Non-Gaussian Distributional Analyses of Reaction Times (RT): Improvements that Increase Efficacy of RT Tasks for Describing Cognitive Processes.

This didactic aims of this review are to demonstrate the advantages of examining the entire reaction time (RT) distribution to better realize the efficacy of mental speed assessment in clinical neuropsychology. RT distributions are typically non-normal, requiring consideration of a host of statistical issues. Specifically, the appropriate model of the mental speed task's distribution (e.g., ex-Gaussian, Weibull, Normal-Gaussian, etc.) must be determined to know what parameters can be used to characterize test performance. While RT mean and standard deviation are typically used to characterize clinical performance, these parameters are usually inappropriate because RT performance rarely conforms to a normal-Gaussian distribution. For illustrative purposes, a tutorial for examining the entire RT distribution is provided that demonstrates differences between an Attention Deficit/Hyperactivity and a neurotypical group of college students. While such analyses are descriptive, it is important to characterize test performance in the context of a theoretical model of RT performance. Therefore, the tutorial includes interpretation that uses the Diffusion model (Ratcliff Psychological Review, 85, 59-108, 1978), which assumes an ex-Gaussian distribution. It is concluded that current results conform to a large literature demonstrating a more nuanced understanding of cognition afforded by non-Gaussian analysis of RT. This literature is compelling neuropsychology to enlarge assessment technology beyond the limitations of paper-and-pencil instruments.

Transverse patterning, aging, and neuropsychological correlates in humans.

Transverse patterning is a learning and memory adaptation of the 'rock/paper/scissors' problem that has been though to depend on the hippocampus, is sensitive to aging, and requires pattern separation to solve. Previous investigators dichotomized cognitively normal older adults who passed a cognitive screening into impaired and unimpaired subsets, and found that impaired older adults were disproportionately deficient in pattern separation abilities. However, this variability in pattern separation ability has not been examined using a transverse patterning task. Our aims, then, were two-fold: First, to determine if impaired older adults were inferior on transverse patterning compared to unimpaired older adults and young adults; second, to identify the neuropsychological correlates of transverse patterning. Our findings revealed that impaired older adults required more trials to criterion on the transverse patterning task than both young adults and unimpaired older adults. Unimpaired older adults also required more trials to criterion than young adults. A detailed analysis of the transverse patterning task confirmed that the aforementioned group differences were only observed in high interference conditions when pattern separation demands were at their peak. Finally, regression analyses showed that both memory and executive functioning neuropsychological composite scores were related to different indices of transverse patterning performance. Consistent with the pattern separation literature, and despite passing a cognitive screening, we found disproportionate transverse patterning deficits in impaired older adults. Forthcoming work should determine if transverse patterning performance is similar between impaired older adults and patients with Mild Cognitive Impairment. © 2016 Wiley Periodicals, Inc.

The role of left occipitotemporal cortex in reading: reconciling stimulus, task, and lexicality effects.

Although the left posterior occipitotemporal sulcus (pOTS) has been called a visual word form area, debate persists over the selectivity of this region for reading relative to general nonorthographic visual object processing. We used high-resolution functional magnetic resonance imaging to study left pOTS responses to combinatorial orthographic and object shape information. Participants performed naming and visual discrimination tasks designed to encourage or suppress phonological encoding. During the naming task, all participants showed subregions within left pOTS that were more sensitive to combinatorial orthographic information than to object information. This difference disappeared, however, when phonological processing demands were removed. Responses were stronger to pseudowords than to words, but this effect also disappeared when phonological processing demands were removed. Subregions within the left pOTS are preferentially activated when visual input must be mapped to a phonological representation (i.e., a name) and particularly when component parts of the visual input must be mapped to corresponding phonological elements (consonant or vowel phonemes). Results indicate a specialized role for subregions within the left pOTS in the isomorphic mapping of familiar combinatorial visual patterns to phonological forms. This process distinguishes reading from picture naming and accounts for a wide range of previously reported stimulus and task effects in left pOTS.

A distributional and theoretical analysis of reaction time in the reversal task across adulthood.

