Monthly Archives: December 2010

A Short Video on Human Evolution

As something of a hobby, over the past 18 months I have been filming primates in various places. To pause and reflect on where we have come from, I am filled with awe at the truth laid out by Charles Darwin. To watch the Ring Tailed Lemur is to see not just a magnificent creature but also our relative. A relative separated from us by over 60 million years. To think that they had turned one way and we another. The circumstances are unclear as one would expect given such a time period. Perhaps our ancestors outpopulated the Lemurs. One thing became clear though. They all but disappeared from other parts of the world. They became isolated on the island of Madagascar. It is thought that they arrived there after the separation of Madagascar from Africa. Indeed it is speculated that they migrated across on driftwood, surviving a long journey on whatever foliage was available. Meanwhile in Africa, our ancestors were taking a very different journey. With the passage of time our ancestors would develop ever more sophisticated skills as brain volume increased and adaptation to challenging environments shaped our history. Yet in the same instance there is still a strong connection. One simple example will suffice. For the Lemur, the digits of the hands and feet are divergent. A little while spent with these creatures is enough to show how versatile their interactions with the environment can be as a result and how this can shape their behavioural strategies. Further along our journey other significant adaptations have occurred and broadly speaking we may think of the primates as consisting of two groups – the Strepsirrhini which include the Lemurs and the Haplorrhini. The latter group includes the Old World Monkeys, the New World Monkeys and the Greater Apes of which we are a member. When looking through the eyes of a primatologist or anthropologist an understanding of the connections becomes a focus for study and the insights gained can be quite profound when applied to our evolution and nature.

So to cut to the chase, what I did was to aggregate footage from my travels into a short 5 minute video. In the first half, our journey is illustrated by reference to the groups that diverged from our ancestors over a given period of time. In the second half, i’ve included public domain footage from the Prelinger Archives enabling me to contrast footage of humans and other primates. The reader i’m sure will disagree with some (or even all!) of the comparisons I’ve made but it is not unreasonable to make comparisons given the success of evolutionary theory (I would also add that some of the clips have been added rather lightheartedly – i’m sure the vertical sit-up wasn’t originated by the Squirrel Monkey).  The general theories of evolutionary psychology or psychiatry can be made more specific through such observations particularly where they are environmentally contextualised. Such comparisons also offer the possibility of ‘centering’ – a movement away from the anthropomorphic into a primatomorphic view that is perhaps necessary for us to gain an insight into the complexities and problems posed by our thoughts, feelings and behaviours. I would also like to thank the various organisations that have supported me in this endeavour as well as the talented musician Rick Clarke who has selflessly made available his music for use by others.

Index: An index of the site can be found here. The page contains links to all of the articles in the blog in chronological order. Twitter: You can follow ‘The Amazing World of Psychiatry’ Twitter by clicking on this link. Podcast: You can listen to this post on Odiogo by clicking on this link (there may be a small delay between publishing of the blog article and the availability of the podcast). It is available for a limited period. TAWOP Channel: You can follow the TAWOP Channel on YouTube by clicking on this link. Responses: If you have any comments, you can leave them below or alternatively e-mail justinmarley17@yahoo.co.uk. Disclaimer: The comments made here represent the opinions of the author and do not represent the profession or any body/organisation. The comments made here are not meant as a source of medical advice and those seeking medical advice are advised to consult with their own doctor. The author is not responsible for the contents of any external sites that are linked to in this blog.

