction time (RT); group means of median and SEM). Statistical test: Mann- Whitney U-test
online, excluded trials contaminated by eye movements. The atten-
blood-alcohol readings. The experiment was double-blind because
tional shift was manipulated by a central arrow cue which, in the
neither the experimenter, who conducted the attention tests, nor
cue-valid cases, indicated the position (left or right) of the target
the subjects were informed about the mixture of the drink.
stimulus. In 20% of the trials, the target appeared at the opposite,unattended side (cue-invalid cases). The subject was asked to react,as fast as possible, by pressing a button upon appearance of the
target stimulus. Normally, the reaction time to a visual target isfaster when attention is shifted to the location of the target by valid
Non-parametric statistics were used (since raw RTs are not
cue compared to when the cue misdirects attention (invalid cue).
normally distributed and there are only 23 subjects per group).
The difference in reaction time between valid and invalid cue con-
The results of the divided-attention task were analysed using the
ditions is referred to as the validity effect, an index of costs and
Mann-Whitney U-test and of the covert shift-of-attention task by
benefits of spatial orienting (Posner 1980; Davidson et al. 1999).
the Wilcoxon test. To explore interaction effects an ANOVA wasadditionally applied. The alpha level was set to 0.05 for all statisticaltests (two-tailed) (statistical software: SPSS 8.0).
In order to familiarise all subjects with the attention tasks, 1 week
before the start of the experiment baseline measurements wereobtained with the computer-based standardised attention test battery. The design of the study involved a double-blind trial with an alcohol
The alcohol and the placebo groups were well matched,
and a placebo condition. Measurements were performed before
as seen in Table 1, being not statistically different in age,
and after an oral dose of 0.6 g/kg alcohol (a mix of vodka and
body mass index (BMI), initial performance in a well-
orange juice) versus placebo (orange juice with 2 ml of vodkafloated on the top). Blood alcohol level (BAL) was continuously
established paper-pencil test of selective attention (d2-test;
assessed using a breath-alcohol analyser (AlcoQuant A 3020,
Brickenkamp 1994), or in the amount of alcohol or
EnviteC-Wismar) and venous blood samples. Post-alcohol recording
cigarette consumption. Moreover, the two groups did not
started after BAL had exceeded the maximum of the individual
differ in the blood alcohol markers CDT (carbohydrate
alcohol curve, i.e., when there was no further increase for fourconsecutive measurements. This peak was reached after approxi-
deficient transferrin), MCV (mean corpuscular volume)
mately 30 min. All subjects were examined following the same
and GGT (gamma glutamyl transferase). The mean
time schedule starting at 11 a.m. A first venous blood sample was
breath alcohol concentration was 0.05% at its peak; the
taken at 11 a.m., followed by questionnaires and a standard meal.
blood alcohol level as determined from the venous
At 1 p.m., the pre-alcohol assessment started. Alcohol intake took
samples was slightly higher (0.06% BAC).
place at 2 p.m., the second blood sample was taken at 2.30 p.m. At2.40 p.m. the post-alcohol assessment was carried out. One experi-
The task of divided attention after alcohol ingestion in
menter prepared and handed out the drinks and also took the
comparison to placebo revealed significant effects both
Table 3 Influence of alcohol on the cue-validity effect in the
times (RT) for valid and invalidcue condition (group means of
Influence of alcohol on the cue-validity effect in the
visuo-spatial attention task (Posner paradigm). Lateralised validityeffect (leftward cue valid/rightward cue valid)
34.5±5.1 43.2±5.1 21.3±6.4 56.1±7.4 –13.2±6.6 35.9±6.2 49.5±6.6 28.4±5.6 44.8±7.5 –7.5±5.6 –4.7±6.4
measurement (P<0.0001 in all four cases; Wilcoxonsigned-rank test; Table 3).
