Biomedical subjects

T Duka

Publications and source records attributed to T Duka.

At least 19 recordsLinked to original sources

PubMed2006

The effect of alcohol and repetition at encoding on implicit and explicit false memories.

RATIONALE: Alcohol impairs explicit memory, whilst leaving implicit memory relatively intact. Less is known about its effects on false memories. AIM: The present study examines the effects of alcohol on explicit and implicit false memories using study list repetition as a tool for modulating learning at encoding. METHODS: Thirty-two participants were given either an alcohol (0.6 g/kg) or placebo beverage before undergoing an encoding phase consisting of 10 lists of nine associated words (veridical items). Each list was associated to a word, which was not presented at encoding (semantically associated non-studied lure; critical item), serving as the measure for false memory. Half of the lists were presented once, and half were repeated three times. The next day, participants underwent an implicit (stem completion and post hoc awareness measurements), and an explicit (free recall) task. RESULTS: Alcohol decreased veridical and false explicit memory for singularly presented lists compared to placebo; no group difference existed for repeated lists. Implicit veridical memory was not affected by alcohol. Awareness memory measures demonstrated in placebo participants an increased ability with repetition in rejecting false memories. The reverse was found in intoxicated participants who with repetition accepted more false memories. CONCLUSION: Alcohol appears to decrease semantic activation leading to a decline in false memories. Increased learning with repetition, which increases the rejection of false memories under placebo, is reversed under alcohol leading to a decrease in rejection of false memories. The latter effect of alcohol may be due to its ability to impair monitoring processes established at encoding.

Adolescent↗

PubMed2006

Gender specific effects of a mild stressor on alcohol cue reactivity in heavy social drinkers.

RATIONALE: Stress plays an important role in the development and maintenance of alcohol-abuse. Some of the effects of stress on alcohol-related behaviours, however, appear to be gender-dependent. AIM: The present study set out to examine the effects of stress on feelings of desire for alcohol, skin conductance response and alcohol consumption in the presence of alcohol-related cues in relation to gender. Participants were heavy non-dependent alcohol drinkers. METHODS: Thirty-two (16 males) participants drinking more than 21 units of alcohol per week were randomly allocated to undergo the experimental stress (based on the 'Trier Social Stress' Test) or the non-stress procedure before the alcohol cue exposure procedure, during which participants handled and smelled their preferred drink. Mood and saliva cortisol level changes were used as indices of the stress effects, while alcohol craving, skin conductance and alcohol consumption were the cue reactivity measures. RESULTS: Self ratings of anxiety and tension increased and cortisol levels remained high in the stress compared to the non-stress condition; no gender differences were found. Stress induced gender-specific effects with regard to skin conductance response and alcohol consumption measurements. Stressed females did not show an increase from baseline in the skin conductance response during the alcohol cue-exposure session, which was observed in the non-stressed females; they also consumed less alcohol than males under stress. CONCLUSION: Female participants respond less to alcohol-related cues when in a negative mood state. Such a finding suggests that females when in a negative mood may be less sensitive to positive incentive processes mediating cue reactivity compared to males.

Affect↗

PubMed2005

The acute effect of alcohol on decision making in social drinkers.

RATIONALE: Many studies have reported the long-term adverse effects of alcohol on executive cognitive function in chronic alcohol abusers, yet little research has investigated the acute effects of alcohol in social drinkers. Studies on acute effects report alcohol-induced deficits on tasks that require executive cognitive processes, with alcohol acting to increase preservative errors and reduce planning. AIM: The present investigation examines the acute effects of a moderate dose of alcohol on a decision-making task that involves participants making a forced choice between two simultaneously presented binary-outcome gambles. METHODS: Alcohol (0.6 g/kg) or placebo was administered to 32 social drinkers. Participants completed the task, making a total of 80 decisions about gambles that varied in the magnitude of expected gains, losses and the probability with which these outcomes were delivered. Participants also chose between gambles probing identified non-normative biases in human decision making, namely, risk aversion for choosing between gains and risk seeking for choosing between losses. RESULTS: All participants picked the experimental gamble more frequently when the probability of winning was high vs low, when the gains were large vs small and when the losses were small vs large; the alcohol group had an impaired ability to factor in the magnitude of gains and the likelihood of winning when the losses were large. Deliberation time did not differ between the groups. CONCLUSION: These data suggest that alcohol given acutely impairs risky decision making. In particular, alcohol impairs one's ability to alter responding in light of changing prospective rewards in order to make favourable decisions.