Novel Drug Discoveries in Alzheimer’s Disease

In a short report titled ‘A diverse portfolio of novel drug discovery efforts for Alzheimer’s disease: Meeting report from the 11th International Conference on Alzheimer’s Drug Discovery, 27-28 September 2010, Jersey City, NJ, USA’ (freely available here), authors Lee and colleagues outline new developments in Alzheimer’s Disease drug therapies. These developments are all at the research stage and so it may be some time before we see them used clinically if they are successful. The authors essentially highlight areas of interest in the conference and their report is broadly divided into biomarkers, targetting Amyloid-Beta pathology, neuroprotection/cognitive enhancement and frontotemporal dementia/tauopathies. In terms of biomarkers, the authors summarise new approaches including metabolomics and immunosignatures as well as quality control in all stages of data management. For the targetting of Beta-Amyloid pathology the authors mention talks on β-secretase and γ-secretase enzymes, RAGE and fibrinogen. Neuroprotective and cognitive enhancement strategies are varied and ultimately will depend on the clinical trials. The authors mention allopregnanolone, cAMP responsive element-binding protein and Sildenafil, hippocampal hyperexcitability and levetriacetam as well as blocking Aβ oligomer binding to neurons amongst other strategies. Finally in terms of frontotemporal dementia and the tauopathies the authors mention mitoxantroneantisense nucleic acid tag and
phosphatase 2A. The field is so complex that the report represents a ‘snapshot of a snapshot’ of the current research in the field of dementia. Nevertheless this highly structured report offers a framework on which to extend an understanding of additional strategies into dementia diagnosis and treatment.

Index: An index of the site can be found here. The page contains links to all of the articles in the blog in chronological order. Twitter: You can follow ‘The Amazing World of Psychiatry’ Twitter by clicking on this link. Podcast: You can listen to this post on Odiogo by clicking on this link (there may be a small delay between publishing of the blog article and the availability of the podcast). It is available for a limited period. TAWOP Channel: You can follow the TAWOP Channel on YouTube by clicking on this link. Responses: If you have any comments, you can leave them below or alternatively e-mail justinmarley17@yahoo.co.uk. Disclaimer: The comments made here represent the opinions of the author and do not represent the profession or any body/organisation. The comments made here are not meant as a source of medical advice and those seeking medical advice are advised to consult with their own doctor. The author is not responsible for the contents of any external sites that are linked to in this blog.

News Round-Up 2010 3rd Edition: Visual Motion Processing in Alzheimer’s Disease and Freud’s Effect on British Culture

A brief report on progress in therapy for Alzheimer’s Disease has been published at the Journal of Alzheimer’s Research and Therapy. The authors summarise different strategies being pursued currently including those  targetting the Amyloid-Beta peptide.

A longitudinal study (n=3494) examining the relationship between caffeine intake and subsequent dementia found that there was no significant association between caffeine intake and forms of dementia including Vascular and Alzheimer’s Dementia. There was found to be  a significant difference between those in the lowest and highest quartiles of caffeine intake with those in the highest quartile having a lower number of dementia associated brain lesions at post-mortem.

In an article freely available here, researchers detail the post-mortem findings on the first person with Alzheimer’s Disease to undergo PET scan imaging with Pittsburgh B compound. The researchers found a strong correlation between the PET findings and the occurrence of plaques but not tangles at post-mortem. Thus this study lends support to the benefits of Pittsburgh B compound in the assessment process although there are limitations on the conclusions that can be drawn.

In a study including 214 subjects – young, middle-aged, older adults and people with Alzheimer’s Disease the latter group were differentiated by performance on a visual motion processing task in which randomly moving dots were presented in the visual field. It will be interesting to see the results of further studies in this area.

A recent paper in the Lancet Neurology reviews developments in behavioural variant Frontotemporal Dementia including a new classification scheme which is characterised by the likelihood that the disease is correct.

There is a write-up here of a study involving participants in their 20’s, 40’s and 60’s. The researchers found evidence that the older adult group were better at reappraising negative events positively but that the other two groups scored more highly on tasks that involved ‘detached appraisal’ in which events are viewed while dissociating feelings.

Mind Hacks has another interesting round-up of Spike Activity featuring links to a radio program on the influence of Freud on British Culture as well as a case-study on a person who was unable to experience fear after a lesion to the Amygdala.

Index: An index of the site can be found here. The page contains links to all of the articles in the blog in chronological order. Twitter: You can follow ‘The Amazing World of Psychiatry’ Twitter by clicking on this link. Podcast: You can listen to this post on Odiogo by clicking on this link (there may be a small delay between publishing of the blog article and the availability of the podcast). It is available for a limited period. TAWOP Channel: You can follow the TAWOP Channel on YouTube by clicking on this link. Responses: If you have any comments, you can leave them below or alternatively e-mail justinmarley17@yahoo.co.uk. Disclaimer: The comments made here represent the opinions of the author and do not represent the profession or any body/organisation. The comments made here are not meant as a source of medical advice and those seeking medical advice are advised to consult with their own doctor. The author is not responsible for the contents of any external sites that are linked to in this blog.

