Tag Archives: Orphanet Encyclopedia

Don’t forget the parietal lobe – the connections are interesting

If you have been reading this blog for a long time you’d know I’ve been trying to figure out which parts of my brain are responsible for my synaesthesia and related experiences. I’ve found that the right fusiform gyrus is a part of the brain that comes up over and over again, in relation to synaesthesia and also face recognition I experience many types of synaesthesia and also have achieved scores in face recognition tests consistent with being a super-recognizer, so this combination seems significant, and despite a lack of any evidence from other case studies linking synaesthesia with superior ability in face recognition, I still think it is a possible relationship that should be scientifically investigated, especially in light of a pattern of associations which I believe suggests that synaesthesia might be a neuropsychological condition that could be seen as the opposite of Benson’s syndrome, which is a type of dementia that involves a loss of visual perception, apparently including a loss of face recognition ability. While synesthesia is generally an inborn developmental condition, and Benson’s or PCA a neurodegenerative condition with a typical onset late in life, I’ve still got to wonder whether inborn factors contribute towards Benson’s. While Benson’s is considered to be a variant of Alzheimer’s, I don’t think anyone knows why it causes deterioration in different areas of the brain as are affected by Alzheimer’s, apparently the same parts of the brain (at the rear) that appear to be enhanced or hyperactive in my brain, and I also doubt that anyone knows why Benson’s has an onset earlier than Alzheimer’s disease. I’m sceptical of the idea that Benson’s is just Alzheimer’s of the back-end of the brain. I suspect that immune system elements microglia and complement might be central to an explanation for Benson’s syndrome. Reading Dr B. Croisile’s paper about Benson’s I’m struck by the many very strange effects of Benson’s on perception, and I wonder at the ways in which a study of it might inform science about  the workings of the brain. I think it is at least as interesting as synaesthesia, which attracts a lot of attention from researchers. Apparently people with Benson’s cannot imitate movements. Does this mean that the mirror-neuron system which so many neuroscientists have gotten so excited about is located at the rear of the brain? I note that the inferior parietal cortex is one of the parts of the brain that are thought to house mirror neurons.

When I set out to write this post I had actually planned to write about a fairly recent review journal paper focusing on recent research about the most common and well-known types of synaesthesia: coloured hearing, coloured graphemes and time units in space synaesthesia. I really like the paper cited below by Professor Karsten Specht from the University of Bergen in Norway, and I’d recommend it to anyone who wants to learn about the latest knowledge about synaesthesia from just one paper. I only have a couple of gripes about he paper. I wouldn’t describe synaesthesia as “rare” as Specht does. Ward, Sagiv and Butterworth wrote in 2009 that around 12% of the population have number forms, and that estimate doesn’t surprise me. Synaesthesia in general can’t be rare if it includes one type that isn’t rare. Time-space synaesthesia or number forms is one type of synaesthesia which the synaesthete can have but not suspect that it is synesthesia, or anything out of the ordinary, so I’d guess it could be very much under-reported and under-estimated. My other gripe with Professor Specht’s paper is this bit; “In recent years, several studies have attempted to investigate whether synaesthesia is primarily a perceptual or conceptual phenomenon.” I think Specht is here presenting the reader with a false dichotomy. In some of the types of synaesthesia and related phenomena which I experience sensory perception, memory and conceptual thinking are connected with synaesthesthetic linkages, so I doubt that there is much point in trying to characterise synaesthesia as one or another type of phenomenon. I was very excited when I read the book Beyond Human Nature by philosopher Jesse Prinz. Professor Prinz argued that we think in mental images rather than in language. He wrote that “It used to be thought that the back part of the brain is used for perceiving and the front is used for thinking. But we now know that the back part of the brain, where most of the senses are located, is very active when people think. Moreover, we know that the front part of the brain does not work on its own, but rather coordinates and reactivates sensory patterns in the back. Recent evidence from Linda Chao and Alex Martin has shown that reading activates the same areas as looking at pictures, suggesting that we visualize what we read.” In a post that I wrote a while ago I described involuntarily “seeing” in my mind’s eye visual images of landscapes and building interiors from imagination and memory while listening to an autobiographical audio-book. I thought it was probably related to synaesthesia, but it appears that everyone’s brain illustrates text with images when reading. Perhaps synaesthetes do this to a greater degree or in a way that is more available to conscious awareness.

