Parallel and identical test-retest reliability of the Tower of London test - Freiburg version.

OBJECTIVES: The Tower of London - Freiburg version (TOL-F) was developed in three parallel-test versions (A, B, and C) that only differ in their physical appearance by interchanged ball colors, but not in their cognitive demands. We addressed the question whether the test-retest reliability of an identical problem set differs from the parallel test-retest reliability of a structurally identical problem set with a marginally different physical appearance. METHODS: Reliabilities were assessed in two samples of young adults over a 1-week interval: In the parallel test-retest sample (n = 93; 49 female), half of the participants accomplished version A at the first session and version B at the second session, while the other half started with version B in the first session and continued with A in the second session. In the identical test-retest sample (n = 86; 48 female), half of the participants performed on version A in both the first and the second session, while the other half went through the same procedure with version B. RESULTS: For overall planning accuracy, intraclass correlation coefficients for absolute agreement were r = .501 for the parallel test-retest and r = .605 for the identical test-retest sample, with Pearson correlations of r = .559 and r = .708 respectively. Greatest lower bound estimates of reliability were adequate to high in the two samples (ranging between .765 and .854) confirming previous studies. CONCLUSIONS: Although the TOL-F revealed only moderate intraclass correlations for absolute agreement, it showed some of the highest psychometric indices compared to repeated assessments with other TOL tests.

Psychometric analyses of the Tower of London planning task reveal high reliability and feasibility in typically developing children and child patients with ASD and ADHD.

The Tower of London (TOL) is probably the most often used assessment tool for planning ability in healthy and clinical samples. Various versions, including our proposed standard problem set, have proven to be feasible and reliable in adults. In contrast, reliability information for typically developing (TD) children and neurodevelopmental disorders during childhood are largely missing. Also, it would be highly desirable to attain a problem set that can be used across the whole lifespan. Therefore, here we examine reliability of our proposed standard problem set using a computerized TOL version in 178 TD children (two different samples), 49 children with high-functioning autism spectrum disorder (ASD) and 56 children with attention-deficit/hyperactivity disorder (ADHD) (age ranges of each group 6 to 13 years), and 130 young adults (age range 18 to 32 years). Greatest lower bound estimates of reliability were adequate to high in the two samples of TD children (.76 and .80) and high to very high in patients (ASD: .90; ADHD: .83). In young adults, all reliability indices were adequate to high. Moreover, a subset of four- and five-move problems exhibited sufficient performance variability and high part-whole correlations with the complete problem set in all samples. These findings demonstrate the reliability of the presented TOL problem set in both clinical and non-clinical child samples. A clinically feasible subset of four- and five-move problems is reflective of overall planning performance at all ages, hence enabling comparisons of planning ability within and between developmental samples across almost the whole lifespan.

Intact Visuospatial Cognition in Amblyopia: Results From the Gutenberg Health Study.

PURPOSE: To determine whether amblyopia interferes with cognitive functions requiring visuospatial processing, measured by the Tower of London (ToL) test. METHODS: The current study was based on a sub-cohort from the population-based Gutenberg Health Study and included 1,569 participants aged 35 to 44 years. Amblyopia was defined as a visual acuity of 0.63 or worse (worse eye) in the presence of an amblyogenic factor; prevalence was 5%. There were three groups: participants with amblyopia (n = 78), participants with a visual acuity of 0.63 or worse (worse eye) without amblyopia (n = 65), and participants with a visual acuity of better than 0.63 (worse eye) (n = 1,426). Visuospatial planning ability was measured by the ToL test (touch-screen version), and the performance score ranged from 0 to 24, depending on the number of correctly solved problems. The authors used linear regression models to investigate the association between amblyopia and ToL test scores, adjusting for age, sex, and socioeconomic status. RESULTS: The mean ± standard deviation of ToL test performance was 15.31 ± 3.29 in participants with a visual acuity of better than 0.63, 14.56 ± 3.76 in the amblyopic group, and 15.14 ± 3.65 in participants with a visual acuity of 0.63 or worse without amblyopia. In a linear regression model, sex, and socioeconomic status significantly predicted planning performance (P <.0001), whereas amblyopic status did not (P = .20). CONCLUSIONS: Amblyopia may affect visuospatial perception, but no such relationships could be found for higher cognitive functions that strongly depend on visuospatial processing. Thus, in adulthood, individuals with amblyopia are unaffected in their visuospatial cognitive abilities, as required by the ToL test. [J Pediatr Ophthalmol Strabismus. 2019;56(6):397-401.].

