Biomedical subjects

J V Filoteo

Publications and source records attributed to J V Filoteo.

13 recordsLinked to original sources

PubMed2006

Neural correlates of rule-based and information-integration visual category learning.

An emerging theory of the neurobiology of category learning postulates that there are separate neural systems supporting the learning of categories based on verbalizeable rules (RB) or through implicit information integration (II). The medial temporal lobe (MTL) is thought to play a crucial role in successful RB categorization, whereas the posterior regions of the caudate are hypothesized to support II categorization. Functional neuroimaging was used to assess activity in these systems during category-learning tasks with category structures designed to afford either RB or II learning. Successful RB categorization was associated with relatively increased activity in the anterior MTL. Successful II categorization was associated with increased activity in the caudate body. The dissociation observed with neuroimaging is consistent with the roles of these systems in memory and dissociations reported in patient populations. Convergent evidence from these approaches consistently reinforces the idea of multiple neural systems supporting category learning.

Adolescent↗

PubMed2001

Quantitative modeling of category learning in amnesic patients.

Category rule learning was examined in two amnesic patients using the perceptual categorization task (e.g., Ashby & Gott, 1988; Filoteo & Maddox, 1999). Traditional accuracy-based analyses as well as quantitative model-based analyses were performed. Unlike accuracy-based analyses, the model-based approach allowed us to examine both categorization rule learning and variability in the trial-by-trial application of the participant's categorization rule. The results indicated that the amnesic patients were as accurate as the controls in learning a complex, nonlinear rule over a large number of trials. The model-based analysis indicated that, in general, the amnesic patients learned the categorization rule as well as controls and applied their rule as consistently as controls. Categorization performance on a second day of testing revealed that amnesic patients can retain the categorization rule over a 24-h period. These results suggest that the brain regions damaged in amnesia are not involved in category learning or memory for the category structures.

Adult↗

PubMed2001

Striatal contributions to category learning: quantitative modeling of simple linear and complex nonlinear rule learning in patients with Parkinson's disease.

The contribution of the striatum to category learning was examined by having patients with Parkinson's disease (PD) and matched controls solve categorization problems in which the optimal rule was linear or nonlinear using the perceptual categorization task. Traditional accuracy-based analyses, as well as quantitative model-based analyses were performed. Unlike accuracy-based analyses, the model-based analyses allow one to quantify and separate the effects of categorization rule learning from variability in the trial-by-trial application of the participant's rule. When the categorization rule was linear, PD patients showed no accuracy, categorization rule learning, or rule application variability deficits. Categorization accuracy for the PD patients was associated with their performance on a test believed to be sensitive to frontal lobe functioning. In contrast, when the categorization rule was nonlinear, the PD patients showed accuracy, categorization rule learning, and rule application variability deficits. Furthermore, categorization accuracy was not associated with performance on the test of frontal lobe functioning. Implications for neuropsychological theories of categorization learning are discussed.

Aged↗

PubMed2001

A possible role of the striatum in linear and nonlinear category learning: evidence from patients with Huntington's disease.

Linear and nonlinear categorization rule learning was examined in patients with Huntington's disease (HD) and a group of controls using the perceptual categorization task. Participants learned to categorize simple line stimuli into 1 of 2 categories over 600 trials. In addition to traditional measures of accuracy, quantitative model-based analyses were applied to each participant's data to characterize better the nature of any observed deficits. In the linear rule condition, HD patients displayed an early-training deficit relative to controls, whereas later in training the HD patients were not statistically different from controls. In the nonlinear rule condition, HD patients displayed both an early- and late-training deficit. The quantitative model-based analyses revealed that the HD patients' deficits in the linear condition were due to an impairment in learning the experimenter-defined rule and not in applying a learned rule inconsistently. In the nonlinear condition, in contrast, the HD patients' deficits were due to an impairment in learning the experimenter-defined rule and in applying a learned rule inconsistently. Overall, these results suggest that HD can result in a deficit in learning both linear and nonlinear categorization rules.

Adult↗

PubMed1999

Quantitative modeling of visual attention processes in patients with Parkinson's disease: effects of stimulus integrality on selective attention and dimensional integration.