What an Ancient Greek Computer Tells us About the Transmission of Scientific Knowledge

In the present age, science and technology have advanced at a rapid pace. There are numerous reasons for this – population expansion, improved communication, education and effective systematisation. We assume that this is a natural progression of civilisation. However every once in a while something comes along which turns everything on its head and makes us question our assumptions. That something in this case is an ancient Greek computer known as the Antikythera mechanism.

The Antikythera Mechanism

In 1900 a group of sponge divers were stranded by a storm on the Greek island of Antikythera. They chose to search for sponges while the storm cleared. During one such dive they discovered the remains of a ship. They initially recovered a number of artifacts from the ship and later others undertook recovery work. Sadly many lives were lost during the recovery of these items.  While many items of historical significance were recovered, none were more startling than the item which later became known as the Antikythera mechanism. The device is dated to approximately 100 BC.

A superficial glance at the picture above reveals two gear-like mechanisms amongst the surrounding bronze, corroded after two thousand years in the sea of Crete.

So What Does It Do?

The obvious question to ask at this point is what is the function of the Antikythera Mechanism if anything? Here’s where the story starts to get really interesting. In 1950, historian Professor Price together with a nuclear physicist Professor Karakalos investigated the device using imaging technology and formulated a hypothesis. They believed the device was a computer that was able to calculate calendar dates and that it used a differential gear mechanism to achieve this (interestingly Professor Price was also known for Price’s law – a variation on the Pareto Principle – he suggested that 75% of the scientific literature was produced by 25% of the scientists).  A series of other investigators have applied ever more sophisticated imaging methods to the device and proposed ever more intricate interpretations of the device’s function. What became clear with these investigations was that the device had a large number of gears some of which were very small. Another team disputed the use of a differential gear mechanism. However so sophisticated is the device that several teams from across the world are continuing to work on a correct interpretation. More than 100 years after the discovery of the device, it is thought to perform several functions. The device is thought to calculate the position of the sun, moon and planets according to the Egyptian Sothic cycle and makes adjustments and eclipse predictions according to the Metonic and Saros cycles. This latter cycle is a product of the Babylonian culture. The device also displays the dates of the Olympics. The writing on the device is in Greek and also includes the first recorded reference to Spain as Hispania rather than Iberia.

Reconstruction Using Lego Bricks

In 2010 the device was reconstructed with lego bricks on the assumption that the device does indeed use a differential gear mechanism. The findings were published in Nature and feature on their YouTube channel. The video demonstrates the mechanism being used to predict a solar eclipse in 2024.

Who Created the Device?

The designer and builders of the device are unknown although candidates for the designer include Hipparchus, Archimedes and Posidonius. These polymaths were directly or indirectly influenced by other cultures including those of Egypt and Babylon which would be consistent with the influence from those cultures seen in the device.

Lost in Translation

If this device and others like it existed then why wasn’t there a gradual process of refinement over the last 2100 years? It is commonly assumed that civilisation advances through gradual improvements in all aspects of that civilisation whether this means science, technology, art, law and so on unless such a civilisation is in decline. However in this case, the discovery comes as a great surprise some 2000 years later and reveals technology that was only just reinvented in Western Civilisation a few hundred years earlier. Already by 100 BC a device of this nature is appropriated by the Romans according to Cicero. In his writing at that time the Roman possessors of this Greek technology are impressed by the device but do not appear to understand how it works. For this to happen then perhaps the only solution is to understand the theory behind the device.  That means going back to the work of the great Greek polymaths thought to have designed the device.

