Interneuronal synchrony in precentral cortex of monkeys during operant conditioning

One hundred thirty-three pairs of precentral neurons were recorded simultaneously from four Macaca mulatta monkeys during participation in an operant conditioning paradigm that required one of the two units to be fired tonically within a 30- to 60-ms interspike interval (ISI) range. At the end of each 5-min behavioral period, a correlation between the two units' firing rate fluctuations was computed. These correlations were used as a measure of synchrony between units. For the majority of unit pairs, the unit for which reinforcement was contingent upon could be controlled independently from the activity of the simultaneously recorded unit. In 75% of experiments the synchrony between units decreased during the operant periods in comparison to the time-out periods. In only 5% of the experiments did unit pairs consistently exhibit increased synchrony during operant periods compared with time-out periods. If the monkey developed EEG signs of drowsiness during time-out periods, the synchrony between units became greater.     

Effects of 4-aminopyridine on rapidly and slowly conducting axons of rat corpus callosum

The action potentials of some normal mammalian peripheral myelinated and non-myelinated nerve fibers are known to differ with respect to the role of voltage-dependent potassium currents in membrane repolarization. Because comparable differences have not been fully established for mammalian cerebral axons, the present work examined the influence of the potassium blocker, 4-aminopyridine (4-AP), on field potentials in the rat corpus callosum. Three successive negative waves could be detected in field potentials obtained with recording electrodes positioned several millimeters from the site of callosal stimulation. Spatial and functional properties of these field components indicated that the two shorter-latency waves were due to activity in callosal fibers. Furthermore, the discontinuity of the first and second waves, not only with respect to latency but also in pattern of recruitment and in refractoriness, suggested that they largely reflected activity in respective myelinated and nonmyelinated groups of callosal fibers. When 4-AP was injected into the callosum, or superfused onto surgically exposed callosal fibers, the duration and amplitude of the second negative wave were markedly increased. The first negative wave either was not affected or was reduced in amplitude by 4-AP application. This contrasting effect was identical to that known to distinguish normal myelinated and nonmyelinated mammalian peripheral nerve fibers and provided some evidence suggesting that mammalian cerebral axons have a functional organization similar to that of peripheral fibers.     

Deficient inhibition of return in chronic but not first-episode patients with schizophrenia

Background

Inhibition of return (IOR) has been tested in patients with schizophrenia with contradictory results. Some studies indicated that patients with schizophrenia have normal levels of IOR; however, other studies reported delayed or blunted IOR. Inconsistency in findings might be due to differences across studies in relevant aspects associated with disease, such as heterogeneity of the disorder, different medications, onset and severity of the illness. The present study was to explore different patterns of IOR in antipsychotic medication free first-episode schizophrenia and chronic schizophrenia.

Methods

Forty two patients with first-episode schizophrenia, 44 patients with chronic schizophrenia, and 38 healthy controls were included in the study. All subjects went through a covert orienting of attention task with seven stimulus onset asynchrony (SOA) intervals (400 ms, 500 ms, 600 ms, 700 ms, 800 ms, 1200 ms and 1500 ms).

Results

Compared with healthy controls, the magnitude and onset of IOR in first-episode patients with schizophrenia were intact. However, in patients with chronic schizophrenia, there was an attenuated cuing effect especially at SOA 700 ms; in addition, there was a robust IOR until at SOAs 800 ms or above. Moreover, the illness duration and the number of psychotic episodes were significantly correlated with the validity effect at SOAs 400 ms and 600 ms.

Conclusion

Our study suggests that deficient IOR presents in chronic but not in first-episode patients with schizophrenia. IOR deficit in schizophrenia may begin during the course of illness and deteriorate over the course of illness. Our findings are consistent with the neurodegenerative model of schizophrenia.     

Short-term plasticity in excitatory synapses of the rat medial preoptic nucleus

The medial preoptic nucleus (MPN) regulates sexual behavior which is subject to experience-dependent modifications. Such modifications must depend on functional plasticity in the controlling neural circuits. Thus, MPN synapses are likely candidates for the site of alterations. The present work is a first systematic study of functional synaptic plasticity at glutamatergic synapses in the MPN. Short-term activity-dependent plasticity was investigated using a slice preparation from young male rats. The average efficacy of AMPA/kainate-receptor-mediated synaptic transmission was activity-dependent, showing a peak at a steady stimulation rate of 2 Hz. The variation in efficacy was attributed to mainly presynaptic factors since the average response amplitude was roughly paralleled by the response probability. Upon paired-pulse stimulation, paired-pulse facilitation as well as paired-pulse depression was observed. In some cases, paired-pulse facilitation as well as paired-pulse depression was recorded from an individual neuron depending on the interval between the paired stimuli. On average, paired-pulse facilitation was observed at intervals <500 ms, and paired-pulse depression at intervals in the range 1-4 s. The findings thus reveal complex activity-dependent short-term plasticity of the functional synaptic properties in the medial preoptic nucleus.     

