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Biomedical subjects

D Delis

Publications and source records attributed to D Delis.

6 recordsLinked to original sources
PubMed1992

The role of alterations in free radical metabolism in mediating cognitive impairments in Down's syndrome.

Down's syndrome (DS) is a genetic disorder involving an excess of chromosome 21 (trisomy 21) in approximately 96% of the cases and comprises approximately 15% of the population with mental retardation (Heller, 1969). In addition to the constitutional mental deficiencies associated with the syndrome many DS patients develop dementia associated with Alzheimer's disease (AD) in their later years of life (Thase et al., 1984). The genetic locus for Cu,Zn-superoxide dismutase (SOD1), a key enzyme in free radical metabolism, is located on chromosome 21, and the activity level of this enzyme is elevated by approximately 50% in a variety of cells of DS patients (see Kedziora and Bartosz, 1988; Sinet, 1982). Because alterations in free radical metabolism may be involved in neuronal death and may be associated with a number of pathological manifestations of DS, it is important to understand the role of free radical metabolism in cognitive impairments of DS, the topic discussed in this chapter.

Aging↗
PubMed1990

Subcortical abnormalities detected in bipolar affective disorder using magnetic resonance imaging. Clinical and neuropsychological significance.

Magnetic resonance imaging was utilized to determine the nature and rate of subcortical abnormalities in bipolar affective disorder. Nine of 19 bipolar patients and no controls demonstrated subcortical signal hyperintensities on blind evaluation of the images. There was no apparent change in the appearance of the hyperintensities in 7 of 7 subjects with abnormal magnetic resonance images who underwent repeated imaging at 1 year. Bipolar patients with abnormalities had a history of more hospitalizations and appeared more impaired on tests of fluency and recall when compared with bipolar patients without abnormalities or with controls. The possible etiology and significance of signal hyperintensities in bipolar affective disorder is discussed.

Adult↗
PubMed1989

Seeing either the forest or the trees: dissociation in visuospatial processing.

Traditionally, visuospatial processing has resisted fractionation into functional substrates. Recently, however, it has been shown that the brain honors the distinction between global and local processing of hierarchical visual stimuli: unilateral left hemisphere brain-damaged subjects were impaired in their ability to draw the local forms of a hierarchical design, whereas right hemisphere-damaged patients demonstrated the opposite pattern (Delis, Robertson, & Efron, 1986; Delis, Kiefner, & Fridlund, 1988). The present study reports a similar pronounced dissociation in hierarchical visual processing but in quite different populations and in the absence of focal structural brain damage. Mentally retarded subjects with Williams Syndrome are considerably more impaired in global relative to local analysis, whereas subjects with Down Syndrome display the opposite pattern. These results, in concert with other neuropsychological data, are provocative because they suggest that certain cognitive deficits may cluster even in the absence of frank cerebral damage, just as they cluster following insult to one hemisphere. These findings should provide clues to the interrelationship of components of visuospatial processing and other cognitive functions.

Adolescent↗
PubMed1982

The effects of thematic context and presentation mode on memory for sentence voice.

A sentence in discourse may appear in the passive voice to emphasize the logical object rather than the logical subject when it is thematically more important. Two experiments are reported that explore the impact of this textual function of voice on sentence memory. The first experiment required subjects to listen to prose passages and then recall them. Sentences were recalled predominantly in the active voice regardless of voice or thematic focus in the prose passage, showing that the English-language bias for the active voice was a more important determinant of sentence reconstruction than was the experiment manipulation of thematic context. The second experiment required subjects to listen to or read either prose passages or lists of unrelated sentences and then to try to recognize "key" sentences that were either unchanged or changed lexically, semantically, or in voice. Recognition, both overall and specifically for voice, was better for sentences that were read than for those that were heard, and recognition for semantic change was consistently higher than for any other. Only when passages were read was there evidence in support of a thematic textual influence on memory for sentence voice.

Humans↗