Haptic localization and the internal representation of the hand in space

As the hand actively explores the environment, contact with an object leads to neuronal activity in the topographic maps of somatosensory cortex. However, the brain must combine this somatotopically encoded tactile information with an internal representation of the hand's location in space if it is to determine the position of the object in three-dimensional space (3-D haptic localization). To investigate the fidelity of this internal representation in human subjects, a small tactual stimulator, light enough to be worn on the subject's hand, was used to present a brief mechanical pulse (6-ms duration) to the right index finger before, during, or after a fast, visually evoked movement of the right hand. In experiment 1, subjects responded by pointing to the perceived location of the mechanical stimulus in 3-D space. Stimuli presented shortly before or during the visually evoked movement were systematically mislocalized, with the reported location of the stimulus approximately equal to the location occupied by the hand 90 ms after stimulus onset. This pattern of errors indicates a representation of the movement that fails to account for the change in the hand's location during somatosensory delays and, in some subjects, inaccurately depicts the velocity of the actual movement. In experiment 2, subjects were instructed to verbally indicate the perceived temporal relationship of the stimulus and the visually evoked movement (i.e., by reporting whether the stimulus was presented before, during, or after the movement). On average, stimuli presented in the 38-ms period before movement onset were more likely to be perceived as having occurred during rather than before the movement. Similarly, stimuli in the 145-ms period before movement termination were more likely to be perceived as having occurred after rather than during the movement. The analogous findings of experiments 1 and 2 indicate that the same inaccurate representation of dynamic hand position is used to both localize tactual stimuli in 3-D space and construct the perception of arm movement.     

Some problems and some solutions in research on psychotherapeutic intervention in cancer

Several requirements of psychotherapeutic intervention (PI) research are presented. Some major problems are discussed. First, confidence in experimental results may be diminished by interference of possible confounders. A large number of these exist, both physical, perhaps more easily measurable, and psychological or psychosocial. Second, the value and limitations of randomization are presented, with special reference to small N. Validity and reliability are addressed, with emphasis on things that may dilute the strength of both of these measures. Natural remedies are proposed. Internal consistency and reliability are compared and cautions are given regarding their use and possible invalid substitution of consistency for reliability. Comparison of different PIs is commented on, with some relevant examples. Finally, a matter of special interest is discussed: the inconsistency between Spiegel's control survival curve and that produced from local population normative data.Presented at the Symposium Psychotherapeutic Interventions in Cancer Patients, Flims, Switzerland, 12–14 January 1995     

Spatial and temporal variations in the magnetic fields produced by human gastrointestinal activity

Magnetoenterography (MENG) is a new, non-invasive technique that measures gastrointestinal magnetic signals near the body surface. This study was undertaken to evaluate the temporal and spatial characteristics of the magnetic signals generated by gastric and duodenal slow wave activity. The gastrointestinal magnetic fields of eight normal subjects were measured for 60 minutes in both the fasting and fed state using 36 magnetic sensors simultaneously. The results were displayed as a succession of maps over time showing the temporal evolution of the spatial distribution of the signal over the upper abdomen. In all subjects, slow wave activity of the stomach centred at 3.0 +/- 0.5 cycles min-1 in both the fasting and fed state was observed. The duodenal signal at 11.0 +/- 1.0 cycles min-1 was observed in four subjects. The spatial distribution of these two signals is distinctly different. The observed spatial and temporal variations are described in terms of a model used previously to explain the potentials observed in electrogastrography (EGG).     

老年学习记忆减退大鼠空间参考记忆和工作记忆能力的改变

目的　探讨老年学习记忆损害鼠空间学习记忆能力的改变特征。方法　用改良Morris 水迷宫检测40 只老年SD 大鼠(24m) 的空间学习记忆能力,按通用标准将其分为老年学习记忆减退组和老年学习记忆正常组,与青年组对照,检测其空间参考记忆和空间工作记忆能力。结果　老年学习记忆损害大鼠的行为学改变特征为:1) 简单学习记忆任务的学习能力没有明显变化。2) 空间参考记忆能力明显减退,寻找平台所用的游泳时间(ST) ,40cm 环内游泳时间(A40T) 和平台跨越次数(PC) 是反映老年学习记忆害大鼠空间参考记忆能力的理想指标。3) 空间工作记忆能力减退不明显。结论　A40T,PC 是反映空间参考记忆能力的敏感指标,ST 结合A40T 可筛选出理想的老年学习记忆减退动物模型。     

Early postnatal treatment with peptide preparations influences spatial navigation of young and adult rats