So the next question is what happened to the works of the Greek polymaths? Copies of these works would have been stored in the Library of Alexandria which was established by Ptolemy, a general in the army of Alexander III of Macedon. The reputation of the Library of Alexandria has lasted through the ages. However the library was partially and completely destroyed at various points in history. In a widely cited story, on the first occasion it is said that Julius Caesar accidentally set fire to the library while burning his own ships during a war against Ptolemy VIII. Work on mechanical devices does however resurface. In Baghdad in 850, a book titled Kitab al-Hiyal or the ‘Book of Ingenious Devices‘ was published and described approximately 100 mechanical devices. This book was widely disseminated and influential. Elsewhere a geared calendar device was identified from the 5-6th century AD. Although much ancient Greek scientific and mathematical theory was included in Western civilisation up until that time, it was during the Renaissance that other Hellenistic works were translated into Latin where they became more accessible.

Using the Antikythera Mechanism to Reinterpret History

If the technology behind the Antikythera Mechanism had been widely and understood, replicated and refined then perhaps history would have looked a little different. Here are a few events that are interesting to interpret in view of this device.

Kepler’s Laws of Motion

It is postulated that the gears in the device modify the course of the moon so that it approximates Kepler’s second law of motion which says that if a planet orbits the sun, then a line joining that planet to the sun will sweep out an equivalent area in an specified time period. Kepler’s laws were revolutionary at the time and later enabled Isaac Newton to formulate his theory of universal gravitation. While it is interesting to ask the question of how these two events might have been influenced by a widely disseminated Antikythera device it should also be noted that the device operates using a geocentric model. This means that the earth is considered to be the centre around which the sun and planets rotate rather than our contemporary understanding. Nevertheless it is interesting to think of how any change in these discoveries would have influenced the course of history given the various applications that have been derived.

Differential Gears and the Industrial Revolution

Richard Roberts was an engineer who in 1832 patented a differential gear mechanism for use in road locomotives which are the precursors of cars. He was an important player in Britain’s Industrial Revolution. The use of differential gears in the Antikythera mechanism has been contested although it is assumed in the video demonstration above. It should be noted that the Chinese South Pointing Chariot is described as having a differential gear mechanism and precedes the Antikythera mechanism by 1000 2500 years although there is no evidence of the original  device itself.

Charles Babbage and the Programmable Computer

The Antikythera Mechanism is an analog computer. That much is clear. Charles Babbage’s concept of a programmable computer was a revolutionary breakthrough although his design wouldn’t be implemented for another few centuries. The first program for his computer was written by Ada Lovelace, daughter of Lord Byron. The question is whether the Greek polymaths had got there first with their device. If the Antikythera mechanism had become widespread perhaps the digital computer would have arrived earlier  would be contingent on developments in electronics.

The Astrolabe and the Americas

An astrolabe is a device for predicting the movement of the sun, moon, planets and stars. Astronomer Abraham Zacuto refined a metal astrolobe and detailed many of his findings in 1496 in a book titled Ha-jibbur Ha-gadol. Portuguese sailors used his device while navigating to South America. While there are subtle differences in the Marine Astrolabe, widespread knowledge of the above device at the time of its invention would have no doubt accelerated the development of the Marine Astrolabe although the Astrolabe has numerous other functions.

Lessons From History?

The lesson to learn from this device are not restricted to physics and engineering but are relevant to other branches of science including medicine.

1. Integrate information from across civilisations. This designers of this device included Hellenistic, Egyptian and Babylonian knowledge in their device. 2000 years later despite advances in our civilisation, this device is still yielding secrets even a century after discovery and intensive study by specialised groups. However there are barriers to integration of knowledge from different civilisations. In contemporary society the modern analogy is with the emerging scientific communities in South East Asia with a potential barrier between Western and South East Asian scientific communities. The barrier in this case is language and a solution to this problem would be the assignation of a taskforce for coordinating translation of the relevant scientific work between communities although this would require considerable resources.

2. Create a civilisation-independent repository for scientific information that can be disseminated in a culturally independent manner. The information here was ‘locked into’ civilisations by various means including language. If knowledge is important then it needs to be transmitted. Science needs a flow of information between civilisations by storing it in a manner which facilitates dissemination. As an example, mathematical notation enables mathematicians globally to understand each other even without speaking the same language.  While science is an integral part of civilisation it also needs to have its ‘own space’ in recognition of the search for ‘truth’ that is common to scientists and which is ideologically and politically independent.

