The goal of this thesis is to track latency changes in three visual evoked potentials (VEP) stimuli as an indication of overall brain development, in order to provide a normative baseline to differentiate visual and neurological development from pathological processes. VEP- neural electrical activity recorded from the scalp surface and synchronized with visual stimulus transitions- is one of the common techniques in understanding infant vision development. Past work has concentrated on responses to pattern reversal and to the latency of the initial positive peak. Here we compare the timing of responses to pattern, orientation, and direction-reversal VEPs, and transient peak latencies to those calculated from the gradient of steady-state phase against reversal rate. The three stimuli were tested in 81 adults at 1- 16 r/s and 137 infants (3.6- 79.0 weeks) at 2- 8 r/s. Initial responses to orientation and direction were as fast as for contrast- around 100 ms, consistent with other findings that V1 is orientation selective. Cortical processing for both OR and DR yielded longer latencies (200 ms) by the calculated method, perhaps reflecting more involvement of higher visual processing in comparison to PR. Orientation and direction latencies also had a delayed onset and longer developmental period to reach maturity. Infants reached adult transient PR latency values by 15 weeks, for OR by 50 weeks, and for DR by 10 weeks. For the calculated latency, infants reached both adult PR and DR latencies by 30 weeks while OR showed little change across age. We successfully confirmed that (1) phase-based calculation of latency is effective, easy to use, and taps into a different cortical pathway; (2) motion processing has an additional, faster, subcortical pathway; (3) a parallel processing of initial contrast and orientation; and (4) later visual processing is not only developmentally delayed for all three stimuli but also more vulnerable to perinatal brain damage. These latency differences provided a baseline for clinical evaluations where identification of delayed latencies should aid early diagnosis and guide therapies for adults and infants.

It is increasingly recognised that, in adulthood, attentional control plays an important role in optimising the ability to encode and maintain items in visual short-term memory (VSTM). Memory capacity limits increase dramatically over childhood, but the mechanisms through which children guide attention to maximise VSTM remain poorly understood. Through a number of experiments manipulating different parameters, the current thesis aimed to explore the developmental trajectories of the neurocognitive mechanisms underlying selective attention within VSTM and to examine whether variations in attentional control are accompanied by individual differences in VSTM capacity. Chapters 2 and 3 investigated the development of attentional orienting in preparation for encoding and during maintenance. Younger children emerged as less able than older children and adults to orient attention to internally held representations. Therefore, Chapter 4 tested whether younger children’s attentional orienting is differentially affected by memory load. While attentional orienting prior to encoding was more beneficial when required to remember a greater number of items, cueing benefits during maintenance were similar across load conditions. Chapter 5 investigated whether temporal parameters influence younger children’s variable ability to orient attention during maintenance. Attentional orienting operated more efficiently on transient iconic traces rather than on VSTM representations due to passive decay of the memory traces as a function of time. Chapter 6 assessed whether the characteristics of the memoranda constrain the efficiency of attentional orienting within VSTM. Attentional orienting supported differentially the maintenance of familiar and meaningless items and pinpointed the quantitative improvement of mnemonic strategies over development. Finally, Chapter 7 examined the temporal dynamics of prospective and retrospective orienting of attention in VSTM. Children deployed neural pathways underpinning attentional orienting less efficiently than adults and differentially across the two orienting conditions suggesting their neural dissociation. Overall, findings from the current thesis define how children develop the ability to deploy attentional control in service of VSTM.

Introduction: Prenatal maternal depression is associated with an increased risk of psychopathology in childhood. The understanding of the mechanisms underlying this association is limited. Further, despite high rates of prenatal depression in the developing world, no research investigating this issue exists from these settings. Objectives: The primary objectives of this thesis are to study the association between prenatal maternal depression and the following early offspring outcomes in a non-smoking, non-alcohol consuming prenatal sample from rural, South India: Foetal stress responsivity, measured through foetal heart rate (FHR). Infant stress responsivity, measured through infant cortisol response to immunisation. Infant temperament. Methods: 194 pregnant women from Solur, India were assessed for depression. The first 67 mothers with elevated symptoms of prenatal depression and the first 66 controls underwent FHR monitoring to study foetal stress responsivity. 58 mother-infant dyads returned at 1.5-3 months post birth. Infant salivary cortisol was measured before and after immunisation. Information on infant temperament and maternal postnatal depression (PND) was also collected. Results: Twenty nine mothers (14.9%) met a diagnosis of major depression during pregnancy while 67 (34.5%) had elevated symptoms of prenatal depression. Whilst there were no linear association between prenatal depression and foetal responsivity, a curvilinear (U shaped) association existed with the foetuses of mothers with very high and very low levels of prenatal depression having elevated stress responses compared to those with moderate levels of prenatal depression. Prenatal depression predicted infant cortisol responsivity independent of PND (B=13.08, p=0.02).The relationship between infant cortisol responsivity and prenatal depression was also U shaped. There was no association between prenatal depression and infant temperament. Conclusions: This is the first study from the developing world investigating the relationship between prenatal depression and offspring outcomes. It provides evidence suggestive of the programming influence of prenatal depression on the developing offspring.