Reversal learning assesses components of executive function important for understanding cognitive changes with age. Extant reversal learning literature has largely assessed measures of accuracy, but reaction time (RT) has not yet been well characterized, perhaps due to the daunting task of analyzing non-normal RT distributions. The current study contributes to the literature by examining distributional and theoretical aspects of the entire RT distribution in addition to accuracy. Participant sample included young (N = 43) and community-dwelling, healthy, middle-aged (N = 139) adults. Results showed a Normal-3 Mixture distribution best fits the sample as a whole, with the ex-Gaussian distribution passing visual inspection. Age related significantly to various measures of RT (p's < 0.5); older age was associated with higher both efficient and overall RT, perhaps due to a more conservative criterion of decision-making. In a generalized adaptive elastic net regression, RT explained age-related differences in performance while accuracy did not contribute. Specifically, middle-aged adults were slower in efficient RT and had increased intra-individual variability which has been previously linked to poorer frontal lobe processes and age-related cognitive decline. Overall, these findings highlight the importance of examining the entire RT distribution and measuring RT as a fractionated construct to further explain age-related differences in reversal learning, even in middle-aged individuals.

Reversal learning in young and middle-age neurotypicals: Individual difference reaction time considerations.

Reversal learning is frequently used to assess components of executive function that contribute to understanding age-related cognitive differences. Reaction time (RT) is less characterized in the reversal learning literature, perhaps due to the daunting task of analyzing the entire RT distribution, but has been deemed a generally sensitive measure of cognitive aging. The current study extends our prior work to further characterize distributional properties of the reversal RT distribution and to distinguish groups of individuals with fractionated profiles of performance, which may be of clinical importance within the context of cognitive aging. Participant sample included young (n = 43) and community-dwelling, healthy, middle-aged (n = 139) adults. To explore individual differences, recursive partitioning analysis achieved a high classification rate by specifying decision tree rules that split participants into young and middle-aged groups. Mu (µ, efficient RT) was the most successful parameter in distinguishing age groups while sigma ( σ) and tau ( τ , ex-Gaussian indices of intra-individual variability) revealed more subtle individual differences. Accuracy measures did not contribute to separating the groups, suggesting that fractionated components of RT, as opposed to accuracy, can distinguish differences between young and middle-aged participants.

Durability, negative impact, and neuropsychological predictors of tic suppression in children with chronic tic disorder.

Chronic tic disorders are characterized by involuntary motor and vocal tics, which are influenced by contextual factors. Recent research has shown that (a) children can suppress tics for brief periods of time, (b) suppression is enhanced when programmed reinforcement is provided for tic-free intervals, and (c) short periods of suppression do not result in a paradoxical "rebound" in tic frequency when active suppression has ceased. The current study extended existing research in three important ways. First, we examined whether tic suppression ability decreased as suppression duration increased from 5 to 25 to 40 min. Second, we examined post-suppression tic frequency to test whether longer periods of suppression were more likely to be associated with a rebound effect. Finally, we explored neuropsychological predictors of tic suppression. Thirteen children with Tourette syndrome or a chronic tic disorder completed the study. Results showed that (a) tic suppression was sustained for all of the suppression durations, (b) rebound effects were not observed following any of the suppression durations, and (c) ability to suppress was correlated with omission, but not commission errors on a continuous performance task. Implications of these findings are discussed.

Stroop interference associated with efficient reading fluency and prelexical orthographic processing.

The Stroop Color-Word Test involves a dynamic interplay between reading and executive functioning that elicits intuitions of word reading automaticity. One such intuition is that strong reading skills (i.e., more automatized word reading) play a disruptive role within the test, contributing to Stroop interference. However, evidence has accumulated that challenges this intuition. The present study examined associations among Stroop interference, reading skills (i.e., isolated word identification, grapheme-to-phoneme mapping, phonemic awareness, reading fluency) measured on standardized tests, and orthographic skills measured on experimental computerized tasks. Among university students (N = 152), correlational analyses showed greater Stroop interference to be associated with (a) relatively low scores on all standardized reading tests, and (b) longer response latencies on orthographic tasks. Hierarchical regression demonstrated that reading fluency and prelexical orthographic processing predicted unique and significant variance in Stroop interference beyond baseline rapid naming. Results suggest that strong reading skills, including orthographic processing, play a supportive role in resolving Stroop interference.

Neuropsychological evaluation in the diagnosis and treatment of Tourette's syndrome.

The neurobiological basis of Tourette's syndrome is reviewed for the purpose of presenting a clinically relevant account of the neuropsychology of the disorder for the clinician who is behaviorally oriented. The neuropathology and neuropsychological deficits typically found in Tourette's are reviewed, and a neuropsychological test battery is described that can be used to help characterize the clinical presentation of the disorder. Although Tourette's syndrome is ultimately diagnosed by behavioral criteria, characterizing the cognitive deficits (or lack thereof) associated with the disorder is integral to fully appreciating the challenges posed by the disorder in any given case. The variety of cognitive deficits associated with Tourette's is reviewed to show the importance of the neuropsychological evaluation in differential diagnostic, therapeutic, and prognostic decisions.

