Search results for "Potentials"
showing 10 items of 1072 documents
Effects of an Earth-strength magnetic field on electrical activity of pineal cells
1980
Although magnetic fields can influence biological systems, including those of man and other vertebrates1–5, no central nervous structure has been identified that might be involved in their detection. From a theoretical point of view, the pineal organ might be such a structure for the following reasons: (1) It is involved in the regulation of circadian rhythms6 and is thus essential for migratory restlessness (‘Zugunruhe’)7. Orientation at that time can be altered by an artificial magnetic field (MF) with a direction differing by 90° from that of the Earth. Circadian rhythms can be inhibited from phase shifting by compensation of the Earth's MF and can be influenced by an artificial MF8. (2)…
Auditory event-related potentials in subcortical vascular cognitive impairment and in Alzheimer's disease.
2006
Few studies exist on ERPs and patients with subcortical vascular cognitive impairment (SVCI). This latter is a quite homogeneous subtype of vascular dementia whose cognitive profile is quite different from that of Alzheimer disease (AD).The present study aims at comparing the ERPs profile both in patients with SVCI and in patients with AD.ERPs and psychometric tests were collected from 39 healthy elderly controls, 51 patients with SVCI and 43 patients with AD. Subjects mentally count high pitched target tones that were randomly intermixed with low pitched frequent tones. We measured ERPs latencies (N1, P2, N2 and P3), and interpeak latencies (N1-P3, N1-P2, N1-N2).Grand averaged potentials i…
Auditory event-related potentials at preschool age in children born very preterm.
2014
Abstract Objective To assess auditory event-related potentials at preschool age in children born very preterm (VP, 27.4±1.9 gestational weeks, n =70) with a high risk of cognitive dysfunction. Methods We used an oddball paradigm consisting of a standard tone randomly replaced by one of three infrequent deviants (differing in frequency, sound direction or duration). Results The P1 and N2 latencies were inversely correlated to age (50–63months) both in VP ( r =−0.451, p r =−0.305, p= 0.01, respectively) and term born controls (TC; n =15). VP children had smaller P1 than near-term ( n =12) or TC (1.70±0.17μV vs 2.68±0.41 and 2.92±0.43, respectively; p Conclusions Our data suggest a fast matura…
Motor intracortical inhibition in PD: L-DOPA modulation of high-frequency rTMS effects
2007
Dopaminergic drugs and deep brain stimulation restore cortical inhibition in Parkinson disease (PD) patients. High-frequency rTMS was also found to increase cortical inhibition in PD but its therapeutic effect is still controversial. Here we hypothesize that, if dopaminergic drugs reverse to normal cortical excitability in M1, the effect of high-frequency (hf)-rTMS in PD patients could depend on whether they are in a medicated or unmedicated state. The present study aims to explore the lasting effects of sub-threshold hf rTMS trains over M1 on cortical inhibition in patients with "on" and without "off" L-DOPA treatment. Fourteen PD patients were examined twice while "on" and "off" medicatio…
Habituation or lack of habituation: What is really lacking in migraine?
2015
Migraine is very prevalent disease with consistent disability and socioeconomic burden (Lipton et al., 2007). Despite intensive research effort, particularly in last decades, allowing significant insight in many aspects of the disease, its precise pathophysiological bases remain still to be defined. One influential view suggests that dysfunctions in sensory information processing could play a critical role (de Tommaso et al., 2014). In this frame a relevant phenomenological marker is considered the inability of migraine patients to habituate to repeated sensory stimulation.
Considerable deficits in the detection performance of the cat after lesion of the suprasylvian visual cortex
1989
The ability of two cats to discriminate between two geometrical outline patterns in the presence of superimposed structured background was tested before and after bilateral removal of the lateral suprasylvian visual areas (PMLS, PLLS, AMLS, ALLS, part of area 7). There were mild deficits when patterns and background were kept stationary; these deficits may be due to a partial undercutting of areas 17, 18 and 19. However, there was a severe impairment in performance when the patterns were moving on a stationary background which may be due to loss of the suprasylvian visual areas. Movement of the background relative to the figure resulted in an intermediate detection deficit.
Cardiac effects of isoliquiritigenin
1997
The effects of isoliquiritigenin on force of contraction (Fc), L-type Ca2+ current (I(Ca)) and intracellular Ca2+ concentration ([Ca2+]i) were investigated in rat ventricular heart muscle. Isoliquiritigenin increased Fc and I(Ca) and, after longer exposure times, resting tension and [Ca2+]i. The effect of isoliquiritigenin (100 microM) on I(Ca) was diminished by Rp-cAMPS (30 microM). 1H-[1,2,4]oxa- diazolo[4,3-a]quinoxalin-1-one (50 microM) did not influence the effects of isoliquiritigenin on Fc and I(Ca). The positive inotropic effects of isoprenaline and forskolin, but not of 3-isobutyl-1-methylxanthine, were potentiated by isoliquiritigenin (100 microM). In the presence of milrinone (10…
Inhibition by Fendiline of the Transient Outward Current in Rat Ventricular Cardiomyocytes
1999
The effects of fendiline on the transient outward current (Ito) were investigated in rat ventricular cardiomyocytes. Extracellularly applied fendiline reduced peak and steady-state current amplitude of Ito; the inactivation of Ito was accelerated by the drug, which reflects onset of block. The described effects were concentration dependent: half-maximal effects were achieved at approximately 3 microM fendiline. Intracellularly applied fendiline (3 microM) did not affect Ito within 5 min. The steady-state current amplitude of Ito was more efficiently suppressed by the drug at 22 +/- 1 degrees C than at 36 +/- 1 degrees C. The recovery of Ito was analyzed by the application of twin depolarizi…
Mechanism of Block by 4-Aminopyridine of the Transient Outward Current in Rat Ventricular Cardiomyocytes
1998
The effects of 4-aminopyridine (4-AP) on the transient outward current (I to ) were investigated in rat ventricular cardiomyocytes at different values of intracellular pH (pH i ) and extracellular pH (pH o ). The 4-AP was administered either extracellularly (bath application) or intracellularly (diffusion from the intrapipette solution). The 4-AP diminished I to given either from inside or outside the cell membrane. The block by extracellularly applied 4-AP (4-AP o ) of the peak amplitude of I to was decreased by external acidification but increased by external alkalinization: conversely. the block by 4-AP o was decreased by internal alkalinization but increased by internal acidification. I…
Effects of Cortical Spreading Depression on Cortical Blood Flow, Impedance, DC Potential, and Infarct Size in a Rat Venous Infarct Model
2000
A cortical venous infarction model has been evaluated as to the degree of regional flow reduction and by studying effects of cortical spreading depression (CSD). Two adjacent cortical veins were occluded photochemically with rose bengal and fiberoptic illumination. Seven rats served to demonstrate effects on regional cortical blood flow using laser Doppler scanning. In 36 rats local CBF, DC potential, and brain tissue impedance were measured continuously for 75 min after vein occlusion. No, 3, or 10 CSD waves were induced by potassium chloride injection during the initial 75 min. Rats were compared for spontaneous CSDs; baseline local CBF, CBF, and impedance response to CSD; and infarct vol…