Biomedical subjects

Peter Lohmann

Publications and source records attributed to Peter Lohmann.

4 recordsLinked to original sources

PubMed2006

Hippocampal synaptic depression following spatial learning in a complex maze.

Activity-dependent alteration in synaptic efficacy is referred to as synaptic plasticity and is the believed hallmark of any learning process. Here we employed a recently validated complex maze for spatial training and investigated the impact of repeated and extensive training on basal synaptic transmission of the hippocampal Schaffer collateral-CA1 synaptic connection in vitro. In the present experiments, male CD-1 mice were trained in a complex maze for eight consecutive days five times a day. Subsequently, input-output functions of field excitatory postsynaptic potentials (fEPSPs) recorded in the CA1 area following stimulation of the Schaffer collateral-commissural fiber pathway were analyzed in acute hippocampal slices. We found a marked right shift of the fEPSP response in trained compared to untrained animals while fiber volley size remained unchanged. The findings provide evidence for a direct implication of homosynaptic hippocampal long-term depression in a spatial learning paradigm.

Animals↗

PubMed2006

The stamp of ancestry: roots of behavioral and neuronal impairment in adulthood.

Exposure of pregnant animals to noxious conditions affects neuronal function in the offspring. However, exposure or treatment of the maternal animal during pregnancy affects both ancestor and offspring. In the present study, female CD-1 mice were repetitively treated with 3-nitropropionate (3-np), a selective inhibitor of succinic dehydrogenase, exclusively prior to mating. Clinically, mice appeared normal during treatment. Five days after cessation of treatment animals were mated with control male animals. At 4 months of age spatial learning, LTP, NADH autofluorescence, and hypoxic tolerance were alike in controls and the offspring of treated female ancestors. However, an additional metabolic challenge in the offspring unmasks impairment of spatial learning, diminution of long-term potentiation (LTP), an altered protein microenvironment of mitochondrial enzymes, and reduced hypoxic tolerance. We conclude that the exposure of maternal ancestors to subclinical repetitive impairment of oxidative phosphorylation fosters impairment of behavior and neuronal function in the adult offspring, becoming apparent only on additional challenge. This finding may ultimately help to understand the causes of neuronal impairment or even neuropsychiatric disease in old age.

Age Factors↗

PubMed2006

Spatial navigation in complex and radial mazes in APP23 animals and neurotrophin signaling as a biological marker of early impairment.

Impairment of hippocampal function precedes frontal and parietal cortex impairment in human Alzheimer's disease (AD). Neurotrophins are critical for behavioral performance and neuronal survival in AD. We used complex and radial mazes to assess spatial orientation and learning in wild-type and B6-Tg(ThylAPP)23Sdz (APP23) animals, a transgenic mouse model of AD. We also assessed brain content of nerve growth factor (NGF), brain-derived neurotrophic factor (BDNF), and neurotrophin-3 (NT-3). Performance was alike in wild-type and APP23 animals in the radial maze. In contrast, performance in the complex maze was better in wild-type than APP23 animals. Contrary to the wild-type, hippocampal BDNF levels decreased on training in APP23 animals. Hippocampal and frontal cortex NGF levels in APP23 animals correlated with the time to solve the complex maze, but correlated inversely with escape time in wild-type animals. NT-3 levels were alike in wild-type and APP23 animals and were unchanged even after training. Both types of mazes depend on hippocampal integrity to some extent. However, according to the cognitive mapping theory of spatial learning, the complex maze because of the increased complexity of the environment most likely depends more strongly on preserved hippocampal function than the radial maze in the working memory configuration applied here. Greater impairment in complex maze performance than in radial maze performance thus resembles the predominant affliction of the loss of hippocampal function in human AD. NGF and BDNF levels on maze learning are different in wild-type and transgenic animals, indicating that biological markers of AD may be altered on challenge even though equilibrium levels are alike.

Amyloid beta-Protein Precursor↗

PubMed2004

Keeping it short: a comparison of methods for brief picture presentation.

Research has shown that backward masking is a powerful tool for studying unconscious mental processes. Whereas studies have traditionally presented stimuli using cathode-ray tube (CRT) monitors or mechanical shutters together with slide projectors, recent studies (mainly in functional magnetic resonance imaging, fMRI) have begun to use methods based on liquid crystal displays (LCDs) and thin-film transistor (TFT) technology. However, because of differences in technology, all methods may not be equally suited for masking. When methods were compared for their accuracy in presenting pictures at short durations, LCD and TFT presentations had poor accuracy, but shutter and CRT presentations had better accuracy. Because CRTs interfere with the imaging process in fMRI, we recommend the use of mechanical shutters. However, our results may not generally apply to all displays, so we advise researchers to validate the presentation parameters of their displays. The procedure described here may be useful for that purpose.

Consciousness↗