Showing papers by "Cognition and Brain Sciences Unit published in 2006"
TL;DR: This work considers three models that have been proposed to account for repetition-related reductions in neural activity, and evaluates them in terms of their ability to accounts for the main properties of this phenomenon as measured with single-cell recordings and neuroimaging techniques.
2,185 citations
TL;DR: There is a clear need for brief, but sensitive and specific, cognitive screening instruments as evidenced by the popularity of the Addenbrooke's Cognitive Examination (ACE).
Abstract: There is a clear need for brief, but sensitive and specific, cognitive screening instruments as evidenced by the popularity of the Addenbrooke's Cognitive Examination (ACE).
Objectives
We aimed to validate an improved revision (the ACE-R) which incorporates five sub-domain scores (orientation/attention, memory, verbal fluency, language and visuo-spatial).
Methods
Standard tests for evaluating dementia screening tests were applied. A total of 241 subjects participated in this study (Alzheimer's disease = 67, frontotemporal dementia = 55, dementia of Lewy Bodies = 20; mild cognitive impairment–MCI = 36; controls = 63).
Results
Reliability of the ACE-R was very good (alpha coefficient = 0.8). Correlation with the Clinical Dementia Scale was significant (r = −0.321, p < 0.001). Two cut-offs were defined (88: sensitivity = 0.94, specificity = 0.89; 82: sensitivity = 0.84, specificity = 1.0). Likelihood ratios of dementia were generated for scores between 88 and 82: at a cut-off of 82 the likelihood of dementia is 100:1. A comparison of individual age and education matched groups of MCI, AD and controls placed the MCI group performance between controls and AD and revealed MCI patients to be impaired in areas other than memory (attention/orientation, verbal fluency and language).
Conclusions
The ACE-R accomplishes standards of a valid dementia screening test, sensitive to early cognitive dysfunction. Copyright © 2006 John Wiley & Sons, Ltd.
1,707 citations
TL;DR: Functional magnetic resonance imaging was used to demonstrate preserved conscious awareness in a patient fulfilling the criteria for a diagnosis of vegetative state and the patient activated predicted cortical areas in a manner indistinguishable from that of healthy volunteers.
Abstract: We used functional magnetic resonance imaging to demonstrate preserved conscious awareness in a patient fulfilling the criteria for a diagnosis of vegetative state. When asked to imagine playing tennis or moving around her home, the patient activated predicted cortical areas in a manner indistinguishable from that of healthy volunteers.
1,427 citations
TL;DR: The current article reviews the IGT findings, arguing that their interpretation is undermined by the cognitive penetrability of the reward/punishment schedule, ambiguity surrounding interpretation of the psychophysiological data, and a shortage of causal evidence linking peripheral feedback to IGT performance.
850 citations
TL;DR: Sound-related somatotopic activation in precentral gyrus shows that, during speech perception, specific motor circuits are recruited that reflect phonetic distinctive features of the speech sounds encountered, thus providing direct neuroimaging support for specific links between the phonological mechanisms for speech perception and production.
Abstract: The processing of spoken language has been attributed to areas in the superior temporal lobe, where speech stimuli elicit the greatest activation. However, neurobiological and psycholinguistic models have long postulated that knowledge about the articulatory features of individual phonemes has an important role in their perception and in speech comprehension. To probe the possible involvement of specific motor circuits in the speech-perception process, we used event-related functional MRI and presented experimental subjects with spoken syllables, including [p] and [t] sounds, which are produced by movements of the lips or tongue, respectively. Physically similar nonlinguistic signal-correlated noise patterns were used as control stimuli. In localizer experiments, subjects had to silently articulate the same syllables and, in a second task, move their lips or tongue. Speech perception most strongly activated superior temporal cortex. Crucially, however, distinct motor regions in the precentral gyrus sparked by articulatory movements of the lips and tongue were also differentially activated in a somatotopic manner when subjects listened to the lip- or tongue-related phonemes. This sound-related somatotopic activation in precentral gyrus shows that, during speech perception, specific motor circuits are recruited that reflect phonetic distinctive features of the speech sounds encountered, thus providing direct neuroimaging support for specific links between the phonological mechanisms for speech perception and production.
618 citations
TL;DR: Results indicate that information about surface form and meaning of a lexical item is first accessed at different times in different brain systems and then processed simultaneously, thus supporting cascaded interactive processing models.
524 citations
TL;DR: The motivation for and advantages of the fROI approach are explained, the criticism of this method is rebutted, and some fROIs may serve as candidate distinct components of the mind/brain worth investigation as such.
513 citations
TL;DR: This work aimed to evaluate levodopa‐induced dopamine neurotransmission in the striatum of patients with DDS compared with PD control patients.