Assessing Planning Ability Across the Adult Life Span in a Large Population-Representative Sample: Reliability Estimates and Normative Data for the Tower of London (TOL-F) Task.

OBJECTIVES: The Tower of London (TOL) test has probably become the most often used task to assess planning ability in clinical and experimental settings. Since its implementation, efforts were made to provide a task version with adequate psychometric properties, but extensive normative data are not publicly available until now. The computerized TOL-Freiburg Version (TOL-F) was developed based on theory-grounded task analyses, and its psychometric adequacy has been repeatedly demonstrated in several studies but often with small and selective samples. METHOD: In the present study, we now report reliability estimates and normative data for the TOL-F stratified for age, sex, and education from a large population-representative sample collected in the Gutenberg Health Study in Mainz, Germany (n=7703; 40-80 years). RESULTS: The present data confirm previously reported adequate indices of reliability (>.70) of the TOL-F. We also provide normative data for the TOL-F stratified for age (5-year intervals), sex, and education (low vs. high education). CONCLUSIONS: Together, its adequate reliability and the representative age-, sex-, and education-fair normative data render the computerized TOL-F a suitable diagnostic instrument to assess planning ability. (JINS, 2019, 25, 520-529).

Myopia and Cognitive Performance: Results From the Gutenberg Health Study.

PURPOSE: To analyze the association between myopia and cognitive performance. METHODS: A cohort of the population-based Gutenberg Health Study included 3819 eligible enrollees between 40 and 79 years. We used the Tower of London (TOL) test to assess cognitive performance. Myopia was defined as a spherical equivalent (SE) ≤ -0.5 diopters (D) via noncycloplegic autorefractometry. We conducted linear mixed models with the SE as the dependent variable and the age, sex, duration of education, and TOL score as covariates. RESULTS: Complete data were available for 3452 participants (90.4%). The mean TOL score was 14.0 ± 3.9 in the myopes versus 12.9 ± 4.0 in the nonmyopes (P < 0.001). The mean TOL score increased with the magnitude of myopia: it was 13.9 ± 3.9 in low (less than -3 D); 14.2 ± 3.7 in moderate (between -3 and -6 D); and 14.6 ± 3.5 in high myopia (-6 D and greater; P < 0.001). Both the duration of education and cognitive performance were correlated with the magnitude of myopia (r = -0.21, P < 0.001 and r = -0.15, P < 0.001, respectively). In a linear mixed model, the duration of education significantly predicted myopia (ß = -0.14; t = -7.55; P < 0.001), whereas cognitive performance did not (ß = -0.017; t = -1.26; P = 0.207). There was a significant effect of age on the SE (ß = 0.049; t = 9.89; P < 0.001). CONCLUSIONS: When regarded separately, cognitive performance is linked to myopia. However, duration of education, which may be directly related to the risk factors for myopia, is more directly and strongly related to myopia than is cognitive performance. Cognitive ability may be associated with myopia primarily through its impact on level of education.

Development of Planning in Children with High-Functioning Autism Spectrum Disorders and/or Attention Deficit/Hyperactivity Disorder.

Planning impairment is often observed in children with high-functioning autism spectrum disorders (ASD), but attempts to differentiate planning in ASD from children with attention deficit hyperactivity disorder (ADHD) and typically developing children (TD) have yielded inconsistent results. This study examined differences between these groups by focusing on development and analyzing performance in searching ahead several steps ("search depth") in addition to commonly used global performance measures in planning. A cross-sectional consecutive sample of 83 male patients (6-13 years), subgrouped as ASD without (ASD-, n = 18) or with comorbid ADHD (ASD+, n = 23), ADHD only (n = 42) and n = 42 TD children (6-13 years) were tested with the Tower-of-London-task. For global performance, ASD+ showed the lowest accuracy in younger children, but similar performance as TD at older ages, suggesting delayed development. Typically, a prolongation of planning time with increasing problem difficulty is observed in older children as compared to younger children. Here, this was most pronounced in ASD-, but under-expressed in ADHD. In contrast to global performance, effects of search depth were independent of age. ASD-, but not ASD+, showed increased susceptibility to raised demands on mentally searching ahead, along with the longest planning times. Thus, examining both global and search depth performance across ages revealed discernible patterns of planning between groups. Notably, the potentially detrimental impact of two diagnosed disorders does not add up in ASD+ in this task. Rather, our results suggest paradoxical enhancement of performance, ostensibly attributable to disruption of behavioral rigidity through increased impulsivity, which did not take place in ASD-. Autism Res 2016, 9: 739-751. © 2015 International Society for Autism Research, Wiley Periodicals, Inc.

