Biomedical subjects

Catherine L Harris

Publications and source records attributed to Catherine L Harris.

11 recordsLinked to original sources

PubMed2006

'Winner-take-all' competition among real and illusory words.

'Winner-take-all' networks are an important theoretical construct in visual neuroscience. An implication of winner-take-all networks is that a stimulus that wins the competition for selection receives maximal activation and will be consciously perceived, even when selection was incorrect. In this study, competition was induced between physically presented ('real') and self-constructed ('illusory') words. Semantic activation was probed by recording event-related potential responses to a downstream target word. The results showed that only words reported by participants triggered a spread of activation in the semantic system, whereas non-reported words failed to prime the target. Both effects were independent of whether the potential primes were 'real' or 'illusory'. Our findings indicate that neural 'winner-take-all' networks extend to the processing of lexical units.

Adult↗

PubMed2004

Cigarette smoking in a student sample: neurocognitive and clinical correlates.

Why do adolescents begin to smoke in the face of profound health risks and aggressive antismoking campaigns? The present study tested predictions based on two theoretical models of tobacco use in young adults: (1) the self-medication model; and (2) the orbitofrontal/disinhibition model. Investigators speculated that a significant number of smokers were self-medicating since nicotine possesses mood-elevating and hedonic properties. The self-medication model predicts that smokers will demonstrate increased rates of psychopathology relative to nonsmokers. Similarly, researchers have suggested that individuals with attention-deficit/hyperactivity disorder (ADHD) employ nicotine to enhance cognitive function. The ADHD/self-medication model predicts that smokers will perform poorly on tests of executive function and report a greater number of ADHD symptoms. A considerable body of research indicates that tobacco use is associated with several related personality traits including extraversion, impulsivity, risk taking, sensation seeking, novelty seeking, and antisocial personality features. Antisocial behavior and related personality traits as well as tobacco use may reflect, in part, a failure to effectively employ reward and punishment cues to guide behavior. This failure may reflect orbitofrontal dysfunction. The orbitofrontal/disinhibition model predicts that smokers will perform poorly on neurocognitive tasks considered sensitive to orbitofrontal dysfunction and will obtain significantly higher scores on measures of behavioral disinhibition and antisocial personality relative to nonsmokers. To test these predictions, we administered a battery of neuropsychological tests, clinical scales, and personality questionnaires to university student smokers and nonsmokers. Results did not support the self-medication model or the ADHD/self-medication model; however, findings were consistent with the orbitofrontal/disinhibition model.

Adolescent↗

PubMed2004

Priming illusory words: an ERP approach.

Repetition blindness (RB) was used to investigate whether illusory words emerge at a lexical-perceptual or a semantic-reconstructional level. Illusory words were evoked by the rapid serial visual presentation (RSVP) of two real words and a word fragment. The initial words share the same string of letters ("CREEP"-"SHEEP"), producing a free-floating word fragment ("SH"). This fragment is likely to be linked to a subsequently presented fragment ("IFT") if both combine to a meaningful word ("SHIFT"). The processing level of the illusions was probed by prime words preceding the RSVP sequence which were semantically related or unrelated to the second real word or to the illusion. Behavioural and electrophysiological correlates of the semantic priming effect were recorded in 14 subjects. Real words related to the prime were perceived more frequently, and evoked widespread N400-like effect in the event-related brain potentials (ERPs). An ERP effect of the same polarity was obtained for illusory words, however, its latency was delayed and the topographical distribution was restricted to left posterior electrode positions. These differences suggest that priming might affect real and illusory words at different levels of word processing: access to real words is facilitated at a semantic level, whereas lexical activation apparently accompanies the generation of illusory words.

Adult↗

PubMed2004

Neurocognitive function in borderline personality disorder.

A battery of neuropsychological measures considered sensitive to dysfunction in prefrontal or temporal cortices was administered to patients with borderline personality disorder (BPD) and healthy controls. BPD patients exhibited striking deficits on measures of nonverbal executive function and nonverbal memory but were unimpaired on tests of alternation learning, response inhibition, divergent thinking, verbal fluency, and verbal working memory. A second study found that university students obtaining high scores on a self-report measure of BPD symptoms exhibited a similar pattern of neuropsychological impairment, although performance deficits were much less pronounced in the student sample. Taken together, these studies suggest that dysfunction of a right hemisphere frontotemporal regions may be associated with borderline personality.

