Event-related potentials for 7-month-olds' processing of animals and furniture items

Abstract

Event-related potentials (ERPs) to single visual stimuli were recorded in 7-month-old infants. In a three-stimulus oddball paradigm, infants watched one frequently occurring standard stimulus (either an animal or a furniture item) and two infrequently occurring oddball stimuli, presenting one exemplar from the same and one from the different superordinate category as compared to the standard stimulus. Additionally, visual attributes of the stimuli were controlled to investigate whether infants focus on category membership or on perceptual similarity when processing the stimuli. Infant ERPs indicated encoding of the standard stimulus and discriminating it from the two oddball stimuli by larger Nc peak amplitude and late-slow-wave activity for the infrequent stimuli. Moreover, larger Nc latency and positive-slow-wave activity indicated increased processing for the different-category as compared to the same-category oddball. Thus, 7-month-olds seem to encode single stimuli not only by surface perceptual features, but they also regard information of category membership, leading to facilitated processing of the oddball that belongs to the same domain as the standard stimulus.

Fig. 1

Stimulus material of the ERP study. Three pictures (rabbit, giraffe, dresser, or dresser, chair, rabbit) were presented in random order: one stimulus in 60% of the trials (standard stimulus; rabbit or dresser), one stimulus from the same superordinate category in 20% of the trials (oddball-same), and another stimulus from the contrasting category in 20% of the trials (oddball-different). The number of pictures reflects the presentation ratio. The rabbit and the dresser were of bluish-gray color, the giraffe and the chair were of reddish-brown color. Half of the infants were randomly assigned to condition A, the other half to condition B. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of the article.)

Fig. 2

Grand-average ERPs at the 13 electrode sites that were analyzed in the present study. ERPs are depicted for single electrodes (F3, Fz, F4, FC5, FC6, C3, Cz, C4, T7, T8, CP5, CP6, and Pz) in response to the standard stimulus (solid gray line), the oddball stimulus from the same category (solid black line), and the oddball stimulus from the contrasting category (broken black line). Gray areas depict the time windows during which Nc peak amplitude and Nc peak latency were analyzed (350–700ms) and during which the mean activity of the late slow waves (LSWs) was analyzed (1000–1500ms).

Fig. 3

Scalp topography of the late-slow-wave activity for the frequently presented stimulus (standard), and for the infrequent stimuli from the same (oddball-same) and from the contrasting category (oddball-different). The scalp topography is an average for a time window from 1000 to 1500ms.