Training of resistance to proactive interference and working memory in older adults: a randomized double-blind study.

BACKGROUND: Working memory (WM) performance is often decreased in older adults. Despite the growing popularity of WM trainings, underlying mechanisms are still poorly understood. Resistance to proactive interference (PI) constitutes a candidate process that contributes to WM performance and might influence training or transfer effects. Here, we investigated whether PI resistance can be enhanced in older adults using a WM training with specifically increased PI-demands. Further, we investigated whether potential effects of such a training were stable and entailed any transfer on non-trained tasks. METHOD: Healthy old adults (N = 25, 68.8 ± 5.5 years) trained with a recent-probes and an n-back task daily for two weeks. Two different training regimens (high vs. low PI-amount in the tasks) were applied as between-participants manipulation, to which participants were randomly assigned. Near transfer tasks included interference tasks; far transfer tasks assessed fluid intelligence (gF) or speed. Immediate transfer was assessed directly after training; a follow-up measurement was conducted after two months. RESULTS: Both groups similarly improved in PI resistance in both training tasks. Thus, PI susceptibility was generally reduced in the two training groups and there was no difference between WM training with high versus low PI demands. Further, there was no differential near or far transfer on non-trained tasks, neither immediately after the training nor in the follow-up. CONCLUSION: PI-demands in WM training tasks do not seem critical for enhancing WM performance or PI resistance in older adults. Instead, improved resistance to PI appears to be an unspecific side-effect of a WM training.

Assessing Planning Ability Across the Adult Life Span: Population-Representative and Age-Adjusted Reliability Estimates for the Tower of London (TOL-F).

Planning ahead the consequences of future actions is a prototypical executive function. In clinical and experimental neuropsychology, disc-transfer tasks like the Tower of London (TOL) are commonly used for the assessment of planning ability. Previous psychometric evaluations have, however, yielded a poor reliability of measuring planning performance with the TOL. Based on theory-grounded task analyses and a systematic problem selection, the computerized TOL-Freiburg version (TOL-F) was developed to improve the task's psychometric properties for diagnostic applications. Here, we report reliability estimates for the TOL-F from two large samples collected in Mainz, Germany (n = 3,770; 40-80 years) and in Vienna, Austria (n = 830; 16-84 years). Results show that planning accuracy on the TOL-F possesses an adequate internal consistency and split-half reliability (>0.7) that are stable across the adult life span while the TOL-F covers a broad range of graded difficulty even in healthy adults, making it suitable for both research and clinical application.

Age differences in behavioral and neural correlates of proactive interference: Disentangling the role of overall working memory performance.

Reliable performance in working memory (WM) critically depends on the ability to resist proactive interference (PI) from previously relevant WM contents. Both WM performance and PI susceptibility are subject to cognitive decline at older adult age. However, the behavioral and neural processes underlying these co-evolving developmental changes and their potential interdependencies are not yet understood. Here, we investigated PI using a recent-probes WM paradigm and functional MRI in a cross-sectional sample of younger (n=18, 10 female, 23.4 ± 2.7 years) and older adults (n=18, 10 female, 70.2 ± 2.7 years). As expected, older adults showed lower WM performance and higher PI susceptibility than younger adults. Resolution of PI activated a mainly bilateral frontal network across all participants. Significant interactions with age indicated reduced neural activation in older adults for PI resolution. A second analysis in a selection of younger and older adults (n=12 each) with matched WM performance also revealed significant differences in PI between both age groups and - on a descriptive level - again a hypo-activation of the older adults' PI network. But the differential effect of age on the neural PI effects did not reach significance in this smaller sample most likely to the reduced statistical power. However, given the highly similar patterns in both the overall and the WM-matched samples, we propose that the hypo-activation of the PI network in the older adults may not be attributable to age-related differences in overall WM performance, hence suggesting that higher PI susceptibility in older adult age does not directly depend on their lower WM performance.

