The acute effect of low-dose alcohol on working memory during mental arithmetic: I. Behavioral measures and EEG theta band spectral characteristics
Introduction
The deleterious and dose-dependent effects of alcohol on various cognitive processes such as attention, memory, etc. are well known (Little, 1999, Koob and Moal, 2006). The consequences of long-term use of ethanol were explored in most of the studies revealing deficits in different cognitive mechanisms (Bartholow et al., 2003, and others). In those studies where acute effects of ethanol were investigated typically the effects of relatively large doses were analyzed, i.e. above 0.5 g/kg (Volkow et al., 1988, Stenberg et al., 1994, Nikulin et al., 2005; and others). These observations, however, may not have direct implications on how alcohol interferes with cognitive abilities in more frequently occurring circumstances when the effect of low “social” dosages have to be accounted for. Only in a few studies have the effect of low (below 0.5 g/kg) dosages been investigated showing that various skills are indeed impaired as a result of such alcohol challenges (Kerr et al., 2004, Banks et al., 2004, Jaaskelainen et al., 1999).
In the present investigation the acute effect of low-dose ethanol was studied on cognitive performance and electrophysiological indices in a paradigm where mental arithmetic was required demanding working memory effort. In such tasks the increase of the theta band, presumably corresponding to working memory load is a rather common finding (Harmony et al., 1999, Sammer et al., 2007). The increase of the theta band associated with working memory load is well known (Klimesch, 1999, Klimesch et al., 2008). This theta activation was found to be associated with increased activation of the insular cortex, hippocampus, superior temporal areas, cingulate cortex, superior parietal, and frontal areas representing the involvement of a large neuronal network (Sammer et al., 2007).
Data related to mental arithmetic and alcohol challenge are scarce. The arithmetic task is usually applied as a stress-inducing factor and the effect of ethanol is measured on various indices such as heart rate (Vogel and Netter, 1990; and others) and other indices but less attention is paid to its effect on cognitive performance itself. The detrimental effect of ethanol on working memory, on the other hand, is quite well known (Saults et al., 2007, Pfefferbaum et al., 2001). The present study was carried out to assess the effect of low dosages of ethanol in a mental arithmetic task. It was hypothesized that alcohol even at a low dose (below 0.5 kg/kg) may negatively effect both behavioral measures (as reflected by reaction time and number of errors) and electrophysiological indices (theta power) characterizing the level of performance in the paradigm used. In the present study, findings related to the changes of the theta frequency band are analyzed in detail, since it seemed reasonable to suppose that in this behavioral paradigm, demanding working memory effort, the effect of alcohol challenge will specifically be manifested in this particular frequency band.
Section snippets
Subjects
The individuals (n = 32) who took part in the study were university students. All of them were right handed males (mean age 22 yrs, SD: 2.31). The subjects signed a written consent and received financial compensation for taking part in the study which was approved by the Ethics Committee of the Institute for Psychology of the Hungarian Academy of Sciences. Throughout the study, subject identity and associated information were kept strictly confidential by a coding scheme. All procedures were
Blood alcohol concentration (BAC)
BAC values in the 3 groups were the following: placebo: below the level of quantization; low dose: 0.15 g/l (SD 0.069); high dose: 0.29 g/l (SD 0.128). The difference between the low- and high-dose BAC values was significant (t(62) = 5.4463 p = 0.0001).
Reaction time (RT)
The RT values in the different conditions were the following: task: 2767.07 ms, SD 239.11; alcohol-placebo: 2598.25 ms, SD 330.30; alcohol-low dose 2814.92 ms, SD 300.34; alcohol-high dose: 2728.11 ms, SD 370.06. One-way analysis of variance showed a
BAC and behavioral results
The BAC levels measured following 30 min after drink consumption were low even after the “high dose”, and are expected to cause only mild changes such as increased sociability and talkativeness (Koob and Moal, 2006). RT is not expected to be altered at such BAC levels (Hernandez et al., 2006, Ando et al., 2008). It is to be noted, however, that RT was found to be the shortest in the placebo condition. Since the subjects were aware that they took part in a study involving alcohol, it is possible
Acknowledgments
This paper was presented at the 14th World Congress of Psychophysiology – the Olympics of the Brain – IOP2008, September 8–13, 2008, in St. Petersburg, Russia.
This study was supported by the Hungarian National Research Fund (OTKA) T048338.
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