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Biomedical subjects

R Ameli

Publications and source records attributed to R Ameli.

10 recordsLinked to original sources
PubMed1992

Startle gating deficits occur across prepulse intensities in schizophrenic patients.

The effects of prepulse stimuli of different intensities in inhibiting the startle reflex was assessed in 14 age-matched and gender-matched schizophrenic patients and 14 normal controls. The subjects were presented with startling stimuli consisting of bursts of white noise (106 dBA) with or without prepulse stimuli. Four intensities of prepulse stimuli were utilized: 75, 80, 85, and 90 dBA. Throughout the testing, the background noise was maintained at 70 dBA. The prepulse stimuli more effectively inhibited the startle reflex in the control group compared to the schizophrenic patients who showed deficient prepulse inhibition (gating) of the startle reflex. These results suggest that schizophrenics have impaired central inhibitory mechanisms over a fairly broad range of background noise to prepulse ratios. Further studies are needed to clarify exactly which ratios are optimal in eliciting prepulse inhibition (PPI) and in differentiating between schizophrenic and control groups.

Adult↗
PubMed1992

The promise of partial hospitalization: a reassessment.

In this review of trends in partial hospitalization since 1987, the authors provide a brief overview of the field, summarize recent research findings, examine the data on the growth of partial hospitals, and outline recent changes in public- and private-sector use of this treatment modality. Support for intermediate and long-term partial hospitalization is diminishing rapidly, while support for short-term partial hospitalization as an alternative to inpatient care is increasing in the private sector and diminishing in the public sector. The future for partial hospitals seems uncertain, as the treatment functions of these programs are being assumed by psychosocial and vocational rehabilitation programs and assertive community treatment teams. In light of these trends, the authors recommend new directions for partial hospital research involving comparisons between short-term day hospitalization and intensive outpatient interventions.

Cost Control↗
PubMed1991

N400 and semantic categorization in schizophrenia.

The N400 component of event-related potentials (ERPs) was investigated in medicated schizophrenic patients and normal controls in a semantic categorization task. The subjects' task was to indicate whether pairs of words were semantically related or unrelated. The ERPs to the unrelated second words of the pairs contained a negative component, N400, which was reduced and delayed in the patients. However, inspection of individual subjects' data indicated that N400 was abnormal only in a subgroup of schizophrenics. Abnormalities in the amplitude of N400 suggest impairments in semantic expectancies, whereas abnormalities in the latency of N400 suggest a delay in information processing.

Adult↗
PubMed1991

Fear-potentiated startle in humans: effects of anticipatory anxiety on the acoustic blink reflex.

The effects of fear/anticipatory anxiety on the acoustic startle reflex were investigated in humans using a paradigm involving anticipation of electric shocks. The eyeblink component of the startle reflex, elicited by an abrupt auditory stimulus, was measured in 9 normal volunteers during either the anticipation of electric shocks (anticipatory anxiety) or periods in which no shocks were anticipated (safe period). The eyeblink was consistently higher in amplitude, and shorter in latency, during periods when the subjects anticipated shocks, compared to the safe periods. This effect could not be attributed solely to a reduction in habituation and was statistically significant before the subjects actually received any shock (a single 30 mA stimulation on the median nerve). These results indicate that anticipatory anxiety can be measured objectively in humans using the fear-potentiated startle reflex in a paradigm not actually requiring any shock. Because a great deal is known about the neuroanatomical and pharmacological mechanisms of fear-potentiated startle in laboratory animals, this test procedure may be especially useful in humans to investigate the neurobiological substrates of anxiety disorders and their pharmacological treatments.

Acoustic Stimulation↗
PubMed1990

Increased distractibility in schizophrenic patients. Electrophysiologic and behavioral evidence.

