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Published on: December 4, 2013
The effect of prenatal hypoxia and malnutrition on memory consolidation in the chick
Candice L Rodricks1, Ilona A Rose, Emily J Camm
1Department of Physiology, Monash University, Melbourne, Victoria 3800, Australia. candice.rodricks@med.monash.edu.au
Insights
Hypoxia during incubation impairs chick memory formation and consolidation. Malnutrition did not significantly affect memory, suggesting hypoxia, not malnutrition, is the primary cause of cognitive deficits in this model.
Area of Science:
- Neuroscience
- Developmental Biology
- Animal Models
Background:
- Prenatal hypoxia, induced by reduced gas exchange during incubation, is known to impair cognitive abilities in young chicks.
- Previous studies linked impaired cognitive function to reduced gas exchange, but the specific contribution of hypoxia versus malnutrition was unclear.
Purpose of the Study:
- To investigate the distinct roles of hypoxia and malnutrition in causing cognitive impairments in chicks.
- To determine if hypoxia or malnutrition is the primary factor affecting memory formation and consolidation during embryonic development.
Main Methods:
- Chicks were incubated with reduced gas exchange (partial eggshell wrapping or environmental hypoxia) or subjected to varying levels of malnutrition (albumin removal).
- Cognitive function was assessed using a discriminated bead avoidance learning task, interpreted within a three-stage memory model.
- Hormonal levels (corticosterone) and brain sparing were measured in malnourished chicks.
Main Results:
- Reduced gas exchange from days 10-14 or 14-18 of incubation significantly inhibited memory formation and consolidation.
- Environmental hypoxia replicated memory deficits observed with partial eggshell wrapping.
- Malnutrition induced by albumin removal did not significantly affect memory consolidation, although it altered corticosterone levels and brain sparing.
Conclusions:
- Prenatal hypoxia, not malnutrition, is the primary cause of cognitive deficits observed in chicks subjected to reduced incubation gas exchange.
- The timing of hypoxic insult during incubation critically influences the nature of the cognitive deficit.
- The chick model effectively isolates the effects of prenatal hypoxia from maternal factors.
Abstract:
The contribution of hypoxia and malnutrition to cognitive impairments was investigated in chicks incubated in conditions of reduced gas exchange. Previous research has shown that reducing gas exchange during incubation by wrapping half the eggshell with an impermeable membrane results in impaired cognitive ability in young chicks. The results were interpreted within a three stage sequential model of memory using discriminated bead avoidance learning. Reducing gas exchange for 4 days from day 10 or 14, of the 21-day incubation, inhibits memory formation and consolidation into permanent storage. The nature of the cognitive deficit depended on the timing of the insult. Environmental hypoxia (14% oxygen), induced from days 10 to 14 and from days 14 to 18, replicated the memory deficits found previously when eggs were partially wrapped with a membrane. Oxygen is necessary to break down food and to provide energy to build tissue proteins, and therefore hypoxia (partial wrapping or environmental incubation) may indirectly cause malnutrition. Malnutrition, induced by removing 5%, 7.5% or 10% albumin from the egg prior to incubation, had no significant effect on memory consolidation. Raised corticosterone levels occurred in chicks malnourished by 5% and 7.5%, but brain sparing was only evident in chicks with 7.5% albumin removal. Hatch rates were very low in 10% malnourished chicks. Using the chick as a model of prenatal stress, we have been able to isolate the effects of hypoxia from contributing maternal factors.