Adult↗

PubMed2004

Does alcohol affect memory for emotional and non-emotional experiences in different ways?

Alcohol has been shown to have both impairing and facilitating effects on memory, depending on the sequencing of learning and ingestion of the drug. Its effects on memory for emotional material, however, have not been shown reliably. The current experiment sought to investigate the effects of alcohol on later recall of emotional and neutral events experienced before and after alcohol drinking. Using an incidental-learning paradigm, alcohol (0.65 g/kg) or placebo was administered in a double-blind randomized design to 34 participants, between two learning phases in which they viewed and rated positive, negative and neutral images. The drug's effects on memory were assessed in a surprise test of free recall. In addition, impact of alcohol on ratings of mood states, and of valence and arousal that the pictures evoked, was examined. Alcohol facilitated memory for material seen before, and impaired memory for material seen after, its administration. Furthermore, under alcohol, emotional images in the first set were more recalled over neutral than in the second set, indicating a higher retrograde facilitation for emotional than for neutral material. Alcohol improved positive mood states but had no effect on negative mood states. Evaluation of pictures with regard to valence showed an increase of the ratings for the positive and neutral images after alcohol and a decrease after placebo. No drug effects were found for arousal ratings. Whether a picture was likely to be remembered or not (tested only for set 2) was dependent on the intensity of the arousal but not of the valence that the picture evoked in the participants. Pictures that were rated high in arousal were also remembered better, and this effect was irrespective of alcohol or placebo ingestion. These data have shown that alcohol elicits retrograde facilitation and anterograde impairment for emotional materials. Furthermore, these data demonstrate that alcohol selectively facilitates memories for emotional events experienced before administration, and suggest a possible explanation for the reinforcing effects of drinking.

Adolescent↗

PubMed2003

Mixed emotions: alcoholics' impairments in the recognition of specific emotional facial expressions.

Facial expression recognition is a central feature of emotional and social behaviour and previous studies have found that alcoholics are impaired in this skill when presented with single emotions of differing intensities. The aim of this study was to explore biases in alcoholics' recognition of emotions when they were a mixture of two closely related emotions. The amygdala is intimately involved in encoding of emotions, especially those related to fear. In animals an increased number of withdrawals from alcohol leads to increased seizure sensitivity associated with facilitated transmission in the amygdala and related circuits. A further objective therefore was to explore the effect of previous alcohol detoxifications on the recognition of emotional facial expressions. Fourteen alcoholic inpatients were compared with 14 age and sex matched social drinking controls. They were asked to rate how much of each of six emotions (happiness, surprise, fear, sadness, disgust and anger) were present in morphed pictures portraying a mix of two of those emotions. The alcoholic group showed enhanced fear responses to all of the pictures compared to the controls and showed a different pattern of responding on anger and disgust. There were no differences between groups on decoding of sad, happy and surprised expressions. In addition the enhanced fear recognition found in the alcoholic group was related to the number of previous detoxifications. These results provide further evidence for impairment in facial expression recognition present in alcoholic patients. In addition, since the amygdala has been associated with the processing of facial expressions of emotion, particularly those of fear, the present data furthermore suggest that previous detoxifications may be related to changes within the amygdala.

Adult↗

PubMed2003

Attentional orienting towards smoking-related stimuli.

According to incentive salience theory, conditioned stimuli (CS+) associated with drug reinforcement acquire the capacity to elicit a conditioned attentional orienting response, which controls drug-seeking and drug-taking behaviour. We sought evidence for this proposal by measuring visual attentional orienting towards smoking pictures presented briefly in the periphery of the visual field, versus control pictures likewise presented, in smokers versus non-smokers. In each trial, smokers and non-smokers responded manually to a dot probe stimulus that appeared in a location previously occupied by either a smoking picture or a control picture. Attentional bias scores were calculated by subtracting the median reaction time (RT) in the former condition from the median RT in the latter condition. In two experiments, light-smokers (smokers of fewer than 20 cigarettes/day) produced a mean bias score that was significantly greater than that of heavy-smokers (smokers of 20 or more cigarettes/day) and non-smokers. In addition, when smokers from the two experiments were pooled, a significant quadratic relationship was found between cigarettes/day and the attentional bias for the smoking stimuli. These findings are consistent with incentive salience theories and dual-process theories of addiction.

