Behavioral and pharmacological modulation of respiration in rhesus monkeys.

Changes in respiration associated with schedule-controlled behavior were determined in seated rhesus monkeys prepared with a pressure-displacement head plethysmograph for monitoring ventilation continuously during behavioral experiments. Subjects were trained to press a lever under fixed-ratio 40 and fixed-interval 300-s schedules of stimulus termination. Episodic increases in ventilation were closely associated with periods of responding under both schedules. Recurring episodes of increased ventilation occurred during fixed-ratio responding, and were separated by brief 10-s timeouts during which ventilation decreased. Under the fixed-interval schedule, both ventilation and response rate typically increased as the 300-s interval elapsed. The effects of cocaine, caffeine, and two adenosine agonists, 5'-N-ethylcarboxamidadenosine (NECA) and 2-(carboxyethylphenylamino)adenosine-5'-carboxamide (CGS 21680), on behavior and respiration were determined using a cumulative-dosing procedure. Drug-induced suppression of behavior eliminated the episodic increases in ventilation during the performance components of both schedules. Schedule-related increases in ventilation were compared to those produced by elevated levels of CO2 in inspired air. Exposure to 4% CO2 mixed in air increased ventilation in all subjects, and the combined effects of CO2 exposure and schedule-controlled responding on respiration appeared to be additive. The results suggest that behavioral activities may increase ventilation through increased metabolic demand and increased CO2 production.     

State-Dependent Memory Effects Using Caffeine and Placebo Do Not Extend to Metamemory

The authors examined the impact of caffeine on human memory and predictions of memory (i.e., metamemory). On Day 1, 83 college students drank a sweetened beverage containing either caffeine (4 mg/kg body weight) or a placebo before they studied 40 pairs of words. While the participants studied, they predicted their future memory performance for each word pair. On Day 2, the participants again received caffeine or a placebo before the memory test. The participants who drank the same beverage on both days (either caffeine or a placebo) recalled more word pairs than did those who drank different beverages (caffeine on 1 day and a placebo on the other day). In contrast, memory predictions were more accurate when the beverages did not match on both days. These data provide evidence for state-dependent memory when caffeine is used, but not for state-dependent metamemory. People's memory and their predictions of memory can be influenced in different ways if they drink caffeine before they study or take a test.     

The effect of chronic caffeine consumption on urinary incontinence in psychogeriatric inpatients

Abstract

Urinary incontinence is a common problem in psychiatric settings, particularly among psychogeriatric patients. In view of the known diuretic action of caffeine, the present study assessed the effect of tea and coffee consumption on level of incontinence in selected psychogeriatric inpatients. A total of 14 patients participated in the study which employed a combined “withdrawal” and “multiple-baseline across subjects” design to examine the effect of alternating phases of caffeine exposure and abstinence on frequency of daytime and nighttime incontinence. Incontinence levels were significantly reduced during periods of caffeine abstinence relative to periods of chronic caffeine exposure. The hypothesis that observed reductions in incontinence may have been due to accompanying reductions in fluid intake was examined but not supported.     

A comparison of two report formats for alcohol and caffeine use

Abstract

The present study compared two different methods of assessing alcohol and caffeine use in a community sample of adults over a one-year period. Daily reporting of beer/wine intake was more stable over time and showed higher correspondence with Quantity-frequency measures than daily reporting of hard liquor use. Coffee and tea use showed high temporal stability and good alternate form reliability, though a tendency to underreport typical use of coffee use was observed. The psychometric properties of substance use measures appear to vary with type of beverage consumed and report format.     

Human coffee drinking: manipulation of concentration and caffeine dose.

In a residential research ward coffee drinking was studied in 9 volunteer human subjects with histories of heavy coffee drinking. A series of five experiments was undertaken to characterize adlibitum coffee consumption and to investigate the effects of manipulating coffee concentration, caffeine dose per cup, and caffeine preloads prior to coffee drinking. Manipulations were double-blind and scheduled in randomized sequences across days. When cups of coffee were freely available, coffee drinking tended to be rather regularly spaced during the day with intercup intervals becoming progressively longer throughout the day; experimental manipulations showed that this lengthening of intercup intervals was not due to accumulating caffeine levels. Number of cups of coffee consumed was an inverted U-shaped function of both coffee concentration and caffeine dose per cup; however, coffee-concentration and dose-per-cup manipulations did not produce similar effects on other measures of coffee drinking (intercup interval, time to drink a cup, within-day distribution of cups). Caffeine preload produced dose-related decreases in number of cups consumed. As a whole, these experiments provide some limited evidence for both the suppressive and the reinforcing effects of caffeine on coffee consumption. Examination of total daily coffee and caffeine intake across experiments, however, provides no evidence for precise regulation (i.e., titration) of coffee or caffeine intake.     

Low-dose caffeine discrimination and self-reported mood effects in normal volunteers.

