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Biomedical subjects

W Lichty

Publications and source records attributed to W Lichty.

9 recordsLinked to original sources
PubMed1999

Cerebral blood oxygenation changes induced by auditory stimulation in newborn infants measured by near infrared spectroscopy.

Recent neuronal activation studies on newborns using functional MRI or near infrared spectroscopy (NIRS) have suggested that the increase in O2 consumption accompanying neuronal activation exceeds the increase in O2 delivery in the visual cortex during photic stimulation. In the present study, we evaluated the cerebral blood oxygenation (CBO) changes induced by auditory stimulation in the frontal lobe of newborns using NIRS. We studied 28 newborns; the postnatal age at CBO measurements was 3.1+/-0.3 days (mean+/-S.E.M.). We measured concentration changes of deoxyhemoglobin (Deoxy-Hb), oxyhemoglobin (Oxy-Hb), and total hemoglobin (Total-Hb) induced by auditory (music) stimulation in the bilateral frontal lobes of the newborns. Twenty-six (92.9%) out of 28 subjects showed increases of Oxy-Hb and Total-Hb during the stimulation. In these subjects, 17 (60.7%) subjects showed an increase of Deoxy-Hb associated with increases of Oxy-Hb and Total-Hb, while nine (32.1%) subjects showed a decrease of Deoxy-Hb. Although the direction of the Deoxy-Hb differed, these two groups did not differ for Oxy-Hb and Total-Hb (P > 0.05). Two (7.1%) subjects showed other changes. The frontal lobe of newborns shows CBO responses similar to those observed in the visual cortex, specifically neuronal activation causes an increase of Deoxy-Hb associated with increases of Oxy-Hb and Total-Hb. These results support the hypothesis that increments in O2 consumption exceed increments in O2 delivery during neuronal activity in newborns.

Acoustic Stimulation↗
PubMed1998

Language-activated cerebral blood oxygenation and hemodynamic changes of the left prefrontal cortex in poststroke aphasic patients: a near-infrared spectroscopy study.

BACKGROUND AND PURPOSE: In normal subjects, regional cerebral blood flow (rCBF) is greatly increased by neuronal activity, whereas the cerebral metabolic rate for O2 is increased only slightly. However, it is not clear what kinds of cerebral blood oxygenation and hemodynamic changes can be induced by language activities in language-relevant areas of poststroke aphasics. In the present study, we investigated the difference in the changes of cerebral blood oxygenation and hemodynamics in the left prefrontal cortex induced by language activities between normal subjects, poststroke nonaphasic patients, and nonfluent aphasic patients using near-infrared spectroscopy (NIRS). METHODS: Twenty-nine participants performed speech tasks, such as confrontational naming, to evaluate changes among poststroke nonfluent (Broca's) aphasia patients (10 cases; mean+/-SEM, 56.9+/-2.2 years), age-matched normal subjects (13 cases; 50.7+/-2.2 years) and poststroke nonaphasic patients (6 cases; 52.5+/-3.9 years). The optodes of NIRS were placed over the left prefrontal cortex. We analyzed the NIRS parameter (oxyhemoglobin [oxy-Hb], deoxyhemoglobin [deoxy-Hb], and total hemoglobin [total-Hb]) changes by qualitative pattern analysis of the parameter changes and quantitative analysis of the parameter values among the groups. RESULTS: The most common NIRS parameter change was an increase in oxy-Hb and total-Hb, with a slight decrease or no change in deoxy-Hb in the normal subjects (5 of 13 cases, 38.5%) and the nonaphasic cerebrovascular disease (CVD) patients (3 of 6 cases, 50.0%). In contrast, the most common pattern in the aphasic patients was an increase of deoxy-Hb, with an increase of oxy-Hb and total-Hb (5 of 10 cases, 50%). However, this pattern was observed in only 3 of 13 cases (23.1%) in the normal subjects and 1 of 6 cases (16.7%) in the nonaphasic CVD patients. The mean (+/-SEM) changes of deoxy-Hb of the aphasic patients, the normal subjects, and the nonaphasic CVD patients were 0.78+/-0.29, 0.06+/-0.16, and -0.18 +/- 0.22, respectively. The statistical analysis demonstrated a significant effect for deoxy-Hb (P<0.05), with the aphasic patients differing significantly from the normal subjects and the nonaphasic CVD patients, while the 2 nonaphasic groups did not differ from each other. CONCLUSIONS: The present results demonstrate a multiplicity of language-activated cerebral blood oxygenation and hemodynamic changes in the left prefrontal cortex in the nonaphasic and aphasic groups. The increase of deoxy-Hb with increases of oxy-Hb and total-Hb in the aphasics during language tasks suggests that the left prefrontal cortex of the aphasics utilizes more oxygen than the nonaphasics during language tasks. Finally, functional MRI, which images the activation area in the brain by detecting the reduced concentration of deoxy-Hb during neuronal activation, should be performed on the patients with cerebral dysfunction, giving special consideration to the possible multiplicity of the rCBF and cerebral oxygen metabolism responses to functional tasks.

