TV Review: Limitless with Chris Hemsworth – Memory

If you don't have your memories, did you ever exist? What are the implications of this for those who suffer with memory loss?

Chris Hemsworth's 'Limitless' is a six-part docuseries in which he challenges his mind and body in different ways over various episodes on a quest to gather and develop habits that may extend his life. Throughout this series, he deals with stress, tests his strength, and considers fasting. In this episode 'Memory', Hemsworth receives worrying results from his DNA tests.

The episode begins with, what I considered to be, an interesting, metaphysical question about how our memory makes us who we are. It's how we know our friends and families and maintain our relationship with them. I felt that this was a gripping and widely relatable introduction.

Hemsworth explains that at the beginning of the series he undertook a 'whole list of tests' to discover his propensity for certain medical conditions. The range of conditions covered by these tests is not specified by longevity expert, Dr Peter Attia. As a researcher, I would have liked to have known more detail about the genetic tests that were undertaken, and I believe the general public would too, particularly considering the ready availability of DNA testing through means such as 23andMe for example. However, one thing that is made clear is that the testing looked at the APOE gene – which is well known to affect Alzheimer's disease risk. Testing revealed Hemsworth to have two copies of the APOE4 variant, increasing his Alzheimer's risk eight- to ten-fold, compared to the general population.

Dr Attia then, in my opinion, controversially, suggests this finding may actually be 'a blessing' for Hemsworth; it highlights the importance of working out the mind as well as the body. While I appreciate the reasoning behind this, I cannot help but wonder how a viewer who has recently undertaken genetic testing and received less than favourable results would perceive this.

After receiving these results, Hemsworth consults leading neurologist, Dr Sharon Sha, to find out what he can do to maintain his memory. Dr Sha explained that the brain begins to degenerate after the age of 30 and attempts to maintain and improve memory are better started early. Such attempts should include novel challenges to help stimulate neuronal connections, improving brain plasticity and enhancing cognition. This leads on to the focus of this episode – to reduce Hemsworth's Alzheimer's risk by challenging him to a 'boot camp for the brain'.

The challenge is set in Australia's Macleay Valley region. Here, Hemsworth disconnects from the outside world by 'going off the grid'. With no phone or GPS, and only a friend for social interaction, he must use his brain to navigate through the wilderness. Dr Sha explained that planning a route and memorising it is one of the most complex actions the human brain can do, and uses the hippocampus. An explanation of what the hippocampus is and its role as the 'brain's memory centre' is provided, which is likely to be understood by both a scientifically knowledgeable audience and novices alike.

At this stage of the episode, I began to question what more practical things viewers can do to reduce their Alzheimer's risk and memory loss. As if on cue, Dr Attia discussed the benefits of lifestyle changes we can all incorporate without setting off to the wilderness! Sleep is discussed here in particular detail. Dr Attia explained that sleep is not a passive process, removing toxins from the brain that could predispose us to Alzheimer's. Hemsworth further explained that as we age, the glymphatic system, responsible for removal of waste from the brain, becomes less effective. Alongside reduced sleep, toxins may build up quicker than they can be removed, leading to inflammation and potentially Alzheimer's. It is important to note here that Alzheimer's is a complex condition that cannot be attributed to one single factor.

The episode then moves on to applying the components of Hemsworth's 'boot camp for the brain', which combined complex cognitive feats with physical activity, to real-life scenarios of improving memory. Research investigating the effect of dance on the brain found that dancing stimulates more hippocampal growth than other, more repetitive forms of exercise. This prompted Professor Notger Müller, research group leader in Neuroprotection at the German Centre for Neurodegenerative Diseases, to hope that dance may be used to prevent cases of dementia. The difference between dementia and Alzheimer's appears lost at this point. Dementia describes conditions where memory loss is a characteristic, while Alzheimer's is a cause of dementia. This distinction is not often made by the general public and it appears that this episode isn't set to change this.

Additionally, as much as I am intrigued and excited by the prospect of preventing dementia, considering my continuous engagement in dementia care, I still found Professor Müller's hopes of implicating dance in this to be premature; it must be acknowledged that more research is needed to corroborate this positive effect and also to consider whether any positive effects of dance on cognition would be more marked if started at a younger age. The latter is particularly important in light of Dr Sha's earlier statement that Alzheimer's develops much earlier than overt symptoms appear.

Investigation into memory is, arguably, more relevant now than ever. Considering that we have an ageing population and dementia is being diagnosed now more than ever, this episode touches on a very topical issue in an interesting way.