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1.  Gamma- and theta-band synchronization during semantic priming reflect local and long-range lexical-semantic networks 
Brain and language  2013;127(3):10.1016/j.bandl.2013.09.003.
Anterior and posterior brain areas are involved in the storage and retrieval of semantic representations, but it is not known how these areas dynamically interact during semantic processing. We hypothesized that long-range theta-band coherence would reflect coupling of these areas and examined the oscillatory dynamics of lexical-semantic processing using a semantic priming paradigm with a delayed letter-search task while recording subjects' EEG. Time-frequency analysis revealed facilitation of semantic processing for Related compared to Unrelated conditions, which resulted in a reduced N400 and reduced gamma power from 150-450 ms. Moreover, we observed greater anterior-posterior theta coherence for Unrelated compared to Related conditions over the time windows 150-425 ms and 600-900 ms. We suggest that while gamma power reflects activation of local functional networks supporting semantic representations, theta coherence indicates dynamic coupling of anterior and posterior areas for retrieval and post-retrieval processing and possibly an interaction between semantic relatedness and working memory.
PMCID: PMC3864756  PMID: 24135132
dynamic connectivity; coherence; electroencephalography; language; oscillatory dynamics
2.  Word Class and Context Affect Alpha-Band Oscillatory Dynamics in an Older Population 
Differences in the oscillatory EEG dynamics of reading open class (OC) and closed class (CC) words have previously been found (Bastiaansen et al., 2005) and are thought to reflect differences in lexical-semantic content between these word classes. In particular, the theta-band (4–7 Hz) seems to play a prominent role in lexical-semantic retrieval. We tested whether this theta effect is robust in an older population of subjects. Additionally, we examined how the context of a word can modulate the oscillatory dynamics underlying retrieval for the two different classes of words. Older participants (mean age 55) read words presented in either syntactically correct sentences or in a scrambled order (“scrambled sentence”) while their EEG was recorded. We performed time–frequency analysis to examine how power varied based on the context or class of the word. We observed larger power decreases in the alpha (8–12 Hz) band between 200–700 ms for the OC compared to CC words, but this was true only for the scrambled sentence context. We did not observe differences in theta power between these conditions. Context exerted an effect on the alpha and low beta (13–18 Hz) bands between 0 and 700 ms. These results suggest that the previously observed word class effects on theta power changes in a younger participant sample do not seem to be a robust effect in this older population. Though this is an indirect comparison between studies, it may suggest the existence of aging effects on word retrieval dynamics for different populations. Additionally, the interaction between word class and context suggests that word retrieval mechanisms interact with sentence-level comprehension mechanisms in the alpha-band.
PMCID: PMC3321481  PMID: 22509171
lexical-semantic; reading; EEG; oscillatory dynamics; alpha; theta
3.  Overt use of a tactile-kinesthetic strategy shifts to covert processing in rehabilitation of letter-by-letter reading 
Aphasiology  2010;24(11):1424-1442.
Letter-by-letter readers identify each letter of the word they are reading serially in left to right order before recognizing 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 kinesthetic strategies have been reported to improve reading in these patients, but only under certain conditions or for a limited set of stimuli.
The primary aim of the current study was to determine whether a tactile/kinesthetic 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/kinesthetic 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/kinesthetic 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 reading untrained words without overt use of the trained tactile/kinesthetic 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.
This study replicates previous findings on the efficacy of tactile/kinesthetic 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 generalization is continuing training beyond the point of initial mastery (i.e. accurate letter naming).
PMCID: PMC3002229  PMID: 21170161
aphasia; cognitive rehabilitation; Speech-Language Pathology; pure alexia; letter-by-letter reading; generalization
4.  Repetition priming in oral text reading: a therapeutic strategy for phonologic text alexia 
Aphasiology  2009;23(6):659-675.
Phonologic text alexia (PhTA) is a reading disorder in which reading of pseudowords is impaired, but reading of real words is impaired only when reading text. Oral reading accuracy remains well preserved when words are presented individually, but when presented in text the part-of-speech effect that is often seen in phonologic alexia (PhA) emerges.
To determine whether repetition priming could strengthen and/or maintain the activation of words during text reading.
Methods & Procedures
We trained NYR, a patient with PhTA, to use a strategy, Sentence Building, designed to improve accuracy of reading words in text. The strategy required NYR to first read the initial word, and then build up the sentence by adding on sequential words, in a step-wise manner, utilizing the benefits of repetition priming to enhance accuracy.