To test the effect of alcohol on spatial orienting, the
validity effect (difference of RT between valid-cue andinvalid-cue cases) was computed for both groups. Inneither group was there a significant pre-post change inthe validity effect over all trials. However, when wereanalysed the data separately for the right versus left
Fig. 2a, b Reaction time measurement in divided-attention task.
hemispace (or visual hemifield, respectively), we found
a Group mean±SEM. b Difference between alcohol-group and placebo-group (pre-post difference)
a significantly reduced validity effect for the left visualfield (right cerebral hemisphere) in the alcohol group(P=0.036), but not in the placebo group (Table 4).
in the error rate (P<0.03) and reaction times (P<0.01,
Moreover, we observed such a left-right asymmetry
Mann-Whitney U-test; Table 2). Reaction times decreased
of the validity effect already at pre-measurement
in the placebo group during the auditory task (by
(P<0.05 in the placebo group and a tendency, P=0.094 in
35.6 ms), probably due to increased familiarity with the
the alcohol group), with the asymmetry substantially
task (practice effect), so alcohol effects must be calculated
increased in the post-measurement, for both groups
as difference from the placebo values (see Fig. 2a, b).
(P<0.001 and P<0.003 for the alcohol and the placebo
There is a relative increase in the alcohol group, of
group, respectively; Table 4). In all comparisons, the
40.5 ms in the visual task and of 29.8 ms in the auditory
validity effect to the leftward targets (valid leftward cue
task. Note that the effects were not strong enough to reach
minus invalid rightward cue) is smaller than the one for
significance when the two sensory tasks were considered
the rightward targets. Since we were mainly interested in
alone (P=0.21, P=0.06, visual and auditory, respectively).
whether this asymmetry would be influenced by alcohol,
In the visuo-spatial attention task, reaction times are
we computed the pre-post differences of the validity
generally shorter in the valid-cue than in the invalid-cue
effects and compared those between left and right hemi-
condition. This finding was confirmed here for both the
space. We found further asymmetry in the alcohol
alcohol and placebo group and both for pre- and post-
(P<0.05), but not in the placebo group (P=0.72) (Table 4
Fig. 3 Shift of covert attention: pre-post differences of the validity effects for the right versus left hemispace in both, the alcohol and the placebo group (mean±SEM)
and Fig. 3). To test for a possible effect of response bias
disturbance for rightward stimuli (by 13 ms), i.e. a later-
we analysed the error rate. There was no significant
alised reaction pattern for spatial orienting.
difference in misses, anticipations and false positives in
For further investigation of an effect of side (left/
the pre- (placebo group: 4%; alcohol group: 3% error
right) of spatial orienting under alcohol consumption,
rate) compared to the post- measurement (both groups:
one can compute pre-post differences of the validity
3% error rate), neither in the alcohol nor in the placebo
effects, for the left and right visual field (VF): Conducting
group (both groups: Z=–1.66, P=0.1). From this we
this analysis, i.e. a two-way ANOVA with side as within-
conclude, that the significant side specific pre-post
subject and group as between-subject factor, we again
difference of the validity effect is caused by the experi-
found a significant effect of side [F(1,44)=5.81, P<0.02]
mental condition alcohol (versus placebo) and does not
and a close-to-significant interaction [F(1,44)=3.77,
For better estimation of the effect of alcohol on
spatial selective attention we conducted an omnibusANOVA (independent variables: group (alcohol/placebo),
time (pre/post), side (left/right); dependent variable:validity effect) and refined the model according to our
Our results show that moderate alcohol consumption
hypothesis. The ANOVA revealed a significant effect of
has a significant effect on both divided attention and
the model tested [F(7,176)=3.07, P<0.004] with a signifi-
covert shift of spatial attention. With respect to divided
cant effect of the side variable (left/right) [F(1,176)=16,
attention, our findings confirm previous reports (e.g. P<0.0001]. Because of the overwhelming effect of side,
Moskowitz and Robinson 1987) that divided-attention is
smaller effects could be covered. Thus, analogous to our
impaired by acute, low levels of alcohol. We now
procedure in the non-parametric analysis aiming to test
showed that this is also true for moderate doses of
for differences in the alcohol and in the placebo group,
alcohol: When results are corrected for improvement
we conducted a two-way ANOVA (time, side) for each
through repeated testing (practice effects), our data
group separately. In the placebo group, we found a
showed that subjects were less capable of dividing
significant effect of side [F(1,88)=5.29, P<0.03], and in
attention under the influence of moderate alcohol doses.