Anyway, back to Specht’s paper. Having read it I now suspect that the parts of my brain that are bigger or better connected or more active or something are: the right fusiform gyrus (including the FFA), the left parietal lobe including the left intraparietal sulcus, the right inferior parietal lobe, the hippocampus (I’m sure is involved with IMLM) and the parahippocampal gyrus. I’d guess that these are the places where interesting things are happening. It appears that the role of the parietal lobe in synaesthesia has been understated in the past. It is now thought that synaesthesia does not solely involve the cross-activation of two different sensory areas (as if it was ever that simple!), but it also requires a “binding” process to happen in the parietal lobe. There is no underestimating the importance of this binding.

If you are as interested in synaesthesia and bits of the brain as I am, you might also like to read a much longer journal paper by Rouw, Scholte and Colizoli that was published last year. It is available in full text at no cost, but I don’t think it covers non-colour types of synaesthesia. Details can be found below. One part of the parietal lobe mentioned in that paper, which is cited by a few studies as involved with synaesthesia is the inferior parietal lobule (IPL, Brodmann areas 39 and 40). It is also known as Geschwind’s territory because the neurologist Geschwind predicted in the 1960s that the parietal lobe played a role in language, and was proven right when the IPL was found to include a second connection between Broca’s area and Wernicke’s area, which are of central importance in language. The IPL is very interesting as a part of the brain involved in synaesthesia because according to a 2004 article in New Scientist magazine the IPL matures at a late age, between the ages of five and seven years, which just happens to be time in life when children typically learn the ability to read and write, and it is also the age range in which some children develop grapheme-colour synaesthesia. I find this very interesting because in my family we have at least three closely related grapheme-colour synaesthetes who are unusually high achievers in reading and writing in testing and academic achievement. Two of these synaesthetes were early readers and also talented at language learning. What’s the betting that some gene that alters the development of the IPL is behind this? The author of the most interesting little science magazine article that brought me this news, Alison Motluk, is herself a synaesthete. Is it just a coincidence that a journalist with a well-connected brain has pointed out a number of interestingly related facts that are connected around the conceptual hub of the inferior parietal lobule?

Specht, Karsten Synaesthesia: cross activations, high interconnectivity, and a parietal hub. Translational Neuroscience. Volume 3 Number 1 (2012), 15-21, DOI: 10.2478/s13380-012-0007-z
http://www.springerlink.com/content/512306132j162437/

Croisile, Bernard Benson’s syndrome or Posterior Cortical Atrophy. Orphanet. September 2004. http://www.orpha.net/data/patho/GB/uk-Benson.pdf

Ward, Jamie, Sagiv, Noam and Butterworth, Brian The impact of visuo-spatial number forms on simple arithmetic. Cortex. Volume 45 Issue 10Pages 1261-1265 (November 2009). http://www.cortexjournal.net/article/S0010-9452(09)00213-5/abstract

Rouw, Romke, Scholte, H. Steven, Colizoli, Olympia Brain areas involved in synaesthesia: A review. Journal of Neuropsychology. Special Issue: Synaesthesia. September 2011 Volume 5 Issue 2 p.214-242. Article first published online: 16 SEP 2011 DOI: 10.1111/j.1748-6653.2011.02006.x  http://onlinelibrary.wiley.com/doi/10.1111/j.1748-6653.2011.02006.x/full

Motluk, Alison Two links good for kids’ language comphrehension. New Scientist. Issue 2478. December 18th 2004. p.12. http://www.newscientist.com/article/mg18424784.300-second-link-discovered-in-human-language-circuit.html

The Opposite of Benson’s Syndrome?