Looking ahead from age 6 to 13: a deeper insight into the development of planning ability.

Planning ability gradually increases throughout childhood. However, it remains unknown whether this is attributable to global factors such as an increased ability and willingness to inhibit premature, impulsive responding, or due to the availability of specific planning operations, such as being able to mentally plan ahead more steps ('search depth') or to derive a clear temporal order of goals by the task layout ('goal hierarchy'). Here, we studied the development of planning ability with respect to these global and problem-specific aspects (search depth and goal hierarchy) of performance in 178 children from 6 to 13 years using the Tower of London task. As expected, global performance gradually developed with age. In accordance, planning durations increasingly reflected global problem demands with longer pre-planning in harder problems. Furthermore, specific planning parameters revealed that children were increasingly capable of mentally searching ahead more steps. In contrast, the ability to derive a goal hierarchy did not show age-related changes. While the global development of planning performance and adaptive planning durations were proposed to primarily reflect enhanced self-monitoring, the specific increase in search depth across childhood that most likely proceeds until young adult age represents more directly planning-related processes. Thus, development of planning ability is supported by multiple contributions.

Transcranial direct current stimulation over left and right DLPFC: Lateralized effects on planning performance and related eye movements.

Left and right dorsolateral prefrontal cortex (dlPFC) were recently found to be differentially affected by unilateral continuous theta-burst stimulation, reflected in an oppositional alteration of initial thinking time (ITT) in the Tower of London planning task. Here, we further explored this finding using bilateral transcranial direct current stimulation (tDCS) and simultaneous tracking of eye movements. Results revealed a decrease in ITT during concurrent cathodal tDCS of left dlPFC and anodal tDCS of right dlPFC. Eye-movement analyses showed that this facilitating tDCS effect was associated with the actual planning phase, thus reflecting a planning-specific impact of stimulation. For the reverse stimulation pattern of cathodal tDCS of right dlPFC and anodal tDCS of left dlPFC, an increase in gaze shifts was observed, without a significant impact on ITT. Taken together, these findings corroborate that enhanced planning performance can be obtained by boosting right dlPFC and dismantling the inhibitory impact of left dlPFC.

Developmental change in proactive interference across the life span: evidence from two working memory tasks.

Working memory (WM) as the ability to temporarily maintain and manipulate various kinds of information is known to be affected by proactive interference (PI) from previously relevant contents, but studies on developmental changes in the susceptibility to PI are scarce. In the present study, we investigated life span development of item-specific PI. To this end, 92 individuals between the ages of 8 and 74 years completed a recent-probes task and an n-back task that both composed experimental manipulations of PI. Regarding global WM development, young adults had higher WM performance than children and older adults in both tasks. Significant PI × Age interactions revealed that susceptibility to PI changed over the life span in both tasks, whereas the developmental course of PI differed between the tasks: Children committed more PI-related errors than young adults in the recent-probes task but showed marginally less PI in the n-back task. Regarding reaction time costs, children did not differ from adults in the recent-probes task and were less affected than adults in the n-back. Older adults showed more PI-related errors than young adults in both tasks. Therefore, as expected, item-specific PI changed over the life span with the young adults being less susceptible to PI than children and older adults. The diverging developmental effects of PI across both tasks, especially in the children, are supposed to reflect different causes for the difficulties regarding resisting PI in children and older adults. These might concern differently developed underlying cognitive processes such as inhibition or recollection, or different responses to task demands across both tasks.

fMRI characterization of visual working memory recognition.

