Psycholinguistics/Neural Basis of Multi-Lingualism/Some thoughts
1) Similarities or differences in the languages being learned. If all languages being learned are similar in structure then it would be easier for the simultaneous multilingual because the rules would be similar and there would be less confusion. For the successive multilingual the primary language would have a minor influence in affecting subsequent languages. Neural organisation: since all languages were learned within the critical period we would assume that similar neural structures would be activated regardless of language or sequence of language acquisition. Different tasks however would activate different neural regions, but we would see the same populations activated in a similar task whether the individual was a simultaneous or successive multilingual. Language interference: a simultaneous multilingual is at a higher risk for confusing the languages learned at the same time. This is because early in development there is a steep learning curve for a new language and proper organisation of the rules pertaining to a particular language can get mixed up if many languages are learned simultaneously. A successive multilingual is less at risk because they learn different languages successfully, therefore the structure of one language is developed before establishing a new language structure. The simultaneous bilingual is more likely to develop one structure to accommodate all the learned languages since they are acquired simultaneously.
2) Early language acquisition individuals would use the same neuronal populations for all their languages therefore they are less likely to suffer from partial aphasias due to cortical insults. If the main language areas of the brain in the left hemisphere are injured we would likely see similar deficits in all the learned languages within a early acquisitioned individual. However in a late language acquisitioned individual, who learned languages after the critical period additional cortical areas are recruited in addition to the regular language regions of the brain. This means that cortical insults to brain regions other than the main language centers of the brain could impose some deficits within certain languages depending on the region of brain injury, the type of language used and the task being performed. An example would be the recruitment of prefrontal cortex in late acquisitioned individuals for certain tasks, whereas no prefrontal cortex activation in early acquisitioned individuals for the same task. Therefore damage to the prefrontal cortex would cause impairments in the late acquisitioned individual, but not to the early acquisitioned individual on that particular task. Damage to main language centers of the brain would cause similar impairments to both early and late acquisitioned individuals because they both activate these regions.
3) Multiple factors can cause speech problems therefore it is hard to say conclusively that therapy in one language will resolve issues in the others. However based on the neural evidence in multiple language tasks we can assume that if the problem arises from a neural standpoint then an early acquisitioned individual will see progress for multiple languages. This is mainly because all the languages acquired will be represented by similar neural structures therefore if therapy resolves the problems in one language, other languages dependent on the same neural populations will also get some benefit. Even if the problems don’t exist on a neural level, the organisational structures will be similar within the different languages, therefore we could speculate that therapy in one language can have different benefits to the other languages on different levels. A late acquisitioned individual however would probably need therapy in the different languages to see the same amount of benefit as the early acquisitioned individual.
- The occipitotemporal cortex would first be activated to transfer the visual information to the temporal cortex. Then the medial temporal gyrus would be activated to decipher the lexical information. If the subject was late acquisitioned and since the information is in L2, additional neural populations in the prefrontal cortex will be activated for working memory possibly for translation from L2 to L1. Finally the medial temporal gyrus and hippocampus will be activated for semantic processing and memory retrieval.
- Since this is a verbal production task the semantic meanings should first be retrieved. In addition this is an L2 language therefore we will expect to see activations in the frontal gyri as well as some temporal gyri. This information is then passed along to Brocca’s area for processing, which also collaborates with the basal ganglia since the language involved is L2. Finally the information is sent to the primary motor cortex to activate the vocal cords and produce speech.
- The primary auditory cortex in the left temporal lobe is first activated since this is a listening task. In addition, since this is also an L2, variable other temporal cortex regions also get activated for semantic processing. Specifically we can see consistent anterior cingulate activation and this region is known to be associated with conscious, laboured effort, which is expected since the information is in L2 and not automatically processed. We can also expect some activations in Brocca’s area and the pre-central gyrus for additional processing from L2 to L1 since the information is not the subjects native language.