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J Larson

Publications and source records attributed to J Larson.

45 records · Page 3Linked to original sources
PubMed1986

Induction of synaptic potentiation in hippocampus by patterned stimulation involves two events.

Electrical stimulation of axons in the hippocampus with short high-frequency bursts that resemble in vivo activity patterns produces stable potentiation of postsynaptic responses when the bursts occur at intervals of 200 milliseconds but not 2 seconds. When a burst was applied to one input and a second burst applied to a different input to the same target neuron 200 milliseconds later, only the synapses activated by the second burst showed stable potentiation. This effect was observed even when the two inputs innervated completely different regions of the postsynaptic cells; but did not occur when the inputs were stimulated simultaneously or when the second burst was delayed by 2 seconds. Intracellular recordings indicated that the first burst extended the decay phase of excitatory postsynaptic potentials evoked 200 milliseconds later. These results suggest that a single burst of axonal stimulation produces a transient, spatially diffuse "priming" effect that prolongs responses to subsequent bursts, and that these altered responses trigger spatially restricted synaptic modifications. The similarity of the temporal parameters of the priming effect and the theta rhythm that dominates the hippocampal electroencephalogram (EEG) during learning episodes suggests that this priming may be involved in behaviorally induced synaptic plasticity.

Animals↗
PubMed1986

Patterned stimulation at the theta frequency is optimal for the induction of hippocampal long-term potentiation.

Short, high frequency stimulation bursts (4 pulses at 100 Hz) were applied to Schaffer/commissural projections to the CA1 field of rat hippocampal slices at 0.1, 0.2, 1.0 or 2.0-s intervals to assess their efficacy in eliciting long-term potentiation (LTP). Bursts repeated at 2-s intervals induced very little LTP; shorter repetition intervals reliably elicited LTP, with the 200-ms repetition interval producing the greatest potentiation. A short-term potentiation effect, which was maximal 20 s after the last burst and decayed within 10 min, was affected differently by the stimulation parameters than was LTP, suggesting that the two phenomena are due to different processes. The results indicate that patterns of stimulation resembling spike discharge patterns of hippocampal neurons in animals in exploratory situations are effective in inducing LTP and suggest temporal constraints on the mechanisms involved in triggering synaptic plasticity.

Animals↗
PubMed1986

Hysterical paralysis in the upper extremity of chronic pain patients.

The patient with chronic pain who develops the conversion symptom of hysterical paralysis in the upper extremity can be treated successfully by rehabilitation medicine services, using a shaping behavioral program. Four case reports illustrate the management of this condition and the basic ingredients for such a program are outlined. The approach is based upon learning principles and experience with conversion reactions affecting gait. Treatment outcome often is related directly to the care and skill with which psychological assessment is performed and to the coordinated effort of the various team members.

Adult↗
PubMed1986

Episodic and residual thought pathology in chronic schizophrenics: effect of neuroleptics.

We sought to determine the effect of neuroleptic treatment on thought disorder in chronic schizophrenics, using the Thought Disorder Index (TDI). We were able to demonstrate that high levels of thought disorder are found in chronic schizophrenic and schizoaffective patients, while in both bipolar patients and normal controls thought pathology is minimal. Moreover, the TDI appears to be particularly well suited to the characterization of thought disorder in chronic schizophrenics. For total scores on the TDI, we were unable to demonstrate a significant reduction in thought pathology, although it was evident that thought disorder as reflected in the Conceptual Disorganization and Unusual Thought Content subscales of the Brief Psychiatric Rating Scale is significantly reduced by neuroleptics. In analyses of subscores of the TDI reflecting four levels of severity, we were able to show that more severe forms of thought pathology are normalized by neuroleptics, while less severe pathology is largely unaffected. Our results suggest that neuroleptic treatment reduces thought pathology associated with acute episodes, but that somewhat milder, though still disabling, residual thought pathology persists after clinical remission has been attained.

Adult↗
PubMedDate not supplied

Screening for Chlamydia trachomatis at a university health service.

Chlamydia trachomatis is the most common sexually transmitted infection in the United States. The aim of this study was to determine the prevalence of Chlamydia in college family planning patients and to identify diagnostic indicators associated with Chlamydia. A thorough history and physical examination was performed, including culture for gonorrhea, cancer (papanicolaou test), and Chlamydia trachomatis. Chlamydia occurred in 12.6% of 419 subjects. The lack of signs and symptoms and the possibility of inaccurate historical data limit the clinical predictability of chlamydial infections. Routine screening of college women is recommended.

Adolescent↗