Aged↗
PubMed1993

Discrimination of insulin-produced hypoglycemia in rats.

Hypoglycemia is an abnormal state that can be induced by administering insulin to a fasting animal. Rats were trained to discriminate the normal state of euglycemia from the hypoglycemia produced by injection of 6 units/kg insulin. A drug discrimination procedure was used with a two-lever operant response. Insulin or water injected 25 min prior to the operant sessions determined whether left or right lever presses were reinforced. During 40 training sessions, reliable discrimination of the insulin-produced cue developed. After insulin injection, mean blood glucose levels dropped to about 75% of preinjection values. At 12 min postinsulin injection, prior to the development of hypoglycemia, noninsulin responses were made. Noninsulin responses were also made after injection with 800 mg/kg ethanol, indicating that a novel interoceptive state did not substitute for the insulin-produced cue. Insulin injections produced less severe hypoglycemia in less food-deprived rats, which again gave noninsulin responses. Animals can be trained to recognize the insulin-produced state, which presumably involves hypoglycemia, and/or counterregulatory process evoked in response to the drop in blood glucose.

Animals↗
PubMed1990

Properties of memory for unattended spoken syllables.

Whereas previous studies on memory for unattended speech have inadvertently included acoustic interference, the present study examines memory for unattended syllables during a silent period of 1, 5, or 10 s. The primary task was to read silently (Experiments 1-3) or whisper the reading (Experiment 4). Occasionally, when a light cue occurred, the subject was to recall the most recent spoken syllable, as well as the recent reading material. Memory for both the vowels and consonants of the syllables decreased across 10 s, confirming that auditory memory does decay in the absence of acoustic interference. However, the specific patterns of memory decay for vowels versus consonants depended on task demands, including the allocation of attention and the opportunity for subvocal coding. We suggest an account of performance that includes auditory sensory and phonetic memory codes with different properties, used in combination.

Attention↗
PubMed1989

The latent factor structure of the WAIS-R: a factor analysis of individual item responses.

Factor analytic examination of a 166 x 166 intercorrelational matrix that represents individual item scores from the 11 subtests of the WAIS-R provided evidence of five interpretable factors (N = 409). Two of these were identified as the Verbal and Performance factors previously encountered in traditional WAIS-R subtest-based factor analyses. The other three factors were characterized readily as involving (1) Advanced Vocabulary skills; (2) Basic Responsivity and (3) Advanced Computational ability. All three of these "new" factors accounted for at least 10% of the total variance, and comments are made with regard to the possible significance of their discovery to such topics as subtest variation and profile psychodiagnostics, theories that pertain to the nature and structure of human intellectual functioning, and subtest-based personality measurement theories.

Adult↗
PubMed1986

Activity duration and adult age differences in memory for activity performance.

Young and elderly subjects performed a series of activities that varied in the duration of their performances (45 s, 90 s, and 180 s). Duration was found to have a negligible effect on the subsequent recall of the activities and on the magnitude of the age deficit in recall. Operationalization of the program for performing an activity seems essential for establishing a memory trace of that activity's performance, but the duration of performing that activity seems to yield no further enhancement of that trace.

Adolescent↗
PubMed1986

Adult age differences in memory for motor versus cognitive activities.

Young and elderly participants performed on a series of 12 sustained activities (3 minutes each) under either incidental or intentional memory conditions regarding subsequent recall of those activities. Half of the activities were primarily motor in nature, half primarily cognitive. A significant overall age deficit was found for recall. Most important, in contrast to the contextual support hypothesis, the age deficit was as pronounced for motor activities as for cognitive activities. For both kinds of activities, incidental memory was as proficient as intentional memory.

Adolescent↗
PubMed1985

Tests of the neural noise hypothesis of age-related cognitive change.

Three predictions were derived from the assumption that with increased age there is a decrease in the effective signal-to-noise ratio of neural representations of visually presented stimuli. Although the results from manipulations designed to examine the internal consistency of the predictions were quite positive, the predicted age differences failed to appear in two of the three dependent measures. Because the same pattern was found in two independent studies and estimates of measurement reliability and statistical power were moderately high, it was concluded that at least some versions of the neural-noise hypothesis of cognitive changes with age may be untenable and that more effort should be devoted to devising experimentally testable implications of the hypothesis.

Adolescent↗