Parkinson's disease (PD) patients and normal controls (NCs) were administered a series of visual attention tasks. The dimensional integration task required integration of information from 2 stimulus dimensions. The selective attention task required selective attention to 1 stimulus dimension while ignoring the other stimulus dimension. Both integral- and separable-dimension stimuli were examined. A series of quantitative models of attentional processing was applied to each participant's data. The results suggest that (a) PD patients were not impaired in integrating information from 2 stimulus dimensions, (b) PD patients were impaired in selective attention, (c) selective attention deficits in PD patients were not due to perceptual interference, and (d) PD patients were affected by manipulations of stimulus integrality and separability in much the same way as were NCs.

Aged↗

PubMed1998

Effects of stimulus integrality on visual attention in older and younger adults: a quantitative model-based analysis.

Twenty-one older and 21 younger adults were administered a series of visual attention tasks. A series of quantitative models was applied to each observer's data to determine whether he or she performed optimally or suboptimally or showed a deficit-in-attentional processing. The results suggested that (a) older and younger observers were affected equally by the integrality-separability manipulation, (b) there are no age-related differences in selective attention performance for either integral or separable-dimension stimuli, (c) there are no age-related differences in dimensional integration performance with separable-dimension stimuli, and (d) older observers were more likely to be suboptimal when asked to integrate information from integral-dimension stimuli. Implications for current theories of attentional processing in normal aging are discussed.

Adult↗

PubMed1998

Is there a "subcortical" profile of attentional dysfunction? A comparison of patients with Huntington's and Parkinson's diseases on a global-local focused attention task.

This study investigated focused attention in two subcortical degenerative disorders by examining the performance of patients with Huntington's disease (HD) and Parkinson's disease (PD) on a task utilizing global-local stimuli. Participants were presented with global-local figures and were instructed to focus their attention on either the global or local level. Stimuli were either "consistent", with the same form at the global and local levels, or "inconsistent", with different forms at the global and local levels. It was found that response times (RTs) of patients with PD were comparable to those of similarly-aged controls regardless of stimulus consistency. In contrast, patients with HD demonstrated disproportionately longer RTs to inconsistent stimuli relative to their age-matched control group. Difference scores between RTs for inconsistent versus consistent stimuli were not correlated with overall level of dementia or disease severity for either the HD or PD group. These results provide further evidence for the heterogeneity of attentional dysfunction among subcortical degenerative illnesses.

Adult↗

PubMed1997

Variable memory profiles in Parkinson's disease.

Thirty-nine patients with Parkinson's disease (PD) were categorized into one of three subgroups using discriminant function analysis and three key indices from the California Verbal Learning Test (CVLT). Patients were classified as having one of three memory profiles: (a) a normal memory profile; (b) a memory profile often observed in patients with Huntington's disease (HD); or (c) a memory profile often observed in patients with Alzheimer's disease (AD). Twenty of the patients with PD were classified as having a normal profile, 10 as having an HD profile, and 9 as having an AD profile. The three subgroups did not differ on measures of global cognitive functioning, letter fluency, confrontation naming, or visuo-construction, suggesting that the patients with PD with an AD memory profile were not experiencing AD, per se. These results demonstrate that the memory deficits associated with PD can be similar to those found in patients with either HD or AD, and argues against the notion that the behavioral manifestations of PD are homogeneous.

Age Factors↗

PubMed1997

Performance of Parkinson's disease patients on the Visual Search and Attention Test: impairment in single-feature but not dual-feature visual search.

Nondemented patients with Parkinson's disease (PD) and a group of age and education matched controls were administered a modified version of the Visual Search and Attention Test (VSAT). This task measures subjects' speed at localizing letter or symbol targets based on either a single-feature or a dual-feature search. Three indices were derived from the VSAT: (a) the amount of time taken to complete each of the trials (completion time), (b) the number of target items not crossed out (omissions), and (c) the number of nontarget items crossed out (commissions). The results indicated that, in terms of completion time, the PD patients were impaired on the single-feature search conditions but not on the dual-feature search conditions, suggesting that PD patients are impaired in selective attention processes. It was also found that the number of target items omitted by the normal controls on the VSAT varied as a function of the nature of the target (letter or form) and the search requirements (single-feature or dual-feature search), whereas the number of targets omitted by the PD patients was not affected by these factors. Correlational analyses suggested that the three measures derived from the VSAT assessed different components of attentional performance in these patients. Overall, the results of this study suggest that the VSAT can be used to detect subtle attentional impairments in nondemented PD patients, and that the pattern of their impairment on this clinical test is similar to that found on experimental attentional measures.

Journal Article↗

PubMed1997

An examination of the nature of attentional deficits in patients with Parkinson's disease: evidence from a spatial orienting task.

