Laurie S. Glezer

Individual variability in location impacts orthographic selectivity in the "visual word form area".

Strong evidence exists for a key role of the human ventral occipitotemporal cortex (vOT) in reading, yet there have been conflicting reports about the specificity of this area in orthographic versus nonorthographic processing. We suggest that the inconsistencies in the literature can be explained by the method used to identify regions that respond to words. Here we provide evidence that the “visual word form area” (VWFA) shows word selectivity when identified at the individual subject level, but that intersubject variability in the location and size of the VWFA causes this selectivity to be washed out if defining the VWFA at the group level or based on coordinates from the literature. Our findings confirm the existence of a word-selective region in vOT while providing an explanation for why other studies have found a lack of word specificity in vOT.

Adding Words to the Brain's Visual Dictionary: Novel Word Learning Selectively Sharpens Orthographic Representations in the VWFA

The nature of orthographic representations in the human brain is still subject of much debate. Recent reports have claimed that the visual word form area (VWFA) in left occipitotemporal cortex contains an orthographic lexicon based on neuronal representations highly selective for individual written real words (RWs). This theory predicts that learning novel words should selectively increase neural specificity for these words in the VWFA. We trained subjects to recognize novel pseudowords (PWs) and used fMRI rapid adaptation to compare neural selectivity with RWs, untrained PWs (UTPWs), and trained PWs (TPWs). Before training, PWs elicited broadly tuned responses, whereas responses to RWs indicated tight tuning. After training, TPW responses resembled those of RWs, whereas UTPWs continued to show broad tuning. This change in selectivity was specific to the VWFA. Therefore, word learning appears to selectively increase neuronal specificity for the new words in the VWFA, thereby adding these words to the brains visual dictionary.

Overt use of a tactile/kinaesthetic strategy shifts to covert processing in rehabilitation of letter-by-letter reading

Background: Letter-by-letter readers identify each letter of the word they are reading serially in left to right order before recognising the word. When their letter naming is also impaired, letter-by-letter reading is inaccurate and can render even single word reading very poor. Tactile and/or kinaesthetic strategies have been reported to improve reading in these patients, but only under certain conditions or for a limited set of stimuli. Aims: The primary aim of the current study was to determine whether a tactile/kinaesthetic treatment could significantly improve reading specifically under normal reading conditions, i.e., reading untrained words presented in free vision and read without overt use of the strategy. Methods & Procedures: Three chronic letter-by-letter readers participated in a tactile/kinaesthetic treatment aimed at first improving letter-naming accuracy (phase 1) and then letter-by-letter reading speed (phase 2). In a multiple case series design, accuracy and speed of reading untrained words without overt use of the trained tactile/kinaesthetic strategy was assessed before phase 1, after phase 1, and again after phase 2. Outcomes & Results: All three patients significantly improved both their speed and accuracy in reading untrained words without overt use of the trained tactile/kinaesthetic strategy. All three patients required the additional practice in phase 2 to achieve significant improvement. Treatment did not target sentence-level reading, yet two of the three patients became so adept that they could read entire sentences. Conclusions: This study replicates previous findings on the efficacy of tactile/kinaesthetic treatment for letter-by-letter readers with poor letter naming. It further demonstrates that this treatment can alter cognitive processing such that words never specifically trained can be read in free vision without overtly using the trained strategy. The data suggest that an important element in achieving this level of generalisation is continuing training beyond the point of initial mastery (i.e., accurate letter naming).

Multivariate Pattern Analysis Reveals Category-Related Organization of Semantic Representations in Anterior Temporal Cortex