Adolescent↗

PubMed2002

The effects of extrinsic context on nicotine discrimination.

There is evidence from memory studies that context acquired in parallel with the encoded material will facilitate retrieval. However, relatively little is known of how context affects drug discrimination behaviour in humans. The present study employs conventional drug discrimination procedures to investigate the effects of music, as an external cue, on nicotine drug discrimination. Subjects were trained to discriminate a low dose of nicotine (1 mg) from placebo while listening to two different types of music [elated (EL) and depressant (DE): thought to induce happy and sad mood respectively]. Half of the subjects received EL music with nicotine and DE with placebo and the other half vice versa. At the end of training, subjects who reached the criterion (80% of trials identified correctly) entered the generalization phase and were required to discriminate different doses of nicotine (0, 0.25, 0.5 and 1 mg) by indicating how similar each sample was to the training dose. Generalization took place in the presence of either EL or DE music. Nicotine-appropriate responding during generalization was linearly related to dose, with subjects being able to distinguish 0.5mg of nicotine from placebo. Nicotine-appropriate responding at generalization was higher when the context (type of music) was the same as the one employed during discrimination training when nicotine was administered (i.e. a context-dependent generalization effect was present). In addition, it was shown that the context-dependent effect was due to the properties of the EL music. These data provide the first evidence that extrinsic context can facilitate nicotine discrimination in humans. In addition, the findings suggest that this facilitatory effect is not a general effect but is sensitive to specific attributes of the context.

Adult↗

PubMed2001

State-dependent effects of alcohol on recollective experience, familiarity and awareness of memories.

RATIONALE: Explicit memory (EM) is the memory for events which occurs with full awareness of where and how the recalled events took place, whereas implicit memory (IM) is the memory which is unfolded without any awareness of these events and usually becomes apparent when performance is facilitated by its presence. These two types of memory can be understood as different systems. Findings attempting to differentiate between the two systems in normal subjects have been controversial, with some researchers arguing that there is a single memory system and only the match in processes used during learning and later at retrieval can be important. OBJECTIVES: The present study compared the effects of alcohol (0.8 g/kg) or placebo administered prior to encoding and/or retrieval on measures of explicit and implicit memory in terms of recollective experience and familiarity. METHODS: At encoding subjects studied a list of 80 words presented in pairs. At retrieval, participants first carried out an implicit stem completion task, followed by an explicitly cued recall task (stem completion) which measured IM and EM respectively. After stem completion participants were required to indicate whether the items from the studied list were consciously recollected ("remember" response) or was known for a fact that were presented in the studied list ("know" response). In the IM task completed items from the studied list but not recognised by the subjects as such indicated memory without awareness. Studied items were of high and low associations. Forty-eight participants were tested in one of four drug conditions: alcohol-alcohol, placebo-placebo, placebo-alcohol, alcohol-placebo. RESULTS: In the implicit stem completion task, alcohol did not affect overall correct completion rates. However, participants who received alcohol prior to encoding reported lower awareness of correctly completed study items. In the cued recall task, alcohol also did not affect overall performance. However, participants in the same drug-state conditions (SS) reported greater recollection than familiarity with study material, whereas participants who encoded and retrieved material in different drug-state conditions (DS) reported recollection and familiarity to the same extent. In addition, DS participants showed more familiarity with study material compared to SS participants. Direct comparisons between IM and EM tasks demonstrated that alcohol at retrieval decreased the cued recall of items from high associations compared to placebo, but did not have any effect on implicit stem completion. CONCLUSIONS: In summary, these results demonstrate a dissociation of alcohol effects on measures of EM and IM. Alcohol administered prior to encoding reduced awareness of implicitly retrieved material, but did not impair IM per se, confirming previous findings with alcohol. In addition, the data provided new evidence for state-dependent retrieval effects on EM but not IM. It was also shown that for explicitly retrieved items, recollective experience benefits from same drug state, whereas familiarity benefits from different drug state between encoding and retrieval.

