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Biomedical subjects

P Arno

Publications and source records attributed to P Arno.

8 recordsLinked to original sources
PubMed2001

Decreased benzodiazepine receptor density in the cerebellum of early blind human subjects.

As a first approach to study the effect of early visual deprivation in the GABA-ergic inhibitory system, the distribution of benzodiazepine receptors (BZR) was accurately estimated using [11C]flumazenil ([11C]FMZ). Measurements were carried out in five subjects who became blind early in life and in five sighted control subjects. The interactions between [11C]FMZ and BZR were described using a non-linear compartmental analysis which permitted to estimate the BZR synaptic density independently of other model parameters. The distribution of BZR in the visual areas and other cortical regions of blind subjects was qualitatively and quantitatively similar to that of controls. However, the BZR density in the cerebellum was significantly lower in blind than in control subjects (P<0.01). Our findings suggest that modifications of the cerebellar neural circuitry may be concomitant to the already observed compensatory reorganization in cerebral areas of blind subjects.

Adult↗
PubMed2001

Occipital activation by pattern recognition in the early blind using auditory substitution for vision.

This PET study aimed at investigating the neural structures involved in pattern recognition in early blind subjects using sensory substitution equipment (SSE). Six early blind and six blindfolded sighted subjects were studied during three auditory processing tasks: a detection task with noise stimuli, a detection task with familiar sounds, and a pattern recognition task using the SSE. The results showed a differential activation pattern with the SSE as a function of the visual experience: in addition to the regions involved in the recognition process in sighted control subjects, occipital areas of early blind subjects were also activated. The occipital activation was more important when the early blind subjects used SSE than during the other auditory tasks. These results suggest that activity of the extrastriate visual cortex of early blind subjects can be modulated and bring additional evidence that early visual deprivation leads to cross-modal cerebral reorganization.

Acoustic Stimulation↗
PubMed1999

Auditory coding of visual patterns for the blind.

Recognition tasks of simple visual patterns have been used to assess an early visual--auditory sensory-substitution system, consisting of the coupling of a rough model of the human retina with an inverse model of the cochlea, by means of a pixel-frequency relationship. The potential advantage of the device, compared with previous ones, is to give the blind the ability to both localise and recognise visual patterns. Four evaluation sessions assessed the performance of twenty-four blindfolded sighted subjects using the device. Subjects had to recognise twenty-five visual patterns, one at a time, using a head-mounted small camera and interpreting the corresponding sounds given by the device. Half the subjects were trained by means of a correction feedback procedure during ten one-hour training sessions embedded in between the evaluation sessions. Results revealed extremely successful training effects. Performance of trained subjects significantly increased with practice compared with the untrained control group. The improvement was also observed for new patterns, demonstrating a learning-process generalisation. The negative correlation observed between scores and processing time showed that the subjects' response accuracy was related to their speed. In conclusion, simple pattern recognition is possible with a fairly natural vision-to-audition coding scheme, given the possibility for the subjects to have sensory--motor interactions while using the device.

Adult↗
PubMed1998

A real-time experimental prototype for enhancement of vision rehabilitation using auditory substitution.

The rehabilitation of blindness, using noninvasive methods, requires sensory substitution. A theoretical frame for sensory substitution has been proposed which consists of a model of the deprived sensory system connected to an inverse model of the substitutive sensory system. This paper addresses the feasibility of this conceptual model in the case of auditory substitution, and its implementation as a rough model of the retina connected to an inverse linear model of the cochlea. We have developed an experimental prototype. It aims at allowing optimization of the sensory substitution process. This prototype is based on a personal computer which is connected to a miniature head-fixed video camera and to headphones. A visual scene is captured. Image processing achieves edge detection and graded resolution. Each picture element (pixel) of the processed image is assigned a sinusoidal tone; weighted summation of these sinewaves builds up a complex auditory signal which is transduced by the headphones. On-line selection of various parameters and real-time functioning of the device allow optimization of parameters during psychophysical experimentations. Assessment of this implementation has been initiated, and has so far demonstrated prototype usefulness for pattern recognition. An integrated circuit of this system is to be developed.

Adaptation, Physiological↗
PubMed1997

Brain energy metabolism in early blind subjects: neural activity in the visual cortex.

As an attempt to better understand the metabolic basis for the previously reported increases in glucose metabolism in the visual cortex of congenitally blind subjects, cerebral blood flow, oxygen consumption and glucose utilization were investigated with multitracer positron emission tomography. Measurements were carried out in three subjects who became blind early in life and in three age-matched blindfolded controls. Regional analysis of cerebral blood flow, metabolic rates for oxygen and glucose utilization revealed that these parameters were relatively higher in the visual cortex in case of early blindness (109.7 +/- 2.4%; 114.3 +/- 1.5%; 118.0 +/- 5.5%, respectively) than in controls (98.1 +/- 3.9%; 108.6 +/- 3.6%; 105.2 +/- 4.8%). There were slight differences, albeit statistically not significant, between early blind and control subjects in terms of oxygen-to-glucose metabolic ratios. The relatively preserved stoichiometry in the visual areas of blind subjects points to the lack of variation in the yield of glucose oxidation in this cortex. Those observations suggest that the high level of energy metabolism disclosed in early blind visual cortex is related to neural activity.

