Subclinical levels of anxiety but not depression are associated with planning performance in a large population-based sample.

BACKGROUND: Major depression and anxiety disorders are known to negatively influence cognitive performance. Moreover, there is evidence for greater cognitive decline in older adults with generalized anxiety disorder. Except for clinical studies, complex executive planning functions and subclinical levels of anxiety have not been examined in a population-based sample with a broad age range. METHODS: Planning performance was assessed using the Tower of London task in a population-based sample of 4240 participants aged 40-80 years from the Gutenberg Health Study (GHS) and related to self-reported anxiety and depression by means of multiple linear regression analysis. RESULTS: Higher anxiety ratings were associated with lower planning performance (ß = -0.20; p < 0.0001) independent of age (ß = 0.03; p = 0.47). When directly comparing the predictive value of depression and anxiety on cognition, only anxiety attained significance (ß = -0.19; p = 0.0047), whereas depression did not (ß = -0.01; p = 0.71). CONCLUSIONS: Subclinical levels of anxiety but not of depression showed negative associations with cognitive functioning independent of age. Our results demonstrate that associations observed in clinical groups might differ from those in population-based samples, also with regard to the trajectory across the life span. Further studies are needed to uncover causal interrelations of anxiety and cognition, which have been proposed in the literature, in order to develop interventions aimed at reducing this negative affective state and to improve executive functioning.

Perceived conflicts and errors in complex problem solving.

In a behavioral experiment on 60 healthy volunteers, the Tower of London was employed as a complex visuo-spatial planning task. After each trial, participants were asked how difficult they found the task and whether they thought their solution was optimal. Results showed that objective problem difficulty affected behavioral performance as well as subjectively experienced difficulty and performance certainty. This pattern was influenced by experimental manipulation of participants' knowledge of objective problem difficulty: For optimally solved problems, performance certainty remained at high levels if such knowledge was provided, and strongly declined in more difficult problems if it was withheld. For nonoptimally solved problems, subjects' ratings indicated awareness of errors when they were informed about objective problem difficulty; otherwise, performance certainty declined from intermediate to low levels in more difficult problems. No such interaction was observed with regard to ratings of subjective problem difficulty. Additional structural equation modeling revealed that subjective awareness of errors and processing conflicts can be considered as independent only for optimally solved trials in which the optimal solution was known to the participants. We conclude that participants' ratings of problem difficulty and performance certainty can be regarded as indicators of at least partly distinct processes of performance monitoring, and that studies of complex problem solving incorporating such subjective measures may enhance the empirical basis of current theories of executive functioning.

Planning abilities and chess: a comparison of chess and non-chess players on the Tower of London task.

Playing chess requires problem-solving capacities in order to search through the chess problem space in an effective manner. Chess should thus require planning abilities for calculating many moves ahead. Therefore, we asked whether chess players are better problem solvers than non-chess players in a complex planning task. We compared planning performance between chess ( N=25) and non-chess players ( N=25) using a standard psychometric planning task, the Tower of London (ToL) test. We also assessed fluid intelligence (Raven Test), as well as verbal and visuospatial working memory. As expected, chess players showed better planning performance than non-chess players, an effect most strongly expressed in difficult problems. On the other hand, they showed longer planning and movement execution times, especially for incorrectly solved trials. No differences in fluid intelligence and verbal/visuospatial working memory were found between both groups. These findings indicate that better performance in chess players is associated with disproportionally longer solution times, although it remains to be investigated whether motivational or strategic differences account for this result.

Tracking the subprocesses of decision-based action in the human frontal lobes.

Situationally adaptive behavior relies on the identification of relevant target stimuli, the evaluation of these with respect to the current context and the selection of an appropriate action. We used functional magnetic resonance imaging (fMRI) to disentangle the neural networks underlying these processes within a single task. Our results show that activation of mid-ventrolateral prefrontal cortex (PFC) reflects the perceived presence of a target stimulus regardless of context, whereas context-appropriate evaluation is subserved by mid-dorsolateral PFC. Enhancing demands on response selection by means of response conflict activated a network of regions, all of which are directly connected to motor areas. On the midline, rostral anterior paracingulate cortex was found to link target detection and response selection by monitoring for the presence of behaviorally significant conditions. In summary, we provide new evidence for process-specific functional dissociations in the frontal lobes. In target-centered processing, target detection in the VLPFC is separable from contextual evaluation in the DLPFC. Response-centered processing in motor-associated regions occurs partly in parallel to these processes, which may enhance behavioral efficiency, but it may also lead to reaction time increases when an irrelevant response tendency is elicited.

What is in a name: comparing the Tower of London with one of its variants.

