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Everyday communication between humans is through language, which is in most cases naturally developed and maintained within the brain, of which more or less 90% is said to be specifically within the left hemisphere. Although it has been found that the right-hemisphere is partly involved in organising what one wants to say (Gardner et al., 1983) and may gain a greater role in the construction of language in the case of the left-hemisphere being damaged early in life (Vikingstad et al., 2000), the left-hemisphere first and foremost specialises in the production and comprehension of words and their associated sounds as it focuses on analysing their individual sequences to be able to form phrases, sentences etc through the organisation of these sequences. There are various ways humans can lose their initial language capabilities, whether their language breakdown is predetermined through their genetic make-up or through brain damage, where if it occurs in a specific area related to functionalising speech it can lead to certain aphasias (losing language through brain damage specifically at the language-related areas) and a primary loss of speech-control.
One of language's functioning concepts in order to convey messages is speech production which has been found specifically occurs within the inferior left frontal lobe, known as Broca's area. Broca's aphasia occurs through a simple lesion or targeted stroke to this area where memories, perceptions and thoughts are typically transformed into speech through neural mechanisms and ultimately leads to the disruption in the expression of words and one's overall ability to speak coherently and fully. All those affected by Broca's aphasia find it very difficult to express their thoughts fluently and appropriately through speech - knowing when errors in speech are made but not being able to fix it themselves - and, dependant on the intensity of damage to this area, face various other difficulties. As Broca's area organises the movement of the speech muscles, most patients have great difficulty in articulating words and phrases and often mispronounce words due to the disorganisation of the sequences of sounds within their memory. Certain words such as function words (those with attached grammatical meaning) have been noted to be more difficult to express than i.e. words with content, though through specific facial characteristics patients have provided non-verbal signs (such as grunting and looking pained) that they are in fact consciously attempting to find and express the right words. Along with this, short grammatical words such as 'the' and 'and are usually found to be absent from their final speeches. Those that have been deeply affected also find major difficulty in constructing and comprehending grammar properly. A study on aggramatic patients showed that they rarely used certain auxiliaries such as 'have' and word endings such as '-ed', equally showing extended troubles with word ordering and thus comprehending grammatical structures within sentences (Saffran, Schwartz, and Marin, 1980). Patients affected by Broca's aphasia can, however, pronounce other types of words in a more naturally meaningful way, which cannot be said for patients affected by damage of different speech-related areas of the brain which are equally involved in maintaining a full language capacity.
Along with the production of speech there is the comprehension of it which is performed within the posterior part of the superior temporal gyrus of the left hemisphere, commonly known as Wernicke's area. Memories of the sequences of sounds of words are stored here in order to be able to recognize words, and through the activation of neurons within the auditory association cortex to perceive these words, understand them as well in various contexts. An aphasia at Wernicke's area thus also leaves patients with speech deficits, some similar to Broca's aphasia such as the inability to always produce the appropriate selection of words in relation to their thoughts within sentences which is most likely due to an existing connection between the two areas within the cerebral cortex. Patients suffering Wernicke's aphasia, however, although also disorganised with word selection, express them in a fluent manner but without realising their own errors themselves when made - which Broca's aphasia patients do acknowledge - due to their comprehension deficit. This typically results in Wernicke's aphasia patients producing meaningless speech as well as showing signs of unconsciously understanding other people's speech incorrectly, leading to patients generally answering other people's questions with unrelated and maybe non-sense responses. Within these responses there is usually a lack of use of content words and those that are used tend to not coincide with the rest of what patients express. In extreme cases, patients unknowingly express only non-sense utterances, sometimes showing a complete incomprehension of what they are being told or asked. At this stage, pure word deafness occurs where although the patients can hear the sounds of words, their ability to retrieve previously saved memories of these sounds in order to recognize its meaning (also known as auditory word recognition) is disabled. This specific form of word recognition also disrupts the patients' total ability to retrieve previously saved words in order to repeat them appropriately in the future. These various difficulties patients face with Wernicke's aphasia equally, however, depend on the extremity of damage which is not the case for other means of acquiring a language disorder when it comes to genetic inclination.
As lesions and strokes can occur to any human being at any time within their life, certain disorders that have been shown to affect people's language capacities are genetically predetermined and leave sufferers with an initial inability at birth to be able to use language as appropriately as others either for a life time or indefinite with the chance of therapeutic treatment dependant on its availability. The alteration of certain chromosomes has lead to a variety of language-related impairments being one of many symptoms of common syndromes within society, e.g. Down syndrome. The addition of an extra 21st chromosome spotted within patients by Lejeune et al. (1959) leaves most Down syndrome patients with an impairment of developmental and cognitive ability. Similar to Wernicke's aphasia it has been noticed that those affected exhibit some problems with properly comprehending things said to them. Their recognition and production of sounds of words is also genetically affected, with a common struggling to begin words with the right speech tone, as well as placing emphasis on certain word sounds incorrectly within their sentences. Similarly the genetically acquired Asperger's syndrome affects people's language abilities with notable difficulties with maintaining proper intonations on words dependant on sentence structures. Those affected by this syndrome, similar to Wernicke's aphasia of miscomprehending spoken words and expressing non-sense phrases, tend to misunderstand metaphorical phrases from literal and produce their own type of metaphors which, although they claim to fully understand themselves - do not make any sense to others. Children with Asperger's syndrome at their early ages especially seem to experience troubles with understanding expressions of humour and irony as they tend to comprehend most sequences of words on a literal level. Similarly, children genetically affected by William's Syndrome also seem to have difficulties with comprehending words and sentences on a more abstract and non-literal level, whereas an overall effect William's Syndrome seems to have on its patients is "that WS language follows a different path to normal acquisition" (Karmiloff-Smith et al., 1997, pg. 258). Delays within this acquisition are also common in patients with fragile X syndrome, who tend to acquire expressive language one third of the speed as compared to normally developing children (Roberts, Mirrett, and Burchinal, 2001). Like Broca's aphasia, fragile X syndrome patients find it difficult to articulate words properly and have been found to consequently make patients utter unintelligible phrases. A study conducted by Abbeduto & Murphy (2004) similarly presented that patients with Down syndrome had a tendency to utter unintelligence phrases, though in specific relation to speeches formed spontaneously.
What links all these aphasias and genetically pre-determined syndromes with language deficits is that they are all attempting to be treated in their own specific ways, dependant on where the speech deficit lies (in its production or its comprehension), how extreme the damage to the brain was, or for example with syndromes how sensitive certain groups of people are genetically as with Fragile X syndrome findings show men are more deeply affected than women (Keysor & Mazzocco, 2002). Although for syndromes which have had therapies developed in order to positively stimulate patients' language deficits, with for example Down Syndrome where there has been evidence to show that language acquisition thus eventually progresses through the child's lifetime (Chapman & Hesketh, 1998), this does not account for all syndromes nor aphasias. Treatments do also tend to rely on time for positive progression and thus many patients with a language production or comprehension deficit will find it difficult to communicate clearly for an unknown time which has wider implications to their lives as it makes it harder to communicate independently and for example get normal jobs when competing with those that do have full language capacities.
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