The inability of schizophrenics to filter irrelevant information has often been implicated in the psychopathology of schizophrenia. Despite numerous attempts at characterizing the behavior of schizophrenics in the presence of distractors, evidence of increased distractibility has been equivocal due to the difficulty of assessing simultaneously the behavioral and neurophysiological effects of distracting stimuli. We report the results of an experiment in which event-related potential and performance measures were used to assess distractibility during reaction time tasks under different distracting conditions. The results supported the view of an increased distractibility in schizophrenic patients. Event-related potential data suggested that in schizophrenic patients, a reduced amount of processing resources is allocated to process external stimuli and attention is abnormally apportioned to task-irrelevant vs task-relevant stimuli.

Adolescent↗
PubMed1990

Effects of rare non-target stimuli on brain electrophysiological activity and performance.

In order to assess the effects of non-target stimuli on task performance and electrophysiological activity, 16 subjects performed reaction time (RT) experiments under 3 conditions. In all conditions, subjects had to press a button upon detection of rare (15%) target stimuli (1600 Hz) presented among frequent (85%) non-target stimuli. The 3 conditions differed based on their non-target stimuli. In one condition, the non-targets consisted of 'standard' stimuli (900 Hz). In the two other conditions, rare and deviant non-target stimuli were randomly added to the standard stimuli. These deviant non-target stimuli consisted of either constant (700-Hz tones) or novel (buzzes, filtered noises and other unusual sounds) stimuli. Both the rare target and non-target stimuli elicited P300, responses. Behavioral (RT) and electrophysiological (event-related potential) data showed that stimuli that followed standard stimuli were processed differently compared to stimuli that followed deviant non-target stimuli. In the conditions containing deviant non-target stimuli, the P3b to the target stimuli was smaller and later, and the mean RT longer than in the condition with no deviant stimuli. These behavioral and electrophysiological changes induced by the deviant non-target stimuli were discussed with reference to two factors, distraction and increased level of task difficulty. It was suggested that each of these factors were differentially sensitive to the novelty of the rare deviant stimuli.

Acoustic Stimulation↗
PubMed1988

Visual memory processes in high-functioning individuals with autism.

High-functioning autistic individuals were compared with age-matched normal control subjects on a visual recognition memory task. In order to evaluate the effects of "meaning" and "delay" on the visual memory of autistic individuals, meaningful (pictures) and meaningless (nonsense shapes) stimuli were presented visually in no delay and 1-minute delay intervals to both groups. It was concluded that autistic subjects perform particularly poorly on meaningless material, but they are able to utilize meaning to aid their visual memory. Contrary to expectations, 1-minute delay intervals did not differentially affect the visual memory performance of autistic individuals compared to control subjects. The results do not support the idea of a simple parallel between autism and mediotemporal lobe amnesias. The visual memory performance of the autistic subjects was discussed in the light of the possibility of a subtle involvement of the mediotemporal brain structures and inflexible cognitive strategies poorly suited to encode novel information.

Adolescent↗
PubMedDate not supplied

Effects of task relevance and attention on P3 in schizophrenic patients.

The P3 component of the event-related potentials (ERPs) to auditory task-relevant and task-irrelevant stimuli in 'Attend Auditory' (i.e., reaction time task) and 'Attend Visual' (i.e., when the auditory stimuli were being ignored) conditions was investigated in 13 RDC/DSM-III diagnosed schizophrenic patients. ERPs were recorded from Fz, Cz, and Pz. Compared to controls, schizophrenics had a significantly smaller P3 in the Attend Auditory than in the Attend Visual condition and to the task-relevant than to the task-irrelevant stimuli. Furthermore, the patients' P3 response to the most salient task-irrelevant stimuli in the Attend visual condition was normal. The results are discussed as suggesting that schizophrenics either allocate relatively more resources to task-irrelevant than task-relevant stimuli or that they fail to habituate to task-irrelevant stimuli.

Adult↗
PubMedDate not supplied

Middle latency auditory evoked potentials (MAEPs) in chronic schizophrenics.

Middle latency auditory evoked potentials were recorded in medicated chronic schizophrenics and controls at stimulation rates of 10/s, 2/s, and 1/s. Increasing the stimulation rate did not change Pa amplitude but decreased Pb amplitude. There was no difference between the two groups.

Acoustic Stimulation↗