3. A global scientific body should recognise when contributions to a scientific field are dependent on the works of  key figures whose understanding is unsurpassed. Without such scientists that body of science is in danger of regressing. In this case, the Hellenistic polymaths did not appear to pass their knowledge onto subsequent generations or if they did then it was not easily recognised. Such work can be distributed amongst teams in a properly coordinated program.

4. For archaeological evidence the standard of reasonable evidence that is required is often incompatible with the probability of locating this physical evidence. In this case, extant written records reference devices of this nature but it is unlikely that serious consideration would be given to these without supporting physical evidence. Only a few of these devices may have been produced and it’s fortuitous that the Antikythera mechanism was discovered. Had it not been so then a certain truth about our history would have been rejected. This implies that the burden of proof should be in refutation of multiple and reliable written historical sources.

5. Important technology should be mass produced and disseminated within culture to minimise the risk of extinction of this technology and associated knowledge.  In this case the relevant science and technology for this device appears to have been restricted to a small population that was vulnerable to the risk of not being able to effectively transmit this information. It is possible to argue that this difficulty has held back science and technology by as much as 1000 years. The important conclusion here is that the rapid dissemination of key technology and science is essential to avoid loss. This applies especially to digital information where both organisational and physical distribution of data is necessary to reduce the probability of data extinction.

6. The problems associated with knowledge loss may be coming more widespread. Given the large increase in the global population together with the marked increase in education standards and an increase in intelligence at the population level (the Flynn effect) as well as systematisation countries now have have at their disposal multiple institutions having resources similar to or even greater than those at the disposal of the Greek polymaths. These institutions are integrated into society. Nevertheless the closure of departments or a change of research direction of a department carries with it the risk of loss of knowledge of a similar magnitude to that characterised by the Antikythera mechanism. While such loss is not evident in the present, the gradual improvement in knowledge had this line of investigation been pursued would compound as time progresses. To draw an analogy – if the Greek polymaths operated as todays researchers in institutes did then it would be as though the ‘research department’  developing the Antikythera mechanism was closed down due to a lack of funding. The implication is that research projects should include knowledge transfer before successful closure.

Aknowledgements

The picture of the Antikythera mechanism is distributed under a Creative Commons 3.0 License and was obtained from the following location – http://en.wikipedia.org/wiki/File:NAMA_Machine_d%27Anticyth%C3%A8re_1.jpg

Index: An index of the site can be found here. The page contains links to all of the articles in the blog in chronological order. Twitter: You can follow ‘The Amazing World of Psychiatry’ Twitter by clicking on this link. Podcast: You can listen to this post on Odiogo by clicking on this link (there may be a small delay between publishing of the blog article and the availability of the podcast). It is available for a limited period. TAWOP Channel: You can follow the TAWOP Channel on YouTube by clicking on this link. Responses: If you have any comments, you can leave them below or alternatively e-mail justinmarley17@yahoo.co.uk. Disclaimer: The comments made here represent the opinions of the author and do not represent the profession or any body/organisation. The comments made here are not meant as a source of medical advice and those seeking medical advice are advised to consult with their own doctor. The author is not responsible for the contents of any external sites that are linked to in this blog.

