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Biomedical subjects

B Rahm

Publications and source records attributed to B Rahm.

14 recordsLinked to original sources
PubMed2006

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.

Adult↗
PubMed2005

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.

Adult↗
PubMed2005

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.

Adult↗
PubMed2005

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.

Adult↗
PubMed2004

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.

Adult↗
PubMed2004

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.

Adult↗
PubMed2003

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.

Adult↗
PubMed1996

Suprasellar meningioma and blindness: a unique experience in Saudi Arabia.

BACKGROUND: The natural history of intracranial meningioma is no different in the Arabian peninsula than in other countries. The extent of the total loss of vision in one or both eyes, however, is unique to this area. METHODS: A retrospective study was conducted at King Faisal Specialist Hospital and Research Centre, a tertiary care institution in Saudi Arabia, on all cases of intracranial meningioma seen over a period of 9 years. The following data were collated: clinical presentation, site and size of tumor, radiologic features, surgical methods, and preoperative and postoperative visual status. RESULTS: Seventy of 232 cases (30.1%) of intracranial meningioma presented in the suprasellar area; the majority of these were more than 5 cm in diameter. Because of the large size it was not always possible to identify the exact point of origin or to achieve complete tumor removal. Deteriorating vision was the cardinal presenting feature and the incidence of blindness in one or both eyes at presentation was high (42.2%); 12.8% were totally blind on admission. None of these patients showed improvement after surgery (complete or subtotal removal of tumor). CONCLUSION: Lack of understanding of the symptoms and cultural influences are direct contributing factors to this complication of a benign intracranial lesion. This represents a serious public health concern in the Arabian peninsula.

Adolescent↗
PubMed1994

Brain tumors in the first 2 years of life in Saudi Arabia.

Thirty-four patients with brain tumors were diagnosed and treated during the first 2 years of life, representing 8% of the 273 children treated for primary brain tumors from 1981 to 1990 inclusive. Large head circumference, vomiting, and altered level of consciousness were the chief findings at the time of presentation. Overall, the tumors were located mainly supratentorially; in patients in the 1st year of life they were equally distributed above and below the tentorium, while two-thirds of the patients presenting in the 2nd year of life had supratentorial tumors. The most common histological types were astrocytomas and medulloblastomas. Treatment methods were ventricular peritoneal shunt, craniotomy with total or partial removal of the tumor, adjuvant radiotherapy, and in a few cases chemotherapy. The 2-month mortality rate was 5.9%. The follow-up period ranged from 3 to 50 months.

Brain Neoplasms↗
PubMed1993

Brain tumors in pediatric patients at King Faisal Specialist Hospital and Research Centre.

We report our experience with brain tumors in pediatric patients, patients who came to our attention when they were aged 14 years or less. In general, the pattern of brain tumors at this Institution is similar to that reported in the neurosurgical literature. Fortunately we have modern diagnostic technology and modern operating instrumentation available to use for dealing with such lesions, which are often in their late stages.

Adolescent↗
PubMed1991

Brain biopsy in tuberculoma: the risks and benefits.

In developing countries, 5 to 8% of the space-occupying lesions of the central nervous system are tuberculomas. Diagnosis can be difficult in the absence of extracranial tuberculosis; computed tomography is suggestive only. To assess the value of brain biopsies in tuberculomas, the records of 15 patients aged 6 to 80 years were reviewed. Histological confirmation was obtained in 15 patients, and acid-fast bacilli were cultured from 12 patients. Intracranial hypertension was the principal sign in 11 patients; other neurological signs were related to the location of the tuberculoma. One patient had evidence of extracranial tuberculosis. Biopsy-related complications consisted of an epidural hematoma in 1 patient and hydrocephalus in another; both required additional surgery. One case of tuberculous meningitis was probably related to surgery and poor drug compliance. There was no postoperative mortality. Thirteen patients (2 were lost to follow-up) were cured after an average of 16 months of antituberculous therapy. It was concluded that the brain biopsy is useful in diagnosing tuberculoma but that there is some associated risk.

Adolescent↗
PubMed1990

[Acute arterial thrombosis: diagnosis and surgical therapy].

There is an increasing frequency of acute ischemic occlusion due to arterial thrombosis; the incidence has a range from 17% to 60%. In contrast to embolism we can observe a prolonged therapy less interval due to a lesser dramatic clinical course; in thrombotic occlusion only 10% can be treated within 6 h after onset of symptoms. In 11 to 93% of all cases extensive and comprehensive surgical techniques have to be performed for limb salvage. Nevertheless this aim only can be achieved in 60-84%.

Diagnosis, Differential↗