Effects Of Frontal Lobe Damage Research Articles

Distracted by relatives: Effects of frontal lobe damage on semantic distraction

When young adults carry out visual search, distractors that are semantically related, rather than unrelated, to targets can disrupt target selection (see Belke, Humphreys, Watson, Meyer, & Telling, 2008; Moores, Laiti, & Chelazzi, 2003). This effect is apparent on the first eye movements in search, suggesting that attention is sometimes captured by related distractors. Here we assessed effects of semantically related distractors on search in patients with frontal-lobe lesions and compared them to the effects in age-matched controls. Compared with the controls, the patients were less likely to make a first saccade to the target and they were more likely to saccade to distractors (whether related or unrelated to the target). This suggests a deficit in a first stage of selecting a potential target for attention. In addition, the patients made more errors by responding to semantically related distractors on target-absent trials. This indicates a problem at a second stage of target verification, after items have been attended. The data suggest that frontal lobe damage disrupts both the ability to use peripheral information to guide attention, and the ability to keep separate the target of search from the related items, on occasions when related items achieve selection.

Role of the left inferior frontal gyrus in covert word retrieval: Neural correlates of switching during verbal fluency

Word retrieval ability is commonly assessed with a semantic verbal fluency task, in which subjects must produce a list of exemplars of a category (e.g., animals). The order in which exemplars are produced is not random; rather, subjects tend to produce “clusters” of semantically related items (e.g., cow, pig, sheep) and occasionally “switch” to other clusters (e.g., lion, tiger, bear). Patients with frontal lobe pathology (associated with focal lesions or Parkinson's disease) exhibit reduced output on semantic fluency tasks that has been characterized as a reduction in switching, in contrast to other impaired patient groups who produce normal switches but smaller clusters (e.g., [Troyer, A. K., Moscovitch, M., Winocur, G., Leach, L., & Freedman, M. (1998). Clustering and switching on verbal fluency tests in Alzheimer's and Parkinson's disease. Journal of the International Neuropsychological Society, 4(2), 137–143]). The ability to initiate a switch between two semantic categories may require the selection of weakly activated representations over active (but already reported) representations. Previous studies have shown that increased demands on selection among competing representations are associated with activity in the left inferior frontal gyrus (LIFG) and with deficits in patients with lesions including LIFG [Thompson-Schill, S. L., Jonides, J., Marshuetz, C., Smith, E. E., D’Esposito, M., Kan, I. P., et al. (2002). Effects of frontal lobe damage on interference effects in working memory. Cognitive Affective & Behavioral Neuroscience, 2(2), 109–120; Thompson-Schill, S. L., Swick, D., Farah, M. J., D’Esposito, M., Kan, I. P., & Knight, R. T. (1998). Verb generation in patients with focal frontal lesions: A neuropsychological test of neuroimaging findings. Proceedings of the National Academy of Sciences of the United States of America, 26, 14792–14797]. In the present study, we investigated the neural correlates of switching in the verbal fluency task, and in particular, the role of the LIFG in switching between semantic sub-categories. We observed greater activation in the LIFG during switching compared to free generation (Experiment 1) and self-reported clustering (Experiment 2), which is consistent with the hypothesis that the switching mechanism is subserved by the LIFG due to high semantic selection demands.

Wisconsin Card Sorting Test performance in patients with focal frontal and posterior brain damage: effects of lesion location and test structure on separable cognitive processes

Forty-six patients with single focal lesions (35 frontal, 11 nonfrontal) were administered the Wisconsin Card Sorting Test (WCST) under three conditions of test administration. The three conditions varied in the amount of external support provided via specificity of instructions. The WCST, while a multifactorial test, is specifically sensitive to the effects of frontal lobe damage if deficits in language comprehension and visual–spatial search are controlled. There is also specificity of functioning within the frontal lobes: patients with inferior medial frontal lesions, unilateral or bilateral, were not impaired on the standard measures although they had increased loss of set when informed of the sorting categories. Verbal instructions may provide a probe to improve diagnosis and prognosis, assessment of the potential efficacy of treatment, and the time frame of plasticity of specific cognitive operations.

