Special Section CLASSICAL DELAY EYEBLINK CONDITIONING IN 4-AND 5-MONTH-OLD HUMAN INFANTS

Abstract-Simple delay classical eyeblink conditioning, using a tone conditioned stimulus (CS) and airpuff unconditioned stimulus (US) , was studied in cross-sectional samples of 4-and 5-month-old Classical eyeblink conditioning has become a successful paradigm for studying cognitive and neural processes underlying learning and memory in several species, including humans. The majority of human studies have involved young or aged adult populations (e.g., Recently, we have been developing procedures for studying eyeblink conditioning in 4-and 5-month-old human infants. Eventually, we expect that these procedures can be adapted for use over a broader age range, be used with infants at high risk for central nervous system damage, and enable complementary studies of eyeblink conditioning in human infants and developing rat pups METHOD Subjects and Design Both 4-and 5-month-old infants (± 10 days) were recruited using local county birth records, and infants of both ages were randomly assigned to either a paired or an unpaired training group. Each group experienced two identical sessions of paired or unpaired training 6 to 8 days apart. Other 5-month-olds were assigned to one of two exposure-control groups. One of the control groups received unpaired presentations of the conditioned stimulus (CS) and unconditioned stimulus (US) during the first session (CS/US-exposure group). The other was exposed only to the training situation, without any CS or US presentations, during the first session (context-exposure group). Both these groups then received paired training 6 to 8 days later. Data are presented here for the 57 infants who completed a criterion number of trials during both sessions (at least 30 paired tone-airpuff trials during paired sessions or 30 tone-alone trials during unpaired sessions). 1 Procedures Each infant sat on a parent's lap facing a platform about 75 cm away. A standardized visual display of brightly colored objects was presented on the platform to attract and maintain the infant's attention. The parent held the infant in a way that gently restrained large motor movements and maintained roughly the same orientation throughout the session. A specially crafted soft band was secured, using Velcro, 4 Copyright © 1999 American Psychological Society VOL. 10, NO. 1, JANUARY 1999 Address correspondence to Dragana Ivkovich, Department of Psychology: Experimental, Duke University, Durham, NC 27708-0086; e-mail: dragana@acpub.duke.edu. 1. An additional 54 infants (twenty 4-month-olds and thirty-four 5-montholds) were excluded from analyses because of failure to achieve the criterion number of trials (n = 25), rescheduling conflicts (n = 26), or technical difficulties (n = 3). Chi-square analyses on subjects with an insufficient number of trials revealed no evidence of selective attrition based on gende