Since the implementation of the Tower of London (ToL) test by Shallice in 1982, numerous variants differing in the tower's physical appearance have been developed. Here we compare behavioral performance (n = 31) on the original Tower of London task consisting of three rods of unequal lengths with a three-ball version of the Ward and Allport Tower Task (1997) using three equally sized rods. In the problem set used, the start and goal states for both tower configurations were identical across all trials. The experiment was divided into two parts: in the first block, the problems presented were equalized with respect to the number of paths for achieving an optimal solution, the minimum number of moves, goal hierarchy, subgoaling patterns, and suboptimal alternatives between the two tower versions. As expected, participants showed the same performance scores for both types of towers when structural problem parameters were identical. In the second block, participants had to solve five-move problems which-due to the different rod sizes of the towers-had only one optimal solution in the original version, but two optimal solutions in the variant with three rods of equal length. Participants revealed lower performance scores and showed longer planning times in the original version than in the second tower version. These findings demonstrate that the two tower versions are only interchangeable when specific planning parameters are equalized. Otherwise, even if problems look identical, significant differences in performance may be found due to the differing problem spaces in the two tower versions.

The influence of sex differences and individual task performance on brain activation during planning.

Several studies have attempted to identify the neuronal basis of sex differences in cognition. However, group differences in cognitive ability rather than genuine neurocognitive differences between the sexes may account for their results. Here, we compare with functional magnetic resonance imaging the relation between gender, individual task performance, and planning-related brain activation. Men and women preselected to display identical performance scores showed a strong relation between individual task performance and activation of the right dorsolateral prefrontal and right inferior parietal cortex activation during a visuospatial planning task. No gender-specific activations were found. However, a different pattern emerged when subjects had to execute the motor responses to the problems. Better performance was associated with right dorsolateral prefrontal and right parahippocampal activations, and females exhibited a stronger right hippocampal activation than males. These findings underline that an individual's performance level rather than his or her sex largely determines the neuronal activation patterns during higher-level cognition.

Planning abilities and the Tower of London: is this task measuring a discrete cognitive function?

The Tower of London (ToL) test is widely used for measuring planning and aspects of problem solving. The primary focus of this study was to asses the relationship among different measures on the ToL. A secondary purpose was to examine the putative relationship between intelligence and working memory with that of ToL performance. Analyses of the interrelation of several ToL parameters indicated that better ToL performance was associated with longer preplanning time and shorter movement execution time. Good performers showed a stronger increase in preplanning duration with task difficulty then intermediate or poor planners. Stepwise multiple regression analysis yield fluid intelligence as the only significant predictor of ToL performance. These result suggest that the Tower of London assesses predominantly planning and problem solving and could not be explained by other cognitive domains.

When planning fails: individual differences and error-related brain activity in problem solving.

The neuronal processes underlying correct and erroneous problem solving were studied in strong and weak problem-solvers using functional magnetic resonance imaging (fMRI). During planning, the right dorsolateral prefrontal cortex was activated, and showed a linear relationship with the participants' performance level. A similar pattern emerged in right inferior parietal regions for all trials, and in anterior cingulate cortex for erroneously solved trials only. In the performance phase, when the pre-planned moves had to be executed by means of an fMRI-compatible computer mouse, the right dorsolateral prefrontal cortex was again activated jointly with right parahippocampal cortex, and displayed a similar positive relationship with the participants' performance level. Incorrectly solved problems elicited stronger bilateral prefrontal and left inferior parietal activations than correctly solved trials. For both individual ability and trial-specific performance, our results thus demonstrate the crucial involvement of right prefrontal cortex in efficient visuospatial planning.

The Tower of London: the impact of instructions, cueing, and learning on planning abilities.

The Tower of London (ToL) is a well-known test of planning ability, and commonly used for the purpose of neuropsychological assessment and cognitive research. Its widespread application has led to numerous versions differing in a number of respects. The present study addressed the question whether differences in instruction, cueing, and learning processes systematically influence ToL performance across five difficulty levels (three to seven moves). A total of 81 normal adults were examined in a mixed design with the between-subject factor instruction (online versus mental preplanning) and the within-subject factors cueing (cue versus non-cue test version) and learning processes (first block and second block). We also assessed general intelligence for further analyses of differences between instruction groups. In general, there was a significant main effect across the difficulty levels indicating that the rate of incorrect solutions increased with problem difficulty. The participants who were instructed to make full mental plans before beginning to execute movements (preplanning) solved significantly more problems than people who started immediately with task-related movements (online). As for the cueing conditions, participants with the minimum number of moves predetermined (cue) could solve more trials than people who were only instructed to solve the problems in as few moves as possible (non-cue). Participants generally increased performance in the second part of the test session. However, an interaction of presentation order of the cueing condition with learning indicated that people who started the tasks with the non-cue version showed significantly better performance in the following cue condition, while participants who started with the cue condition stayed at the same performance level for both versions. These findings suggest that instruction, cueing conditions, and learning processes are important determinants of ToL performance, and they stress the necessity of standardized application in research and clinical practice.