Effects of caffeine on cognition and mood without caffeine abstinence.

The objective of this study was to evaluate the effects of low doses (75 mg and 150 mg) of caffeine on mood and cognition in healthy people, with minimal abstinence of 1 h from caffeine. Improvements were obtained in cognition for attention, problem solving and delayed recall, but not immediate recall or working memory, but performance in the placebo condition was close to the maximum, giving little margin for improvement. For mood, there were statistically significant increase in clearheadedness, happiness and calmness and decreases in tenseness. These mood and performance-enhancing effects of caffeine cannot be seen as representing an alleviation of deficits induced by caffeine abstinence, because there was only minimal deprivation from caffeine.

Nicotine issues.

This issue has covered most of the important concerns of nicotine researchers. Inevitably, there are gaps, because the selection of papers could only cover those which had been submitted or were known to be in preparation and about to be submitted. Nevertheless, these articles should serve to stimulate further discussion of and investigation into all aspects of nicotine use.

Facilitation of memory by post-trial administration of nicotine: evidence for an attentional explanation.

In human studies, reported performance improvements with post-trial administration of nicotine have all involved associative learning (Mangan and Golding 1983; Colrain et al. 1992; Warburton et al. 1992). In this study, post-trial nicotine, obtained through smoking a cigarette, improved free recall of lists of unrelated words under conditions which limited the opportunity for associative learning. However, the nicotine-induced advantage was not observed when volunteers were required to complete a secondary (attention) task during the post-trial period in which they smoked. The results suggest that post-trial effects depend on the opportunity for stimulus processing after input, and that nicotine improves performance by increasing the attentional resources available for such strategic processing.

The effects of scopolamine on working memory in healthy young volunteers.

Twenty healthy young adults completed a series of nonverbal and problem solving tasks in a repeated measures design involving placebo and 0.6 mg scopolamine, administered by subcutaneous injection. Subjects completed the test battery under standard presentation conditions and with concurrent articulation, which precludes verbal recoding of test material. Under standard presentation conditions, scopolamine significantly impaired performance on the problem solving task and on tasks of visuo-spatial and spatial memory; memory for abstract shapes was not impaired. Concurrent articulation impaired performance on the shape recognition and interacted with drug treatment on the problem solving task. The results suggest that scopolamine impairs working memory, and that the decrement is at the level of the central executive mechanisms rather than the subsystems which it controls.

Improvements in performance without nicotine withdrawal.

Two tests were made of the withdrawal-relief explanation of the improvements in performance obtained with smoking. Study 1 examined the extent to which abstinence from smoking produced poorer performance in smokers in comparison with non-smokers. No evidence was obtained of differences in performance in smokers who were deprived of cigarettes for 10 h and non-smokers. Study 2 tested smokers with a standard cigarette or sham smoking after one hour and 12 h of deprivation. There was no difference in performance for the two deprivation intervals either in the sham smoking condition, or after smoking the lit cigarette. This study gave no evidence for withdrawal-relief being an explanation of the improvements in performance obtained with smoking.

Effects of scopolamine and nicotine on human rapid information processing performance.

In the first experiment, after a 10-min baseline test on a rapid information processing task, subjects received oral doses of either placebo, methscopolamine 1.2 mg, scopolamine 0.6 mg or scopolamine 1.2 mg, and 1 h later performed the task again for a 20-min period. Following scopolamine 1.2 mg, correct detections were significantly lower over the 20-min period, whereas no such decrement was observed in the other three conditions. In the second experiment a similar design was used to study the effects of nicotine 0.5 mg, 1.0 mg and 1.5 mg and placebo, except that post-drug testing was carried out 10 min after baseline due to the faster absorption of nicotine. Nicotine helped prevent both the decline in detections and the increase in reaction time which occurred over time in the placebo condition. These findings indicate that compounds with opposite effects on central cholinergic pathways produce opposite effects on the performance of a task involving rapid information processing, and are consistent with previous findings from this laboratory.

The effects of cigarettes of varying yield on rapid information processing performance.