Adolescent↗

PubMed2001

Attentional bias associated with alcohol cues: differences between heavy and occasional social drinkers.

RATIONALE: Previous research has shown an attentional bias toward drug-related stimuli in opiate addicts and toward emotionally threatening words in anxiety patients. OBJECTIVE: The primary aim of this study was to investigate whether non-dependent heavy social drinkers would differ in their selective attention towards alcohol-related stimuli in comparison with a group of occasional social drinkers. METHODS: Attentional bias was assessed using alcohol-related pictures and words in a dot probe detection task. Picture and word pairs were visually presented, followed by a dot probe that replaced one of the items. Attentional bias was determined from latencies in responding to the dot probe. Questionnaires were used to examine the relationships among attention, outcome expectancies after alcohol consumption, and personality traits. Higher-order executive function was also measured with two cognitive tasks, recognition memory and attentional shift. RESULTS: The heavy social drinkers showed an attentional bias towards the alcohol-related stimuli when compared to the occasional social drinkers. The heavy social drinkers also scored more highly on expectancy factors of sociability and sexuality and lower on the personality traits of self-directedness and persistence. CONCLUSION: The results support cognitive theories of addictive behaviour in which the ability of drug-related stimuli to capture attention is suggested to play a part in drug dependence, craving and relapse.

Adolescent↗

PubMed2001

A low dose alcohol drug discrimination in social drinkers: relationship with subjective effects.

RATIONALE: Although well characterised in animals, relatively little is known about alcohol discriminative stimulus effects in humans. OBJECTIVE: The study was carried out to investigate the correspondence of subjective effects and the discriminative response during the acquisition of a low dose alcohol discrimination in humans. METHODS: Healthy volunteers completed an Alcohol Use Questionnaire and were then trained to discriminate a dose of 0.2 g/kg alcohol from placebo using a money reinforced technique. Subjects sampled drinks during training, but also completed rating scales measuring Taste, Like/Dislike and Subjective Effects for each drink. RESULTS: Thirty-two subjects learned the discrimination (discriminators; Ds). In these subjects, differences between placebo scores and alcohol scores for Lightheadedness, Relaxed, Arousal and Fatigue were greater following acquisition of the discrimination, compared with differences at the start of training. Differences in other measures remained consistent. Twenty-six of the volunteers failed to learn the discrimination (non-discriminators; NDs). These subjects reported drinking approximately twice as much alcohol during the preceding 6 months, as the Ds (4.35+/-0.53 g/kg per week versus 2.08+/-0.19 g/kg per week, respectively, P<0.001). There were no alcohol specific differences in ratings for Lightheadedness, Relaxed, Arousal or Fatigue between the Ds and the NDs. However, Dislike scores did differentiate between the Ds and the NDs in that the NDs had reduced ratings for the alcohol drink only compared with the Ds (P<0.02). CONCLUSIONS: These results support the suggestion from animal studies, that the alcohol stimulus is a compound, and characterise the subjective effects which contribute to a low dose cue in humans. In addition, the data suggest that previous drinking experience may selectively alter aversive responses to alcohol and that this, in addition to differences in general arousal levels, may have affected subjects' ability to learn the discrimination.

Adolescent↗

PubMed2001

Impaired fear conditioning but enhanced seizure sensitivity in rats given repeated experience of withdrawal from alcohol.