Endogenous and exogenous shifts of attention were examined in nondemented patients with Parkinson's disease (PD). In the endogenous condition, an arrow was used to cue participants' attention to the possible location of an impending target, whereas in the exogenous condition, a brightened box was used to cue attention. Cues were either valid (i.e., the target appeared in the cued location) or invalid (i.e., the target appeared in a noncued location). The time between cue onset and target onset (stimulus onset asynchrony or SOA) was varied in each condition. The results indicated that PD patients were not differentially impaired in shifting attention at the shorter SOAs relative to normal controls. However, at longer SOAs, the PD patients demonstrated less of an effect from cueing than did the normal control participants. PD patients' differential effect from cueing was evident in both exogenous and endogenous conditions. These results suggest that PD patients may experience a rapid decay of attentional inhibition and do not support the notion that a decrement in processing resources underlies their attentional deficits. Moreover, these findings further support the notion that the basal ganglia may play an important role in attentional functions.

Aged↗

PubMed1995

Visual attention and perception in patients with Huntington's disease: comparisons with other subcortical and cortical dementias.

Shifts in attention were examined in patients with Huntington's disease (HD) using a divided attention paradigm that involved the presentation of global-local stimuli. The HD patients' pattern of performance was compared to the previously reported results of groups of patients with Alzheimer's disease (AD; Filoteo et al., 1992) or Parkinson's disease (PD; Filoteo et al., 1994). Across consecutive trials of the divided attention task, a visual target could appear at either the same global-local level or at a different level. When the target changed levels across consecutive trials, the AD patients demonstrated an impairment in disengaging attention from the level at which the last target appeared, whereas the PD patients were impaired in maintaining their attention at the previously attended level. In contrast to these patterns of performances, the HD patients did not demonstrate a significant impairment in shifting attention between hierarchical levels. Both the AD and the PD patients' abnormal shifting ability was significantly related to the number of errors they made in identifying target stimuli; however, the pattern of the relationship was qualitatively distinct. These results suggest that different attentional mechanisms may underlie AD and PD patients' visual-perceptual deficits. The HD patients' shifting ability was not related to the number of errors they made in identifying target stimuli, suggesting that a different mechanism may account for the visual-perceptual impairments exhibited by these patients.

Aged↗

PubMed1992

Directed and divided attention in Alzheimer's disease: impairment in shifting of attention to global and local stimuli.

This study investigated the relative performance of Alzheimer's disease (AD) patients and normal controls on directed and divided attention reaction time (RT) tasks that involved the use of global-local stimuli (e.g., a large '1' made from small '2s'). Relative to normals, AD patients displayed disproportionately greater impairment on the divided attention task compared to the directed attention task. On the divided attention task, when the target remained at the same global-local level across consecutive trials, the AD patients displayed a greater facilitation effect than did the controls when responding to the second stimulus. However, when the target changed levels across consecutive trials (i.e., from the global to the local, or vice versa) the AD patients' RTs to the second stimulus were disproportionately slower than were the controls' RTs. These results demonstrated that AD patients are impaired in disengaging and shifting attention across levels of perceptual organization within the same stimulus.

Aged↗

PubMed1992

Spatial cognition in Alzheimer's disease: subtypes of global-local impairment.

This study investigated whether subgroups of AD patients exhibit different patterns of impairment in analyzing global (configural) and local (detail) features of complex visual stimuli. A High Spatial AD subgroup (i.e., patients with better block constructions than naming) and a High Verbal AD subgroup (i.e., patients with better naming than block constructions) were impaired in analyzing both global and local forms. As predicted, however, the High Spatial AD patients exhibited greater impairment in analyzing the local forms than the High Verbal AD patients and normal controls. In contrast, the High Verbal AD patients exhibited greater impairment in analyzing the global forms than the High Spatial AD patients and normal controls. There was a striking separation of the subgroups: Using the local-global difference score, the hit rate for classifying these patients into the two subgroups was 91%. Robust correlations were found between the AD patients' ability to construct global and local forms and their scores on traditional visuospatial and verbal tests, respectively. The findings suggest that it may be misleading to subdivide AD patients using a verbal/spatial dichotomy, because even those AD patients who appear to have relative strengths on traditional visuospatial tests are likely to exhibit a primary impairment in analyzing local features of complex visual stimuli. The results underscore the importance of a process (qualitative) approach to neuropsychological assessment for a more valid understanding of the behavioral subtypes of Alzheimer's disease.

Aged↗