Encoding and maintenance of information in visual working memory have been extensively studied, highlighting the crucial and capacity-limiting role of fronto-parietal regions. In contrast, the neural basis of recognition in visual working memory has remained largely unspecified. Cognitive models suggest that recognition relies on a matching process that compares sensory information with the mental representations held in memory. To characterize the neural basis of recognition we varied both the need for recognition and the degree of similarity between the probe item and the memory contents, while independently manipulating memory load to produce load-related fronto-parietal activations. fMRI revealed a fractionation of working memory functions across four distributed networks. First, fronto-parietal regions were activated independent of the need for recognition. Second, anterior parts of load-related parietal regions contributed to recognition but their activations were independent of the difficulty of matching in terms of sample-probe similarity. These results argue against a key role of the fronto-parietal attention network in recognition. Rather the third group of regions including bilateral temporo-parietal junction, posterior cingulate cortex and superior frontal sulcus reflected demands on matching both in terms of sample-probe-similarity and the number of items to be compared. Also, fourth, bilateral motor regions and right superior parietal cortex showed higher activation when matching provided clear evidence for a decision. Together, the segregation between the well-known fronto-parietal activations attributed to attentional operations in working memory from those regions involved in matching supports the theoretical view of separable attentional and mnemonic contributions to working memory. Yet, the close theoretical and empirical correspondence to perceptual decision making may call for an explicit consideration of decision making mechanisms in conceptions of working memory.

Planning steps forward in development: in girls earlier than in boys.

The development of planning ability in children initially aged four and five was examined longitudinally with a retest-interval of 12 months using the Tower of London task. As expected, problems to solve straightforward without mental look-ahead were mastered by most, even the youngest children. Problems demanding look-ahead were more difficult and accuracy improved significantly with age and over time. This development was strongly moderated by sex: In contrast to coeval boys, four year old girls showed an impressive performance enhancement at age five, reaching the performance of six year olds, whereas four year old boys lagged behind and caught up with girls at the age of six, the typical age of school enrollment. This sex-specific development of planning was clearly separated from overall intelligence: young boys showed a steeper increase in raw intelligence scores than girls, whereas in the older groups scores developed similarly. The observed sex differences in planning development are evident even within a narrow time window of twelve months and may relate to differences in maturational trajectories for girls and boys in dorsolateral prefrontal cortex.

Differential impact of continuous theta-burst stimulation over left and right DLPFC on planning.

Most neuroimaging studies on planning report bilateral activations of the dorsolateral prefrontal cortex (dlPFC). Recently, these concurrent activations of left and right dlPFC have been shown to double dissociate with different cognitive demands imposed by the planning task: Higher demands on the extraction of task-relevant information led to stronger activation in left dlPFC, whereas higher demands on the integration of interdependent information into a coherent action sequence entailed stronger activation of right dlPFC. Here, we used continuous theta-burst stimulation (cTBS) to investigate the supposed causal structure-function mapping underlying this double dissociation. Two groups of healthy subjects (left-lateralized stimulation, n = 26; right-lateralized stimulation, n = 26) were tested within-subject on a variant of the Tower of London task following either real cTBS over dlPFC or sham stimulation over posterior parietal cortex. Results revealed that, irrespective of specific task demands, cTBS over left and right dlPFC was associated with a global decrease and increase, respectively, in initial planning times compared to sham stimulation. Moreover, no interaction between task demands and stimulation type (real vs. sham) and/or stimulation side (left vs. right hemisphere) were found. Together, against expectations from previous neuroimaging data, lateralized cTBS did not lead to planning-parameter specific changes in performance, but instead revealed a global asymmetric pattern of faster versus slower task processing after left versus right cTBS. This global asymmetry in the absence of any task-parameter specific impact of cTBS suggests that different levels of information processing may span colocalized, but independent axes of functional lateralization in the dlPFC.

Linking planning performance and gray matter density in mid-dorsolateral prefrontal cortex: moderating effects of age and sex.

Planning of behavior relies on the integrity of the mid-dorsolateral prefrontal cortex (mid-dlPFC). Yet, only indirect evidence exists on the association of protracted maturation of dlPFC and continuing gains in planning performance post adolescence. Here, gray matter density of mid-dlPFC in young, healthy adults (18-32 years) was regressed onto performance on the Tower of London planning task while accounting for moderating effects of age and sex on this interrelation. Multiple regression analysis revealed an association of planning performance and mid-dlPFC gray matter density that was especially strong in late adolescence and early twenties. As expected, for males better planning performance was linked to reduced gray matter density of mid-dlPFC, possibly due to maturational processes such as synaptic pruning. Most surprisingly, females showed an inverted, positive interrelation of planning performance and mid-dlPFC gray matter density, indicating that sexually dimorphic development of dlPFC continues during early adulthood. Age and sex are hence important moderators of the link between planning performance and gray matter density in mid-dlPFC. Consequently, the assessment of moderator effects in regression designs can significantly enhance understanding of brain-behavior relationships.