Abstract: OBJECTIVE: A small group of Parkinson's disease (PD) patients compulsively use dopaminergic drugs despite causing harmful social, psychological, and physical effects and fulfil core Diagnostic and Statistical Manual (of Mental Disorders) Fourth Edition criteria for substance dependence (dopamine dysregulation syndrome [DDS]). We aimed to evaluate levodopa-induced dopamine neurotransmission in the striatum of patients with DDS compared with PD control patients. METHODS: We used a two-scan positron emission tomography protocol to calculate the percentage change in (11)C-raclopride binding potential from a baseline withdrawal (off drug) state to the binding potential after an oral dose of levodopa. We related the subjective effects of levodopa to the effects on endogenous dopamine release of a pharmacological challenge with levodopa in eight control PD patients and eight patients with DDS. RESULTS: PD patients with DDS exhibited enhanced levodopa-induced ventral striatal dopamine release compared with levodopa-treated patients with PD not compulsively taking dopaminergic drugs. The sensitized ventral striatal dopamine neurotransmission produced by levodopa in these individuals correlated with self-reported compulsive drug "wanting" but not "liking" and was related to heightened psychomotor activation (punding). INTERPRETATION: This provides evidence that links sensitization of ventral striatal circuitry in humans to compulsive drug use.
432 citations
TL;DR: This study investigated, for the first time, the abstract linking of linguistic and odour information using modern neuroimaging techniques (functional MRI) and suggested the activation of widely distributed cortical cell assemblies in the processing of olfactory words.
406 citations
TL;DR: It is concluded that localiser scans can be unnecessary and, in some instances, lead to a biased and inappropriately constrained characterisation of functional anatomy.
388 citations
TL;DR: It appears that social reasoning is disrupted in a number of ways in fvFTD, and the findings provide a basis for the understanding and further study of abnormal behaviour in this disease.
TL;DR: The results challenge the view that amnesia in early AD can be explained by the degree of MTL damage alone while showing that semantic impairment can occur with damage restricted to the rostral temporal lobes.
TL;DR: A theory of visual word recognition is presented that assumes that, in the tasks of word identification, lexical decision, and semantic categorization, human readers behave as optimal Bayesian decision makers, which leads to the development of a computational model of word recognition, the Bayesian reader.
Abstract: This article presents a theory of visual word recognition that assumes that, in the tasks of word identification, lexical decision, and semantic categorization, human readers behave as optimal Bayesian decision makers. This leads to the development of a computational model of word recognition, the Bayesian reader. The Bayesian reader successfully simulates some of the most significant data on human reading. The model accounts for the nature of the function relating word frequency to reaction time and identification threshold, the effects of neighborhood density and its interaction with frequency, and the variation in the pattern of neighborhood density effects seen in different experimental tasks. Both the general behavior of the model and the way the model predicts different patterns of results in different tasks follow entirely from the assumption that human readers approximate optimal Bayesian decision makers.
TL;DR: It is suggested that positive training can be enhanced through imagery as opposed to verbal processing, and the first test of a standardized intervention using an "interpretive bias training" paradigm to improve positive mood is provided.
TL;DR: Analysis of spatio-temporal patterns of generator activations underlying the MMN to speech may be an important tool for investigating the brain dynamics of spoken language processing and the activated distributed cortical circuits acting at long-term memory traces.
TL;DR: This study aimed to characterize a large group of progressive aphasic patients from a single center first clinically by case note review, and then pathologically.
Abstract: Objective
The clinical and neuropathological categorization of patients presenting with progressive aphasia is an area of controversy. This study aimed to characterize a large group of progressive aphasic patients from a single center (n = 38), first clinically by case note review, and then pathologically.
Methods
Hierarchical cluster analysis of the cases according to their clinical language deficits was used to establish an unbiased, data-driven classification.
Results
This analysis revealed two groups of cases corresponding to the syndromes of progressive nonfluent aphasia (n = 23) and semantic dementia (n = 15). Postmortem analysis showed a majority in both groups of pathologies from the spectrum of frontotemporal lobar degeneration: the most frequent were non–Alzheimer's disease (AD) tauopathy in the nonfluent cases (10 of 23) and frontotemporal lobar degeneration with ubiquitin-positive, tau-negative inclusions in the fluent cases (8 of 15). Despite rigorous exclusion of cases with clinically significant memory deficits or other cognitive impairments, the pathology of AD was present in approximately one third of each group (overall 12 of 38), although often with an atypical neuroanatomical distribution.
Interpretation
Progressive aphasia is best seen as a composite of two conditions, on both clinical and pathological levels: progressive nonfluent aphasia and semantic dementia. Ann Neurol 2006;59:156–165
TL;DR: This work considers different levels of attention and their basis in physiological mechanisms of biased competition, and suggests that biased competition is characteristic of many different cognitive domains and brain systems.