Repeated experience of withdrawal from chronic alcohol treatment increases sensitivity to seizures. It has been argued by analogy that negative affective consequences of withdrawal also sensitize, but repeated experience of withdrawal from another sedative-hypnotic drug, diazepam, results in amelioration of withdrawal anxiety and aversiveness. We tested whether giving rats repeated experience of withdrawal from alcohol altered their ability to acquire a conditioned emotional response (CER). Male Hooded Lister rats were fed a nutritionally complete liquid diet as their only food source. Different groups received control diet, or diet containing 7% ethanol. Rats receiving ethanol diet were fed for either 24 days (Single withdrawal, SWD), or 30 days, with two periods of 3 days, starting at day 11, and 21, in which they received control diet (Repeated withdrawal, RWD). All rats were fed lab chow at the end of their liquid diet feeding period. Starting 12 days after the final withdrawal, groups of Control, SWD and RWD rats were given pentylenetetrazole (PTZ; 30 mg/kg, i.p.) three times a week, and scored for seizures. The occurrence of two successive Stage 5 seizures was taken as the criterion for full PTZ kindling. Other groups of control, SWD and RWD rats were trained to operate levers to obtain food, and were then exposed, in a fully counterbalanced design, to light and tone stimuli which predicted unavoidable footshock (CS+), or which had no consequences (CS-). Rats consumed approximately 17.5 g/kg/day of ethanol, resulting in blood alcohol levels of approximately 100 mg/dL. Repeated administration of PTZ resulted in increasing seizure scores. RWD rats achieved kindling criterion faster than either Control or SWD rats. No differences were seen in the groups in flinch threshold to footshock (0.3 mA). At a shock intensity of 0.35 mA, Control, but not RWD or SWD rats showed significant suppression to the CS+ CS- presentation did not affect response rates. The three groups differed in their response to pairing the CS+ with increasing shock levels, the Controls remaining more sensitive to the CS+. SWD rats showed significant suppression of lever pressing during CS+ presentations only at 0.45 and 0.5 mA, and RWD rats only at 0.5 mA. Giving rats repeated experience of withdrawal from chronic ethanol results in increased sensitivity to PTZ kindling, but reduces their ability to acquire a CER. Withdrawal kindling of sensitivity to anxiogenic events does not seem to occur under circumstances which give rise to kindling of seizure sensitivity.

Acoustic Stimulation↗

PubMed2001

Smoking expectancy mediates the conditioned responses to arbitrary smoking cues.

Smokers' responses to smoking cues may be the result of a classical conditioning process. There is evidence that classical conditioning may not proceed in human subjects unless subjects are consciously aware of the stimulus (CS)-reinforcer (UCS) contingencies. In two experiments the role of CS<-->UCS contingency awareness in the expression of conditioned responses (craving, salivation, and skin conductance) was studied. A discriminative classical conditioning paradigm was used during which subjects were presented with one stimulus (the CS +) always paired with cigarette smoking (the UCS) and another (the CS -) never paired with cigarette smoking. Half of the subjects were given instructions to discover the CS<-->UCS contingencies (group 'aware', AWR), whereas the other half were not (group 'unaware', UWR). In experiment 1, all subjects responded to the CS + with increased cigarette craving relative to the CS -; this effect was more pronounced in the AWR group compared to the UWR group. A lower amount of salivation in response to the CS + compared to the CS - was found in the UWR group. These between-group differences were interpreted as a consequence of the enhanced expectancies of smoking in the presence of CS + in group AWR compared to group UWR. In experiment 2, the observed craving responses to CS + and CS - were consistent with those seen in experiment 1, but no discriminative salivary response to the stimuli was found. When, after conditioning training, subjects' expectancies of smoking were removed by instructions, and their responses to CS + and CS - were again measured, the discriminative craving response to CS + and CS - was eliminated and all subjects demonstrated a lower amount of salivation in response to the CS + compared to the CS -. These data suggest that presentation of arbitrary cues previously paired with cigarette smoking can elicit CRs and that facilitation of awareness of the CS<-->UCS contingency by instructions can potentiate craving CRs. In addition, these data suggest that craving CRs can be eliminated, whereas compensatory CRs can be facilitated, when cigarette expectancy is removed with instructions.

Adolescent↗

PubMed2000

The effects of 3-week estrogen hormone replacement on cognition in elderly healthy females.