Effort in college undergraduates is sufficient on the word memory test.

A prior report found unusually high rates of performance validity test (PVT) failure in undergraduate research participants (31%-56%). The present study examined 110 undergraduate volunteers in three conditions (positive, neutral, or negative demand characteristics) in either an easy to hard or a hard to easy progression of neuropsychological tests using the Word Memory Test PVT. Neither demand characteristics nor test order had a substantial effect on test performance, and only a 6.4% failure rate was found on the PVT. These results suggest that neuropsychological testing experiments are completed faithfully by the vast majority of college undergraduates, although excluding the small number of participants failing PVTs would strengthen the internal validity of most studies.

Visuoperceptual-orthographic reading abilities: a confirmatory factor analysis study.

The current study examined the psychometric properties of a hypothetical visuoperceptual-orthographic (VPO) reading construct in a sample of nonimpaired college students (N = 152). Participants were administered a battery of standardized and experimental measures of VPO, including Woodcock-Johnson III (WJ-III) Letter-Word Identification (Woodcock, McGrew, & Mather, 2001), Visual-Naming Speed (word page of the Stroop), Letter-Identification Task, Same/Different Letter Decision Task, Word Matching Task, Homophone Decision Task, Pseudohomophone Decision Task, and Word Jumble Task. The LISREL 8.54 computer program (Jöreskog & Sörbom, 2003) was employed for confirmatory factor analysis to assess the tenability of a multifaceted, unitary VPO reading construct. Goodness-of-fit statistics indicated that VPO is a hierarchically organized construct with one 2nd-order factor (i.e., VPO) and three 1st-order factors (i.e., perceptual processing speed, prelexical accuracy, and lexicosemantic accuracy). Alternative models were tested but produced unsatisfactory goodness-of-fit statistics. Altogether these findings are in agreement with those of previous cognitive and neuroscientific studies and further support the notion that VPO should be viewed as a unique factor in the assessment, diagnosis, and remediation of developmental dyslexia.

The word reading test of effort in adult learning disability: a simulation study.

The Word Reading Test (WRT) was designed to detect effort problems specific to a learning disability sample. The WRT and the Word Memory Test (WMT) were administered to two simulator and normal control groups. The WRT showed excellent receiver operating characteristics (e.g., 90% sensitivity and 100% positive predictive power) and outperformed the WMT in detecting both reading and mental speed simulators. This finding and a double dissociation between reading and speed simulators on WRT errors and reaction time suggested specific effort effects while poor effort of simulators on the WMT suggested general effort effects. Results are supportive of the WRT as a potential effort indicator in learning disability.

Processing abilities associated with math skills in adult learning disability.

This study evaluated college adults (N = 138) referred for learning problems using a Cattell-Horn-Carroll based intelligence measure (Woodcock Johnson-Revised: WJ-R) and spatial and executive function neuropsychological measures to determine processing abilities underlying math skills. Auditory and visual perceptual (WJ-R Ga and Gv), long- and short-memory (WJ-R Glr and Gsm), crystallized and fluid intellectual (WJ-R Gc and Gf), and spatial and executive function (Judgment of Line Orientation [JLO] and Category Test) measures differentiated those with and without math deficits. Multiple regression revealed selective processing abilities (Gf, JLO, and Category) predicting about 16% of the variance in math skills after variance associated with general intelligence (also about 16%) was removed. Cluster analysis found evidence for a selective spatial deficit group, a selective executive function deficit group and a double deficit (spatial and executive function) group. Results were discussed in relation to a double deficit hypothesis associated with developmental dyscalculia.

Processing abilities associated with phonologic and orthographic skills in adult learning disability.

Measures of orthographic and phonologic skills were related to co-normed Woodcock Johnson-Revised (WJ-R) cognitive measures in 138 college age, learning problem adults. Only orthographic deficits were associated with a processing disorder (p<.001). Selective processing abilities were associated with phonologic (p<.001, Delta adj R(2)=.053) and orthographic (p<.001, Delta adj R(2)=.047) skills after removal of variance associated with general intelligence. Analyses found common processing abilities across both phonologic and orthographic skills for WJ-R visual processing (-Gv) and short-term memory processing factors (Gsm) (p<.001). Cluster analysis established a phonologic deficit and a double deficit (phonologic and orthographic) group. Discussion relates results to the differences between adult and child reading decoding deficits, the lack of a selective orthographically impaired subtype of dyslexia, and the evidence of visual processing compensation for reading problems.