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"Shallice, Tim"
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Manipulability and object recognition: is manipulability a semantic feature?
Several lines of evidence exist, coming from neuropsychology, neuroimaging and behavioural investigations on healthy subjects, suggesting that an interaction might exist between the systems devoted to object identification and those devoted to online object-directed actions and that the way an object is acted upon (manipulability) might indeed influence object recognition. In this series of experiments on speeded word-to-picture-matching tasks, it is shown how the presentation of pairs of objects sharing similar manipulation causes greater interference with respect to objects sharing only visual similarity (experiment 1). Moreover, (experiment 2) it is shown how the repeated presentation of pairs of objects sharing a similar type of manipulation leads to a ‘negative’ serial position effect, with the number of errors increasing across presentations, a behaviour that is typically found in patients with access deficits to semantic representations. By contrast, the repeated presentation of pairs of objects sharing only visual similarity leads to an opposite ‘positive’ serial position effect, with errors decreasing across presentations. It is argued that a negative serial position effect is linked to interference occurring within the semantic system, and therefore that the way an object is manipulated is indeed a
semantic
feature, critical in defining manipulable object properties at a semantic level. To our knowledge, this constitutes the first
direct
evidence of manipulability being a
semantic
dimension. The results are discussed in the light of current models of semantic memory organization.
Journal Article
Limitations of the Trail Making Test Part-B in Assessing Frontal Executive Dysfunction
Part B of the Trail Making Test (TMT-B) is one of the most widely used neuropsychological tests of “executive” function. A commonly held assumption is that the TMT-B can be used to detect frontal executive dysfunction. However, so far, research evidence has been limited and somewhat inconclusive. In this retrospective study, performance on the TMT-B of 55 patients with known focal frontal lesions, 27 patients with focal non-frontal lesions and 70 healthy controls was compared. Completion time and the number of errors made were examined. Patients with frontal and non-frontal lesions performed significantly worse than healthy controls for both completion time and the number of errors. However, there was no significant difference for both completion time and the number of errors when patients with frontal and non-frontal lesions were compared. Performance was also not significantly different between patients with focal lesions within different regions of the frontal lobe (orbital, left lateral, right lateral, medial). Our findings suggest that the TMT-B is a robust test for detection of brain dysfunction. However, its capacity for detecting frontal executive dysfunction appears rather limited. Clinicians should be cautious when drawing conclusions from performance on the TMT-B alone. (JINS, 2015, 21, 169–174)
Journal Article
Bringing the Cognitive Estimation Task into the 21st Century: Normative Data on Two New Parallel Forms
The Cognitive Estimation Test (CET) is widely used by clinicians and researchers to assess the ability to produce reasonable cognitive estimates. Although several studies have published normative data for versions of the CET, many of the items are now outdated and parallel forms of the test do not exist to allow cognitive estimation abilities to be assessed on more than one occasion. In the present study, we devised two new 9-item parallel forms of the CET. These versions were administered to 184 healthy male and female participants aged 18-79 years with 9-22 years of education. Increasing age and years of education were found to be associated with successful CET performance as well as gender, intellect, naming, arithmetic and semantic memory abilities. To validate that the parallel forms of the CET were sensitive to frontal lobe damage, both versions were administered to 24 patients with frontal lobe lesions and 48 age-, gender- and education-matched controls. The frontal patients' error scores were significantly higher than the healthy controls on both versions of the task. This study provides normative data for parallel forms of the CET for adults which are also suitable for assessing frontal lobe dysfunction on more than one occasion without practice effects.
Journal Article
Anatomical Modularity of Verbal Working Memory? Functional Anatomical Evidence from a Famous Patient with Short-Term Memory Deficits
Cognitive skills are the emergent property of distributed neural networks. The distributed nature of these networks does not necessarily imply a lack of specialization of the individual brain structures involved. However, it remains questionable whether discrete aspects of high-level behavior might be the result of localized brain activity of individual nodes within such networks. The phonological loop of working memory, with its simplicity, seems ideally suited for testing this possibility. Central to the development of the phonological loop model has been the description of patients with focal lesions and specific deficits. As much as the detailed description of their behavior has served to refine the phonological loop model, a classical anatomoclinical correlation approach with such cases falls short in telling whether the observed behavior is based on the functions of a neural system resembling that seen in normal subjects challenged with phonological loop tasks or whether different systems have taken over. This is a crucial issue for the cross correlation of normal cognition, normal physiology, and cognitive neuropsychology. Here we describe the functional anatomical patterns of JB, a historical patient originally described by Warrington et al. (1971), a patient with a left temporo-parietal lesion and selective short phonological store deficit. JB was studied with the H
O PET activation technique during a rhyming task, which primarily depends on the rehearsal system of the phonological loop. No residual function was observed in the left temporo-parietal junction, a region previously associated with the phonological buffer of working memory. However, Broca's area, the major counterpart of the rehearsal system, was the major site of activation during the rhyming task. Specific and autonomous activation of Broca's area in the absence of afferent inputs from the other major anatomical component of the phonological loop shows that a certain degree of functional independence or modularity exists in this distributed anatomical-cognitive system.