the alcohol group we also found a significant effect of
In particular, error rates increased significantly in the
side [F(1,88)=11.22, P<0.01] and, additionally, a significant
interaction [F(1,88)=4.01, P<0.048]. Thus, the results
In light of the global-slowing hypothesis (Maylor and
from parametric statistics confirm the results from non-
Rabbitt 1993), it can be questioned whether effects of
alcohol on human performance are specific to a process
Whereas under placebo conditions the validity effect
or more general, processing of all tasks being affected
is slightly reduced during the course of the experiment
by reduced cognitive resources. The global-slowing
(by 7.5 and 4.7 ms), alcohol induces a more pronounced
hypothesis assumes that the longer a process takes without
decrease of the validity effect for the leftward-valid cues
alcohol, the more it will be slowed by alcohol (Ryan et
but leads to an increased validity effect for rightward-
al. 1996). In our study, the overall longer RTs in the
valid cues. Thus, under the influence of moderate alcohol
divided attention task indicate that it was more difficult
there is a reduction of false-cueing disturbance for left-
than the selective spatial attention task, so that the
appearing stimuli (by –13.2 ms) but an increase of
global-slowing hypothesis would predict a higher slowing
of RTs in the divided attention task. We did, in fact, find
some similarity with the neglect syndrome, wherein
a clear alcohol effect in the divided attention task, but we
patients fail to recognise the presence of objects presented
also found a side-specific alcohol effect in the selective
in their contralesional hemispace (Marshall and Halligan
spatial attention task (with short RTs). Moreover, in
1994). Neglect predominantly occurs in the left hemi-
detailed analyses of the divided-attention performance,
space (after damage of the right hemisphere), suggesting
alcohol significantly affected the auditory domain (with
a major right-hemispheric influence on spatial attentional
shorter RTs) whereas the changes in the visual domain
processes (DeRenzi 1982). In a PET study Corbetta et
(with longer RTs) did not reach significance. The two
al. (1993) found lateralised parietal processing such that
tasks imposed different demands on attention: The visual
in the right superior parietal lobe, two distinct responses
task was the more complex, and intake of alcohol led to
were localised, attending to the left and to the right
prolonged reaction times whereas a shortening of RTs
visual field (VF) respectively, whereas in the left superior
(after placebo) in the relatively easy auditory task was
parietal lobe no difference in the activated cortical area
prevented by alcohol, thus RTs were only slightly
was seen. Furthermore, attention to the left VF is mostly
reduced (see Table 2). We assume that the attentional
controlled by one region in the right parietal lobe while
interference depends upon task characteristics that
attention to the right VF is controlled more bilaterally,
require either preattentive or attentive mechanisms
by a left parietal and a distinct right parietal region.
(Treisman and Gelade 1980). A break in the alternating
These results correspond with the assumption of visuo-
tone sequence of the auditory task is easy to detect,
spatial attention of Mesulam (1985) and Heilman et al.
“popping out” of the sequence of events might thus
(1985) who proposed that the right parietal lobe orients
invoke preattentive mechanisms. In contrast, performing
attention into both hemifields whereas the left parietal
the visual task seems to require deliberate attentive
lobe directs attention only contralaterally, i.e. that the
mechanisms: During visual search, subjects have to
right VF is doubly presented and the left only singly.
detect four crosses forming the edges of a square, which
Thus, one should have a right-left difference of visuo-
do not “pop out” from the stimulus array. From this we
spatial attention, with a better ability of covert orienting
argue that alcohol impairments in cognitive tasks after
in the right visual field (RVF) resulting in a greater RVF
moderate alcohol consumption (0.6 g/kg body weight)
validity effect because of its bilateral representation. We
originate from limitations on process-specific resources.