Dissociable stages of problem solving (II): first evidence for process-contingent temporal order of activation in dorsolateral prefrontal cortex.

In a companion study, eye-movement analyses in the Tower of London task (TOL) revealed independent indicators of functionally separable cognitive processes during problem solving, with processes of building up an internal representation of the problem preceding actual planning processes. These results imply that processes of internalization and planning should also be distinguishable in time and space with respect to concomitant brain activation patterns. To investigate this possibility, here we conducted analyses of fMRI data for left and right dorsolateral prefrontal cortex (dlPFC) during problem solving in the TOL task by accounting for the trial-by-trial variability of onsets and durations of the different cognitive processing stages. Comparisons between stimulus-locked and response-locked modeling approaches affirmed that activation in left dlPFC was elicited particularly during early processes of internalization, comprising the extraction of goal information and the generation of an internal problem representation, whereas activation in right dlPFC was predominantly attributable to later processes of mental transformations on this representation, that is planning proper. Thus, present data corroborate the proposal that often observed bilateral dlPFC activation patterns during complex cognitive tasks such as problem solving may reflect functionally and, to some extent, even temporally separable processes with opposing lateralizations.

Visuospatial over verbal demands in predicting Tower of London planning tasks.

The role of verbal and visuospatial information processing in Tower of London (TOL) tasks was investigated. The first part of the investigation examined the verbal and visuospatial abilities and preferred cognitive style (visualizer vs. verbalizer) of 79 participants, in an inter-individual differences approach. Visuospatial abilities significantly predicted TOL performance, but the impact of cognitive style was negligible. The second part applied a dual-task manipulation of concurrent interference of TOL planning tasks on verbal and visuospatial memory, using the same participants. Concurrent processing of the TOL tasks diminished visuospatial memory performance considerably but had no effect on verbal memory, and there was no interaction between cognitive style and memory. These findings clearly underscore the role of visuospatial information processing in TOL tasks and indicate little bearing of verbal or visual cognitive style on TOL problem solving. These results have important implications for TOL and cognitive style in clinical application and cognitive neuroimaging research.

Assessing planning ability with the Tower of London task: psychometric properties of a structurally balanced problem set.

In clinical and experimental settings, planning ability is typically assessed using the Tower of London (ToL) or one of its variants. For enhancing the comparability across studies, a common ToL problem set was recently suggested comprising a collection of 4- to 7-move problems. Based on previous theoretical and empirical analyses of problem space and task structure, development of the problem set accounted particularly for the influence of structural problem parameters on the detection of individual differences in planning ability. To assess its adequacy as a clinical and research instrument, the present study evaluated the psychometric properties of the suggested problem set. Results showed a clear and nearly perfect linear increase of task difficulty across minimum moves. Given a broad range of item difficulty, high- and low-achieving subjects could be well discriminated. The test scores' split-half reliability (r = .72) and internal consistency (α = .69) were satisfactory. Taken together, the ToL problem set evaluated here proved to have good psychometric qualities and constitutes a conceptually sound basis for diagnostic and research purposes.

Dissociable contributions of left and right dorsolateral prefrontal cortex in planning.

It is well established that the mid-dorsolateral prefrontal cortex (dlPFC) plays a critical role in planning. Neuroimaging studies have yielded predominantly bilateral dlPFC activations, but the existence and nature of functionally specific contributions of left and right dlPFC have remained elusive. In recent experiments, 2 independent parameters have been identified which substantially determine planning: 1) the degree of interdependence between consecutive steps (search depth) and 2) the degree to which the configuration of the goal state renders the order of single steps either clearly evident or ambiguous (goal hierarchy). Thus, search depth affects the actual mental generation and evaluation of action sequences, whereas goal hierarchy reflects the extraction of goal information from an encountered problem. Here, both parameters were independently manipulated in an event-related functional magnetic resonance imaging study using the Tower of London task. Results revealed a double dissociation as indicated by a significant crossover interaction of hemisphere and task parameter: in left dlPFC, activations were stronger for higher demands on goal hierarchy than on search depth, whereas the reversed result emerged in right dlPFC. In conclusion, often observed bilateral patterns of dlPFC activation in complex tasks may reflect the concomitant operation of specific cognitive processes that show opposing lateralizations.