Abstract: There are many varieties of “attention”, to some extent separate yet working together to produce coherent perception, thought, and behaviour. Using data from human behaviour, functional neuroimaging, and single-cell recording in the behaving monkey, I consider different levels of attention and their basis in physiological mechanisms of biased competition. Beginning with visual attention, I suggest that processing is competitive in many brain systems that code visual input. Competition is biased towards stimuli that match task requirements and is integrated between systems coding different object properties. The result is flexible, object-based attentional selection. In the second part of the paper, I describe recent experiments on attentional competition within and between sensory modalities. Though competition is often modality specific, more global levels of interference are also easy to demonstrate. In the third part of the paper, I move to frontoparietal cortex and to a pattern of similar brain region...
TL;DR: A 'forward inference' that one can make from patterns of brain activity to distinguish between cognitive theories is described, which resembles the dissociation logic long-used in behavioural studies of healthy and brain-damaged people.
TL;DR: Neuropsychological and PE T functional imaging data are combined to show that when healthy subjects identify concepts at a specific level, the regions activated correspond to the site of maximal atrophy in patients with relatively pure semantic impairment.
Abstract: Studies of semantic impairment arising from brain disease suggest that the anterior temporal lobes are critical for semantic abilities in humans; yet activation of these regions is rarely reported in functional imaging studies of healthy controls performing semantic tasks. Here, we combined neuropsychological and PET functional imaging data to show that when healthy subjects identify concepts at a specific level, the regions activated correspond to the site of maximal atrophy in patients with relatively pure semantic impairment. The stimuli were color photographs of common animals or vehicles, and the task was category verification at specific (e.g., robin), intermediate (e.g., bird), or general (e.g., animal) levels. Specific, relative to general, categorization activated the antero-lateral temporal cortices bilaterally, despite matching of these experimental conditions for difficulty. Critically, in patients with atrophy in precisely these areas, the most pronounced deficit was in the retrieval of specific semantic information.
TL;DR: Mix is a Windows program that can generate pseudorandomized orders according to complex, user-specified constraints and can be used to generate a novel item order for each individual participant, even for complex experiments in which stimulus and/or response repetition is an experimental variable of interest, or for which automated randomization would not normally be possible.
Abstract: In psychological experiments involving multiple trials, the order in which individual trials are presented to participants influences the results obtained. For this reason, experimenters often create carefully constrained experimental lists or check randomly generated lists to avoid known causes of order artifacts (e.g., short-term stimulus or response repetition). Creating appropriately structured pseudorandom lists can be a difficult and time-consuming task in generating psychological experiments. Mix is a Windows program that can generate pseudorandomized orders according to complex, user-specified constraints. Mix can be used to generate a novel item order for each individual participant, even for complex experiments in which stimulus and/or response repetition is an experimental variable of interest, or for which automated randomization would not normally be possible. The program also contains a number of other practical features for generating files for use with a variety of experiment control software. A Mix executable for Windows, a complete manual, and terms of use are available at www.mrc-cbu.cam.ac.uk/personal/maarten.van-casteren/Mix.htm. Use is limited to academic or other nonprofit applications.
TL;DR: The finding that the manipulation ofinterpretive bias modified emotional reactivity supports the hypothesis that interpretive bias can indeed play a causal role in anxiety vulnerability.
Abstract: Elevated anxiety vulnerability is associated with a tendency to interpret ambiguous stimuli as threatening, but the causal basis of this relationship has not been established. Recently, procedures have been developed to systematically manipulate interpretive bias, but the impact of such manipulation on anxiety reactivity to a subsequent stressor has not yet been examined. In the present study, training procedures were used to induce interpretive biases favoring the threatening or nonthreatening meanings of ambiguous information in a sample of 48 undergraduate students. Following this interpretive training, participants' emotional reactions to a stressful video were assessed. The finding that the manipulation of interpretive bias modified emotional reactivity supports the hypothesis that interpretive bias can indeed play a causal role in anxiety vulnerability.
TL;DR: The findings suggest that semantic memory impairments occur early in the course of AD, more specifically in patients with "amnesic" MCI, and provide further evidence that impaired category fluency reflects semantic breakdown.
TL;DR: Depressed and manic patients exhibited abnormal neural responses to sad, fearful, and happy facial expressions, and the attentional level of sad facial affect processing has important consequences for abnormalities of amygdala and cingulate activation in manic patients.
TL;DR: Previous evidence from ERP studies of atypical brain function related to automatic change detection in autism is confirmed, and neurophysiological processes underlying autistic 'resistance to change' are thrown light.
