• Pregnancy Brain

    Over the past few years I’ve been working with ITV Global. It all started a couple of years back when I was invited to give my Sort Your Brain Out and Neuroscience of Negotiation talks for various members of their senior leadership team, both domestically and worldwide. This year and last the focus shifted to my Science of Creativity talk which I gave for their 100+ leaders across the full breadth of the organisation over the course of six live events. After one of these speaking engagements I was approached by an audience member who’d had a question on her mind since falling pregnant shortly after one of the talks I’d given previously (nothing to do with me!). She had noticed that her usually exceptional memory had gradually eroded as the pregnancy progressed. The burning question was: is the phenomenon of ‘pregnancy brain’ fact or fiction and, more to the point, was there any hope of her getting her previously brilliant memory back again? Had she asked me this question a year earlier I would have had to admit that science hadn’t yet addressed the question properly. As it happens her timing was excellent – a brain imaging study had just been published that might just provide the answer she was hoping for. I promised I’d write a blog about it, so here it is…

    The groundbreaking study by lead author Elseline Hoekzema and colleagues at the Autonomous University of Barcelona and Leiden University was published in the journal Nature Neuroscience. They used Magnetic Resonance Imaging (MRI) to measure the key changes that take place in the female brain as a result of pregnancy. They found that the grey matter consistently shrinks in brain areas commonly associated with social cognition and the greater the degree of volume reduction in these areas, the deeper the mother-child bond. The brain areas in question included in the Superior Temporal Sulcus (STS) and Inferior Frontal Gyrus (IFG) on the outward-facing surface of the left and right hemisphere, and the Precuneus and medial Prefrontal Cortex (mPFC) of the inward-facing surface where left and right hemispheres meet in the middle. Far from reflecting a withering away of brain areas under assault from the tsunami of hormones that regulate gestation (mothers are exposed to progesterone levels over ten times greater than the highest levels of the normal menstrual cycle and more oestrogen during pregnancy than the rest of their lives put together) the changes actually reflect adaptations specialising the brain for maternal attachment.

    Volume reductions were also observed in the hippocampus which could explain the degradation of memory that many women experience during and just after pregnancy. While memory wasn’t rigorously tested (they did a couple of tests but only found a trend towards memory loss) in this particular study, new mothers may take comfort from the observation that while the brain areas involved in social cognition remained two years after completion of the pregnancy, the volume of the left hippocampus had partially recovered (in 11 of the 25 mothers who had not fallen pregnant again). Assuming that the hippocampal volume continues to increase at the same rate, it would fall back into the normal range by around five years after the completion of pregnancy. Given the vital importance of the hippocampus for memory and navigation this seems to be a very promising result.

    This study used MRI to scan the brains of 50 women, of which 25 later fell pregnant for the first time. All were re-scanned after the babies were born, or after a similar period of time had elapsed for those who hadn’t fallen pregnant, so that brain structure could be compared before and after. Those women who did not fall pregnant served as the controls in which no significant structural changes were observed. Changes in brain tissue volume were only observed in those women who did fall pregnant confirming that pregnancy was the likely cause of the changes. They also performed an fMRI study looking for brain areas that were more strongly activated by pictures of each mother’s own baby compared to photos of other people’s babies. As there was considerable overlap between the brain areas more strongly activated by the mother’s own baby and those in which the brain volume reductions occurred, it seems likely that it reflects a process of specialisation for maternal attachment rather than collateral damage.  As these areas are commonly associated with the capacity for Theory of Mind, i.e. the ability to see the world from another’s perspective, these changes presumably reflect a tailoring of the mother’s brain to help them better anticipate the needs of their child.

    In addition to these monthly blogs I regularly tweet (@drjacklewis) interesting articles about recent breakthroughs in brain science and do a fortnightly Geek Chic’s Weird Science podcast on strange and wonderful stories from the world of science. Season 2 of my television series Secrets of the Brain starts on Insight TV later this month… so if you are in the UK or Ireland have Sky television you might consider setting your box to record the series on HD channel 564 and if you are elsewhere in Europe you will find it on other satellite/cable providers (check which channel it’s on in your country here). If it’s not available on your TV you can also stream it online via www.insight.tv

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  • Hold On To Your Grey Matter – Take a Walk by Dr Jack

    Older brain on the left, younger brain on the right

    From adolescence onwards we all begin to lose brain cells. As a consequence our brains gradually and inexorably shrink (compare the “old” brain on the left to the “young” brain on the right). In fact by the age of 80 your brain will occupy 15% less of the space within your skull than in the prime of life. Yet over the course of adulthood, as our brains are losing more and more cells, our knowledge and repertoire of skills nonetheless continues to grow as we accumulate more and more experience. How is this possible? Well, despite the incremental decrease in quantity of brain cells over the years connections between neuronal networks that are in regular and intensive communication with each other are selectively reinforced. This enables increased efficiency in execution of the mental processes that those networks support. Hence we can do more with less as we age. Sadly, for all of us, there will always come a time when the degree of brain cell loss is such that mental function begins to decline. In other words, if we all could live forever, dementia will inevitably strike at some point in time.

    Although we cannot halt the process of grey matter loss completely, the good news is that we can slow down its progression. This month a study conducted at the University of Pittsburgh and published in the journal “Neurology” describes the influence of regular exercise on the rate of reduction of brain volume and cognitive function in 299 elderly individuals.

    It was observed that those individuals of this group of average age 78 who walked in excess of 6 miles per week had a significantly reduced rate of grey matter loss and consequently a lesser degree of cognitive decline. The greater the distance walked each week, the smaller the reduction in volume over a 9 year period within their frontal lobe, occipital lobe, entorhinal cortex and critically, in the hippocampus. My post last month described the vital role that the hippocampus plays in the creation and recall of long term memories.

    This begs the question – how and why does exercise slow down the rate at which grey matter shrinks? An exciting possibility is that all that walking might actually increase the rate at which new brain cells are created; a process known as neurogenesis. This boost in the creation of new brain cells might help to compensate for the loss of old brain cells. Evidence to support this hypothesis comes from research conducted over a decade ago suggesting, in the mouse brain at least, that exercise does indeed increase the rate of neurogenesis.

    Exactly why this happens is unclear, but I would propose that, given the hippocampus is heavily involved in navigation, particularly when it comes to flexibility in finding the best route from A to B, it would make sense for physical activity to trigger production of new cells in this brain area. A greater number of hippocampal neurons would presumably support a greater capacity to memorise routes and landmarks encountered whilst exploring the environment. This could feasibly convey a critical survival advantage by helping to prevent people from getting lost. Over the thousands of years of our species evolultion, getting lost was probably an excellent way of deleting oneself from the gene pool and so those with movement-triggered hippocampal neurogenesis may have been more likely to survive.

    This seems a plausible (but by no means concrete) account of why older individuals who take regular exercise appear to have more grey matter and superior cognitive function than those who do not. Whatever the true explanation, it seems clear if you want to hang onto your marbles in the long term then it’s probably a good idea to take a regular stroll for the rest of your life.

    You can follow Dr Jack’s daily #BrainTweets by clicking here, and pushing the “Follow” button.

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