Having a baby is hard work. No sleep, unsolvable crying and demands for attention bring a whole new dimension to the word ‘knackered’. A phenomenon which is experienced by many new parents is a state of mind described as ‘baby brain’. Symptoms include forgetfulness, loss of concentration and altered decision making. While these symptoms can happen to all of us due to tiredness or stress, having cognitive fogginess day to day can be frustrating and debilitating; especially when you have a little human to look after and a life to lead. For many years, baby brain has simply been thought of as an old wives tail, but what physically occurs in the brain during pregnancy is something which has recently been explored. So, how does becoming a new parent alter structures in the brain and how does this explain the common condition of baby brain?
Could you repeat that please: Cognitive Symptoms
Baby brain is thought to start during pregnancy. A cognitive study of pregnant and non-pregnant woman revealed pregnant woman in their third trimester had reduced cognitive function, executive functioning and memory compared to their non-pregnant counterparts . For example, pregnant women were less good at remembering numerical sequences than non-pregnant women, implying their ability to hold novel information and process it is impaired. These symptoms begin in the first trimester of pregnancy, with problems in memory and cognitive function significantly changing between the first and second trimester. However, this decline stabilises in the second trimester until the end of the pregnancy. This study aids the confirmation that baby brain is a real cognitive condition as this impairment is seen across many pregnant women. So, if you are pregnant and feel ridiculous for forgetting to drink that cup of tea you made 4 hours ago, don’t. It seems to be a normal part of growing a human.
We’re goin’ through changes: Pregnancy-Induced Brain Alterations
Symptoms of baby brain are hard to experience and explain to others, but what is causing these alterations to your normal cognitive function? Research has found that pregnancy induces changes to the number of neurons and their connections in your brain; described by alterations to the levels of grey matter. Grey matter describes sections of the brain packed with neurons and throughout pregnancy, the volume of this matter reduces in specific brain regions associated with social cognition . It is believed these changes are adaptive and help prepare a woman for motherhood, as a study found the levels of these changes corresponded to the level of attachment a mother showed towards her child. This loss of grey matter still persists two years after pregnancy, suggesting long-term alterations to social cognition processes. However, a reduction of grey matter does not necessarily equate to a loss of function, but could potentially represent a fine tuning of ‘important’ connections. This is what happens during infant development and adolescence with the aim of keeping only the most important synaptic connections; allowing you to channel your focus. The implications of this study could explain why it is difficult to leave a baby to go on a night out with the girls or go back to work as the focus of your social priorities have shifted massively compared to the days before you were a parent.
Rewiring Circuits: Neuron Changes in Pregnant Rodents
As a cell neurobiologist, I am always interested in the small changes made at the neuron level which lead to these huge shifts in cognitive balance. However, with baby brain, it is somewhat of a challenge to study individual live neurons inside a pregnant woman’s brain. However, we can learn a lot about our own neuron’s experience of baby brain from our furry siblings.
Behaviour wise, many rodent experiments show postpartum mothers have reduced anxiety, improved memory and resistance to stress . But what is going on at the cellular level? During pregnancy, some studies have shown there is reduced activity of neurons in brain regions associated with stress and anxiety, as well as HPA Axis down regulation, which would be important for directing energy normally used for stress into the pregnancy. There is also an increase in synaptic number in the hippocampus; the region associated with memory; as well as an increase in the generation of new neurons in a region called the sub-ventricular zone, meaning novel connections needed for maternal behaviours can be made upon the birth of the pups. The majority of these changes are carried through to initial postpartum stages, however there is a decrease in the production of new neurons in the dentate gyrus (part of the hippocampal formation). Finally, in the stages following weaning, anxiety behaviours are increased and in memory regions, there is a decrease in synaptic connections in first-time mothers but an increase in mother’s who have given birth before. These final changes in rodents are probably important for the mother’s survival and to increase the chance of multiple mating’s.
From studying rodents in a controlled environment during gestation, we can see how complex alterations to the brain during pregnancy and postpartum periods are. Trying to translate these data into a human setting is difficult as human’s do not have large litters of pups or are driven to mate as soon as their offspring is weaned like rodents. Plus, human brains experience different hormone changes during pregnancy and have much more complex, higher-functioning behaviours than rodent brains, which could also be altered while pregnant. However, what the rodent studies do tell us is that pregnancy drives plasticity in the brain, including alterations to synaptic number and new neuron production, and these are mainly in the regions associated with anxiety and memory. In humans, memory and anxiety are two behaviours altered in soon-to-be mothers, so it will be interesting to explore the cellular basis of these behaviours once technology permits.
Bye-Bye Baby: Concluding Remarks
With pregnancy and being a new mother comes a lot of burdens, alterations to hormones and changes to routine which can undoubtedly lead to huge bouts of stress. However, plasticity experienced in the brain was a process over-looked due to lack of research and understanding. However, the study confirming grey matter changes in pregnant women which last at least 2 years following birth gives the first true evidence for the scientific process of 'baby brain'.
If you are struggling with focus and memory on any tasks other than your new little one, this is completely normal. Your brain has just gone through a huge rewiring job to prepare you for motherhood. This most likely makes trying to act like you were ‘before’ a challenge, so don’t be hard on yourself if you are struggling to get back into routine. In the future, it will be interesting to explore the molecular basis of these alterations in order to provide a deeper explanation for pregnant women as to why they feel ‘brain foggy’ and also develop successful coping mechanisms. Studying if any of these changes occur in new dad's will also be interesting as different hormones and environmental influences would also have to be researched. But for now, if you forget to go to an appointment or accidentally dunk a piece of lego in your tea, relax; it's completely normal behaviour after growing a new human.
1. Davies et al (2018), Cognitive impairment during pregnancy: a meta-analysis, Med J Aust, 208 (1): 35-40
2. Hoekzema et al (2017). Pregnancy leads to long-lasting changes in human brain structure. Nature Neuroscience 20: 287–296.