By: Angela D. Friederici Presented By: Karol Krzywon

 Despite this being my last class in BCS before graduation, this is the first time I have run into an actual model of how language comprehension occurs within the brain.  I find that a little startling.  So naturally I found this article rather fascinating.

 In general we know where certain types of stimuli are processed within the brain.  visual cortex, auditory cortex, prefrontal cortex, motor cortex etc.  Based on lesion and brain injury studies, we even have some specific knowledge of what smaller sections do.  Broca’s, Wernicke’s, and other less easy to remember regions  And what those injuries would likely cause  The various forms of aphasia for example

 But the moment we try to establish a model that explains how various portions of the brain work together to form language comprehension, the ideas we have are compartmentalized and focus mostly on particular areas.  Large amounts of data have been collected which now allows us to venture and create such models as Friederici does in this article.

Initially sound is processed in the Primary Auditory Cortex (PAC) BLUE Here basic phonemes are analyzed The next step involves the anterior Superior Temporal Gyrus (aSTG) PINK Processing of auditory words occurs here. Finally the signal travels to the Inferior Frontal Gyrus (IFG) RED

This process involves the processing of syntactic and semantic meanings of the signal. Higher order structures are formed as a result. Sounds -> Words -> Phrases

In the Inferior Frontal Gyrus (IFG) the signal begins to differentiate Sematic information is processed in the anterior section YELLOW Als o known as B45 Syntactic information is processed in the posterior sections GREEN Also known as B44 From here onward the two signals travel in two distinct paths But that does not mean the two don’t communicate with each other

Currently there appears that there is a single integration center in the posterior Superior Temporal Gyrus (pSTG) BLACK The Dorsal Pathway carries the syntactic information While the Ventral Pathway travels through the Middle Temporal Gyrus (MTG) BLUE for more semantic processing

These two pathways are believed to work in somewhat opposite manners The Semantic processing within the Ventral path is considered to work via top-down processing. Works off of general ideas and context to help establish the meaning. Can use clues within the conversation or setting

The Dorsal path utilizes specific syntax and structure to help piece together the full meaning of the. It is thought it may offer predictions as to what may be said or meant when a person is speaking. For example: one would expect a direct object after a verb in the English Language It is somewhat more of a bottom up process in that it focuses on specific expectations to create the larger picture

In the posterior Superior Temporal Gyrus, the signals are integratted. With the ventral pathway utilizing top-down processing and the dorsal utilizing bottom up processing, the two are integrated Since each works from an opposite end any deficit one signal may have can be supplemented from the other. It is here where understanding the meaning of a sentence finally comes to completion

 We now have a decent idea of how auditory perceptions are integrated and processed into sentences with meaning.  Or at least one possible pattern by which it may happen  It offers jumping off points for new research and the formation of new hypothesis.  At the very least it is the culmination of large amounts of data and this is gives us insight.

 The current model only considers the left hemisphere  We know the basal ganglia and the thalamus are involved in language processing  Their role needs to be evaluated  The syntactic working memory in the Prefrontal Cortex and the phonological working memory in the Parietal Cortex also need to be integrated.  The role of bottom-up processing and top-down processing need to be further investigated.  The later can only occur after language is already acquired

 This model is mainly a compilation of many separate bodies of work that dealt with mostly individual aspects  It would be excellent if researchers focused specifically on this issue to determine this models validity.

 Do you believe the Model is helpful in understanding language, or merely an interesting idea that does not offer much except a nice picture?  Since there are a fair number of omitted sections of the brain, do you think this Model offers a good base a to start integrating more sections of the brain or that it may hinder us and lead us astray before we have enough information present to draw reasonable conclusions?  Are there any sections that you strongly believe should have been included but were not?