 

A note of warning – If you are thinking about copying or plagiarizing any of the text, ideas or descriptions in this post and using it is your own work without giving me (C. Wright, author of the blog “Am I a Super-recognizer?”) the proper acknowledgement and citations, then think again. If you do that you will be found out and you will regret it. If you want to make reference to this post or any of the ideas in it make sure that you state in your work exactly where you first read about these ideas. If you wish to quote any text from this post be sure to cite this post at this blog properly. There are many established citation methods. If you quote or make reference to material in this blog in your work, it would be a common courtesy to let me know about your work (I’m interested!) in a comment on any of the posts in this blog. Thank you.

 

Today I had a look through someone else’s copy of today’s West during an idle moment. It’s not much of a newspaper, but one never knows what one might discover in a paper.  On page three I saw a sad but interesting story about the retired principal of a top private school in Perth who has had to cut short her career due to a rare type of dementia, early onset Benson’s syndrome. This is like Alzheimer’s except that it affects specific parts of the brain, and it takes away the ability of the brain to process visual information, among other things. Some of the first symptoms of this disease noticed by Dr Glenda Parkin were an inability to play a card game, an inability to spell and an inability to write notes. This terrible disease robs people of basic visual, literacy and numeracy skills such as reading, spelling, handling money and recognizing familiar objects. Why did I find this particularly interesting, aside from the sadness and the personal courage in the story? Because this disease seemed to be the opposite of the special intellectual gifts that run in our family. We have kids who were early and advanced readers, consistently testing as years ahead of their age peers in reading ability. One of our kids spells effortlessly, tackling long foreign words in their junior primary school years, and picking up a bit of Polish just for fun. I am able to write pieces like this without needing to use a spellchecker. I suspect that this ease in literacy skills is linked with our shared and obviously inherited grapheme-colour synaesthesia, the same variety of synaesthesia that ran in the family of the respected novelist Vladimir Nabokov. I suspect that, like some other synaesthetes, I have a memory for colour that is above average. I can recall the exact colours and the names of the colours of a watercolour set that I was given as a young child. I am also often puzzled by the labels that other people give to colours, which don’t seem even vaguely accurate to me. I know that I have unusually good face recognition abilities because I got a perfect score in the short form of the Cambridge Face Memory Test, which is I believe the state-of-the-art in facial recognition tests. The natural reading skill in our family could be seen as the opposite of the loss of ability to read which is an early symptom of Bensons syndrome or PCA.

Although the story in The West Australian about Dr Glenda Parkin’s battle with Benson’s syndrome did not mention anything about recognizing faces or body language, I was willing to bet that prosopagnosia is one of the symptoms of Benson’s that wasn’t mentioned in the newspaper article. I was curious to find out more about Benson’s syndrome for two reasons – to check if face recognition is indeed affected by it as I predicted, and to also find out which specific parts of the brain are affected by Benson’s, because I thought this would be a good clue about which parts of my brain, and the brains of my blood relatives, are naturally enhanced or over-developed or hyper-connected. I would also discover another fact that shows how different elements of different types of synaesthesia that I experience are connected. I find that if you follow the clues far enough, you will often find that things are connected, especially when you are investigating synaesthesia. I already had a few clues about which parts of my brain are different and give rise to my face recognition abilities and The Strange Phenomenon. The fusiform face area, within the fusiform gyrus were two obvious likely choices. Grapheme-colour synaesthesia, which I have, and which runs in my family, is associated with extra activation in the fusiform gyrus (Rouw and Scholte 2007) and greater volume in the grey matter of the right fusiform gyrus (Weiss and Fink 2008), so I figure this part of my brain has got to be doing strange things. I believe the fusiform gyrus is in the temporal lobe, and the temporal lobe is associated with a love of music, and we do appear to have an emotional connection with music that is above the ordinary in our family, so the temporal lobe in general seems like a likely prospect. I had also formed the opinion that the right side of the brain is likely to be hyper-developed or hyper-connected in me or in our family, based on my reading about face recognition face processing and colour-grapheme synaesthesia.

