Tag Archives: Number form synaesthesia

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

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


Time-blind, face-blind, smell-impaired, touch-disabled, dyslexic – there’s an amazing variety of disabilities of perception

It goes to show how common synaesthesia is, when a host of a radio show episode about super-recognition that I have referred to previously at this blog just happens to be a synaesthete. I know this because she was on the radio yesterday morning promoting her latest pop psychology book, which looks like it will be an interesting read. The BBC broadcaster, author and psychologist Claudia Hammond experiences the days of the week as having their own colours and insists that Monday is a pillar-box red, an assertion which to my mind does not seem odd but simply incorrect. Sure enough, the letter M is red (but certainly not pillar-box red) but surely it is plain to anyone that Mondays are white? Hammond and the cheery radio show host Natasha Mitchell also discussed other varieties of synaesthesia: time-space synaesthesia and mental number lines. Hammond’s new book is about the perception of time and it looks like it will include discussion of disability in perceiving time, and will also probably cover time-space synaesthesia.

I’ve had a look on the internet for more info about Hammond’s new book titled Time Warped, and while reading an excerpt of the book at Amazon I’ve found yet another obscure and highly specialized type of disability of perception, an inability to sense the passing of time, a condition which appears to be so obscure that it still has no name. Hammond gives a fascinating description of Eleanor, who has a deficit in sensing the passing of time that goes way beyond poor time management skills, and also has dyslexia, probably not coincidentally.

In this blog which is primarily about exploring possible links between synaesthesia and high ability in face perception and also an exploration of the opposite condition of prosopagnosia or face-blindness, I have discovered that prosopagnosia is by no means the only highly specialized disability of perception. Prosopagnosia is only one of a range of visual agnosias, which is a sub-set of the agnosias, which are a huge range of brain-based diabilities (not associated with memory loss) in recognizing specific things such as people, voices, shapes, smells, time, faces, colours, classes of objects, images of objects, pain, speech, text, body language, intonation, etc. Prosopagnosia appears to be often associated with another agnosia which is a disability in establishing visual memories of scenes, including things like streetscapes and buildings, and it seems possible that it could be linked with other better-known disabilities such as dyslexia. Each case is different, and prosopagnosia and other agnosias can be caused by genetics or damage in the brain, so one should not make sweeping generalizations. There appears to be no standard term or definition of the issue with place memory, with a variety of terms in use. I guess most people would be aware of the sensory and perception disabilities of blindness, deafness, paralysis and dyslexia, but there is also a huge range of other specific disabilities and disorders of perception and understanding, some affecting taste, smell, balance, mathematical and number sense, touch, music and tone perception. Many of these can be naturally-occuring or the result of brain injury. New Scientist magazine reported a while ago that a deficit in the sense of touch appears to be genetically linked with deafness. Scientists are only now beginning to establish knowledge about the nature of these disabilities and possible relationships between them. On top of this bewildering range of agnosias and disabilities are sensory disorders and visual disturbances that can be asociated with mental illness or are similar to mental illness. And on top of that are sensory-cognitive experiences that are simply odd or unusual but not disordered or a deficit. Synaesthesia fits into this category, of which there are more types than any sensible person would claim to know.

I find these things endlessly fascinating because it gives an insight into the significant fact that there can be many important differences between the way that apparently normal, intelligent people percieve and understand what appear to be simple sensory inputs from the world around us. The more I study this subject, the more I understand that there is nothing simple about perception and the understanding of sensory inputs. This kind of brain-work is hugely complex and it is no wonder that many areas of the brain are involved in this kind of work, and that sensory processing is very much involved in thinking in general. It is impossible to guess how many different ways that the person sitting next to you on the train might differ from you in perception and sensing, and it isn’t only about disability. For many of the agnosias and diabilities of perception and sensing there are conditions that are opposites or give rise to superior abilities that are like opposites. Does the old bloke across the way see violet mauve in his mind’s eye when he hears the train driver sound her horn, because the horn is at a pitch that his mind links with this colour, in an interaction between his perfect pitch and his coloured sound synesthesia? Does the super-recognizer in the carriage feel a tingle of familiarity from looking at two of the faces in the carriage? Is the super-taster still recovering from the second-rate coffee that he paid too much for at a fancy cafe? Is one passenger watching the screen display of info about which station the train is at like a hawk, instead of using her spare time to catch up on some reading, because she was born without any sense of time passing and can’t remotely judge the duration of her planned train journey?

Time warped: changing your perception of time. Life Matters. Radio National. July 2 2012. http://www.abc.net.au/radionational/programs/lifematters/claudia-hammond/4100994

Embodied cognition and number-form synaesthesia connected with effect found in this study?

Leaning to the left makes the world seem smaller. New Scientist. 13 December 2011 issue 2842 p.   http://www.newscientist.com/article/mg21228424.000-leaning-to-the-left-makes-the-world-seem-smaller.html

I can’t believe it’s not synaesthesia! – embodied cognition

Yes indeed, this is a fascinating article from New Scientist magazine. This is the article that made me feel incredulous the first time that I read it last year, that the word “synaesthesia” was not even once mentioned in it, because it seemed to be an article about a number of different types of synaesthesia. I could go into details about why I believe this, but I’d risk restating most of the text of this two-page article. Basically, this is an article about embodied cognition. It is clear to me that the researchers studying embodied cognition have a lot to gain from sharing ideas with synaesthesia researchers (and synaesthetes), and vice versa.

A study by Australian academic Tobias Loetscher that was published in the journal Current Biology and another study by Daniel Casasanto, an academic in the Netherlands, which was published in the journal Cognition are discussed in this article. The “metaphor theory” of George Lakoff and Mark Johnson is discussed. Much of this article seems to be very relevant to the idea proposed by some synaesthesia researchers that synaesthesia is the origin of metaphorical language. Wouldn’t synaesthesia or some very similar mental process be the link between study subjects’ emotional feelings of being socially isolated and their reported physical sensations of feeling physically colder?

Other parts of this article seem to be very relevant to, or a description of, number form synaesthesia and other mental mappings of concepts onto “spatial schema”. The study by Casasanto is about a psychological process that is very similar to the forward and backward vection that was the subject of the study in PLoS ONE that I discussed in a previous blog posting, in that it shows an influence on abstract thought from performing a physical task that focused the mind on one or other spatial directions. The vection study that I previously discussed was about backward and forward motion influencing abstract thought. The Casasanto study was about moving something upwards and moving something downwards influencing abstract thought.

Many of the more general conclusions in this article, based on the study findings, also seemed to be very relevant to my experiences of fine motor performances determining the content of my thoughts, often involving links with conceptual thinking, by a process that I believe is synaesthesia. “The results also led to a deeper question: does physical movement have the power to change not just the speed at which people talk, but also what they choose to talk – or even think – about?” A study by Casasanto found this to be true. “Isn’t that somewhat scary?” Casasanto asked. Yes, I think it is scary, but it is only by being aware of the irrational and arbitrary things that can influence cognition that we can ever hope to detect, control and transcend such influences.

Ananthaswamy, Anil Let your body do the thinking. New Scientist. Number 2753 March 27th 2010 p.8-9.

Two articles about embodied cognition from Miller-McCune:

Jacobs, Tom To feel good, reach for the sky. Miller-McCune. February 4th 2010. http://www.miller-mccune.com/health/to-feel-good-reach-for-the-sky-8445/

Hilo, Jessica Power poses really work. Miller-McCune. November 15th 2010. http://www.miller-mccune.com/culture-society/power-poses-really-work-25322/