indeed found a greater validity effect in the baseline
Presumably, global slowing takes place after higher
conditions for targets in the right than for those in the
left visual field, supporting the theory of Mesulam
Activities like driving an automobile and simulta-
neously listening to surrounding noise and sounds may
Additionally, it is assumed that both hemispheres
pose similar kinds of combined auditory-visual demands.
interact with each other in a dynamic push-pull fashion
Johnston (1982) assumed that secure driving requires the
to equilibrate the direction of visuo-spatial attention
ability of dividing attention, e.g. of continuously tracking
(Kinsbourne 1977; Kinsbourne aand Bruce 1987; Reuter-
the curve path while assessing the degree of curvature to
Lorenz et al. 1990). In this activation-orienting model it
adjust driving speed. Maylor et al. (1990) found that the
is postulated that attention in space is biased in the direc-
effects of both alcohol and practice on speed of detection
tion contralateral to the more activated hemisphere.
were significantly greater under dual-task than under
Differences of covert orienting between hemifields result
single-task conditions. Under alcohol, performance is
from the interaction of the two hemispheres, i.e. a
impaired although the underlying mechanisms are not
dynamic balance achieved by reciprocal inhibitory pro-
yet clear. From several studies it appears that the visual
cesses. In attentional orienting, rivalry may take place
modality is not more affected by alcohol than the auditory
between the two hemispheres. In that model alcohol may
domain, indicating that central factors are involved
lead to a reduction in the right-hemispheric predominance
(see Koelega 1995, for review). Neuroimaging studies
of activation in response to visual stimulation (Levin
suggest that the dorsolateral prefrontal cortex and the
et al. 1998) or to an attenuation of the right-over-left
anterior cingulate gyrus are involved in tasks of divided
attention (Posner and DiGirolamo 1999).
The model of Mesulam (1985), in accordance with
With regard to results of previous studies, our findings
the PET results of Corbetta et al. (1993) and our behav-
concerning spatial attention are unexpected. Post et al.
ioural data, argue for a double bilateral presentation of
(1996) suggested that alcohol impairs performance in
the RVF and a single contralateral presentation of the
tasks that place demands on visual spatial attention, but
LVF. As in the model of Kinsbourne (1977; Kinsbourne
we found no effect on the spatial shift of attention when
and Bruce 1987), both hemispheres encode the contralat-
we compared the pre and post measurement (see
eral VF. In combination of the two models we conclude
Table 3). We did find an effect, however, when we
from our results, that alcohol might affect the interhemi-
compared hemispheres, uncovering a lateralised influence
spheric balance resulting in a reduction of validity
of alcohol upon spatial attention (see Table 4). The
effects, i.e. the ability of covert orienting. Because the
leftward decrease and rightward increase of the validity
right hemisphere additionally encodes the ipsilesional
effect can be interpreted as reduced leftward and
VF, the validity effect in the RVF was enhanced in con-
improved rightward spatial orienting. The effect bears
trast to the validity effect in the LVF, which was reduced.
In the literature there is no clear explanation of how
mechanisms. Egly et al. (1994) found in patients with
exactly the influence of alcohol affects visuo-spatial
left-hemispheric lesions that the deficit of disengage-
selective attention and why an effect could be lateralised.
