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Biomedical subjects

Tim M Gale

Publications and source records attributed to Tim M Gale.

16 recordsLinked to original sources
PubMed2006

Are placebo-controlled trials still important for obsessive compulsive disorder?

The use of placebos as reference agents in randomised controlled trials for psychiatric disorders has come under question for ethical reasons. Alternative methods for validating the efficacy of new treatments exist, but may not be as reliable as placebo. In this paper we examine arguments for and against the ongoing use of placebo agents in the development of new treatments for obsessive compulsive disorder in the context of evidence from randomised controlled trials.

Controlled Clinical Trials as Topic↗
PubMed2005

Crowded and sparse domains in object recognition: consequences for categorization and naming.

Some models of object recognition propose that items from structurally crowded categories (e.g., living things) permit faster access to superordinate semantic information than structurally dissimilar categories (e.g., nonliving things), but slower access to individual object information when naming items. We present four experiments that utilize the same matched stimuli: two examine superordinate categorization and two examine picture naming. Experiments 1 and 2 required participants to sort pictures into their appropriate superordinate categories and both revealed faster categorization for living than nonliving things. Nonetheless, the living thing superiority disappeared when the atypical categories of body parts and musical instruments were excluded. Experiment 3 examined naming latency and found no difference between living and nonliving things. This finding was replicated in Experiment 4 where the same items were presented in different formats (e.g., color and line-drawn versions). Taken as a whole, these experiments show that the ease with which people categorize items maps strongly onto the ease with which they name them.

Adult↗
PubMed2005

Comorbid depression in obsessive compulsive disorder (OCD): symptomatic differences to major depressive disorder.

In this study, we compared the depressive symptom profile of a group of obsessive compulsive disorder (OCD) patients, with comorbid depression, to a group of patients with major depressive disorder (MDD). The two groups (n=52 per group) were pair-wise matched on severity of depression as measured by the MADRS (mean 24.3 for each group) and we examined between-group differences on the individual MADRS item scores. The OCD group was significantly more symptomatic on items 3 (inner tension) and 9 (pessimistic thoughts) and significantly less symptomatic on items 4 (sleep) and 5 (appetite). We discuss these findings in the context of neurobiological bases for the two disorders.

Comorbidity↗
PubMed2005

When is category specific in Alzheimer's disease?

Mixed findings have emerged concerning whether category-specific disorders occur in Alzheimer's disease. Factors that may contribute to these inconsistencies include: ceiling effects/skewed distributions for control data in some studies; differences in the severity of cognitive deficit in patients; and differences in the type of analysis (in particular, if and how controls are used to analyse single case data). We examined picture naming in Alzheimer's patients and matched elderly healthy normal controls in three experiments. These experiments used stimuli that did and did not produce ceiling effects/skewed data in controls. In Experiment 1, we examined for category effects in individual DAT patients using commonly used analyses for single cases (chi2 and z-scores). The different techniques produced quite different outcomes. In Experiment 2a, we used the same techniques on a different group of patients with similar outcomes. Finally, in Experiment 2b, we examined the same patients but (a) used stimuli that did not produce ceiling effects/skewed distributions in healthy controls, and (b) used statistical methods that did not treat the control sample as a population. We found that ceiling effects in controls may markedly inflate the incidence of dissociations in which living things are differentially impaired and seriously underestimate dissociations in the opposite direction. In addition, methods that treat the control sample as a population led to inflation in the overall number of dissociations detected. These findings have implications for the reliability of category effects previously reported both in Alzheimer patients and in other pathologies. In particular, they suggest that the greater proportion of living than nonliving deficits reported in the literature may be an artifact of the methods used.

Aged↗
PubMed2004

Evidence-based pharmacotherapy of obsessive-compulsive disorder.

