Perceptual and Motor Skills, 1975, 40, 126. @ Perceptual and Motor Skills 1975
PARADOXICAL EFFECTS OF CAFFEINE ROBERT H. KLEIN AND LEONARD F. SALZMAN University o f Rocbested
Tecce and Cole (1974) reported recently on paradoxical drowsiness and lowered electrical brain activity in a group of normal a d u l ~given 10 mg. of dextroamphetamine. They infer that "amphetamine is not a simple stimulant of the central nervous system and can produce an early transient depression in brain activity." In the course of analyzing data obtained during a study of the effects of caffeine on vertex averaged evoked-potentials (AEP) produced by stimuli of varying intensity, we observed that in a group of 10 male Ss, AEP amplitudes to stimuli of low intensity (1000 cps, 60 d b ) were lower 2 hr. after ingestion of 300 mg. of caffeine than responses to the same stimuli under placebo conditions (see table). Seven of 10 male Ss showed the paradoxically lower amplitude response to stimuli under caffeine administration; only 2 of 10 females showed the paradoxical effect (x' = 5.05, df = 1, p = .05). These differences were obtained from our unpublished measurements of the early components ( P 1 N1 P 2 ) of the evoked response sampled for 500 msec. following stimulus onset and averaged over 160 trials. The effect was not observed under the same conditions with female Ss who tended to respond in a non-paradoxical fashion, with increased amplitude of evoked responses to the stimulant. This interaction approached significance when tested by a 2 X 2 analysis of variance (F = 3.63, df = 1/19, p = .07). As Buchsbaum and Pfefferbaum (1971) found, a significant sex difference in AEP amplitude was also noted ( F = 4.19, df = 1/18, p = .05).
+
+
Placebo
Caffeine .-
Males Females
2 1.40 2 7.40
11.67 8.76
17.10
3 1.90
14.84 13.78
Our data suggest that the transient depression in brain activity observed by Tecce and Cole may be a phenomenon also observable with ocher stimulants, although the time at which this effect manifests itself may vary from drug to drug. Taken together, these findings support the suggestion that psychopharmacologica1 studies should include longitudinal investigations of the effects of drugs It is apparently not tenable to assume that the predominant or typical effect of a drug is exerted uniformly over the course of its action. REFERENCES BUCHSBAUM, M., & PFEFPERBAUM, A. Individual differences in stimulus intensicy response. Psychophysiology, 1971, 8, 600'-611. TECCE,J. J., & COLE,J. 0. Amphetamine effects in man: paradoxical drowsiness and lowered electrical brain activity. Science, 1974, 185, 451. Accepted December 2, 1974.
'School of Medicine and Dentistry, Rochester, New York 14620.
PARADOXICAL EFFECTS OF CAFFEINE ROBERT H. KLEIN AND LEONARD F. SALZMAN University o f Rocbested
Tecce and Cole (1974) reported recently on paradoxical drowsiness and lowered electrical brain activity in a group of normal a d u l ~given 10 mg. of dextroamphetamine. They infer that "amphetamine is not a simple stimulant of the central nervous system and can produce an early transient depression in brain activity." In the course of analyzing data obtained during a study of the effects of caffeine on vertex averaged evoked-potentials (AEP) produced by stimuli of varying intensity, we observed that in a group of 10 male Ss, AEP amplitudes to stimuli of low intensity (1000 cps, 60 d b ) were lower 2 hr. after ingestion of 300 mg. of caffeine than responses to the same stimuli under placebo conditions (see table). Seven of 10 male Ss showed the paradoxically lower amplitude response to stimuli under caffeine administration; only 2 of 10 females showed the paradoxical effect (x' = 5.05, df = 1, p = .05). These differences were obtained from our unpublished measurements of the early components ( P 1 N1 P 2 ) of the evoked response sampled for 500 msec. following stimulus onset and averaged over 160 trials. The effect was not observed under the same conditions with female Ss who tended to respond in a non-paradoxical fashion, with increased amplitude of evoked responses to the stimulant. This interaction approached significance when tested by a 2 X 2 analysis of variance (F = 3.63, df = 1/19, p = .07). As Buchsbaum and Pfefferbaum (1971) found, a significant sex difference in AEP amplitude was also noted ( F = 4.19, df = 1/18, p = .05).
+
+
Placebo
Caffeine .-
Males Females
2 1.40 2 7.40
11.67 8.76
17.10
3 1.90
14.84 13.78
Our data suggest that the transient depression in brain activity observed by Tecce and Cole may be a phenomenon also observable with ocher stimulants, although the time at which this effect manifests itself may vary from drug to drug. Taken together, these findings support the suggestion that psychopharmacologica1 studies should include longitudinal investigations of the effects of drugs It is apparently not tenable to assume that the predominant or typical effect of a drug is exerted uniformly over the course of its action. REFERENCES BUCHSBAUM, M., & PFEFPERBAUM, A. Individual differences in stimulus intensicy response. Psychophysiology, 1971, 8, 600'-611. TECCE,J. J., & COLE,J. 0. Amphetamine effects in man: paradoxical drowsiness and lowered electrical brain activity. Science, 1974, 185, 451. Accepted December 2, 1974.
'School of Medicine and Dentistry, Rochester, New York 14620.