The neural substrates of semantic representation have been the subject of much controversy. The study of semantic representations is complicated by difficulty in disentangling perceptual and semantic influences on neural activity, as well as in identifying stimulus-driven, “bottom-up” semantic selectivity unconfounded by top-down task-related modulations. To address these challenges, we trained human subjects to associate pseudowords (TPWs) with various animal and tool categories. To decode semantic representations of these TPWs, we used multivariate pattern classification of fMRI data acquired while subjects performed a semantic oddball detection task. Crucially, the classifier was trained and tested on disjoint sets of TPWs, so that the classifier had to use the semantic information from the training set to correctly classify the test set. Animal and tool TPWs were successfully decoded based on fMRI activity in spatially distinct subregions of the left medial anterior temporal lobe (LATL). In addition, tools (but not animals) were successfully decoded from activity in the left inferior parietal lobule. The tool-selective LATL subregion showed greater functional connectivity with left inferior parietal lobule and ventral premotor cortex, indicating that each LATL subregion exhibits distinct patterns of connectivity. Our findings demonstrate category-selective organization of semantic representations in LATL into spatially distinct subregions, continuing the lateral-medial segregation of activation in posterior temporal cortex previously observed in response to images of animals and tools, respectively. Together, our results provide evidence for segregation of processing hierarchies for different classes of objects and the existence of multiple, category-specific semantic networks in the brain. SIGNIFICANCE STATEMENT The location and specificity of semantic representations in the brain are still widely debated. We trained human participants to associate specific pseudowords with various animal and tool categories, and used multivariate pattern classification of fMRI data to decode the semantic representations of the trained pseudowords. We found that: (1) animal and tool information was organized in category-selective subregions of medial left anterior temporal lobe (LATL); (2) tools, but not animals, were encoded in left inferior parietal lobe; and (3) LATL subregions exhibited distinct patterns of functional connectivity with category-related regions across cortex. Our findings suggest that semantic knowledge in LATL is organized in category-related subregions, providing evidence for the existence of multiple, category-specific semantic representations in the brain.

The role of effort in errorless and errorful learning

The technique of errorless learning (EL) has recently been applied to studies of the rehabilitation of anomia. In EL, the situation surrounding the performance of the desired task is controlled to prevent errors, sometimes through the use of descending cueing hierarchies. Another approach used in anomia treatments is ascending cueing hierarchies, in which errors are allowed. This is an example of errorful learning (EF). While both EL and EF paradigms have been used in anomia rehabilitation research, these approaches have never been directly compared (Fillingham, Hodgson, Sage, Lambon, & Ralph, et al., 2003). To address this issue, Treatment Comparison 1 (TC1) was designed to compare EL and EF treatments in training picture-naming with an anomic patient. The treatments were designed to be parallel in every way except that one was designed to prevent errors while the other allowed errors to occur. Treatment Comparison 2 (TC2) was designed to examine the role of effort in these same two treatment paradigms. The EL treatment was made more difficult but kept relatively errorfree so that it required more effort from the patient. The same manipulation was made to the EF treatment, enabling us to directly compare the two paradigms.

Evidence for rapid localist plasticity in the ventral visual stream: the example of words

ABSTRACT Our recent work has shown that the visual word form area (VWFA) in the left occipitotemporal cortex contains an orthographic lexicon based on neuronal representations highly selective for individual written real words (RWs) and that learning novel words selectively increases neural specificity in the VWFA. But, how quickly does this change in neural tuning occur and how much training is required for new words to be codified in the VWFA? Here, we present evidence that plasticity in the VWFA from broad to tight tuning can be obtained in a short time span, with no explicit training, and with comparatively few exposures, further strengthening the case for a highly plastic visual lexicon in the VWFA and for localist representations in the visual processing hierarchy.

Orthographic and phonological selectivity across the reading system in deaf skilled readers

ABSTRACT People who are born deaf often have difficulty learning to read. Recently, several studies have examined the neural substrates involved in reading in deaf people and found a left lateralized reading system similar to hearing people involving temporo‐parietal, inferior frontal, and ventral occipito‐temporal cortices. Previous studies in typical hearing readers show that within this reading network there are separate regions that specialize in processing orthography and phonology. We used fMRI rapid adaptation in deaf adults who were skilled readers to examine neural selectivity in three functional ROIs in the left hemisphere: temporoparietal cortex (TPC), inferior frontal gyrus (IFG), and the visual word form area (VWFA). Results show that in deaf skilled readers, the left VWFA showed selectivity for orthography similar to what has been reported for hearing readers, the TPC showed less sensitivity to phonology than previously reported for hearing readers using the same paradigm, and the IFG showed selectivity to orthography, but not phonology (similar to what has been reported previously for hearing readers). These results provide evidence that while skilled deaf readers demonstrate coarsely tuned phonological representations in the TPC, they develop finely tuned representations for the orthography of written words in the VWFA and IFG. This result suggests that phonological tuning in the TPC may have little impact on the neural network associated with skilled reading for deaf adults. HighlightsAn fMRI rapid adaptation paradigm explored neural tuning in skilled deaf readers.Both the left and right VWFA showed selectivity to whole word orthography.Sensitivity, but not selectivity to phonology was found in temporoparietal cortex.Skilled deaf readers develop finely tuned neural representations of written words.Phonological tuning may have little impact on reading success for deaf adults.