title: Response patterns and cardiovascular effects during response sequence acquisition by humans.
abstract: The effects of temporal delays imposed between successive responses and of vitamin C administration were examined on the acquisition of response sequences and on cardiovascular reactivity during sequence acquisition. Thirteen adult subjects (6 female, 7 male), in good health, gave written consent prior to participating in 12 weekly 45-min sessions. Points, exchanged for money after each session, were presented when subjects completed 15-response sequences on a touch-sensitive three-response keypad. A position counter increased from 0 to 14 as subjects emitted correct responses in the sequence. Four novel 15-response sequences were presented each session. No delays were imposed between successive responses during the acquisition of one sequence; delays were imposed immediately following each response during the acquisition of a second sequence, thereby delaying response feedback; delays were imposed following feedback during acquisition of a third sequence, resulting in the removal of the stimulus correlated with sequence position; and, as a control condition, delays were imposed following feedback, but stimuli correlated with sequence position were reinstated prior to the next response during acquisition of a fourth sequence. Subjects were exposed to one of two delay durations (0.2 and 0.5 or 0.5 and 1.0 s) each session, and delay durations alternated every session. During Weeks 5 to 8, subjects received 3 grams of vitamin C per day, whereas during Weeks 1 to 4 and 9 to 12, subjects received placebo under single-blind conditions. All subjects acquired the sequences, as evidenced by decreasing percentages of incorrect responses across trials. When temporal delays were imposed between successive responses during sequence acquisition, acquisition efficiency was enhanced. Examination of response latencies suggested that the status of preceding responses (i.e., correct or incorrect) rather than the status of the position counter influenced subsequent responding. Cardiovascular effects were inversely related to the length of the temporal delay. Neither cardiovascular reactivity or sequence acquisition were related to vitamin C administration.
authors.affiliation: Department of Psychiatry and Behavioral Sciences, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205.
authors.forename: T H
authors.initials: TH
authors.lastname: Kelly
authors.forename: M W
authors.initials: MW
authors.lastname: Fischman
authors.forename: R W
authors.initials: RW
authors.lastname: Foltin
authors.forename: J V
authors.initials: JV
authors.lastname: Brady
mesh_terms: D000328:Adult; D001143:Arousal / Q000187:drug effects; D001205:Ascorbic Acid / Q000008:administration & dosage / Q000493:pharmacokinetics; D001288:Attention / Q000187:drug effects; D001794:Blood Pressure / Q000187:drug effects; D005260:Female; D005934:Glucagon / Q000097:blood; D006339:Heart Rate / Q000187:drug effects; D006801:Humans; D006854:Hydrocortisone / Q000097:blood; D007328:Insulin / Q000097:blood; D008297:Male; D011939:Mental Recall / Q000187:drug effects; D012055:Reinforcement Schedule; D012691:Serial Learning / Q000187:drug effects
chemical_list: D007328:Insulin; D005934:Glucagon; D001205:Ascorbic Acid; D006854:Hydrocortisone