We conducted two additional exploratory analyses

We conducted two additional exploratory analyses. First, following up a recent examination of the developmental trajectories of the EEG from children in the BEIP study (Stamoulis et al., 2015), we also wanted to examine continuing changes in the three frequency bands between ages 8- and 12-years. Second, over the duration of the BEIP study some of the children in the FCG have experienced disruptions to their caregiving environment. Recently, Humphreys et al. (2015) found that children in stable placement in foster care had fewer internalizing and externalizing symptoms compared to those with unstable placements. Therefore, we also examined the effects of stability of placement on the EEG.
Methods
Results
Discussion The aim of this study was to examine the continuing impact of a foster care intervention on neural activity following early psychosocial deprivation. At 12 years, children who were removed from institutions and placed into foster care demonstrated continuing benefits as a result of intervention as indexed by their resting EEG activity; specifically, children placed into high quality foster care displayed marginally decreased theta power and elevated alpha power compared to children who received care as usual. This finding is illustrated by the measures of relative power where the FCG children resembled the NIG children with an increasing proportion of power in the alpha band while the CAUG showed an immature pattern of acetylcholine chloride activity with greater distribution of power in the theta band (Benninger et al., 1984; Matthis et al., 1980; Raine et al., 2001). The distribution of greater power in slower frequencies of the EEG is not only characteristic of extreme deprivation or social isolation (Gendreau et al., 1972; Marshall et al., 2004; Zubek et al., 1963), but has been observed in typically developing populations of children living in impoverished environments. A number of studies have shown that children living in low resource homes (e.g., poor nutrition, unsanitary living conditions, less responsive or sensitive caregiving) show a similar “immature” pattern of EEG activity as we have observed in the BEIP sample. For example, Otero and colleagues (Otero, 1994, 1997; Otero et al., 2003), have followed a sample of middle-low and low socioeconomic status infants from 18-months to 6 years and measured EEG at three different time points and found that children with lower resources – compared to children with more cognitive and social stimulation through parental involvement – demonstrated greater EEG activity in slower frequencies (delta and theta bands) and lower power in higher frequencies often associated with better attention and cognitive performance (alpha and beta bands; Fernandez et al., 2000). Indeed, an enriched nursery school intervention has been shown to alter the neural activity of impoverished children, increasing power in fast EEG activity and improved attentional orienting during a cognitive task (Raine et al., 2001); suggesting that early intervention may improve outcomes for all children. There appears to be a high degree of stability in the EEG trajectories between the 8- and 12-year assessments. A recent study examined the developmental trajectories of EEG activity in the BEIP sample from baseline through 8 years (Stamoulis et al., 2015). They found that intervention group assignment was significantly related to the trajectories of the alpha and beta bands. There are differences in the methods that preclude direct comparison, however, examination of the changes in the EEG between 8 and 12 years suggest that all groups continue to show maturational changes in the EEG that remain dependent upon early experiences consistent with those reported by Stamoulis and colleagues. Moreover, the decreases in relative theta, increases in relative beta, and stability of relative alpha power within this age range are consistent with other longitudinal studies of EEG in typically developing children (Benninger et al., 1984; Clarke et al., 2001; Matthis et al., 1980).