Adolescent↗

PubMed2004

Repetition blindness occurs in nonwords.

Theorists have predicted that repetition blindness (RB) should be absent for nonwords because they do not activate preexisting mental types. The authors hypothesized that RB would be observed for nonwords because RB can occur at a sublexical level. Four experiments showed that RB is observed for word-nonword pairs (noon noof), orthographically similar nonwords (glome glame), and identical repetitions (plass plass). More RB was found for words than for nonwords. Prior researchers may have failed to find RB for nonwords because display conditions that allow 2 words to be reliably encoded are insufficient for nonwords, or because observers coped with low ability to encode nonwords by using guessing strategies that do not require creating a mental type or tokenizing it.

Humans↗

PubMed2004

Repetition blindness: out of sight or out of mind?

Does repetition blindness represent a failure of perception or of memory? In Experiment 1, participants viewed rapid serial visual presentation (RSVP) sentences. When critical words (C1 and C2) were orthographically similar, C2 was frequently omitted from serial report; however, repetition priming for C2 on a postsentence lexical decision task was equivalent whether or not C1 was similar to C2. In Experiment 2, participants monitored RSVP sentences for a predetermined target. Participants frequently failed to detect the target when it was preceded by an orthographically similar word. In Experiment 3, the authors investigated the role of the attentional blink in this effect. These experiments suggest that repetition blindness is a failure of conscious perception, consistent with predictions of the token-individuation hypothesis.

Adult↗

PubMed2003

Neuropsychological function in obsessive-compulsive disorder: effects of comorbid conditions on task performance.

BACKGROUND: Neuropsychological testing reveals a pattern of impairment among patients with obsessive-compulsive disorder (OCD) which implicates the orbitofrontal region. Studies of neuropsychological function in OCD differ regarding performance deficits on classical tests of frontal executive function. In some studies, OCD patients did not demonstrate impaired performance on tests of executive function. However, other researchers have documented performance deficits among OCD patients on measures of executive function. Patients with OCD also exhibit performance deficits on tests of visual/spatial memory and verbal memory. Again, in some studies, OCD patients did not demonstrate impaired performance on tests of memory function. How can we account for the conflicting findings? One possibility is that performance deficits on tests of cognitive function are associated with comorbid conditions. In prior work, we observed that OCD patients who did poorly on executive function tasks obtained high scores on a measure of schizotypal personality. A second possibility is that executive function deficits among patients with OCD are associated with comorbid depressive symptoms. METHOD: In the present study, a comprehensive neuropsychological test battery was administered to patients with OCD and matched healthy control subjects. We also administered dimensional measures of schizotypal personality and depression to patients with OCD and controls. We conducted analyses of covariance (ANCOVA), with scores on measures of schizotypal personality and depression used as covariates. RESULTS: OCD patients demonstrated performance deficits on measures of delayed memory, response inhibition, alternation learning, and obtained significantly higher scores on measures of disinhibition, impulsivity, and temporolimbic symptoms; however, OCD patients did not exhibit impaired performance on tests of executive function and verbal fluency, and did not report a significantly greater number of dysexecutive symptoms, when coexistent depressive and schizotypal symptoms were taken into account. CONCLUSION: Findings are consistent with the contention that dysfunction of an orbitofrontal-limbic network underlies OCD.

Adult↗

PubMed2003

Subtyping obsessive-compulsive disorder: neuropsychological correlates.

We administered neuropsychological measures considered sensitive to prefrontal dysfunction (both orbitofrontal and dorsolateral prefrontal neocortex) to obsessive-compulsive disorder (OCD) patients and control subjects. OCD subjects exhibited performance deficits, in comparison to community controls, on three measures sensitive to orbitofrontal neocortex dysfunction. Contrary to expectation, OCD patients also exhibited performance deficits on measures sensitive to dorsolateral prefrontal neocortex dysfunction. However, distinct neurocognitive profiles emerged when we examined the impact of comorbid schizotypal personality features on neuropsychological test performance. Primary OCD patients displayed impaired performance on measures sensitive to orbitofrontal dysfunction; however, they did not differ from control subjects on tests of dorsolateral function. OCD subjects presenting with schizotypal personality features performed poorly not only on tests sensitive to orbitofrontal dysfunction, but also on tests sensitive to dorsolateral dysfunction. Findings suggest that OCD can be subdivided into clinical subtypes, and distinct prefrontal subsystems may be differentially involved in these subtypes.

