Imaging Imageability: Behavioral Effects and Neural Correlates of Its Interaction with Affect and Context.

The construct of imageability refers to the extent to which a word evokes a tangible sensation. Previous research (Westbury et al., 2013) suggests that the behavioral effects attributed to a word's imageability can be largely or wholly explained by two objective constructs, contextual density and estimated affect. Here, we extend these previous findings in two ways. First, we show that closely matched stimuli on the three measures of contextual density, estimated affect, and human-judged imageability show a three-way interaction in explaining variance in LD RTs, but that imagebility accounts for no additional variance after contextual density and estimated affect are entered first. Secondly, we demonstrate that the loci and functional connectivity (via graphical models) of the brain regions implicated in processing the three variables during that task are largely over-lapping and similar. These two lines of evidence support the conclusion that the effect usually attributed to human-judged imageability is largely or entirely due to the effects of other correlated measures that are directly computable.

Now you see it, now you don't: on emotion, context, and the algorithmic prediction of human imageability judgments.

Many studies have shown that behavioral measures are affected by manipulating the imageability of words. Though imageability is usually measured by human judgment, little is known about what factors underlie those judgments. We demonstrate that imageability judgments can be largely or entirely accounted for by two computable measures that have previously been associated with imageability, the size and density of a word's context and the emotional associations of the word. We outline an algorithmic method for predicting imageability judgments using co-occurrence distances in a large corpus. Our computed judgments account for 58% of the variance in a set of nearly two thousand imageability judgments, for words that span the entire range of imageability. The two factors account for 43% of the variance in lexical decision reaction times (LDRTs) that is attributable to imageability in a large database of 3697 LDRTs spanning the range of imageability. We document variances in the distribution of our measures across the range of imageability that suggest that they will account for more variance at the extremes, from which most imageability-manipulating stimulus sets are drawn. The two predictors account for 100% of the variance that is attributable to imageability in newly-collected LDRTs using a previously-published stimulus set of 100 items. We argue that our model of imageability is neurobiologically plausible by showing it is consistent with brain imaging data. The evidence we present suggests that behavioral effects in the lexical decision task that are usually attributed to the abstract/concrete distinction between words can be wholly explained by objective characteristics of the word that are not directly related to the semantic distinction. We provide computed imageability estimates for over 29,000 words.

Bayes' rule for clinicians: an introduction.

Bayes' Rule is a way of calculating conditional probabilities. It is difficult to find an explanation of its relevance that is both mathematically comprehensive and easily accessible to all readers. This article tries to fill that void, by laying out the nature of Bayes' Rule and its implications for clinicians in a way that assumes little or no background in probability theory. It builds on Meehl and Rosen's (1955) classic paper, by laying out algebraic proofs that they simply allude to, and by providing extremely simple and intuitively accessible examples of the concepts that they assumed their reader understood.

Tuning of the human left fusiform gyrus to sublexical orthographic structure.

Neuropsychological and neurophysiological evidence point to a role for the left fusiform gyrus in visual word recognition, but the specific nature of this role remains a topic of debate. The aim of this study was to measure the sensitivity of this region to sublexical orthographic structure. We measured blood oxygenation (BOLD) changes in the brain with functional magnetic resonance imaging while fluent readers of English viewed meaningless letter strings. The stimuli varied systematically in their approximation to English orthography, as measured by the probability of occurrence of letters and sequential letter pairs (bigrams) comprising the string. A whole-brain analysis showed a single region in the lateral left fusiform gyrus where BOLD signal increased with letter sequence probability; no other brain region showed this response pattern. The results suggest tuning of this cortical area to letter probabilities as a result of perceptual experience and provide a possible neural correlate for the 'word superiority effect' observed in letter perception research.

Randomized controlled trial of modafinil for the treatment of fatigue in postpolio patients.

The purpose of this study was to test whether modafinil is effective in alleviating the symptoms of fatigue in postpolio patients, because it has been helpful for such symptoms in other neurologic disorders. Using a double-blind, randomized, placebo-controlled cross-over design, 14 postpolio patients with moderate to severe fatigue were assigned to receive modafinil or placebo first. Piper Fatigue Scale, Epworth Sleepiness Scale, digit span, and reaction time tests were done at baseline and then at weekly intervals. The Piper Fatigue Scale scores improved by 27 +/- 40% (mean +/- SD) following modafinil and by 43 +/- 36% following placebo. Scores for most of the other tests did not change during the study. Therefore, we conclude that modafinil was not effective in alleviating the symptoms of fatigue in postpolio patients.

Applicability, validity, and reliability of the Piper Fatigue Scale in postpolio patients.

OBJECTIVE: To identify a scale that is potentially applicable for measuring the fatigue in postpolio patients and to evaluate its validity and reliability in this population. DESIGN: Interview survey of 64 individuals with postpolio syndrome and 25 healthy controls of similar age range, with retest in a subset of postpolio patients. The sample was recruited from a postpolio support group, a postpolio clinic, and the general community. Subjects completed the Piper Fatigue Scale, the Beck Depression Inventory, and the Chalder Fatigue Questionnaire during the interview. RESULTS: Face and content validity of the Piper Fatigue Scale was established by a team of experts and by a group of postpolio patients. The postpolio subjects had significantly higher Piper Fatigue Scale scores than the healthy control subjects (P < 0.001), demonstrating extreme groups validity. Convergent validity was shown with a strong positive correlation between Piper Fatigue Scale scores and Chalder Fatigue Questionnaire scores (r = 0.80). Reliability was also demonstrated with the Piper Fatigue Scale's high internal consistency (alpha = 0.98) and strong test-retest agreement (intraclass correlation coefficient = 0.98). CONCLUSIONS: The Piper Fatigue Scale is a valid and reliable tool for measuring postpolio fatigue. This scale may be useful in other studies of postpolio fatigue, including those gauging the effectiveness of various treatments for this fatigue.