RATIONALE: Estrogen concentrations decline with age and menopause is often followed by an acceleration of the age effects on cognition. It is suggested that replacement of estrogen would reinstate, at least in part, cognitive abilities. Effects of estrogens on memory have been reported in studies with women in a clinical setting who either needed or wished to have the estrogen replacement and are mostly in the perimenopausal age-band. OBJECTIVE: The present study investigated the effects of estradiol on memory and on frontal lobe function in elderly female subjects who did not suffer any of the postmenopausal symptoms and had never taken estrogen hormone replacement (EHR) previously. METHODS: EHR (Progynova TS, transdermal estradiol; n=19) or placebo (n=18) was given for a period of 3 weeks to elderly healthy female subjects. Memory, frontal lobe functions (inhibition and planning) and visuospatial abilities (mental rotation) were tested before and after treatment. Estrogen plasma levels were measured to confirm the result of EHR. Cortisol plasma levels were also measured before and after cognitive performance in order to evaluate the effects of EHR on the sensitivity of the hypothalamo-pituitary-adrenal (HPA) axis to mild mental stress. RESULTS: Plasma estradiol levels in the drug group increased to levels equivalent to that of a fertile woman (0.21+/-0.5 nmol/l). Memory function as well as visuospatial abilities as measured by a mental rotation task improved significantly with EHR. However, there was no effect of EHR on frontal lobe functions. The cognitive effects were not dependent on an improvement in mood or general well-being as may be the case with EHR in women at peri- or post-menopausal stage. EHR was found to increase the HPA response to task-induced stress, as indicated by an increase in cortisol plasma levels. CONCLUSIONS: The present study has provided evidence of a beneficial effect of EHR on cognitive abilities given for first time to healthy elderly women. Furthermore, the present study has demonstrated a differential effect of EHR on memory, visuospatial abilities and frontal lobe function.

Aged↗

PubMed2000

State-dependent effects of alcohol on explicit memory: the role of semantic associations.

RATIONALE: Memory performance can be facilitated when the context in which retrieval occurs matches the context in which learning initially took place in two separate ways, in form of interactive or independent context. In the present study, the differential effects of alcohol, as independent context, on the free recall of items of high or low semantic associations were investigated. The high and low associations offer different strengths of interactive context at stimulus input, i.e. context that influences what will be stored. METHODS: Using a state-dependent retrieval paradigm, alcohol (0.8 g/kg) or placebo was administered prior to encoding and/or retrieval and their effects were tested using measures of free recall. Forty-eight participants were tested according to a traditional state-dependent retrieval design where half of the subjects studied the items under alcohol (A), half under placebo (P) followed by retrieval of the items under A or P giving four groups (AA, AP, PA, PP). RESULTS: Delayed free recall was significantly impaired when alcohol was administered prior to both encoding and retrieval of study material (P<0.05). Alcohol administered prior to encoding and prior to retrieval decreased especially the recall of high association items (P<0.05). Participants in the same-state groups (AA, PP) recalled fewer low association items than participants in disparate state groups (AP, PA; P<0.05). This effect of drug state on low associations may reflect an inability of weaker cues to facilitate retrieval in the presence of stronger cues (i.e. high associations and drug). Indeed, participants in the same-state groups recalled a greater percentage of material in form of high association items than participants in disparate-state groups (P<0.05). CONCLUSIONS: These results demonstrate that alcohol given at encoding and at retrieval specifically impairs retrieval of high association items. However, if the drug state is the same at encoding and at retrieval, the items with the high associations represent a higher proportion of the total recalled items. These data suggest that alcohol may provide an internal context that can facilitate retrieval of information, acquired in semantic context, which otherwise would have been lost.

Adult↗

PubMed2000

Hemispheric lateralisation in a manual-verbal task combination: the role of modality and gender.

Differences in hemispheric lateralisation between males and females were tested using a manual-verbal task combination. The manual task was finger tapping and the verbal task required reciting words. Words were presented either visually or aurally in order to examine a possible role of modality of presentation on hemispheric lateralisation. The influence of the verbal task on motor task performance was evaluated by changes in the number of taps from single to dual-task condition. The influence of the motor task performance on the verbal task was examined by changes in the number of words recalled. Cognitive performance differences between males and females were also examined in a mental rotation task. The results showed a greater right finger (RH) tapping than left finger (LH) tapping interference, but only when the verbal task was presented in the visual mode. There was no difference in this pattern between males and females, both showing a greater RH tapping than LH tapping interference. The interference in finger tapping for both RH and LH was greater when the verbal task was presented aurally than when presented visually. Furthermore, females compared to males showed a greater interference in finger tapping when the verbal task was presented aurally than when presented visually. Later recall of verbal information was impaired equally by concurrent RH or LH tapping; however, later recall was better when the verbal task was presented visually than when presented aurally. No gender differences were found in delayed recall. Performance in the mental rotation task was better in males than in females. The data are discussed on the basis of theories of dual task interference and/or of brain asymmetry.