I did the obvious, I looked up the Wikipedia page for Benson’s syndrome, and from there I clicked on a link that looked like to might be something detailed and professional-level. I found a short paper by a Dr Bernard Croisile, outlining the basics of Benson’s. Indeed prosopagnosia is one of the symptoms of Benson’s, as I predicted. I found a fairly general description of the damage to the brain associated with Benson’s “bilateral parieto-occipital aptrophy, more frequently in the right hemisphere”, and “bilateral atrophy in the parieto- and temporo-occipital areas that is more severe in the right hemisphere.” My prediction about the right hemisphere was on the money, and there seemed to be overlap between my prediction and the reported areas affected by Benson’s, but I’m not a neuroscientist, so I’m not sure about the relationship between the areas affected by Benson’s and the areas of my brain that should be expected to be unusual.

I discovered one thing of interest in Dr Crosisile’s paper that hasn’t apparent in the newspaper report – that Benson’s has two major types of symptoms, the visual agnosia described in the newspaper report, and also apraxia. Apraxia is the loss of the ability to execute or carry out learned purposeful movements despite having the desire and the physical ability to perform the movements. By one account it is caused by damage to specific areas of the cerebrum, and another account states that it is caused by damage to specific areas in the parietal lobes. I’m not sure what to make of this. Why is apraxia of interest to me? Because this seems to be a link between the use of hand movements in the performance of chores and one of the types of synaesthesia that I discussed in my first post, my description of “the strange phenomenon”. I don’t have apraxia, but I do get a type of visual synaesthesia triggered by the types of tasks that are impaired in apraxia. When I perform very specific household chores I experience automatic and involuntary very specific visual memories of places that I have visited in the past. For example, when I squeeze a half a lemon on a citrus squeezer with a twisting action of the wrist, I will invariably experience a vision in my mind’s eye of the backyard of the home of my Godparents, just as it was when I visited the place when I attended a birthday party and child-minding there in my preschool years, around four decades ago. No, I’m not making this up – I travel all around Australia while I do household chores, and usually to places that I don’t much desire to revisit. How is this all connected to face recognition? Please follow me as I take you on a tour of the connections.

The Strange Phenomenon (my strange phenomenon) is a type of synaesthesia that I experience which is associated with face recognition – it is triggered by seeing a specific face under very specific conditions and the experience triggered is the quite old visual memory of another specific face that looks very similar. I only experience two types of synaesthesia that evoke visual memories – The Strange Phenomenon with visual memories of faces and my fine motor chore synaesthesia triggering visual memories of places. Faces and places are linked because they are both things that prosopagnosics are reported to have trouble recognizing. It is reasonable to assume that whatever part of the brain is malfunctioning in prosopagnosics (people who are bad at recognizing faces) should be involved with visual processing of both faces and places. It makes sense to expect that super-recognizers, the opposite of prosopagnosics, might also have unusual visual processing of faces and also of places. This is true of me – my visual memories of places and faces can both also be synaesthesia concurrents (the experience triggered in synaesthesia). I also score like a super-recognizer in tests – further evidence linking me with unusual face processing. So the link between the faces and the places seems clear enough, with a face acting as the inducer / trigger of my synesthesia and another face and scenes of places acting as the synesthesia concurrents. This  leaves only one synaesthesia trigger unexplained – how do fine-motor chores as synesthesia triggers fit into this picture? It now appears that whatever is up with my brain could in some way resemble the opposite of Benson’s syndrome, and Benson’s involves degeneration of whatever part of the brain does skilled familiar movements such as using a key, a pencil or a razor. Synaesthesia is caused by hyper-connections in the brain, and it seems reasonable to predict a high degree of overlap between the parts of my brain that are hyper-connected and the parts of the brain that degenerate in Benson’s syndrome. So it appears that the bits of my brain that are responsible for dreary household tasks such as squeezing lemon juice or scrubbing clean the rounded end of a wooden spoon are hyper-connected, so when I do some of these tasks, the thoughts associated with my movements trigger synaesthesia in which the part of my brain that recognizes faces and also places is activated by some “weird wiring”, resulting in me seeing dated vistas in my mind’s eye.