Obsessive-compulsive disorder is a prevalent and disabling lifespan disorder. Clomipramine and the SSRIs have been found to be effective across the range of symptoms, both in acute and longer-term studies. Meta-analyses have reported a larger treatment effect for clomipramine relative to the SSRIs, but this is not supported by evidence from head-to-head comparator studies and, based on their superior safety and tolerability, SSRIs are the preferred option for long-term treatment in most cases. The treatment-effect is usually gradual and partial, and many patients fail to respond adequately to first-line treatment. Pharmacological options for refractory cases include switching SRI, increasing the dose, or augmenting with an antipsychotic agent. Novel strategies are under investigation for this highly morbid group. This paper reviews the key questions related to OCD pharmacotherapy, synthesizing evidence derived from randomized controlled trials, meta-analyses and consensus guidelines.

Antidepressive Agents, Tricyclic↗
PubMed2003

Basic-level visual similarity and category specificity.

The role of visual crowding in category deficits has been widely discussed (e.g.,;; ). Most studies have measured overlap at the superordinate level (compare different examples of 'animal') rather than at the basic level (compare different examples of 'dog'). In this study, we therefore derived two measures of basic-level overlap for a range of categories. The first was a computational measure generated by a self-organising neural network trained to process pictures of living and non-living things; the second was a rating of perceived visual similarity generated by human subjects to the item names. The computational measure indicated that the pattern of crowded/uncrowded does not honour a living/non-living distinction. Nevertheless, different superordinates showed varied degrees of basic-level overlap, suggesting that specific token choice affects some superordinates more than others e.g., individual fruit and vegetable tokens show greater variability than any other items, while tools and vehicles produce more reliable or overlapping basic-level visual representations. Finally, subject ratings correlated significantly with the computational measures indicating that the neural model represents structural properties of the objects that are psychologically meaningful.

Humans↗
PubMed2003

The influence of surface and edge-based visual similarity on object recognition.

The role of 'visual similarity' has been emphasised in object recognition and in particular, for category-specific agnosias. [Laws and Gale, 2002] recently described a measure of pixel-level visual overlap for line drawings (Euclidean Overlap: EO[line]) that distinguished living and nonliving things and predicted normal naming errors and latencies ( [Laws et al., 2002]). Nevertheless, it is important to extend such analyses to stimuli other than line drawings. We therefore developed the same measure for greyscale versions of the same stimuli (EO[grey]), i.e., that contain shading and texture information. EO[grey], however, failed to differentiate living from nonliving things and failed to correlate with naming latencies to the greyscale images. By contrast, EO[line] did correlate with the naming latencies. This suggests that similarity of edge information is more influential than similarity of surface characteristics for naming and for categorically separating living and nonliving things (be they line drawings or greyscale images).

Discrimination, Psychological↗
PubMed2003

Inflated and contradictory category naming deficits in Alzheimer's disease?

Although some studies have documented category-specific deficits in patients with Alzheimer's disease, others have not. One possible reason is that where control groups have been used in previous studies, they have performed at ceiling; and this may spuriously affect the incidence and type of deficit reported (especially with common statistical techniques such as z-scores). We examined this issue in 18 Alzheimer's patients and 26 elderly controls, who named two picture sets: a simple set that typically produces ceiling effects (Set 1) and one that produces a normal distribution in controls (Set 2). Sets 1 and 2 produced inconsistent and even contradictory deficits in the same patients. The results also show that ceiling effects may inflate the number of living thing deficits and hence, distort the reported ratio of living to nonliving cases.

Aged↗
PubMed2003

How common is obsessive-compulsive disorder in a dermatology outpatient clinic?

BACKGROUND: This study was prompted by reports suggesting a high prevalence of unrecognized obsessive-compulsive disorder (OCD) in the dermatology clinic. METHOD: 92 consecutive dermatology referrals were screened for DSM-IV OCD using the Mini-International Neuropsychiatric Inverview (MINI), the Yale-Brown Obsessive Compulsive Scale (YBOCS), and the 5-item screening questionnaire from the International Council on OCD. Illness severity was rated on the YBOCS, and symptom profiles and dermatologic diagnoses were established for screen-positive cases. RESULTS: 18 patients (20%) qualified for a DSM-IV diagnosis of OCD, of whom 17 were previously undiagnosed. The range and type of OCD symptoms covered the normal clinical spectrum. Most patients had more than 1 symptom, and among obsessions (including somatic obsessions), checking, washing, and symmetry were common. The mean total YBOCS score was 16/40 (SD = 7.2), indicating moderate OCD, and 40% of the positive cases scored 16 or higher. Dermatologic diagnoses were various and did not seem to bear a direct relationship with the OCD. CONCLUSION: These results suggest that there is a high prevalence of clinically relevant OCD in the dermatology clinic. This is an area that merits attention with regard to better recognition and treatment for OCD sufferers.