Blogging About Pharmacology: Pharmacology Corner

For those interested in pharmacology there’s a interesting blog on the subject over at ‘Pharmacology Corner‘. The ‘About‘ section tells us that the blog is by Flavio Guzmán, an Argentinian physician lecturing in pharmacology. The blog is self-hosted and in my experience of navigating the blog, it was for me slightly slow in moving between pages. There are also frequent pop-ups asking the reader to subscribe to the blog which further slowed down the navigation. These things aside however, the blog has a nice design. The design is simple and aesthetic with a central white pane containing the articles and the surrounding background in yellowish grey contrasting distinctively with the eyes being particularly drawn to the central diagram of a synapse with alpha receptors highlighted. There are also some very colourful diagrams in the articles which contribute effectively to the overall design. There are links to exam topics and animations in the header section. On the right hand side of the central pane there is also a pharmacology blogroll. Articles are indexed according to categories including pharmacodynamics and pharmacokinetics on the right side of the central pane facilitating navigation. If those categories don’t appeal to the reader, then they must navigate backwards through the blog. While I may have overlooked something, the only means of navigating backwards I could see was to click on the links to articles sited beneath the older posts heading at the bottom of the screen. Indeed at the time of writing four such articles were linked to in this manner. Clicking on the bottom link led to an article on aspirin pharmacokinetics. However I couldn’t see an obvious way to move backwards from this article and needed therefore to depend on the category index to reach other articles. This seemed to indicate that there were only a few articles.  Nevertheless by clicking on one of the categories – in this case antihypertensives – a group of articles were displayed some of which dated back as far as 2009. This meant in effect that the backwards navigation (at the bottom of the screen) wasn’t revealing all of the articles – in my attempts I could only reach back as far as 2010. For this reason, the category index looked to me to be the best way to navigate the blog.

Turning to the content the articles were I thought well presented. Take as an example an article on differences between tricyclic and SNRI mechanism of action. As well as a detailed description of the mechanisms of action of both classes of drugs there are lists of drugs and also a memory aid in the form of a mind-map. The exam sections of the blog reveal that it is exam orientated and these features make sense in that context. There are also references for further reading and links to related articles which make these posts a useful starting point for further study. There is also a link to a facebook page at the bottom of the screen. Returning to the results in the antidepressants section, there are also links to videos and powerpoint presentations providing additional multimedia options for study. For me, the blog had more of a feel of being an encyclopedia with presentation of predominantly factual information which can be accessed using multiple approaches. Maybe this is a bloglopedia for want of a better neologism. The site is well presented and there is enough material and references to other sources for this to be a useful resource for those with an interest in pharmacology.

Index: An index of the site can be found here. The page contains links to all of the articles in the blog in chronological order. Twitter: You can follow ‘The Amazing World of Psychiatry’ Twitter by clicking on this link. Podcast: You can listen to this post on Odiogo by clicking on this link (there may be a small delay between publishing of the blog article and the availability of the podcast). It is available for a limited period. TAWOP Channel: You can follow the TAWOP Channel on YouTube by clicking on this link. Responses: If you have any comments, you can leave them below or alternatively e-mail justinmarley17@yahoo.co.uk. Disclaimer: The comments made here represent the opinions of the author and do not represent the profession or any body/organisation. The comments made here are not meant as a source of medical advice and those seeking medical advice are advised to consult with their own doctor. The author is not responsible for the contents of any external sites that are linked to in this blog.

The Insular Cortex: Part of the Brain that Connects Smell and Taste?

The connection between smell and taste is sometimes obvious but where in the brain does it occur? In a paper titled ‘The Insular Taste Cortex Contributes to Odor Quality Coding’ (freely available here), Veldhuizen and colleagues investigate where the ‘sweetness’ of odours is located in the brain. There are two candidates for this. One is the piriform cortex. Activity in the piriform cortex is thought to encode the smells that we experience. The other is a small region within the insular cortex known as the insular taste cortex  (check out this article for a closer look at the insular cortex). As its name suggests, activity in this region is thought to encode the quality of taste. So now that the researchers had narrowed down their options they chose to investigate their question using functional Magnetic Resonance Imaging. This imaging approach involves the application of strong magnetic fields to the brain. Without going into too much detail this aligns the molecules in the brain tissues and with the application of a pulsed radio frequency there is a realignment of the molecules with a corresponding release of energy. This energy is released in the form of photons and using some clever transformations, information about the tissues can then be deduced. A variation on this is the use of BOLD signals – that is blood oxygenation-level dependent signals. In essence this means that information about the blood flow in the brain can be deduced. Crudely speaking, the theory goes, if a region of the brain suddenly becomes active, it will become hungry for energy and will need more blood flow and will use up more oxygen. There are a number of reasons why it is not so simple but for the moment the argument holds – if a brain region is active, the researchers can tell this from the BOLD signal. That means that they can work out which part of the brain someone is using when they perform a certain task.

