A test of the role of the medial temporal lobe in single-word decoding.

The degree to which the MTL system contributes to effective language skills is not well delineated. We sought to determine if the MTL plays a role in single-word decoding in healthy, normal skilled readers. The experiment follows from the implications of the dual-process model of single-word decoding, which provides distinct predictions about the nature of MTL involvement. The paradigm utilized word (regular and irregularly spelled words) and pseudoword (phonetically regular) stimuli that differed in their demand for non-lexical as opposed lexical decoding. The data clearly showed that the MTL system was not involved in single word decoding in skilled, native English readers. Neither the hippocampus nor the MTL system as a whole showed significant activation during lexical or non-lexical based decoding. The results provide evidence that lexical and non-lexical decoding are implemented by distinct but overlapping neuroanatomical networks. Non-lexical decoding appeared most uniquely associated with cuneus and fusiform gyrus activation biased toward the left hemisphere. In contrast, lexical decoding appeared associated with right middle frontal and supramarginal, and bilateral cerebellar activation. Both these decoding operations appeared in the context of a shared widespread network of activations including bilateral occipital cortex and superior frontal regions. These activations suggest that the absence of MTL involvement in either lexical or non-lexical decoding appears likely a function of the skilled reading ability of our sample such that whole-word recognition and retrieval processes do not utilize the declarative memory system, in the case of lexical decoding, and require only minimal analysis and recombination of the phonetic elements of a word, in the case of non-lexical decoding

The right posterior paravermis and the control of language interference

Auditory and written language in humans' comprehension necessitates attention to the message of interest and suppression of interference from distracting sources. Investigating the brain areas associated with the control of interference is challenging because it is inevitable that activation of the brain regions that control interference co-occurs with activation related to interference per se. To isolate the mechanisms that control verbal interference, we used a combination of structural and functional imaging techniques in Italian and German participants who spoke English as a second language. First, we searched structural MRI images of Italian participants for brain regions in which brain structure correlated with the ability to suppress interference from the unattended dominant language (Italian) while processing heard sentences in their weaker language (English). This revealed an area in the posterior paravermis of the right cerebellum in which gray matter density was higher in individuals who were better at controlling verbal interference. Second, we found functional activation in the same region when our German participants made semantic decisions on written English words in the presence of interference from unrelated words in their dominant language (German). This combination of structural and functional imaging therefore highlights the contribution of the right posterior paravermis to the control of verbal interference. We suggest that the importance of this region for language processing has previously been missed because most fMRI studies limit the field of view to increase sensitivity, with the lower part of the cerebellum being the region most likely to be excluded

Meaning in words - How social context amplifies processing of emotional language

Schindler S. Meaning in words - How social context amplifies processing of emotional language. Bielefeld: Universität Bielefeld; 2016.Language is a unique and core human ability. Language is abstract and arbitrary and yet it enables us to communicate with each other. Language allows communication and communication is inherently social. Communicating with and about others is of highest interest for humans, as humans are social beings. This is why receiving human feedback is often extremely emotional. Although we have an extensive knowledge about the neuronal bases of emotional language processing, there are only a few studies yet conducted to investigate socio-communicative influences on language processing. In my dissertation I examine the influence of a social communicative partner on emotional language processing. Three studies systematically manipulated the expertise and identity of putative interaction partners. These interaction partners gave feedback on positive, negative and neutral adjectives while a high-density Electroencephalogram (EEG) was recorded. Actually, in all conditions random feedback was presented, thus a differential processing could only be attributed to sender characteristics. By means of event-related potentials (ERPs), the influence of sender characteristics, emotional content and their interaction was observed. In studies I and II - as a proof of principle - a 'human sender' was compared to a random computer (unequal expertise, unequal humanness). In this study, both feedback anticipation (study I) as well as feedback presentation was investigated (study II). In study III the 'human sender' was compared to a socially intelligent computer (similar expertise, unequal humanness). Eventually, in a fourth study a 'human expert' was compared to a 'layperson' and a random computer sender (unequal expertise, but the 'expert' and 'layperson' were both 'humans'). During anticipation of 'human' feedback, an extremely early enhanced general processing was found. On later stages a more intense processing of emotional adjectives was found in the 'human sender' condition. In general, effects during feedback presentation were substantially larger than during feedback anticipation. Here, large effects were found on early and late ERP components, for both human-generated and emotional feedback. Further, emotional feedback given by a 'human' was additionally amplified. Eventually, in study IV 'expert-feedback' was processed most intensely, followed by 'layperson-feedback' and finally 'computer-feedback'. Localization methods found enhanced sensory processing for 'human-generated' and emotional feedback. Studies III and IV showed additionally increased activations in somatosensory and frontal effects for 'human senders'. Overall, these experiments showed that not only emotional content but particularly also communicative context influences language processing. We automatically seem to take context factors into account when processing language. Here, 'expertise' results in an enhanced processing aldready on early and highly automatic stages, while supposed humanness seems to be of highest relevance: 'Human-generated' feedback led to enhanced processing in sensory, but also somatosensory and frontal areas. This shows that in human interactions language is amplified processed, which is especially true for emotional language. This dissertation shows for the first time that in realistic communicative settings (emotional) language processing is altered. Here, it seems that first sender information is processed, while emotional content affects later processing stages. The use of state of the art source localization methods enabled to get next to the extremely high temporal resolution (when something happens), a good and reliable spatial resolution (where something happens) of the cortical generator structures of the ERP effects

The role of the left inferior parietal lobule in reading.

One of the regions that have consistently been included in the neurological models of reading is the left inferior parietal lobule (IPL), however, the precise functional and temporal contributions of this region to reading have not yet been fully established. There are three hypotheses concerning IPL contributions to visual word recognition. The first one claims that the IPL is the site of stored visual word forms although it remains unclear whether these are stored in supramarginal (SMG) or angular (ANG) fields of the IPL. The second hypothesis argues that the procedures for converting spelling-to-sound are a function of the IPL, but it is unclear whether these are specifically located in SMG or ANG, or both. Finally, a third hypothesis suggests that SMG and ANG preferentially contribute to phonological and semantic processing of written words, respectively. In this thesis, I empirically evaluated these hypotheses using repetitive transcranial magnetic stimulation (rTMS) to temporarily and selectively disrupt processing in left SMG and ANG during visual word recognition and measure the effect on reading behaviour. I also investigated the time course of SMG and ANG involvement to visual word recognition using double-pulse TMS. My research demonstrates that SMG contributes preferentially to phonological aspects of word processing and the processing begins early and over a sustained period of time (between 80 to 200 msec post-stimulus onset). ANG contributes preferentially to semantic aspects of word processing but the temporal dynamics of this contribution were not successfully revealed in this thesis and require further investigation. In addition, I empirically evaluated the efficiency of using functional magnetic resonance (fMRI) and TMS to functionally localize a target site for TMS experiments. I demonstrated that both methods are similarly accurate in identifying stimulation site but neither of them is 100% accurate