A caffeine versus placebo discrimination procedure was used to determine the lowest caffeine dose that could produce discrimination and self-reported mood effects in normal volunteers. During daily sessions under double-blind conditions, caffeine-abstinent subjects orally ingested a capsule containing 178 mg caffeine or placebo. Before beginning discrimination training, the compounds were identified to subjects by letter codes. Fifteen, 30, and 45 min after capsule ingestion, subjects guessed the capsule's letter code. Correct guesses at 45 min earned money. After each session, subjects received a supplementary capsule containing caffeine or placebo to ensure that, within each phase of the study, subjects received the same daily dose of caffeine equal to the training dose. Five of the 15 subjects acquired the caffeine versus placebo discrimination within the first 20 sessions (greater than or equal to 75% correct); 6 other subjects acquired the discrimination with additional training. Nine subjects who acquired the discrimination were subsequently trained at progressively lower caffeine doses. In general, the lowest dose to produce discrimination (greater than or equal to 75% correct) was also the lowest dose to produce self-reported mood effects: 4 subjects showed discrimination and self-reported mood effects at 100 mg caffeine, 2 at 56 mg, 1 at 32 mg, and 1 at 18 mg. One of these subjects also showed self-reported mood effects at 10 mg. The present study documents discriminative stimulus and self-reported mood effects of caffeine at doses below those previously shown to affect any behavior in normal volunteers.     

Frightfully funny: combining threat and humour in health messages for men and women

Objective: It is imperative for public health to investigate what factors may reduce defensive responses and increase the effectiveness of health information. The present research investigated gender differences in responses to threatening health-promoting information communicated with humour.

Design: Male and female participants were exposed to a health message stressing the negative consequences of binge drinking (Experiment 1; N = 209) or caffeine consumption (Experiment 2; N = 242), that did or did not contain a funny visual metaphor (Experiment 1) or a slapstick cartoon (Experiment 2).

Main Outcome Measures: Message evaluation, message attention, and attitudes and intentions towards the behaviour were measured.

Results: Results showed that health messages were more persuasive when communicated with humour, although humour played a different role for men and women. Whereas men responded more in line with message goals when the message combined high threat with humour, women preferred the low threat humour messages.

Conclusion: By uncovering the moderating role of gender as a key audience characteristic, this research contributes to designing effective future health campaigns and provides important insights for future studies investigating the underlying mechanisms responsible for the different effects of threat and humour appeals for men and women.     

Reinforcing effects of caffeine in coffee and capsules.

In a residential research ward the reinforcing and subjective effects of caffeine were studied under double-blind conditions in volunteer subjects with histories of heavy coffee drinking. In Experiment 1, 6 subjects had 13 opportunities each day to self-administer either a caffeine (100 mg) or a placebo capsule for periods of 14 to 61 days. All subjects developed a clear preference for caffeine, with intake of caffeine becoming relatively stable after preference had been attained. Preference for caffeine was demonstrated whether or not preference testing was preceded by a period of 10 to 37 days of caffeine abstinence, suggesting that a recent history of heavy caffeine intake (tolerance/dependence) was not a necessary condition for caffeine to function as a reinforcer. In Experiment 2, 6 subjects had 10 opportunities each day to self-administer a cup of coffee or (on different days) a capsule, dependent upon completing a work requirement that progressively increased and then decreased over days. Each day, one of four conditions was studied: caffeinated coffee (100 mg/cup), decaffeinated coffee, caffeine capsules (100 mg/capsule), or placebo capsules. Caffeinated coffee maintained the most self-administration, significantly higher than decaffeinated coffee and placebo capsules but not different from caffeine capsules. Both decaffeinated coffee and caffeine capsules were significantly higher than placebo capsules but not different from each other. In both experiments, subject ratings of "linking" of coffee or capsules covaried with the self-administration measures. These experiments provide the clearest demonstrations to date of the reinforcing effects of caffeine in capsules and in coffee.     

EFFECTS OF CAFFEINE ON CLASSROOM BEHAVIOR,SUSTAINED ATTENTION,AND A MEMORY TASK IN PRESCHOOL CHILDREN

The effects of caffeine on the behavior of young children is an important issue, as children in our society consume considerable amounts of caffeine, primarily in soft drinks. This study investigated the effects of normative amounts of caffeine on the behavior of 6 normal children in a kindergarten setting. Using a reversal design, counterbalanced for order of conditions, children's behavior was examined during a baseline condition, a caffeinated beverage condition, and a noncaffeinated beverage condition. Measures included direct observation of off-task and gross motor activity, actometer readings of movement, a Continuous Performance Test, a Paired Associates Learning Test, and teacher ratings of classroom behavior. Results suggest that caffeine exerts only small and inconsistent effects on the classroom behavior of kindergarten children. These results cast doubt on the importance of caffeine as a variable controlling the classroom behavior of normal kindergartners.