The purpose of this study was to determine the effects of four cigarettes having a range of covarying nicotine and "tar" yields on the performance of a rapid information processing task. Twenty five smokers were tested on different days with each of the cigarettes and in a non-smoking control condition. The order of testing was counterbalanced over days using a 5 x 5 Latin Square Design. Not only did smoking help to prevent the decrease in speed and accuracy which occurred over time in the non-smoking conditions, but it actually improved performance over baseline levels. Furthermore, the greatest improvements were found with the higher nicotine yielding cigarettes. These objectively measured effects of the cigarettes on performance matched the subjective evaluations of the effects of the cigarettes outside the laboratory, and are discussed in relation to other questionnaire studies and a survey of smoking at work.

Evaluation of the information processing and mood effects of a transdermal nicotine patch.

The purpose of this study was to determine whether a transdermal nicotine patch will produce the same effects on performance and mood as cigarette smoking. The nicotine patch improved attentional processing and produced some improvements in memory. It produced the calming effects of smoking and induced feelings of happiness which were increased with smoking. These effects were obtained 6 h after application of the patch, showing that acute tolerance for these behavioural effects had not developed completely, if at all, after exposure to nicotine, although it is still possible that tolerance might occur with longer exposure.

Puff-by-puff sensory evaluation of a low to middle tar medium nicotine cigarette designed to maintain nicotine delivery to the smoker.

Puff-by-puff assessments of a range of sensory and subjective attributes were made for three cigarettes, with tar and nicotine yields of: 10.0 and 1.4; 17.0 and 1.7; and 8.8 and 0.8 mg/cigarette, respectively. Seven attributes were assessed: mouth impact, throat impact, chest effect, roughness, intensity of flavour, satisfaction and quality of flavour. Significant differences between the three cigarettes were obtained for most of these attributes. Principal component analysis of the data revealed three principal components related to the cigarettes under investigation. Components 1 and 2 accounted for approximately 47 and 28% of the total variance and component 3 only added a further 7%. Principal component 1 was a complex combination of intensity-related characteristics, i.e. mouth and throat impact, chest effect, intensity of flavour, roughness, while quality of flavour and satisfaction contributed to the separation of samples on principal component 2. However, the two major components could not be defined simply in terms of the yields of tar and nicotine for the products determined on a smoking machine.

A comparison of the attentional and consolidation hypotheses for the facilitation of memory by nicotine.

Studies examining facilitation of human memory by the administration of nicotine have given equivocal results and it has been argued that the positive findings on memory may have resulted indirectly from an effect on attention, rather than from a direct effect on memory storage. This study compared the "attentional" and the "mnemonic" hypotheses directly, by using both immediate and delayed recall tasks in a verbal free recall study, in which volunteers smoked on a fixed regime during presentation of a 32 word list (namely, one puff after each of eight 4-word blocks). The serial position curve for immediate recall demonstrated a significant improvement on the later blocks of the list (an attentional effect) when volunteers smoked a nicotine-containing cigarette. However, improved performance was found for items at the beginning of the list on the delayed recall measure and this improvement was significant on the first block of 4 words. Since nicotine input had been taken after presentation of this information, the results demonstrate post-learning facilitation of memory by nicotine.

Improved incidental memory with nicotine after semantic processing, but not after phonological processing.

RATIONALE: A number of lines of evidence suggest that a nicotinic cholinergic system is mediating attentional processing. However, the evidence is less clear for a nicotinic system being involved in mnemonic processing. OBJECTIVES: The present study investigated the effects of nicotine on memory using a depth of processing paradigm. METHODS: A double-blind design was used with participants (n = 40) smoking either a nicotine containing cigarette (n = 20) and a denicotinized cigarette (n = 20). After smoking, each set of these participants was further subdivided into two groups (n = 10 for each). One group were presented with a series of trials each beginning with the presentation of a "decision word" which they had to say whether it represented something which was living or non-living (semantic-orienting). The second group had to say whether the word had one syllable or two syllables (phonological or non-semantic orienting condition). This decision was followed by a word in coloured ink whose colour participants were required to name as quickly as possible. On completion of the whole task the participants were given an unexpected free recall test. RESULTS: The nicotine-containing cigarette reduced the latencies for decision-making and colour naming in comparison with the denicotinized cigarette. The free recall test showed that nicotine-containing cigarette increased the number of words remembered, but only for the semantic-orienting condition and not the non-semantic condition. CONCLUSIONS: There is a nicotinic cholinergic system that mediates effortful processing. It can be deployed for attentional processing, including the associative processing required for memory encoding.