ment occurred only for shifts between attended objects
However, a number of findings may provide a working
from the ipsilesional to the contralesional field and not
model through the mediation of GABA and its influence
during within-object shifts. This right-left hemisphere
on the brain structures involved. In recent pharmacological
asymmetry in the shift of attention between and within
studies, Witte and others investigated the effect of
objects was confirmed in a commissurotomised patient
clonidine, an α adrenoceptor agonist that stimulates
with disconnected neocortices (Egly et al. 1994). One
endogenous GABA release, on cue-target detection tasks
could test whether alcohol consumption affects shifting
(CTD) in rhesus monkeys (Witte et al. 1992, 1997;
of attention between visual-field locations only, assumed
Davidson et al. 1994; Witte and Marocco 1997). They
to be predominantly a right-hemispheric function, or
found no effect on validity effects using low doses of
whether it also affects the shifting of attention between
clonidine but did find an effect on alerting scores. Clark
objects rather than locations, assumedly a left hemi-
et al. (1989), though, found somewhat differing results in
spheric function. Coull and Nobre (1998) found that
humans. Clonidine affected the validity effect (valid
visuo-spatial selective attention is lateralised with a
RTs–invalid RTs) by decreasing response cost (invalid
dominance of the right hemisphere whereas tasks
RTs–neutral RTs) with no change in response benefit
concerning temporal selective attention are found to be
associated with left hemispheric processing. Another
Clonidine stimulates the release of endogenous
concept is that of the local/global dichotomy. Robertson
GABA in rat cerebral cortex and the release of GABA
et al. (1988) for example found, in patients with left-
was found to be region specific. It was pronounced in the
versus right-sided parietal lesions, an asymmetry in
parietal and frontal cortex (Pittaluga and Raitieri 1988),
their ability to focus attention on global versus local
i.e., main structures involved in attentional processing.
pattern characteristics (Navon patterns), with the right-
Ethanol in turn seems to potentiate the action of endoge-
parietal lesioned patients missing the global aspects and
nous GABA by increasing the sensitivity of the GABA
left-parietal lesioned missing the local aspects. Yamguchi
receptor subunit (in rats: Criswell et al. 1993; Soldo et
et al. (2000) confirmed the above results providing an
al. 1994). Alcohol may thus act on the parietal cortex
asymmetrical basis for the allocation of attention to
by increasing GABA-receptor sensitivity and on the
global and local features in a study using event-related
behavioural side by decreasing spatial-attentional
In summary, we have demonstrated that, following
The cognitive act of shifting attention from one posi-
ingestion of a moderate amount of alcohol in tasks of
tion in the visual field to another has been conceptualised
divided and covert attention, performance is impaired.
as composed of three mental operations (Posner and
Our data indicate that the way alcohol influences
Petersen 1990), each being associated with a different
attentional performance depends upon task characteris-
brain region: disengagement of attention from its current
tics. To our surprise, alcohol did not simply decrease
focus (parietal cortex), moving attention to the target
attentional performance in a task of covert attention but
(superior colliculus), and (re-)engagement of attention at
had a lateralised effect, presumably having a neuronal
the target (lateral pulvinar of the thalamus) (see Ward
base in the different roles of right versus left parietal
and Brown 1996). Robinson and Petersen (1992) provide
lobes processing visuo-spatial information. Thus, alco-
data on the influence of GABA on the pulvinar. When
hol seems to have a predominant and specific influence
one side of the pulvinar is temporarily deactivated by
on attentional priming in the right hemisphere of the
injecting the GABA-agonist muscimol in the awake,
behaving rhesus monkey, the animal can no longer properlyengage attention in the contralateral field. Frontal cortex,
Acknowledgements This research was supported by a grant from the Cultural Ministry of Sachsen-Anhalt, Germany. A preliminary
parietal cortex and the pulvinar are the main parts of a
report of the data was presented at the Annual Meeting of the
complex network of spatial attention (La Berge 1983), in
Society for Neuroscience, Miami Beach, Florida, October 1999.
which a change in one structure will affect the whole
We would like to thank Elke Berger, Ulrike Bunzenthal and Ute
network. Whereas the pulvinar is probably not lateralised
Hopstock for technical assistance and data acquisition, Dr. Sabine
(subserving the respective contralateral visual field), the
Westphal and Dr. Jutta Dierkes for the measurement of bloodparameters, and Dorothe Poggel for comments on the manuscript.
parietal cortex certainly is (as can be seen from thepredominance of left-field neglect) even though the preciserole separation between left and right parietal cortex is
still under debate. The difference that we found betweenvisual fields in the cued target-detection task might thus
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