Acoustic Stimulation↗

PubMed1999

Relationship of components of an alcohol interoceptive stimulus to induction of desire for alcohol in social drinkers.

The ability of a low (0.2 g/kg) oral dose of ethanol to provide a drug discriminative stimulus was studied in young healthy human volunteers, who were social drinkers. Seventeen of 24 subjects acquired the discrimination following 10 trials in which they received aliquots of ethanol or of placebo drink (tonic water mixed with Tabasco sauce). In generalization studies, in which the dose of ethanol was varied, discrimination performance was dose dependent; doses greater than 0.05 g/kg gave rise to significant ethanol-appropriate responding. Concurrent estimates of the subjective effects of doses administered as discriminative stimuli revealed that two factors--taste and light-headedness--were associated with discrimination: at the training dose, 0.2 g/kg, although both the factors taste and light-headedness were significantly increased, only taste predicted discrimination performance. At lower doses, taste did not contribute to discrimination, but the subjective rating light-headedness correlated significantly with discrimination accuracy. Post hoc analyses of the influence of the amount of alcohol regularly drunk by the volunteers, on discrimination performance suggested light-headedness correlated with discriminative performance only in social drinkers drinking more than 20 units per week. In a second experiment, groups of "high" (mean 40 units per week) and "low" (mean 10 units per week) social drinkers were prospectively identified. Discrimination performance of 0.2 g/kg ethanol in orange juice vs. orange juice vehicle indicated that both groups were able to perform the discrimination following a single training trial, and that generalization curves over the range 0.05-0.2 g/kg were dose dependent, and not different between the groups. At the lowest dose, discrimination performance was predicted by taste, stimulation, and light-headedness in the "high" group, but not in the "low" group. The ability of these ethanol doses to induce feelings of craving for ethanol were assessed in parallel, using the Desire for Alcohol Questionnaire (DAQ). "High" drinkers showed higher desire for ethanol on all factors of the DAQ except the "positive negative reinforcement" factor, and sampling ethanol tended to increase desire in these measures. However, at each dose, the induction of feelings of desire for ethanol showed a negative correlation with discrimination performance. These findings are discussed in the context of the ability of animals and humans to use several components of drug-induced stimuli in the performance of drug discrimination, and the role of such discriminative stimuli in priming of ethanol drinking.

Alcohol Drinking↗

PubMed1999

Left-hemispheric superiority for visuospatial orientation in homing pigeons.

To test for lateralisation of visuospatial orientation during homing, pigeons who had binocularly learned the homeward route from remote release sites were tested monocularly on either their left or their right eye for homing performance. In two experiments with three different release sites, birds using their right eye showed considerably better homing performance. If sun compass information was available, there was no difference in the direction of vanishing. Without this information, a difference between pigeons using their left or right eye emerged. Results show that visuospatial orientation in birds can be lateralised in favour of the left brain hemisphere and lend further support to the view that vision is important for pigeons homing on a familiar route. Cognitive mechanisms which might account for the observed pattern of lateralisation are discussed.

Animals↗

PubMed1999

AMPA-receptor involvement in c-fos expression in the medial prefrontal cortex and amygdala dissociates neural substrates of conditioned activity and conditioned reward.

Exposure to an environment, previously conditioned to amphetamine (1 mg/kg, i.p.), induced locomotor activity and c-fos expression (a marker for neuronal activation) in the mouse medial prefrontal cortex (mPFC) and amygdala; acute or repeated amphetamine (1 mg/kg, i.p.) administration induced c-fos expression additionally in the nucleus accumbens. An alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionate (AMPA)-receptor antagonist, 2, 3-dihydroxy-6-nitro-7-sulphamoyl-benzo(f)quinoxaline (NBQX), blocked expression of conditioned activity, and prevented the increase in c-fos expression in mPFC, implicating mPFC AMPAergic transmission in the conditioned component of behavioural sensitization to amphetamine. NBQX failed to block the expression of amphetamine-conditioned place preference, a measure of conditioned reward, or conditioned c-fos expression in the amygdala, an area implicated in the expression of conditioned place preference. These findings indicate that the conditioned components of behavioural sensitization depend on AMPA-receptor-mediated activation in mPFC, but that conditioned reward does not.

Amygdala↗