The effects of frontal lobe damage on everyday problem solving

The prefrontal cortex plays an especially important role in human social-cognitive behavior. It has been difficult to quantify deficits in this domain in patients with frontal lobe lesions using standardized psychological instruments. We administered the Everyday Problem Solving Inventory (EPSI), which is composed of a range of scenarios depicting everyday social problems and their possible solutions, to a group of patients with frontal lobe lesions who were required to rate each of 4 possible solutions to each problem for their effectiveness. Our sample consisted of 27 normal controls (NCs), 33 patients with focal frontal lobe lesions (FLL), and 3 patients with frontal lobe dementia (FLD). The performance of the FLL patients on the EPSI instrument was also compared with their performance on traditional neuropsychological tests. The results indicated that the FLD patients' EPSI rank ordering of social problem solutions was uncorrelated with the performance of NCs and about half of the FLL patients EPSI rank orderings of solutions also varied substantially from those of the NCs. These same FLL patients also had the lowest scores, compared to FLL patients whose judgements on the EPSI were similar to that of the NCs, on a set of neuropsychological tasks sensitive to frontal lobe dysfunction. There was no obvious relationship between locus of lesion within the frontal lobes and performance on the EPSI. These results suggest that some patients with prefrontal lobe lesions may have impaired social judgement that can be directly revealed through the use of a conventional psychological inventory such as the EPSI.

Methodological and theoretical issues in neural network models of frontal cognitive functions.

Neural network models have made significant strides in recent years toward modeling of neuropsychological data. In particular, three different research groups, including that of the present authors, have simulated in model networks some of the behavioral effects of frontal lobe damage. In this article we review these models and discuss their significance in terms of hierarchical organization in the nervous system. These models, to varying degrees, incorporate several widely used neural network principles that have also been used to model a wide range of data in other areas such as categorization, conditioning, and motor control. These principles include associative learning, competition, opponent processing, neuromodulation, and interlevel resonant feedback. Specifically, we show how combinations of these principles serve to model the attentional requirements of cognitive tasks and motor plans.

Deficits of problem-solving ability in patients with focal brain damage: neuropsychological investigation of prediction and hypothesis behavior.

Deficits of problem-solving ability in focal brain-damaged patients, with special reference to frontal lobe dysfunction, were investigated by two neuropsychological tests: Temporal rule induction test and Hypothesis-testing measure. Subjects consisted of 84 chronic brain-damaged patients (31 with anterior cerebral lesions and 53 with posterior lesions). The study's aim was to investigate the effects of frontal lobe damage on two aspects of inductive reasoning, prediction and hypothesis behavior. When prediction was examined by Temporal rule induction test, patients with anterior lesions showed deficits in predicting a rule, even in the memory-aid condition in which memory factors were excluded. The poor results on Temporal rule induction test in frontal patients did not appear to be related to deficits in temporal integration, which is generally interpreted as frontal dysfunction. Rule induction may be impaired by frontal damage whenever complicated information-processing is required, even when temporal succession is not involved. Second, two stages of hypothesis behavior, hypothesis-formation and hypothesis-testing, were evaluated. Patients with anterior lesions showed impairment in hypothesis-formation. Their decreased fluency in hypothesis production affected the hypothesis-testing process. However, frontal patients committed fewer errors, most of which were perseverative (lose-stay errors) on hypothesis-testing. Patients with posterior lesions revealed other characteristic errors, such as inconsistent responses and divergent-type errors (improper lose-shift errors). The hemispheric site of the lesion affected only the ability to maintain a hypothesis (win-shift errors). The results illustrated the differences in problem-solving deficits in these two groups of patients. Disturbed prediction of future events, decreased hypothesis fluency, and abnormal lose-stay behavior in patients with frontal lobe damage may be crucial factors in coping with daily problem-solving situations.

Frontal lobe damage and flicker fusion frequency.

Flicker fusion frequency is the number of light-dark cycles per second at which an intermittent light is perceived by a particular subject as a steady point of light without semblance of flicker. Investigations of this phenomenon have indicated a linkage between it and various physiological and psychological characteristics.* Two studies in particular have raised the possibility that frontal lobe damage may be reflected in a depressed fusion point or in the variability displayed in fixing the point of fusion.† The present study was designed to assess the long-range or permanent effects of bilateral prefrontal lobotomy on flicker fusion frequency when adequate control groups are employed. Procedure A total of 116 subjects were involved in the investigation. Three matched groups were directly concerned with the effects of frontal lobe damage on the fusion point: A group of 26 patients lobotomized 8.6 years prior to testing. A group of 18 control patients

The effects of frontal lobe damage upon habit reversal in the white rat.

The effects of frontal lobe damage upon habit reversal in the white rat.