TL;DR: It is suggested that antero-medial temporal cortex may be important for processing and differentiating between concepts that are 'tightly packed' in semantic space, such as living things, whereas (ii) inferolateral temporal cortex might play a more general role within the semantic system.
Abstract: Both herpes simplex virus encephalitis (HSVE) and semantic dementia (SD) typically affect anterior temporal lobe structures. Using voxel-based morphometry (VBM), this study compared the structural damage in four HSVE patients having a semantic deficit particularly affecting knowledge of living things and six SD patients with semantic impairment across all categories tested. Each patient was assessed relative to a group of control subjects. In both patient groups, left anterior temporal damage extended into the amygdala. In patients with HSVE, extensive grey matter loss was observed predominantly in the medial parts of the anterior temporal cortices bilaterally in SD patients the abnormalities extended more laterally and posteriorly in either the left, right or both temporal lobes. Based on a lesion deficit rationale and converging results from several other sources of evidence, we suggest that (i) antero-medial temporal cortex may be important for processing and differentiating between concepts that are 'tightly packed' in semantic space, such as living things, whereas (ii) inferolateral temporal cortex may play a more general role within the semantic system.
TL;DR: The findings are consistent with intertwined, but functionally distinct, neural representations of the human face and body.
TL;DR: The results suggest that the perception of vowel sounds is compatible with a hierarchical model of primate auditory processing in which early cortical stages of processing respond indiscriminately to speech and nonspeech sounds, and only higher regions, beyond anatomically defined auditory cortex, show selectivity for speech sounds.
TL;DR: An overview of recent behavioural and neuroimaging studies that have employed the Tower of London task is presented to draw specific conclusions about the likely neural and cognitive basis of planning function.
Abstract: This article provides an overview of recent research on human planning and problem solving. As an introduction, these two cognitive domains will be described and discussed from the perspective of experimental and cognitive psychology. The following sections will focus on the role of the prefrontal cortex in planning and problem solving and on disorders of these functions in patients with frontal-lobe lesions. Specific emphasis will be placed on the Tower of London task, a well established and widely used neuropsychological test of planning ability. We will present an overview of recent behavioural and neuroimaging studies that have employed the Tower of London task to draw specific conclusions about the likely neural and cognitive basis of planning function. Finally, we turn to a number of new directions and recent studies exploring different aspects of planning and problem solving and their association to related cognitive dimensions.
TL;DR: This article predicted that patients with semantic dementia would reveal a specific pattern of impairment on six different tasks typically considered "pre-" or "non-" semantic: reading aloud, writing to dictation, inflecting verbs, lexical decision, object decision, and delayed copy drawing.
Abstract: On the basis of a theory about the role of semantic knowledge in the recognition and production of familiar words and objects, we predicted that patients with semantic dementia would reveal a specific pattern of impairment on six different tasks typically considered "pre-" or "non-" semantic: reading aloud, writing to dictation, inflecting verbs, lexical decision, object decision, and delayed copy drawing. The prediction was that all tasks would reveal a frequency-by-typicality interaction, with patients performing especially poorly on lower-frequency items with atypical structure (e.g., words with an atypical spelling-to-sound relationship; objects with an atypical feature for their class, such as the hump on a camel, etc). Of 84 critical observations (14 patients performing 6 tasks), this prediction was correct in 84/84 cases; and a single component in a factor analysis accounted for 87% of the variance across seven measures: each patient's degree of impairment on atypical items in the six experimental tasks and a separate composite score reflecting his or her degree of semantic impairment. Errors also consistently conformed to the predicted pattern for both expressive and receptive tasks, with responses reflecting residual knowledge about the typical surface structure of each domain. We argue that these results cannot be explained as associated but unrelated deficits but instead are a principled consequence of a primary semantic impairment.
TL;DR: This study used an adaptation paradigm to investigate the functional organization of gaze perception in humans and provided evidence that humans have distinct populations of neurons that are selectively responsive to particular directions of seen gaze.
Abstract: Gaze direction is an important social signal in humans and other primates. In this study, we used an adaptation paradigm to investigate the functional organization of gaze perception in humans. Adaptation to consistent leftward or rightward gaze produced a powerful illusion that virtually eliminated observers' perception of gaze in the adapted direction; gaze to that side was seen as pointing straight ahead, though perception of gaze to the opposite side was unimpaired. This striking dissociation held even when retinotopic mapping between adaptation and test stimuli was disrupted by changes in size or head orientation, suggesting that our findings do not reflect adaptation to low-level visual properties. Moreover, adaptation to averted gaze did not affect judgments of line bisection, illustrating that our findings do not reflect a general spatial bias. Our findings provide evidence that humans have distinct populations of neurons that are selectively responsive to particular directions of seen gaze.