Adult↗
PubMed1996

U.S. hospital care for HIV-infected persons and the role of public, private, and Veterans Administration hospitals.

Hospitals are a major provider of medical care for human immunodeficiency virus (HIV)-infected persons. Although utilization and patterns of care profiles in public and private hospitals have been evaluated for acquired immunodeficiency syndrome (AIDS)-related Pneumocystis carinii pneumonia (PCP), one of the most costly and common severe complications of AIDS, information from Veterans Administration (VA) hospitals has not been reported previously. This article reports on inpatient care for PCP patients by obtaining data from VA, private, and public hospitals. Cost and resource utilization data were obtained from reviews of medical records, claims, and provider bills from 26 non-VA hospitals and 18 VA hospitals in 10 cities in the United States. Data on severity of illness, patterns of care, and outcomes for PCP were obtained from medical record reviews from 2,174 PCP cases treated in 82 non-VA and 14 VA hospitals in five U.S. cities. Estimates were made of the average costs and the rates of use of diagnostic tests, anti-PCP medications, and intensive care units for samples of public hospital, private hospital, and VA patients with PCP. With mean charges for a single PCP episode of $14,500 to $16,060, PCP remains one of thea most costly complications of AIDS. Although the severity of PCP illness at admission was greatest at public hospitals, the intensity of care was lowest: for frequency of cytologic diagnosis (48% at public, 62% at VA, and 66% at private hospitals), bronchoscopy (45% at public, 60% at VA, and 66% at private hospitals), and intensive care unit use (11% at public, 22% at VA, and 19% at private hospitals). In-hospital mortality rates for PCP also differed in the three types of hospitals (20% at public, 24% at VA, and 18% at private hospitals). Patterns of PCP care differ among VA, public, and private hospitals. Future studies on the HIV epidemic should include data collected from uniform data sources from VA hospitals, in addition to public and private hospitals, to provide insight on the processes of care and outcomes for HIV-infected persons.

AIDS-Related Opportunistic Infections↗
PubMed1994

Results of the ACSUS for pediatric AIDS patients: utilization of services, functional status, and social severity.

OBJECTIVE: This study describes demographic characteristics of pediatric AIDS patients, describes hospital and community-based service utilization patterns, and analyzes medical and social support service usage patterns with respect to patient demographic characteristics, clinical trial participation, functional/developmental status, and social environment. DATA SOURCES AND STUDY SETTING: Data reported in this study are from the AIDS Costs and Service Utilization Survey (ACSUS) and cover the six-month period beginning March 1991 (N = 135). Pediatric patients who sought care for HIV-related problems were sampled at seven different hospitals in five metropolitan regions of the United States. All of the participating hospitals had clinics specifically serving pediatric patients infected with HIV. The sample consists of HIV-positive patients who had had at least one HIV-related symptom or condition. STUDY DESIGN: A stratified probability sample design guided the sampling strategy, which included oversampling in two large hospitals from two of the five metropolitan areas. Survey data cover an 18-month time period of health care utilization, cost, and financing information from HIV-infected patients and their providers. Utilization measures are standardized to a six-month period. Per capita income, family structure, informal personal network, functional status, and clinical trial participation are tested for associations with patterns of utilization. In addition, a weighted ten-point social severity scale was developed to assess family/household stability. DATA COLLECTION: Data were collected through a screener instrument completed by the person accompanying the child to a hospital clinic visit (usually a a parent), and through two interviews conducted in person with the patients' primary caregivers. Data from the questionnaires were coded and assembled into computerized SAS analysis files by WESTAT: PRINCIPAL FINDINGS: Children in this sample are 62 percent African American, 25 percent Hispanic, and 10 percent White. Medicaid is the primary payer for 92 percent. Mean per capita income is $3,440. Fewer than one-half (41 percent) of the families of the children receive Aid to Families with Dependent Children (AFDC). (AFDC). Within the six-month period, approximately one-third of the sample (29.6 percent) was hospitalized. Mean length of stay was 16.0 days. Clinical trial participation was positively related to mean number of hospital clinic visits and receipt of formal (paid) home care. There were no differences in use of community clinic, mental health, and inpatient facilities by clinical trial status. Participation in clinical trials was positively related to income and negatively related to social severity. In four cities, emergency room use was consistently lower for clinical trial participants than for nonparticipants. CONCLUSIONS: Data from the first six months of the ACSUS pediatric sample suggest that participation in clinical trials may bring about access to social services that appear to reduce emergency room use. However, the findings reported here are descriptive and exploratory. Further multivariate, nonparametric analyses of the full 18-month provider-patient merged data set are necessary to confirm the simple correlations found in this study.

Acquired Immunodeficiency Syndrome↗