Talkin’ the talk: better than walkin’ the walk?

Have you ever stood back and tried to imagine a world without language? A world, not just without spoken speech, but without written text and also without that little voice in your head which is constantly thinking in words. Have you ever tried to make a conscious effort to try and turn off that voice in your head when you cannot sleep, or are stressing about something? Or tried to give someone the “silent treatment” when they’ve pissed you off? Or glanced at written text in your native language and tried NOT to start reading it? Many people find these basic tasks much more challenging than they would originally seem for one key reason- the immense strength of the innate disposition humankind have, to learn and interact using language. Key brain areas essential for these language functions are ingrained to be active from day 1. Incredibly, a human embryo can distinguish vowel sounds in utero. Even individuals who are born death use equivalent brain regions for sign language communication. 

Language is one of the only qualities that is truly unique to humankind. No other animals have the ability to communicate in such an expressive and articulate manner. Although dogs and monkeys may understand simple words such as “sit” or “walkies”, there is a long jump between that and the sorts of communication we are capable of. Even if a meaning of a word is known, the complexity of our language means that we have to be able to adapt the meaning depending on the context. In fact, this may be the one thing which enabled us a thrive to dominate so many other species. Not only can we communicate to work together to catch prey or warn others of predators, we can also chat, debate and gossip about concepts which are completely imaginary and man-made entities such as religion, separate provinces, royalty or the economy. 

But what is it that makes us, firstly, able to perform the intricate and complex task of communication and secondly, what gives us the such strong urge right from the day we were born to want to learn and use this skill?

To try and understand this, first we need to delve into how the brain comprehends, processes and articulates language. 

The Chatty Left Hemisphere

Pierre Broca was a leading figure in the field of linguistics, performing a series on examinations on stroke victims who had suffered damage to particular brain areas, altering their ability to articulate fluent sentences. He cottoned the famous phrase “on parle avec l’hemisphere gauche”- one speaks with their left hemisphere: and this is true in 97% of people (interestingly, the remaining 3% are far, far more likely to be left handed). He identified “Broca’s area” in 1861, of the left brain hemisphere, an area seeming highly responsible for the coordinating all the required micro-movements needed to form fluent language. Stroke patients with damage to this area were able to understand speech but found it extraordinary difficult to respond, often only managing a few disjointed words- this condition was termed Broca’s aphasia. However, the brain has a remarkable ability to adapt, and dedicated practise over time was able to restore at least some language function in these patients. 

Language function is predominantly in the left side of the brain in a healthy individual (left pictures) but can recover after damage to these areas (right) in perinatal stroke victims

The 1960s was a time when, if you suffered with severe epilepsy, a commonplace and often devastating surgery, severing connections between your left and right hemispheres, would be performed, supposedly helping to stop the “flow of the fit” between both sides of the brain. Roger Sperry performed a series of famous studies on such epileptic patients who lacked the connections between the right and left brain hemispheres. Patients were blindfolded and presented with an array of distinct household objects, which they were asked to blindly feel with their left and right hands separately.  Sensory inputs from the right hand flow up the arm, across to the opposite side of the spinal cord, and run into the left side of the brain. The objects felt with the right hand, therefore, could be eloquently identified and named with ease e.g. a ball. However, when feeling with the left hand, the inputs from which would be received by the right brain, the descriptions were either completely absent or were mostly indirect, disjointed associations e.g. “round thing”. 

Roger Sperry’s simplified model of brain lateralisation, created from experiments with “Split Brain” epileptic patients, 1968

More recent work has demonstrated that the entire language system is an extremely complex network of multiple brain regions which is different for each individual. The idea that it was solely lateralised to the left hemisphere of the brain, was primitive, but a solid model to start. However, these basic principles suggest a common innate pattern is genetically encoded for and laid out in development, but is plastic and adaptable depending on environmental conditions. So what is it about our unique development that has built our brains with such elaborate tools and building blocks needed to develop this advanced and useful skill?

The language gene – FoxP2

It was Hurst in 1990, who first described a family known as the “KE family” – a family with an inherited language disorder. This family appeared to be affected by a genetic mutation which could be passed, dominantly, from parent to child and resulted in severe speech and language problems, with children unable to pick up and produce language. This was coupled with low performance IQ, developmental delay and brain abnormalities. 

The pattern of effected individuals in the KE family: a family suffering from an inherited speech disorder

Later, it was discovered, via genome studies, that this gene was the FoxP2 gene. When this gene is active, it is able to bind to the DNA and ultimately dampen down expression of over 100 different genes in key brain regions involved in the motor coordination of creating language. In the long sequence code for this gene, it was just a one letter change that caused catastrophic effects on the childhood ability to produce and understand language. The single change renders the FoxP2 protein unable to bind DNA efficiently and this has knock-on effects on the 100 other genes also influenced by FoxP2. The fMRI brain imaging of these studies showed that the lateralisation of language function had disappeared and whereas in an unaffected individual, Broca’s area clearly and independently lit up in response to a mental verb task, the affected individuals had multiple and disordered over-activity. 

The lateralisation of the language system in healthy (left) is disrupted in members of the KE family suffering with the inherited speech disorder (right)

FoxP2 in other animals

Mouse pups will make ultrasonic vocalisations when removed from their mother

What is remarkable about this properties of this gene is that it is strikingly conserved throughout many other species – yet, it is minuscule differences between species render them relatively inarticulate. For example, the mouse FoxP2 has 3 DNA bases different from the human FoxP2. But if you make a genetically modified mouse, in which the mouse FoxP2 has been replaced with the healthy human isoform, these mice have significantly increased number and plasticity of neural connections in key vocalisation areas of the brain. The ultrasonic vocalisations, for example the cries pups make in response to being removed from their mother, also increase in frequency. But, if you put the KE family’s damaged gene into mice it causes motor impairment and severe alternations in ultrasonic vocalisations, damaging pup-mother relationships. 

When did language start? 

Depiction of a Neanderthal

In 2007, the “modern speech gene” was found in the Neanderthal’s genome. Whether Neanderthal’s had mastered the art of language is a hotly debated topic. Considering modern day humans have about 1-4 % Neanderthal DNA, it would suggest they were capable of at least some, if primitive, type of lingual interaction. Issues with extraction of such ancient DNA and the fact that language is so multi-factorial means that the fact they possessed the humanised form of the gene does not prove they had language as we know it. However, it definitely makes the concept a viable option.

It is highly likely that FoxP2 is just the tip of the iceberg, especially when you consider that there are more than 7000 languages around the world, each with its own set of rules, rhythms and rhymes. This really allows you to marvel at how amazingly complex, but also how flexible, the language system is in your brain, with all the intricate components wired together and interlaced just so to allow you to gossip, chat, fret, argue, debate and get heard but also to listen, learn, read and develop. 

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