Biochemical, behavioural and electrophysiological investigations of brain maturation in chickens

Changes in mid‐to‐late latency auditory evoked reponses in the chicken during neural maturation

“…This chicken model of hypothyroidism produces a moderate reduction in thyroid hormone levels of a similar order to that found clinically in areas of endemic iodine deficiency (Wang & Rostas, 1996). This mild late-onset hypothyroidism delays or inhibits the normal developmental change in the subcellular distribution of calcium/calmodulin stimulated protein kinase II (CaMKII) that is responsible for the accumulation of CaMKII at the postsynaptic density (PSD), which is one of the molecular markers of maturation (Atkinson et al, 2008). The change induced by the hormone deficiency is a selective alteration in the normal developmental program since there was no change in the level of expression of CaMKII or in the subcellular distribution of other proteins or signaling pathways examined (Wang & Rostas, 1996).…”

“…Furthermore, many of the maturation changes observed in chicken forebrain are also matched with corollaries seen in human brain development (Atkinson et al, 2008). These formation and maturation changes are progressive, widespread and appear to represent a highly organized spatial and temporal program of maturation that is likely to be affected by genetic, hormonal and environmental factors.…”

“…The development of synaptic networks can be conveniently divided into two phases: an initial synapse formation phase, during which functional synaptic contacts are established accompanied by a net increase in the number of synapses, followed by a subsequent maturation phase during which synaptic circuits are fine tuned and the properties of individual immature yet functional synapses are altered to become like those found in adult brain (Rostas, 1991;Rostas et al, 1991). In chicken forebrain synapse formation has broadly finished by 10-14 days posthatch with the maturation of synaptic networks occurring mainly after 3 weeks and complete by 8-10 weeks posthatch (Atkinson et al, 2008;Rostas, 1991;Rostas et al, 1991).…”

“…The main developmental changes in the latency of this response occur after the second posthatch week and mostly between weeks 3 and 8. This is the period of development in which biochemical and anatomical studies that have shown that neuronal circuits are attaining their adult properties (Atkinson et al, 2008;Rostas, 1991).…”

“…The widespread nature of the many changes involved in brain maturation is illustrated in chicken forebrain as many of the molecular and cellular changes (Atkinson et al, 2008;Kavanagh et al, 1991Kavanagh et al, , 1995Rostas, 1991;Rostas et al, 1984Rostas et al, , 1991Migues et al, 2007;Weinberger and Rostas, 1988), and progressive changes in the quantitative characteristics of the basal EEG (Hunter, Battilana, Bragg, & Rostas, 2000) can be measured in whole forebrain during maturation. Furthermore, many of the maturation changes observed in chicken forebrain are also matched with corollaries seen in human brain development (Atkinson et al, 2008).…”