Predictors of Lexical Accessibility of Common and Proper Nouns in Older Age: Evidence from the Tip-of-the-Tongue State

One of the notable language difficulties experienced by healthy older adults is word retrieval failure, specifically the tip-of-the-tongue state (TOT). A TOT occurs when one has a strong sense of knowing the word, such that the semantic content is accessed, but the entirety of the word’s phonology is temporarily inaccessible. Such retrieval difficulty is attributable, at least in part, to characteristics of the target word. Psycholinguistic features may uniquely influence the semantic and/or phonological stages of word production. An additional factor known to influence TOT-likelihood is noun type: proper nouns elicit TOTs more often than do common nouns. The discrepancy between the likelihood of a TOT for the two noun types is hypothesized to be due to their differential representation in the mental lexicon. The difference hinges on the connection architecture at the semantic level (between semantic nodes and the lemma node) for common and proper nouns – the former characterized by convergent, many-to-one connections and the latter by one-to-one connections. The extent to which the representation of common and proper nouns accounts for retrieval difficulties as a consequence of psycholinguistic factors known to interact with the semantic level and phonological levels is poorly understood. Therefore, this dissertation examined the contribution of several psycholinguistic features to the likelihood of successful retrieval at the semantic and phonological stages in a set of common and proper nouns. Fifty-two monolingual English-speaking, healthy older adults between the ages of 54 and 89 participated in a TOT-inducing, computerized word naming task. Participants named targets from a selected subset of the total stimulus set of 1,102 words (587 proper nouns and 515 common nouns). Each target was cued independently from a picture and definition; however, cue type was counterbalanced across participants such that no-one saw the same target in both cue modalities. Analyses focused on the influence of the psycholinguistic features (namely self-rated frequency and familiarity, Zipf frequency, MRC familiarity, word-length in phonemes, neighborhood density, and first-syllable frequency) on word-retrieval performance at both stages of retrieval using a two-step model of TOTs. The results of the current research offer novel evidence for the independent influence of frequency and familiarity on the likelihood of retrieval success at the semantic and phonological levels of lexical processing. Specifically, frequency was found to benefit both stages of retrieval for proper names and the phonological stage alone for common nouns. This finding suggests a frequency-related advantage such that one-to-one connections are favored at the semantic and phonological levels. By contrast, familiarity benefited retrieval at both stages for both noun types, indicating that an effect of familiarity is agnostic to connection architecture at each level. The present study also offers new evidence for a cue-related retrieval advantage at the semantic level for common nouns (but not proper nouns) retrieved from picture cues. There was no effect of the other psycholinguistic features tested for either word type or stage of lexical processing. This research establishes the independent contribution of psycholinguistic features to TOT occurrence in common and proper nouns in relation to the overall architecture of the semantic and phonological systems

Home-administered transcranial direct current stimulation is a feasible intervention for depression: an observational cohort study

Transcranial direct current stimulation (tDCS) is an emerging treatment for major depression. We recruited participants with moderate-to-severe major depressive episodes for an observational clinical trial using Soterix Medical's tDCS telehealth platform as a standard of care. The acute intervention consisted of 28 sessions (5 sessions/week, 6 weeks) of the left anodal dorsolateral prefrontal cortex (DLPFC) tDCS (2.0 mA × 30 min) followed by a tapering phase of weekly sessions for 4 weeks (weeks 7–10). The n = 16 completing participants had a significant reduction in depressive symptoms by week 2 of treatment [Montgomery–Åsberg Depression Rating Scale (MADRS), Baseline: 28.00 ± 4.35 vs. Week 2: 17.12 ± 5.32, p < 0.001] with continual improvement across each biweekly timepoint. Acute intervention responder and remission rates were 75 and 63% and 88 and 81% following the taper period (week 10)

Translational treatment of aphasia combining neuromodulation and behavioral intervention for lexical retrieval: implications from a single case study

Background: Transcranial direct current stimulation (tDCS), a non-invasive method of brain stimulation, is an adjunctive research-therapy for aphasia. The concept supporting translational application of tDCS is that brain plasticity, facilitated by language intervention, can be enhanced by non-invasive brain stimulation. This study combined tDCS with an ecologically focused behavioral approach that involved training nouns and verbs in sentences. Method: Participant: A 43-year-old, right-handed male with fluent-anomic aphasia who sustained a single-left-hemisphere-temporal-parietal stroke was recruited. Treatment: Instrumentation included the Soterix Medical 1 × 1 Device. Anodal tDCS was applied over Broca’s area. Behavioral materials included: sentence production, naming in the sentence context, and implementation of a social-conversational-discourse treatment. Design and Procedures: The independent variable of this crossover case-study was tDCS, and the dependent variables were language and quality-of-life measures. In each session the subject received language treatment with the first 20 minutes additionally including tDCS. Results: Performance in naming nouns and verbs in single words and sentences were obtained. Verb production in the sentence context increased after active anodal tDCS and speech-language treatment. Conclusion: Aphasia treatment that involves naming in the sentence context in conjunction with translational application of tDCS may be a promising approach for language-recovery post stroke

Tolerability and feasibility of at-home remotely supervised transcranial direct current stimulation (RS-tDCS): Single-center evidence from 6,779 sessions

Introduction: The ability to deploy transcranial direct current stimulation (tDCS) at home is a key usability advantage to support scaling for pivotal clinical trials. We have established a home-based tDCS protocol for use in clinical trials termed remotely supervised (RS)-tDCS. Objective: To report the tolerability and feasibility of tDCS sessions completed to date using RS-tDCS in clinical trials. Methods: We analyzed tolerability (i.e., adverse events, AEs) reported in six Class I/II/III trials using RS-tDCS to study symptom outcomes over 10 to 60 daily applications. Across the six clinical trials, 308 participants (18-78 years old) completed an average of 23 sessions for a total of 6779 RS-tDCS administrations. The majority of participants were diagnosed with multiple sclerosis, and open-label trials included those diagnosed with a range of other conditions (e.g., Parkinson\u27s disease, post-stroke aphasia, traumatic brain injury, cerebellar ataxia), with minimum-to-severe neurologic disability. Clinical trial feasibility (i.e., treatment fidelity and blinding integrity) was examined using two Class I randomized controlled trials (RCTs). Results: No serious AEs occurred. Across administrations, three sessions (0.04%) were aborted due to discomfort, but no participant discontinued due to tolerability. The AEs most commonly reported by participants were tingling (68%), itching (41%) and warmth sensation (42%) at the electrode site, and these were equally reported in active and sham tDCS conditions. The two Class I RCTs resulted in rapid enrollment, high fidelity to treatment completion, and blinding integrity. Conclusions: At-home RS-tDCS is tolerable, including when used over extended periods of time. Home-based RS-tDCS is feasible and can enable Class I tDCS clinical trial designs