Frontal Cortex Functioning in Infancy

Abstract

The functional status of the frontal cortex in infancy and early childhood is relatively poorly understood, and not much is known about the relationships between the few tasks developed to assess such functioning. The work presented in this thesis investigated these questions using an individual differences approach. Two cohorts of children were tested longitudinally on a set of tasks that have been associated with the frontal cortex in an attempt to establish whether these tasks share common functional mechanisms. Cohort 1 (n = 24) was tested at 9 and 24 months of age, and Cohort 2 (n = 104) was tested at 4 and 9 months of age. Furthermore, a new task, termed the Freeze-Frame task, was developed to assess inhibitory functioning in infancy using eye movements as the dependent measure. The relationship between performance on infant frontal cortex tasks and measures of temperament and general development was also investigated. Finally, a common genetic variation, the COMT Val 158 Met polymorphism, which has been specifically associated with variation in the neurobiology of the frontal cortex, was investigated in relation to performance on the infant frontal cortex tasks. The results indicated that frontal cortex tasks administered at the same age shared functional mechanisms.Performance indices from the new Freeze-Frame task were associated with performance on several other infant and toddler frontal cortex tasks. Associations between frontal cortex tasks administered at 9 months were stronger than between the tasks administered at 4 months.Longitudinal associations were generally lacking between 4 and 9 months, but some strong associations were found between 9 and 24 months of age. At 4 months of age frontal cortex tasks tended to be associated with better self-regulation as assessed by a parent-report temperament questionnaire. However, at 9 and 24 months of age this pattern had reversed indicating that more reactive children tended to perform better on frontal cortex tasks. Some of the frontal cortex tasks were associated with measures of general cognitive development. However, the associations found between frontal cortex tasks could generally not be accounted for by variation in general cognitive ability. The COMT Val 158 Met polymorphism was found to be related to a selective aspect of performance on the new Freeze-Frame task, but not to any of the other frontal cortex tasks. The results are discussed in terms of their implications for our understanding of frontal cortex functioning in infancy and early childhood.4

Early Development of Visual Attention: Change, Stability, and Longitudinal Associations

“…Individual differences in latencies to shift attention during infancy appear to be concurrently associated with the ability to regulate emotion. An initial finding that 4-month-olds better able to disengage during Overlap trials were less susceptible to distress and more easily soothed (Johnson et al 1991b) was not replicated in two cohorts of similar-aged infants (Holmboe 2008, McConnell & Bryson 2005. However, saccadic reaction times in the Gap (and to a lesser extent the Overlap) conditions were positively associated with parentreported fear amongst 4-month-olds (Holmboe 2008, McConnell & Bryson 2005.…”

“…An initial finding that 4-month-olds better able to disengage during Overlap trials were less susceptible to distress and more easily soothed (Johnson et al 1991b) was not replicated in two cohorts of similar-aged infants (Holmboe 2008, McConnell & Bryson 2005. However, saccadic reaction times in the Gap (and to a lesser extent the Overlap) conditions were positively associated with parentreported fear amongst 4-month-olds (Holmboe 2008, McConnell & Bryson 2005. Longer latencies to disengage during Overlap trials at 6 months of age have been associated with greater parent-reported distress and less smiling (McConnell & Bryson 2005) and with less soothability (Nakagawa & Sukigara 2019).…”

The early childhood inhibitory touchscreen task: A new measure of response inhibition in toddlerhood and across the lifespan

“…Children in the toddler study were a subset of a larger group of 48 infants, which was assessed monthly from 5 to 12 months of age. During the infant (5 to 12 month) phase, the study focused on two visual inhibitory control tasks: the looking A-not-B and Freeze-Frame tasks [ 55 , 56 ] (these data are the topic of separate manuscripts). At the completion of the 12-month visit, families were invited to continue participation by also becoming part of the toddler study.…”

The neural correlates of inhibitory control in 10-month-old infants: a functional near-infrared spectroscopy study

“…One important form of inhibitory control is response inhibition; the ability to inhibit a prepotent or well-learned response which is often motoric in nature (Friedman & Miyake, 2004). Whilst response inhibition abilities are immature during infancy, it is possible to reliably measure early forms of response inhibition from the second half of the first year of life (Hendry et al, 2021;Holmboe et al, 2008Holmboe et al, , 2018Holmboe et al, , 2020. However, very little is known about the brain mechanisms supporting response inhibition in infancy and toddlerhood.…”