Adult↗

PubMed2002

Positive and negative schizotypy in a student sample: neurocognitive and clinical correlates.

Positive and negative schizotypy may represent discrete factors or dimensions. To determine if distinct neurocognitive profiles are associated with these dimensions or factors, we classified university students on the basis of positive and negative schizotypal symptoms and conducted separate analyses. Following prior work in the neuropsychiatric literature, we predicted that subtle prefrontal deficits would be selectively associated with negative schizotypal personality features in a nonclinical student sample. We also investigated the relationship between positive/negative schizotypy and associated clinical states or personality dimensions including antisocial personality disorder, obsessive-compulsive personality traits, generalized and social anxiety, empathy, and impulsivity. Classification of subjects into positive and negative schizotypy groups revealed distinct neurocognitive and clinical profiles. We observed a positive relation between measures of temporolimbic dysfunction, impulsivity, antisocial behavior, and positive schizotypal phenomena. Negative schizotypy was associated with subtle performance deficits on measures of frontal executive function, increased social anxiety, and obsessive-compulsive phenomena. Findings are consistent with the contention that positive and negative schizotypy represent discrete factors.

Adolescent↗

PubMed2002

Sentence context, word recognition, and repetition blindness.

When the sentence She ran her best time yet in the rice last week is displayed using rapid serial visual presentation, viewers sometimes misread rice as race (M. C. Potter, A. Moryadas, I. Abrams, & A. Noel, 1993). Seven experiments combined misreading and repetition blindness (RB) paradigms to determine whether misreading of a word because of biasing sentence context represents a genuine perceptual effect. In Experiments 1-4, misreading a word either caused or prevented RB for a downstream word, depending on whether orthographic similarity was increased or decreased. Additional experiments examined temporal parameters of misreading RB and tested the hypothesis that RB results from reconstructive memory processes. Results suggest that the effect of prior context occurs during perception.

Analysis of Variance↗

PubMedDate not supplied

Assessing adult attention-deficit/hyperactivity disorder: a Turkish version of the current symptoms scale.

We report normative data for a Turkish translation of the Current Symptoms Scale (CSS), a screening measure of adult attention-deficit/hyperactivity disorder (ADHD). The CSS yields 3 scores reflecting diagnostic criteria for: (1) ADHD, predominantly hyperactive-impulsive type; (2) ADHD, predominantly inattentive type, and (3) ADHD, combined type. For comparison purposes, we also present normative data from a community sample in the United States. Central tendency, variability, and correlation patterns among Turkish subjects (n=181) were similar to patterns demonstrated by respondents in the United States (n=114). Mann-Whitney U tests revealed that the Turkish and US groups did not differ significantly on the subscales assessing inattentive and hyperactive-impulsive symptoms. Both versions demonstrated acceptable levels of internal consistency (Cronbach's alpha coefficients ranged from 0.65 to 0.78 for the Turkish version, and from 0.63 to 0.75 for the English version). The Turkish version of the CSS demonstrated excellent test- retest reliability. The test-retest coefficient for the CSS (total score) was 0.82. The inattentive type subscale also showed good test-retest reliability, with r=0.78. The test-retest coefficient for the hyperactive-impulsive type subscale was appreciably lower, with r=0.68; albeit, in the acceptable range. Investigators have determined that many adults, initially diagnosed with ADHD as children, continue to demonstrate clinically significant symptoms. Since adult ADHD is associated with a number of comorbid psychiatric conditions and treatment of the underlying attentional, executive, and impulse control difficulties is associated with a reduction in comorbid psychiatric symptoms, the routine screening for adult ADHD in psychiatric and mental health settings may be warranted.

Adolescent↗