An evaluation of a caffeinated taurine drink on mood, memory and information processing in healthy volunteers without caffeine abstinence.

RATIONALE: Caffeine is present in a wide variety of beverages, often together with a number of other ingredients, such as sugars, taurine, glucuronolactone and vitamins. However, the majority of psychopharmacological studies have used pure caffeine tablets or drinks with doses in excess of those normally consumed in daily life. In addition, all the participants are usually deprived of caffeine for 10 h or more before the study. Consequently, it has been argued that any improvement in performance is only due to a reversal of caffeine withdrawal. OBJECTIVE: The present two studies tested participants who had minimal deprivation from caffeine (an hour or less) with an 80-mg caffeinated (80 mg/250 ml), taurine-containing beverage (commercially available) verum, which also contained sugars, glucuronolactone and vitamins. The placebos in the two studies were a sugar-free and a sugar-containing drink, in order to examine the effects of the sugar. METHODS: In total, 42 participants were tested with a rapid visual information test, a verbal reasoning test, a verbal and non-verbal memory test and a set of mood measures. Prior to testing, they were allowed ad libitum caffeinated beverages until 1 h before testing (study 1) and unrestricted caffeine use before testing (study 2). RESULTS: In both studies, the caffeinated, taurine-containing beverage produced improved attention and verbal reasoning, in comparison with a sugar-free and the sugar-containing drinks. The improvement with the verum drink was manifested in terms of both the mean number correct and the reaction times. Another important finding was the reduction in the variability of attentional performance between participants. No effects on memory were found. There were no differences in performance between the glucose and sugar-free drinks. CONCLUSIONS: Moderate doses of caffeine and taurine can improve information processing in individuals who could not have been in caffeine withdrawal.

A comparison of the effects of scopolamine and diazepam on working memory.

Two drug models of memory dysfunction, namely the benzodiazepine and the cholinergic models, have emerged from the considerable number of studies which have examined drug effects on information processing. The reported impairments produced by administration of compounds from these two families appear to be more similar than dissimilar, and to date, direct comparisons on traditional memory tasks have failed to differentiate the models. This study compared the effects of diazepam and scopolamine on tasks associated with separable components of working memory. The results indicate that this model also fails to discriminate between the drug models; both compounds selectively impaired tasks associated with the central executive mechanism and failed to disrupt tasks associated with the articulatory loop or the visuospatial scratchpad.

Facilitation of learning and state dependency with nicotine.

Two studies of nicotine and memory encoding were carried out using a state-dependent design. The first experiment used cigarettes and involved memory for stimuli that could not be encoded phonemically or semantically. The results of this recognition study show that nicotine was facilitating the input of non-phonemicably encodable and non-semanticably encodable information to storage and that nicotine produced state-dependent learning. The second study used nicotine tablets and involved memory for concrete words. The results of the free recall study show that nicotine produced state-dependent learning, that nicotine was facilitating the input of information to storage, but there was no evidence that associative processes had been changed by nicotine. These findings give no support for the suggestion that a cholinergic system in the brain is controlling the encoding of intrinsic cues relating to phonemic and semantic properties of things but not those involving mnemonic encoding by mental imagery, but rather that the cholinergic system is non-specifically involved in encoding.

Selective effects of nicotine on attentional processes.

RATIONALE: It is now well established from electrophysiological and behavioural evidence that nicotine has effects on information processing. The results are usually explained either by a primary effect of nicotine or by a reversal effect of a nicotine-induced, abstinence deficit. In addition, there is dispute about the cognitive processes underlying the changes in performance. METHODS: This study has approached the first question by using the nicotine patch, in order to administer nicotine chronically. In addition, we examined the effects of nicotine on attention with a selection of tests which assessed the intensity and selectivity features of attention, using the Random Letter Generation test, the Flexibility of Attention test and the Stroop test. RESULTS: Nicotine enhanced the speed of number generation and the speed of processing in both the control and interference conditions of the Stroop test. There were no effects on attentional switching of the Flexibility of Attention test. CONCLUSION: The results are consistent with the hypothesis that nicotine mainly improves the intensity feature of attention, rather than the selectivity feature.

