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Biomedical subjects

L R Warren

Publications and source records attributed to L R Warren.

11 recordsLinked to original sources
PubMed1985

Age differences in cerebral blood flow during rest and during mental activation measurements with and without monetary incentive.

This experiment compared the diffuse and regional cerebral blood flow (CBF) during rest and during cognitive activation with and without incentive-induced arousal in young, middle-aged, and older adults. Two normal rest CBF measurements were followed by two mental mathematics activation CBF measurements. For the first activation measurement, half the participants in each age group were offered monetary incentive for correct performance and half the participants received no monetary incentive. All participants were offered monetary incentive on the final activation measurement. Older participants had lower resting blood flow at all detectors, but age-related reductions in blood flow were statistically significant only in anterior and inferior rolandic regions. The effect of monetary incentive was to increase blood flow at the inferior rolandic detector in both hemispheres. The CBF response to cognitive activation and monetary incentive did not differ in the three age groups.

Adult↗
PubMed1985

Memory for self-generated stimuli in young and old adults.

Young and elderly adults were required to generate or study synonyms or rhymes of stimulus words. In one experiment, multiple-trial free recall was used to assess possible developmental differences in the generation effect, a 48-hr delayed recognition task was used in the second experiment. There was a significant generation effect for young and old adults on both retention tasks. The effect, however, did not emerge for the elderly participants in free recall until the second or third trial. The implications of utilizing internal stimulus generation as a potent mnemonic device were discussed.

Adolescent↗
PubMed1984

Focal changes in cerebral blood flow produced by monetary incentive during a mental mathematics task in normal and depressed subjects.

The purpose of this experiment was to determine the effect of incentive-induced arousal on the diffuse and regional cerebral blood flow (rCBF) response during cognitive activation for normal and depressed groups. Two normal rest CBF measurements were followed by two mental mathematics activation CBF measurements. For the first activation measurement, half the subjects in each group were offered monetary incentive for correct performance and half the subjects received no monetary incentive. All subjects were offered monetary incentive on the final activation run. The effect of monetary incentive on the first activation run was to increase CBF activation at four detectors in the left hemisphere. Incentive did not affect the CBF activation response when introduced following practice on the activation task (on the final run). Depressed groups had lower resting blood flow than normals, but the distribution of flow and the CBF response to incentive were almost identical in the two groups.

Adult↗
PubMed1983

Event-related potentials to match and mismatch letters in an immediate item recognition task.

During an immediate item recognition task, ERP differences to match and mismatch letters occurred in the N1 component, as well as the P3 component, of the stimulus related wave form. The pattern of ERP differences was similar to that reported previously for words in a delayed list recognition task, (Warren, 1980). The ERP differences to match and mismatch letters appeared unaffected by visual field of presentation (left, center, right) or hemisphere of recording site (P3, P4). It is suggested that the N1-P3 differences to match and mismatch stimuli may possibly reflect a pattern of neural activity associated with a two-stage recognition memory process.

Adult↗
PubMed1981

Alpha asymmetry as a function of cognitive mode: the role of lateral eye movements.

When monitored concurrently, the spontaneous lateral eye movements and alpha asymmetry associated with mental activity were themselves interrelated. Left eye movements were associated with a decrease in the ratio of right to left hemisphere alpha, while right eye movements resulted in an increase in this ratio, independent of cognitive task. The results were interpreted as evidence for a direct effect of oculomotor activity on alpha asymmetry.

Adult↗
PubMed1980

Evoked potential correlates of recognition memory.

During word recognition tasks, differences in the stimulus related potentials to 'old' (previously presented) and 'new' (not previously presented) words occurred as early as 160-190 ms after stimulus onset (N1) as well as in the late component of the wave forms (P3). The N1 differences may possibly reflect underlying neural activity directly related to the recognition memory process.

Electroencephalography↗
PubMed1979

Changes in event related potentials during processing of Stroop stimuli.

In a simplified Stroop test, subjects responded with a button press to either the color or word dimension of Stroop stimuli. Response times were analyzed as a function of condition (color or word), stimulus type (congruent or noncongruent color-word pairing) and visual field of presentation (left or right). Changes in the stimulus evoked potential (Experiment I) and the preresponse (premotor) potential (Experiment II) were measured as a function of the independent variables and hemisphere of recording site. Stimulus type had the expected Stroop effect on response time, with noncongruent stimuli associated with longer RTs. The pattern of changes in the event related potentials suggested that the typical Stroop interference effect (color condition) is localized in the response selection stage of processing. However, the less common reverse Stroop effect (word condition) probably results from more complex processing interactions during encoding of the color and word dimensions.

Brain↗
PubMed1978

Binaural analysis in the aging auditory system.

In a simulation of the "cocktail party" problem, subjects listened to recordings of a target voice, obscured by four background voices from adjacent locations in space. Listening conditions were either dichotic (with interaural directional cues preserved) or diotic (same input to both ears, directional cues removed). Elderly subjects were unable to use binaural directional cues as effectively as young subjects to improve intelligibility of the target voice. The results suggest that there is an age related deficit in the ability to perform the binaural signal analysis necessary to effectively separate speech signals from noise.

Adult↗