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
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.
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