Development of fear acquisition and extinction in children: effects of age and anxiety

Abstract

Development of anxiety disorders is associated with neurobiological changes in areas that are a critical part of the fear neurocircuitry. Fear conditioning paradigms can offer insight into the mechanisms underlying the neurobiological ontogeny of anxiety. A small number of studies have focused on the effects of age and anxiety separately in school age children. The present study aimed to investigate these effects in 8-13 year old children with higher and lower trait anxiety. We examined differential fear conditioning and extinction using skin conductance responses and fear-potentiated startle in 60 children recruited from a low-income urban population. The results indicated that children under 10 years of age show poor discrimination of conditioned stimuli, and that anxiety increases fear responses during fear acquisition. After controlling for age and trauma exposure, fear-potentiated startle to the safety cue predicted child anxiety levels suggesting that impaired safety signal learning may be a risk factor for anxiety disorders in adulthood. Identifying risk phenotypes in children may provide opportunities for early intervention and prevention of illness.

Keywords: Anxiety; Children; Development; Extinction; Fear conditioning.

Figure 1

Schematic diagram of the fear conditioning and extinction protocol.

Figure 2

Skin conductance responses (SCR) during fear acquisition (A) and extinction (B) to the CS+ and CS−. There was a significant Block by Trial Type interaction during acquisition, F(2, 118)=8.04, p=.001, and a significant effect of Block during extinction, F(3, 135)=4.24, p<.01. Abbreviations: CS+=reinforced conditioned stimulus; CS−=non-reinforced conditioned stimulus. **=p<.001 effect of Trial Type, CS+ vs CS− in Acq 2 and 3; *=p<.01 main linear effect of Extinction Block (Ext1, Ext2, Ext3, and Ext4) across Trial Type

Figure 3

Startle magnitude responses during fear acquisition (A) and extinction (B) to the NA, CS+, and CS−. There was a significant Block by Trial Type interaction during acquisition, F (4, 184)=2.99, p<.05. Contrasts comparing NA to CS+ and CS+ to CS− indicated that both comparisons changed across blocks (both p’s <.05). The RM-ANOVA of the extinction phase showed a significant effect of Block, F(3, 120)=3.15, p<.05. Abbreviations: NA=noise alone trials; CS+=reinforced conditioned stimulus; CS−=non-reinforced conditioned stimulus **=p<.001 effect of Trial Type, NA vs CS+; in Acq 2 and 3; CS+ vs CS− in Acq3 *=p<.01 main linear effect of Extinction Block (Ext1, Ext2, Ext3, and Ext4) across Trial Type

Figure 4

SCR during late acquisition of CS+ and CS− (A) and extinction to the CS+ (B) across Age and Anxiety groups. During late acquisition (blocks 2 and 3), there was a significant effect of Trial Type, F(1, 50)=5.85, p<.05, and a trend for an interaction of Anxiety and Trial Type, F(1, 50)=3.71, p=.06. There were no significant effects during extinction. Abbreviations: CS+=reinforced conditioned stimulus; CS−=non-reinforced conditioned stimulus *=p<.05 interaction effect of Age and Anxiety

Figure 5

Fear-potentiated startle (FPS) during late acquisition of the CS+ and CS− (A) and extinction to the CS+ (B) across Age and Anxiety groups. During late acquisition (blocks 2 and 3), there was a significant effect of Trial Type, F(1, 40)=8.89, p=.005, as well as an interaction of Age and Anxiety, F(1, 40)=6.44, p<.05. Analyses of each Age category separately showed that only children over 10 years old discriminated between the CS+ and CS−, F(1, 25)=10.48, p<.005, while the younger children did not, F(1, 15)=1.50, p>.1. There was a main effect of Anxiety in the older children, F(1, 25)=5.06, p<.05. During extinction, there was a significant effect of extinction Block, F(3, 99)=4.28, p<.01 and a significant main effect of Anxiety, F(1, 33)=3.97, p=.05. FPS was derived as follows: Percent Startle Potentiation = 100 x (startle magnitude during CS trials – NA startle magnitude during same session) / (NA startle magnitude during same session). Abbreviations: CS+=reinforced conditioned stimulus; CS−=non-reinforced conditioned stimulus. *=p<.01 effect of Trial Type (CS+ vs CS−); **=p<.01 effect of age on the CS−; #=p<.05 interaction of Age and Anxiety; +=p<.01 main effect of Extinction Block