Outcomes & Results
When using the strategy, NYR displayed improved accuracy not only for sentences she practiced using the strategy, but unpracticed sentences as well. Additionally, NYR performed better on a test of comprehension when using the strategy, as compared to without the strategy.
In light of research linking repetition priming to increased neural processing efficiency, our results suggest that use of this compensatory strategy improves reading accuracy and comprehension by temporarily boosting phonologic activation levels.
PMCID: PMC2906786  PMID: 20664804
phonologic text alexia; repetition priming; aphasia; alexia; rehabilitation
5.  Neural Mechanisms Underlying Learning following Semantic Mediation Treatment in a case of Phonologic Alexia 
Brain imaging and behavior  2008;2(3):147.
Patients with phonologic alexia can be trained to read semantically impoverished words (e.g., functors) by pairing them with phonologically-related semantically rich words (e.g, nouns). What mechanisms underlie success in this cognitive re-training approach? Does the mechanism change if the skill is “overlearned”, i.e., practiced beyond criterion? We utilized fMRI pre- and post-treatment, and after overlearning, to assess treatment-related functional reorganization in a patient with phonologic alexia, two years post left temporoparietal stroke. Pre-treatment, there were no statistically significant differences in activation profiles across the sets of words. Post-treatment, accuracy on the two trained sets improved. Compared with untrained words, reading trained words recruited larger and more significant clusters of activation in the right hemisphere, including right inferior frontal and inferior parietal cortex. Post-overlearning, with near normal performance on overlearned words, predominant activation shifted to left hemisphere regions, including perilesional activation in superior parietal lobe, when reading overlearned vs. untrained words.
PMCID: PMC2812907  PMID: 20119495
phonologic alexia; cognitive rehabilitation; functional reorganization; fMRI; lateralization index; overlearning
6.  A patient with phonologic alexia can learn to read "much" from "mud pies" 
Neuropsychologia  2008;46(10):2515-2523.
People with phonologic alexia often have difficulty reading functors and verbs, in addition to pseudowords. Friedman et al (2002) reported a successful treatment for phonologic alexia that paired problematic functors and verbs with easily read relays that were homophonous nouns (e.g. "be" paired with "bee"). The current study evaluates the efficacy of pairing problematic grammatical words with relays that share initial phonemes, but vary in the relationship of their final phonemes. Results showed that reading of target grammatical words improved to criterion level (90% accuracy over two consecutive probes) in all experimental conditions with shared phonology, but remained far below criterion level in control conditions. There was a significant correlation between degree of phonologic relatedness and error rate. Maintenance of the treatment effect was poor as assessed by traditional measurement, however a dramatic savings during relearning was demonstrated during a subsequent treatment phase. The finding that reading can be re-organized by pairing target words not only with homophones, but with other phonologically related relays, suggests that this approach could be applied to a wide corpus of words and, therefore, potentially be of great use clinically. We suggest, within a connectionist account, that the treatment effect results from relays priming the initial phonologic units of the targets.
PMCID: PMC2536527  PMID: 18513760
aphasia; treatment; maintenance; savings of learning; phonologic priming
7.  The Underlying Mechanisms of Semantic Memory Loss in Alzheimer’s Disease and Semantic Dementia 
Neuropsychologia  2007;46(1):12-21.
Patients with Alzheimer’s Disease (AD) and patients with Semantic Dementia (SD) both exhibit deficits on explicit tasks of semantic memory such as picture naming and category fluency. These deficits have been attributed to a degradation of the stored semantic network. An alternative explanation attributes the semantic deficit in AD to an impaired ability to consciously retrieve items from the semantic network. The present study used an implicit lexical-decision priming task to examine the integrity of the underlying semantic network in AD and SD patients matched for degree of impairment on explicit semantic memory tasks. The AD (n=11) and SD (n=11) patient groups were matched for age, education, level of dementia and impairment on four explicit semantic memory tasks. Healthy elderly participants (n=22) were matched for age and education. Semantic priming effects were evaluated for three types of semantic relationships (attributes, category coordinates, and category superordinates) and compared to lexical associative priming. Healthy controls showed significant priming across all conditions. In contrast, AD patients showed normal superordinate priming, and significant (although somewhat reduced) coordinate priming, but no attribute priming. SD patients showed no priming effect for any semantic relationship. All groups showed significant associative priming. The results indicate that SD patients do indeed have substantial degradation of semantic memory, while AD patients have a partially intact network, accounting for priming in superordinate and coordinate conditions. These findings suggest that AD patients’ impairment on explicit semantic tasks is the product of deficient explicit retrieval in combination with a partially degraded semantic network.
PMCID: PMC2255584  PMID: 17897685

Results 1-7 (7)