The researchers used a scanner with a strong field strength – 3 Tesla. Then their volunteers were asked to rate solutions and smells using measures including ‘edibility’, ‘familiarity’ and ‘pleasantness’. There were numerous subtleties to the design paradigm to ensure that other factors didn’t influence the test results and these are described in more detail in the paper. From the methodology section it looks as though the researchers created visual analogue scales for each of the psychological measures. In other words, they draw a line and ask the subjects to mark on it where their experience lies. So for instance the subject might be asked to rate the sweetness of a taste. The Visual Analogue Scale (VAS) would be minimal at one end and maximal at another end. This is a very flexible approach that can be used to give the researchers numbers that they can crunch. One drawback with this approach though is that sometimes it might not be as rigorous as the more thoroughly investigated scales that have been created to investigate these experiences.

When the researchers analysed the fMRI data, they factored in the ‘sniff volume’ and ‘tongue movements’ to ensure that the activity they were picking up didn’t represent these ‘movements’. They were of course interested only in the perception but movements themselves create activity in the brain. They then looked at an average activity for the ‘group’. In other words they looked at a ‘group brain’ representing the average activity amongst all subjects during a given response or task. Using this approach, they created a mask specifically for the strength of sweetness. So they discriminated between the perception of strong and weak tastes and then looked at where these occurred in the ‘group’ brain. Now in order to produce a map of activity in the brain, the researchers first of all divide up the brain into small cubes. These are known as voxels. In order to say a voxel is ‘active’ they have to set a threshold. It just so happens that if you take a large number of voxels, your bound to get some that will be firing above the threshold by chance when in fact they’re not really playing any role in the experience a person is having. This is where the statistics come in. Researchers have developed a strategy for dealing with this known as correcting for multiple comparisons (see this article for a very interesting debate on this subject). A very simple approach is to divide the probability used for the threshold calculation by the number of comparisons being made. In this manner, if more comparisons are being made then it means that it will be more difficult for an individual voxel to reach the threshold.  There are many other ways to do this which involve varying degrees of sophistication.

Now that the researchers had the ‘mask’ that separated out regions of the brain associated with strong and weak sweet tastes, they combined the mask with the multiple comparison approach to select out regions of the ‘group’ brain that was likely to be associated with strong sweet tastes. The researchers also used a special approach to analysing the activity in the voxels. Since a previous study (mentioned above) by Vul and colleagues had discussed ways in which strong associations could be wrongly produced with certain methods of analysing voxels, the researchers used a very specific analysis of the voxels in which they looked at how strongly individual voxel firing activity correlated with the stimulus of interest (e.g smell or taste). This constrasts with another approach in which average activity in groups of voxels is considered first of all. The researchers argue that their approach would reduce the likelihood of identifying false connections between brain activity and perceptions.

The researchers recruited 19 subjects for the study, but the data from 15 subjects was used in their analysis. The subjects were presented with food and floral odours. Subjects are also presented with odorless stimuli and they will undergo a run of stimulus presentations. The researchers found that two regions in the insular cortex were more strongly activated by strong sweet tastes than weak sweet tastes. This evidence suggested that these regions of the insular cortex were thus associated with strong sweet tastes. The researchers also found that activity in the insular cortex was strongly correlated with the sweetness perception of food odours. This did not apply to floral odours suggesting that there may be a strong biological value for this association (i.e in evolutionary terms it provides a strong adaptive value to detecting potentially high energy nutrients). The researchers then looked at areas which were activated with both strong smells and strong tastes. They found that two brain regions – the insular cortex bilaterally (right and left side of the brain) and the operculum were activated in this manner. The other areas that they were interested in – the piriform cortex and the orbitofrontal cortex – didn’t fire strongly in association with sweetness perception of odours. More significantly still the researchers found that there was an overlap in the insular cortex between regions active in response to sweet tastes and sweet smells and the strength of the sweetness perception.