Effortful processing is a requirement for nicotine-induced improvements in memory.

We report two studies examining the effects of nicotine on memory in minimally deprived smokers. In experiment 1, semantically related words were recalled significantly better than unrelated words following nicotine, even when volunteers were explicitly instructed to target the unrelated word set for recall. Experiment 2 examined the effect of nicotine on two different types of lexical association: association by joint category membership (semantically related items), and association by derived meaning ("encapsulated" word pairs). Nicotine-induced improvements in recall were observed only for category associates and not for encapsulated word pairs. This implies that explicit, effortful processing of material in the presence of nicotine is necessary for improved recall performance to be observed.

Effects of acute subcutaneous nicotine on attention, information processing and short-term memory in Alzheimer's disease.

This single-blind, placebo controlled study reports on the effects of administering three acute doses of nicotine (0.4, 0.6 and 0.8 mg) subcutaneously to a group of Alzheimer's disease (DAT) patients (n = 22), young adult controls (n = 24), and normal aged controls (n = 24). The study extends our previous findings obtained using smaller groups of subjects. Drug effects were examined on three computerised tests: the first measuring rapid visual information processing, sustained visual attention and reaction time (RVIP task); a delayed response matching to location-order task measuring sustained visual attention and visual short-term memory (DRMLO task); and a finger tapping test measuring simple reaction time (FT task). The critical flicker fusion test (CFF) was used as a measure of perception and the WAIS digit span forwards (DS), of auditory short-term memory. Tests were graded in difficulty, titrated to avoid floor and ceiling effects so that meaningful, direct comparisons between groups could be made. Nicotine significantly improved sustained visual attention (in both RVIP and DRMLO tasks), reaction time (in both FT and RVIP tasks), and perception (CFF task--both ascending and descending thresholds). Nicotine administration did not improve auditory and visual short-term memory. There were no consistent, overall patterns of difference in performance between smokers and non-smokers in the control groups, or between males and females in any group. Despite the absence of change in memory functioning, these results demonstrate that DAT patients have significant perceptual and visual attentional deficits which are improved by nicotine administration.(ABSTRACT TRUNCATED AT 250 WORDS)

Nicotine as a cognitive enhancer.

1. Nicotine improves attention in a wide variety of tasks in healthy volunteers. 2. Nicotine improves immediate and longer term memory in healthy volunteers. 3. Nicotine improves attention in patients with probable Alzheimer's Disease. 4. While some of the memory effects of nicotine may be due to enhanced attention, others seem to be the result of improved consolidation as shown by post-trial dosing.

Patterns of facilitation of memory by nicotine.

A single oral dose of 1.5mg of nicotine was administered to healthy young normal males in a placebo-controlled double-blind study. The nicotine produced a significant improvement in the number of words recalled from a 32 item list. An examination of the individual serial position curves showed that most subjects were recalling either predominantly from the first half of the list or predominantly from the second half of the list. Examination of these groups separately showed that nicotine improved recall for the part of the list that was being recalled better in the placebo condition. These results are consistent with the hypothesis that nicotine was supplying additional processing resources and that deployment of these is under the strategic control of the subject.

Pharmacology of human memory and cognition: illustrations from the effects of benzodiazepines and cholinergic drugs.

The current research methods, findings and questions that are being addressed in studies of the pharmacology of human memory and cognition are reviewed. Memory is not a unitary function. Neuropsychological studies of brain-damaged memory-impaired patients, as well as neuroimaging and drug studies in normal individuals indicate that different forms of learning and memory are subserved by different brain systems. Animal drug studies have also provided evidence that, while distinct, memory systems are not independent, but operate in close interaction with one another. Recent human studies of benzodiazepines and of cholinergic drugs demonstrate the value of the psychological models and of the experimental paradigms that are available from cognitive sciences for exploring how drugs alter cognitive and memory functions. They also show how drugs can be used as tools for analyzing the distinct neurochemical mechanisms underlying independent cognitive processes, and so find effective drugs rationally from a knowledge of the neurochemical bases of cognition. This research leads to specific recommendations concerning treatments that may improve memory functioning, for instance in Alzheimer's disease.