A comparison of rCBF patterns during letter and semantic fluency.

To evaluate the functional neuroanatomies underlying letter and category fluency, 18 normal controls were studied with oxygen-15 water regional cerebral blood flow positron emission tomography. Three counterbalanced conditions each consisted of 6 trials (45 s each): letter fluency (generating words when cued with a particular letter), semantic fluency (generating words when cued with a particular category), and a control condition (generating days of the week and months of the year). Relative to the control, participants activated similar brain regions during both fluency tasks, including the anterior cingulate, left prefrontal regions, thalamus, and cerebellum; reductions were found in parietal and temporal regions.

Neuropsychological performance of monozygotic twins discordant for bipolar disorder.

Background: A paradigm that involves cognitive assessment of monozygotic (MZ) twins discordant for a neuropsychiatric disorder (here bipolar illness) allows for the examination of both disease-specific impairments (in the comparison of affected to unaffected twins) and risk factors (in the comparison of unaffected twins to normal twins).

Methods: Neuropsychological functions were evaluated in seven MZ twin pairs discordant for bipolar illness and seven pairs of normal MZ twins in an attempt to highlight cognitive abilities associated with manifestations of disease and genetic risk factors. At the time of testing, 3 of the affected twins were euthymic, 2 had depressive symptoms, and 2 had manic symptoms; all were receiving medication.

Cognitive substrates of thought disorder, II: specifying a candidate cognitive mechanism.

Objective: In part I of this series, the authors found that semantic knowledge and organization accounted for most of the variance in thought disorder in a group of chronic schizophrenic patients. In the present study, they examined a possible cognitive mechanism within the semantic system that might produce thought disorder.

Method: Twenty patients with chronic schizophrenia and 21 normal comparison subjects were assessed on priming (the ability to respond to a stimulus word more quickly when it is preceded by a semantically related word than when it is preceded by an unrelated word).

Cognitive substrates of thought disorder, I: the semantic system.

Objective: Few studies have explored in detail the relation of cognitive deficits in attention, working memory, and semantics to thought disorder. The authors sought to determine whether thought disorder resides in the semantic system or elsewhere.

Method: Twenty-three normal comparison subjects and 23 patients with schizophrenia participated in the study.

An investigation of semantic space in patients with schizophrenia.

There has been increasing interest in the semantic cognitive system in schizophrenia. Recent findings suggest a possible breakdown of semantic information processing in this disorder. The current study attempts to further examine semantic organization in schizophrenia.

Interhemispheric transfer in children with early-treated phenylketonuria.

Phenylketonuria (PKU) is a genetic disorder of amino acid metabolism that is associated with brain catecholamine depletion and deficient myelination. Although neuropsychological deficits have been documented in children with early-treated PKU (ETPKU), no study to date has examined possible effects of impaired myelination in this population. In the present study, interhemispheric transfer time was assessed for 14 children with ETPKU, 22 children with attention deficit-hyperactivity disorder, and 48 normal children, using a manual reaction time paradigm previously validated with callosal agenesis patients (Milner, 1982).

Lateralized deficits in visual attention in males with developmental dopamine depletion.

Children with early treated phenylketonuria (ETPKU), a disorder associated with developmental dopamine depletion, were tested with a visual orienting paradigm to determine the existence of lateralized deficits in specific attentional operations. Male ETPKU subjects showed a right visual field impairment in disengaging attention, indicating left hemisphere dysfunction, and overall slowed reaction times. Female ETPKU and normal subjects did not differ.