The idea that I have something like the opposite of Benson’s syndrome would neatly draw together all the elements of some odd phenomena that I have observed over a number of years – it would at least partly explain The Strange Phenomenon and confirm that it is indeed a type of synaesthesia because it is based on hyperconnection in the fusiform gyrus, and the idea of the opposite of Benson’s would also explain my fine motor task -> visual place memory synaesthesia as one of only two types of synaesthesia that I have that are the result of hyperconnection between the fusiform gyrus and other parts of the brain that fall within the range of areas affected by Benson’s syndrome. I guess the million-dollar question is  – why does Benson’s syndrome affect only some specific parts of the brain? What is it about a certain group of areas of the brain that appear to make these areas prone to hyperconnectivity in some families, and vulnerable to dysfunction in Benson’s syndrome? Is there some magic chemical or process that regulates growth in these areas of the brain? I doubt that the answer could be so simple.

From this complicated story I have arrived at three conclusions – that one should never pass up the opportunity to read a newspaper, however uninspiring the paper might be, that one should count one’s blessings, and that dementia patients and research into dementia should be supported.

Do you think I’m brainy enough to figure out how my own brain works? I dunno, but it’s sure fun.

Hiatt, Bethany Penrhos principal’s hardest battle.  The West Australian January 3, 2011. http://au.news.yahoo.com/thewest/a/-/mp/8588194/glenda-parkin/

Croisile, Bernard Benson’s syndrome or Posterior Cortical Atrophy. Orphanet. September 2004. http://www.orpha.net/data/patho/Pro/en/PosteriorCorticalAtrophy-FRenPro10748.pdf

Rouw, Romke and Scholte, H. Steven Increased structural connectivity in grapheme-color synesthesia. Nature Neuroscience. Volume 10 Number 6 June 2007. http://www.fmrib.ox.ac.uk/systems-plasticity/jc/potential-papers/rouw_2007.pdf

Weiss, Peter H. and Fink, Gereon R. Grapheme-colour synaesthetes show increased grey matter volumes of parietal and fusiform cortex. Brain (2009) 132 (1): 65-70. doi: 10.1093/brain/awn304 First published online: November 21, 2008. http://brain.oxfordjournals.org/content/132/1/65.full

Postscript February 2013

I’ve got two things to point out. Firstly, if you found the above article interesting, you should read this:

Is synaesthesia caused by low levels of complement? Is Benson’s syndrome (PCA) caused by too much complement C3? Could synesthesia and posterior cortical atrophy be considered in some way opposites?

https://superrecognizer.wordpress.com/2012/06/07/is-synaesthesia-caused-by-low-levels-of-complement-is-bensons-syndrome-caused-by-too-much-complement-c3/

Secondly, if you look carefully at the above article I think you can see hints that Benson’s syndrome or PCA affects the parietal lobe. This would very much fit in with my theory that synaesthesia is like the opposite of Benson’s, because it is becoming clear that the parietal lobe plays a major role in synaesthesia. See these papers:

Specht, Karsten Synaesthesia: cross activations, high interconnectivity, and a parietal hub. Translational Neuroscience. Volume 3 Number 1 (2012), 15-21, DOI: 10.2478/s13380-012-0007-z
http://www.springerlink.com/content/512306132j162437/

Rouw, Romke, Scholte, H. Steven, Colizoli, Olympia Brain areas involved in synaesthesia: A review. Journal of Neuropsychology. Special Issue: Synaesthesia. September 2011 Volume 5 Issue 2 p.214-242. Article first published online: 16 SEP 2011 DOI: 10.1111/j.1748-6653.2011.02006.x http://onlinelibrary.wiley.com/doi/10.1111/j.1748-6653.2011.02006.x/full