Characterization and comparison of autistic subgroups: 10 years' experience with autistic children.

To summarize our 10-year experience with autistic children at the Tel Aviv Child Development Center, the files of all 55 children with autism treated at our center over a 10-year period were retrospectively reviewed. Particular attention was addressed to the value of the medical work-up in detecting the etiology of autism and to factors differentiating infantile autism (IA) from autistic-like behavior (ALB). Twenty-four subjects (44%) had IA and 31 (56%) had ALB. These subgroups were compared for demographic, perinatal, familial, neurological, and psychological findings, and outcome at discharge. Associated medical conditions and the yield of metabolic work-up and neuroimaging and electroencephalography studies are discussed. The two subgroups differed only in severity of autistic symptoms and cognitive function (P<0.05), but not in demographic or neurobiological findings. It was concluded that IA and ALB are similar conditions, and autism has a wide continuum of clinical expressions.

Clinical characteristics of children referred to a child development center for evaluation of speech, language, and communication disorders.

Speech, language, and communication disorders are prominent reasons for referrals to a child development center. From 1984 to 1988, 1,090 preschool children were referred to our child development center, which serves the Tel Aviv metropolitan area. Of all referrals, 432 (41%) were primarily due to speech, language, and communication problems. After exclusion of those with IQ < 50 and those with non-language-related disabilities, 323 children remained. The children were classified into different subtypes of developmental language disorders and autistic spectrum disorders. The main developmental language disorder subtypes were combined expressive-receptive (49%) and expressive (44%). Central processing deficits were less common, occurring in 20 (7%) of the children. Parents of children with developmental language disorders had educational levels similar to those of parents of children referred to the child development center for other causes. However, parents of children with infantile autism had higher educational levels than parents of children with developmental language disorder or parents of children referred for other causes (P < .001). Our results reflect the distribution of language and related problems in an unselected population of preschool children referred to a child development center.

Comparative extracellular current flow at dendrites and soma of dentate granule cells during long-term potentiation.

In the study of long-term potentiation (LTP) in the dentate gyrus, the magnitude of the initial slope of the evoked synaptic potential (ESP) in the region of the granule cell layer, is commonly used as a measure of synaptic efficacy at the site of the perforant path (PP) input. To investigate the viability of this assumption, in rats anesthetized with either chloropent or urethane, LTP was induced by tetanic stimulation of the PP and ESPs were measured simultaneously at both the soma and dendritic site of the PP input. Following LTP, the two responses were decoupled, the somal response being greater than the dendritic in rats anesthetized with chloropent, the opposite being true in urethanized animals. We conclude that in investigating changes in synaptic efficacy following LTP, measurements should be taken at the site of the PP input.

Long-term potentiation in the dentate gyrus is preferentially induced at theta rhythm periodicity.

In urethane-anesthetized rats, high frequency stimulation was applied to the medial perforant pathway at various time intervals (50, 100, 200, 350 and 500 ms) following stimulation of the same pathway by a single pulse of equal intensity. Recordings of dentate gyrus granule cell evoked responses were made to investigate the range of stimuli that are effective in inducing long-term potentiation (LTP). LTP was induced almost exclusively at the 200 ms interval, corresponding to the periodicity of the theta rhythm. Taken in conjunction with similar findings reported in the CA1 field of the hippocampal slice, these results suggest that the correlation between theta rhythm periodicity and LTP is a general phenomenon within the hippocampal formation and lends further support to the hypothesis that the naturally occurring theta rhythm may play a modulatory role in the induction of LTP.

Long-term potentiation in the dentate gyrus is induced preferentially on the positive phase of theta-rhythm.

Long-term potentiation (LTP), a long lasting enhancement of synaptic efficacy is considered a model for learning and memory. In anesthetized rats, theta-rhythm was induced in the dentate gyrus by midbrain stimulation. Short trains of pulses were applied to the perforant pathway either at the peak of theta-rhythm or its trough. Trains applied at the peak of theta-rhythm induced LTP while trains applied at the trough produced a decrease of synaptic efficacy or had no effect. Thus, theta-rhythm may play a modulating role in the induction of LTP, suggesting a possible mnemonic function for the rhythm during the behaviors in which it occurs.

Divided attention in brain-injured patients.

Clinical observations have shown that brain-injured patients perform poorly in tasks requiring attention. While selective and sustained attention has been extensively investigated, there is little systematic information on how brain-injured patients perform on divided attention tasks requiring simultaneous handling of and responding to two sources of information. This study was designed to analyse the behavior of hospitalized brain-injured patients as compared with matched normal controls in performing a dual task consisting of pursuit motor tracking coupled with delayed digit recall (DDR). Four two-minute trials were given. Time on target (TOT) and number of recall errors were recorded. It was assumed that the brain-injured group would (a) have lower TOT and more recall errors; and (b) show less learning effect. Results confirmed both expectations: (1) for the brain-injured group, TOT was lower and did not improve across trials; moreover, the number of recall errors was higher, increasing across trials; (2) for the control group, the number of recall errors was negligible across trials and TOT improved with time; (3) the normal trade-off between two simultaneous difficult tasks was not observed in the brain-injured group as they failed in both tasks; (4) the number of recall errors of the brain-injured subjects markedly increased towards the end of each trial, suggesting rapidly increasing fatigue. Thus, brain-injured patients appeared limited not only in their attention capacity but also in the variety of strategies they employ in processing information.