What this meant to the researchers was that a region within the insular cortex probably rates the sweetness of tastes and odours and links these perceptions together. Savouring the aroma of a food can make the mouth water and we can anticipate how that food might taste. More importantly if we or our ancestors were searching for sweet foods, a smell emanating from that food would allow an anticipation of how that food might taste. Linking the two in the brain would enable us to quickly home in food sources with the aid of our smell. Additionally the insular cortex is plugged into emotional networks in the brain and this rapid integration of our smell and taste might influence and be guided by our emotions. While in humans our sense of smell isn’t as sophisticated as our vision, our ancestors have a much more sophisticated sense of smell. Richard Dawkins in his book ‘The Ancestor’s Tale‘ writes about our common ancestor with lemurs which we shared some 63 million years ago! If the reader watches the video below they will no doubt be impressed by the prominent snout of our primate relatives which is a reminder of just how important the sense of smell was in our distant past. I have selected the clip below which shows the lemur’s use of both smell and taste in examining an object.

Index: An index of the site can be found here. The page contains links to all of the articles in the blog in chronological order. Twitter: You can follow ‘The Amazing World of Psychiatry’ Twitter by clicking on this link. Podcast: You can listen to this post on Odiogo by clicking on this link (there may be a small delay between publishing of the blog article and the availability of the podcast). It is available for a limited period. TAWOP Channel: You can follow the TAWOP Channel on YouTube by clicking on this link. Responses: If you have any comments, you can leave them below or alternatively e-mail justinmarley17@yahoo.co.uk. Disclaimer: The comments made here represent the opinions of the author and do not represent the profession or any body/organisation. The comments made here are not meant as a source of medical advice and those seeking medical advice are advised to consult with their own doctor. The author is not responsible for the contents of any external sites that are linked to in this blog.

A Case of Infarct Connecting the Insular Cortex and the Heart

Cho and colleagues have published a case study linking the insular cortex with the heart. The paper is titled ‘Takotsubo Cardiomyopathy Following Cerebral Infarction Involving the Insular Cortex’ and is freely available here. The link between the insular cortex and the cardiovascular system has been known for quite a while now. For instance, the insular cortex is thought to have a role in regulation of blood pressure as well as other autonomic functions. This has been elaborated on by A Craig in several of his papers.

This is a case of 52 year-old man who presents with symptoms including

chest pain, speech disturbance and right hemiparesis

The authors note that while having features of an acute myocardial infarct they are unable to demonstrate obstruction of the coronary arteries on angiography but echocardiography reveals

hypokinesia of the middle and apical walls of the left ventricle

There is also ST elevation on the ECG. Digitalisation and heparinisation were associated with improvement on the echocardiogram and in the ST elevation. The term takotsubo refers to a Japanese fishing pot used to catch Octupus and in this case refers to the appearances identified on the ventriculogram. In their discussion the authors discuss Takotsubo Cardiomyopathy in more detail and then draw links with the insular cortex and suggest that these links should be further investigated. This reminded me of another study reviewed here.  There were associations with homocysteine elevation in this other report and T-wave inversion although this is the later phase of T-wave changes in the current report. Although there is hemiparesis in the current study, the other findings are different. While its difficult to disentangle cause and effect given the other areas involved, the authors conclusions are persuasive in the context of other literature in this area and assuming no confounding factors.

The implication is that an infarct to the Insular Cortex is sufficient in itself to change the manner in which the walls of the heart contract. The authors draw links with the sympathetic nervous system and if this is correct then it suggests that the insular cortex is able to influence the contraction of the heart through its role in the sympathetic nervous system. What is even more intriguing is that the contraction normalises despite the persistence of the infarct suggesting either rapid adaptation or an acute role for the insular cortex in changes in cardiac contractions. This latter interpretation is supported by studies showing rapid changes in insular cortex activity which correlate with exercise-induced changes in blood-pressure. How this all relates to emotions is another matter although here as Craig would suggest there is an important role for the insular cortex. The case report raises interesting questions as well as building up the evidence for the relationship between the insular cortex and sympathetic control of cardiac contractions.

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