Showing papers by "Tim Shallice published in 2007"
TL;DR: Support is provided for a general proposal that the supervisory system is constructed of distinct subsystems that impair cognitive control for a Stroop task, and the mechanisms of impairment are specific to the region of injury.
Abstract: Background: Lesions of the frontal lobes may impair the capacity of patients to control otherwise intact cognitive operations in the face of ambiguous sensory input or conflicting possible responses. Objective: To address the question of whether focal lesions in different regions of the frontal lobes produced specific impairments in cognitive control. Methods: We evaluated 42 patients with chronic frontal lesions and 38 control subjects on a modified Stroop test that allowed measurement of reaction times and errors. Planned, stratified analyses permitted identification of discrete frontal lesions that are critical for impaired performance. Results: Lesions of the left ventrolateral region produced an increased number of incorrect responses to distractors. Lesions of a large portion of the right superior medial region, including anterior cingulate, supplementary motor area (SMA), pre-SMA, and dorsolateral areas, caused a slow reaction time and a decreased number of correct responses to targets. Conclusion: Lesions in two distinct frontal regions impair cognitive control for a Stroop task, and the mechanisms of impairment are specific to the region of injury. This is support for a general proposal that the supervisory system is constructed of distinct subsystems.
125 citations
TL;DR: The results consistently suggest different ontogenetic time courses for the two effects: the sequential effects are already present in the youngest group (4-5 years old), whereas the FP effect appears gradually some years later.
Abstract: In a variable foreperiod (FP) paradigm, reaction times (RTs) decrease as a function of FP on trial n (FP effect) but increase with FP on trial n - 1 (sequential effects). These phenomena have traditionally been ascribed to different strategic preparation processes. According to an alternative explanation, common conditioning laws underlie both effects. The present study aims to disentangle these opposite views using a developmental perspective. In Experiment 1A, 4- to 11-year-old children and a control group of adults performed a simple RT task with variable FPs (1, 3, and 5 s). Furthermore, 12 4- to 5-year-old children were retested after 14 months (Experiment 1B). In Experiment 2, a narrower pool of participants (4, 5, and 6 years old) performed a variable FP paradigm with different FPs (1, 2, and 3 s). The results consistently suggest different ontogenetic time courses for the two effects: The sequential effects are already present in the youngest group (4-5 years old), whereas the FP effect appears gradually some years later. These findings are not fully compatible with previous views. A dual-process account is proposed to explain the data.
115 citations
TL;DR: Testing acute cerebral tumor patients represents a viable neuropsychological approach for the fractionation and localisation of cognitive processes and dissociation between the two effects supports a dual-process account of the variable FP phenomena.
90 citations
TL;DR: A brain operation that allows this novel computational process to be proposed as well as a physics-inspired mechanism that could explain its rather recent emergence without invoking unlikely genetic or structural changes are proposed.
89 citations
TL;DR: The data from RH suggest that the right hippocampus is necessary for recollection and familiarity for topographical materials, whilst the left hippocampus is sufficient to underpin these processes for at least some types of verbal materials.
75 citations
TL;DR: Patients with left dorsolateral lesions (9/46v) showed slower learning of the task as indicated by a high error rate early on and patients with Superior Medial lesions showed both a general slowing of reaction time (RT) and a significantly increased switch cost as measured by RT.
Abstract: This study examined the performance of 41 patients with focal prefrontal cortical lesions and 38 healthy controls on a task-switching procedure. Three different conditions were evaluated: single tasks without switches and two switching tasks with the currently relevant task signalled either 1500 ms (Long Cue) or 200 ms (Short Cue) before the stimulus. Patients with Superior Medial lesions showed both a general slowing of reaction time (RT) and a signifi cantly increased switch cost as measured by RT. No other prefrontal group showed this increased reaction time switch cost. Increased error rates in the switching conditions, on the other hand, were observed in patients with Inferior Medial lesions and, to a lesser extent, ones with Superior Medial lesions. Patients with left dorsolateral lesions (9/46v) showed slower learning of the task as indicated by a high error rate early on. Several different processes are involved in task-switching and these are selectively disrupted by lesions to specifi c areas of the frontal lobes.
69 citations
TL;DR: Two explanations are offered for the pattern of performance in the Right Lateral group: failure of a right lateralised error detection and checking system, or an impairment in the active uncued initiation of a supervisory operation.
51 citations
TL;DR: The results support the assumption of a functional organization of the reading process that involves a series of orthographic units (i.e., single letters, sublexical letter groups, and the lexical unit), which can be selectively damaged.
Abstract: In this study we investigated two patients with pure alexia, F.C. and L.D.S., in order to make inferences about how processes and levels involved in the early stage of visual word recognition are organized and how they can be selectively damaged. Moreover, we investigated whether pure alexia can be caused by different functional deficits. F.C. and L.D.S. were presented with tasks of letter processing and tasks of orthographic integration. There was a clear double dissociation between the pattern of performance of F.C. and L.D.S. F.C. was able to process single letters rapidly and accurately, but was unable to group together the letters that he had correctly identified. By contrast, L.D.S. was slower and more impaired at letter identification, but she could use letter groups to assist reading. Thus, two different forms of pure alexia emerged: F.C. has a higher level deficit in integrating letters, whereas L.D.S. has a lower level deficit in letter processing. The results support the assumption of a functio...
45 citations
TL;DR: Advances in neuroscience have now led to wide acceptance in science and medicine that all aspects of the authors' mental life—their thoughts and memories—are derived from biological material.
Abstract: For centuries, the relation of the human mind to the brain has been debated. How can seemingly immaterial entities such as thoughts and memories arise from biological material? Advances in neuroscience have now led to wide acceptance in science and medicine that all aspects of our mental life—our
24 citations
01 Jan 2007
TL;DR: In this article, the authors present a compendium of Neuropsychological Impairments of Short-Term Memory (SSTM) for the Spanish language with a precio of 66,09 €.
Abstract: Tienda online donde Comprar Neuropsychological Impairments of Short-Term Memory al precio 66,09 € de Tim Shallice | Giuseppe Vallar, tienda de Libros de Medicina, Libros de Psiquiatria - Neurologia
8 citations