Neural correlates of within-level and across-level attention to multiple compound stimuli

Event-related potentials (ERPs) were recorded to investigate the neural mechanisms of attention to the same or different levels of two compound letters presented concurrently in the left and right visual fields, respectively. Relative to the condition when attention was allocated to the global level of one compound stimulus and the local level of another one (across-level attention), attention to the same level of the two compound stimuli (within-level attention) increased an early positivity between 100 and 140 ms (P1) over the occipito-parietal cortex. A long-latency positivity between 320 and 560 ms (P3) over the central-parietal area was also increased in the within-level relative to across-level attention conditions. The ERP results suggest that, relative to across-level attention, within-level attention to multiple compound stimuli facilitates both early sensory-perceptual processing and late process of stimulus evaluation and identification in hierarchical analysis.     

A model-based analysis of physiological properties of the striatal medium spiny neuron

As the principal cell of the striatum, medium spiny neurons (MSNs) are closely associated with various motor dysfunctional diseases. In this paper, we describe an electric compartment model constructed in NEURON with a realistic morphology. Based on a 554-compartment computational model, we researched the influence of external current stimuli, different ions conductance, and the removal of partial dendrites on the physiological properties of the MSN. The main results are the following: (1) in the case of external current stimuli, various firing patterns appear in the MSN and the model produces a clear period-adding bifurcation phenomenon; (2) the effect of distinct types of ion channels vary and significant differences in discharge rhythm exist even among ion channels of the same type; (3) the closer the removed dendrite was to the soma, the larger the impact this had on the discharge pattern of the MSN.     

急性脑梗死血瘀证与活化血小板、胰岛素抵抗的相关性研究

目的研究活化血小板、胰岛素抵抗与急性脑梗死血瘀证的关系。方法应用CT/MRI、流式细胞仪对30例急行脑梗死患者和30例健康人进行检测与对比分析。30例急性脑梗死患者中血瘀证13例,非血瘀证17例。结果与对照组比较,脑梗死组活化血小板（CD62p、CD63）、空腹血糖（FPG）、空腹胰岛素（FINS）、胰岛素敏感指数（ISI）存在统计学差异（P〈0.05或P〈0.01）。直线相关分析表明：CD62p与ISI呈明显正相关（r=0.443,P〈0.05）。脑梗死血瘀证组FPG、FINS、ISI、CD62p、CD63水平较对照组、脑梗死非血瘀证组明显升高,差异有统计学意义（P〈0.05或P〈0.01）。结论急性脑梗死血瘀证患者存在着明显血小板活化及胰岛素抵抗的异常,CD62p、CD63、胰岛素敏感指数可能是血瘀证微观辨证的指标之一。     

Reliability of point-of-care prothrombin time testing in a community clinic: a randomized crossover comparison with hospital laboratory testing

The success in achieving therapeutic international normalized ratio (INR) targets in the control of warfarin using a whole-blood point-of-care testing (POCT) monitor (CoaguChek) in a community clinic was compared with hospital laboratory coagulometer prothrombin time (PT) testing in a randomized crossover study. Forty-six patients were randomized into two groups. At each visit, capillary blood was taken for the POCT monitor and venous blood for the laboratory coagulometer. In Group 1, for 6 months, dosage was based on the CoaguChek and for the second 6 months on the coagulometer. In the second group, the order was reversed. Dosages were determined using the dawn ac computer programme. Success was assessed by the percentage of time patients were maintained within the INR targets. Agreement between laboratory and monitor INR, and patient satisfaction were also assessed. Results with the POCT monitor compared well with the hospital coagulometer. Time in INR target range between the groups was similar, with 60.9% on the POCT monitor and 59.3% with the laboratory coagulometer in Group 1 and in Group 2, respectively, 64.3% and 63.4% with no significant difference in mean INR. An INR above 4.0 gave some discrepant results. International Sensitivity Index calibrations of the two test systems indicated that the INRs were dependable. Patient questionnaires showed greater satisfaction with community POCT monitoring.