Journal Article
Neural basis of pantomiming the use of visually presented objects
Neuropsychological studies of patients suffering from apraxia strongly imply a left hemisphere basis for skilful object use, the neural mechanisms of which, however, remain to be elucidated. We therefore carried out a PET study in 14 healthy human volunteers with the aim to isolate the neural mechanisms underlying the sensorimotor transformation of object-triggers into skilled actions. We employed a factorial design with two factors (RESPONSE: naming, pantomiming; and TRIGGER: actions, objects) and four conditions (IA: imitating the observed pantomime; IO: pantomiming the use of the object shown; NA: naming the observed pantomime; NO: naming the object shown). The design thus mainly aims at investigating the interaction [i.e. (IO–IA)–(NO–NA)] which allows the assessment of increased neural activity specific to the sensorimotor transformation of object-triggers into skilled actions. The results (
P < 0.05, corrected) showed that producing a wide range of skilled actions triggered by objects (controlled for perceptual, motor, semantic, and lexical effects) activated left inferior parietal cortex. The data provide an explanation for why patients with lesions including left parietal cortex suffer from ideational apraxia as assessed by impaired object use and pontomining to visually presented objects (Brain 111 (1988) 1173; Cogn. Neuropsychol. 18 (2001) 671).
Journal Article
Neural correlates of episodic retrieval: An fMRI study of the part-list cueing effect
Episodic retrieval is supported by multiple forms of cognitive control that depend on prefrontal cortex. However, within prefrontal cortex, the regional specificity for different control processes is still largely underspecified. Here we used fMRI to investigate the processes involved in part-list cueing, a phenomenon entailing the reduction of memory performance when some of the “to-be-remembered items” are presented during retrieval. Retrieval inhibition and strategy disruption have been proposed as possible underlying causes of this surprising effect. Critically, different encoding conditions can dissociate these two hypotheses, as this is thought to have a different impact on strategy-related versus inhibition-related processes. Accordingly, we compared part-list versus no part-list retrieval conditions, following high versus low associative encoding conditions. This revealed activation of the left frontopolar and right dorsolateral prefrontal cortex in conditions of part-list cueing retrieval, but only following low associative encoding. These results are consistent with the inhibitory or interference resolution accounts of part-list cueing, suggesting a critical role of between-items competition and high monitoring demands at retrieval. In addition, we also examined brain activation during the encoding phase, specifying further possible anatomo-functional links between encoding and retrieval processes. The results suggest that different encoding conditions induce distinct patterns of activation at retrieval, corroborating the idea that they promote the adoption of different retrieval strategies. The implications of the results are discussed in relation to the cognitive mechanisms of inhibition, interference resolution, and encoding/retrieval strategies for episodic memory.
Journal Article
The Declining Influence of Cognitive Theorising: Are the causes intellectual or socio-political?
A rough division is drawn between the cognitive and biomedical strand of theorising concerning cognitive processes. It is asserted that the cognitive strand is losing influence by comparison with the biomedical strand. Three types of intellectual reasons why this might be occurring are considered and each is rejected as idequate. Three types of socio-political reasons are then proposed as important factors.
Journal Article
Multiple effects of prefrontal lesions on task-switching
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 significantly 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 specific areas of the frontal lobes.
Journal Article
Cognitive Reserve Proxies Do Not Differentially Account for Cognitive Performance in Patients with Focal Frontal and Non-Frontal Lesions
Cognitive reserve (CR) suggests that premorbid efficacy, aptitude, and flexibility of cognitive processing can aid the brain's ability to cope with change or damage. Our previous work has shown that age and literacy attainment predict the cognitive performance of frontal patients on frontal-executive tests. However, it remains unknown whether CR also predicts the cognitive performance of non-frontal patients.
We investigated the independent effect of a CR proxy, National Adult Reading Test (NART) IQ, as well as age and lesion group (frontal vs. non-frontal) on measures of executive function, intelligence, processing speed, and naming in 166 patients with focal, unilateral frontal lesions; 91 patients with focal, unilateral non-frontal lesions; and 136 healthy controls.
Fitting multiple linear regression models for each cognitive measure revealed that NART IQ predicted executive, intelligence, and naming performance. Age also significantly predicted performance on the executive and processing speed tests. Finally, belonging to the frontal group predicted executive and naming performance, while membership of the non-frontal group predicted intelligence.
These findings suggest that age, lesion group, and literacy attainment play independent roles in predicting cognitive performance following stroke or brain tumour. However, the relationship between CR and focal brain damage does not differ in the context of frontal and non-frontal lesions.
Journal Article