Adolescent↗
PubMed2002

Category-specific naming and the 'visual' characteristics of line drawn stimuli.

It has been argued that greater intra-category structural similarity for living things may make them more difficult to recognize and name (e.g. Humphreys et al., 1988). Nevertheless, the precise meaning and quantification of 'structural similarity' remain unclear. We developed three new visual measures derived from the Snodgrass and Vanderwart (1980) corpus and examined their relationship with picture naming in a speeded presentation paradigm. The three measures were: the proportion of black pixels (PB); the degree of pixel overlap within subcategories using Euclidean Overlap (EO); and the degree of consistency in inter-pixel distribution across each picture (IPC). Within-category EO was greater for nonliving than living things, indicating less within-category visual overlap for living things. Finally, EO correlated significantly with error rates (PB and IPC did not). These findings contradict existing notions that line drawings of living things have greater visual similarity than nonliving things.

Adult↗
PubMed2002

The effect of 'masking' on picture naming.

It is frequently assumed that because compared to nonliving things, living things are less familiar, have lower name frequency, and are more visually complex, this makes them more difficult to name by patients and normal subjects. This has also been implicitly accepted as an explanation for the greater incidence of living thing disorders. Patient studies do not, however, typically contain any premorbid data and so, we do not know that the same variables would have necessarily predicted their 'normal' performance. To examine this issue, we measured picture-naming latencies in normal subjects presented with unmasked and masked versions of the same line drawings. In accord with other recent studies, living things were named faster than nonliving things. Furthermore, contrary to some theories of category naming, the living thing advantage persisted regardless of whether stimuli were undegraded, degraded or the density of degradation. Finally, multiple simultaneous regression analyses showed that one visual variable (Euclidean Overlap) and one linguistic variable (Age of Acquisition) predicted naming latencies across all masked and unmasked conditions. Other variables either had no predictive value (Contour Overlap; Name Frequency; Category); predicted only high masking (Visual Complexity; Familiarity), or normal and low masking (Number of Phonemes). These findings imply that the more commonly documented deficits for living things do not reflect an exaggeration of the normal profile (be it with masked or unmasked stimuli) or the influence of the same variables that affect normal naming.

Adult↗
PubMedDate not supplied

The role of global and feature based information in gender classification of faces: a comparison of human performance and computational models.

Most computational models for gender classification use global information (the full face image) giving equal weight to the whole face area irrespective of the importance of the internal features. Here, we use a global and feature based representation of face images that includes both global and featural information. We use dimensionality reduction techniques and a support vector machine classifier and show that this method performs better than either global or feature based representations alone. We also present results of human subjects performance on gender classification task and evaluate how the different dimensionality reduction techniques compare with human subjects performance. The results support the psychological plausibility of the global and feature based representation.

Algorithms↗
PubMedDate not supplied

Visual similarity is greater for line drawings of nonliving than living things: the importance of musical instruments and body parts.

It has been argued that greater intra-category structural similarity for living things, and the subsequent "visual crowding," makes them more difficult to recognize and name for neurologically damaged individuals and normal subjects (Humphreys et al., 1988). Nevertheless, the precise meaning and quantification of structural similarity remains unclear, as does the rationale for why it necessarily should be greater for living things. We derived a new measure of visual overlap from the Snodgrass and Vanderwart corpus of line drawings: the degree of pixel overlap within subcategories (Euclidean distance: ED). Contrary to existing notions of visual crowding and extant measures of contour overlap, within-category ED indicated less within-category visual overlap for living things. Furthermore, musical instruments clustered with living things (having low overlap), while body parts clustered with nonliving things (having high overlap). These counter-intuitive findings accord with patient data and thus, provide evidence for the psychological reality and utility of ED.

Humans↗