The brain derived peptidergic drug Cerebrolysin has been found to support the survival of neurons in vitro and in vivo. Positive effects on learning and memory have been demonstrated in various animal models and also in clinical trials. In the present study the effects of early postnatal administration of Cerebrolysin (Cere, 10 mg/ml peptides) or an enriched peptide fraction of Cere (E021, 80.6 mg/ml peptides) were investigated in young, young adult, and old adult rats. Rat pups received the drugs or saline for control on postnatal days 1–7. The animals were tested in the Morris water maze (MWM) either in the 5th week, in the 3rd or the 16th month of life for 6 consecutive days (test days 1–6), eight trials per day. In order to prevent the chance finding of the hidden platform, the rigid underwater platform was replaced by a collapsible island, resting at the bottom of the pool. The platform was raised when the animal stayed in the target area for 2 s. In the young and young adult rats both Cere and E021 treated rats showed shorter escape latencies than saline treated controls on all 6 test days. No significant differences in the swimming speed were evaluated for the young rats, although in 3-month-old drug-tested animals a moderate increase of the swimming speed was investigated. For 16-month-old animals no significant differences in either escape latencies or swimming speed was found. Summarizing, early postnatal application of Cere or E021 improved the spatial learning and memory of young rats and led to long-lasting behavioural effects at least up to 3 months after treatment.     

不同发育期铅暴露对大鼠空间认知能力的影响

用不同发育期大鼠的接铅史来探讨铅暴露的敏感期及铅对年轻大鼠空间认知能力的影响。结果发现,生前和生后持续接铅的染毒１组和经母体间接接铅的染毒３组,两者Ｍｏｒｉｓ水迷宫的测试成绩均显著低于对照组,而断乳后接铅的染毒２组,虽然血铅水平显著增高,但脑铅水平和水迷宫测试成绩却与对照组无差别,提示在神经发育早期（胎儿期和婴儿期）对铅更敏感。     

MK-801 neurotoxicity in male mice: histologic effects and chronic impairment in spatial learning

Several histological and behavioral experiments were conducted to investigate the neurotoxic effects of MK-801 in male mice. Moderate subcutaneous (s.c.) doses of MK-801 (0.5 and 1.0 mg/kg) induced the formation of intracytoplasmic vacuoles in pyramidal neurons in layers III and IV of the posterior cingulate/retrosplenial (PC/RS) cortex in 50% and 100% of the mice from the two respective treatment groups. Electron microscopic analysis of the vacuoles indicated that mitochondria and endoplasmic reticulum are the cellular organelles most prominently involved in this pathomorphological change. Treating mice with a high systemic dose of MK-801 (10 mg/kg s.c. or intraperitoneal (i.p.)) caused selective, irreversible degeneration of a small number of PC/RS cortical neurons. Compared to saline controls, the acquisition performance of mice treated i.p. with 10 mg/kg MK-801 was chronically impaired on a spatial learning task (modified hole board food search task) when tested at several posttreatment intervals (up to at least 5 months), although the groups did not differ on activity or sensorimotor tests conducted 2 weeks posttreatment. In summary, MK-801 caused histopathological changes in the mouse brain similar to those observed in the rat. Furthermore, high dose MK-801 treatment that killed a small number of mouse PC/RS cortical neurons resulted in a chronic acquisition impairment in spatial learning, an effect not previously demonstrated in any species.     

Scopolamine Effects on Visual Information Processing, Attention, and Event-Related Potential Map Latencies

We measured performance and event-related brain potential (ERP) map latencies in 12 subjects during four visual discrimination tasks to compare the timing of scopolamine effects on information processing and attention. "Topographic component recognition" found ERP map latencies at times of best fit with a component model map. This "common topography" criterion minimized topographic differences among conditions to facilitate latency interpretations. Scopolamine slowed N1 latency in all tasks, and P3 and reaction time in some tasks. The drug delayed responses to easy targets more than to hard targets. It also induced a disproportionate N1 delay for unilateral high spatial frequency gratings. Both effects reflect a scopolamine-induced impairment when processing targets that usually capture attention. Scopolamine also impaired accuracy for unilateral high spatial frequency gratings, and for gratings presented at probable locations, confirming and extending previous findings. Scopolamine-induced P1 and N1 delays showed that visual processing was affected. Several results were inconsistent with a serial stage model. We suggest that scopolamine both delays selected processes and impairs a processing mode based on automatic capture of attention, inducing more serial processing.     

Phospholipid composition and levels are altered in Down syndrome brain

Individuals chronically exposed to low levels of organophosphate insecticides may present with subtle impairments in cognition. In addition, low level diisopropylflurophosphate (DFP) exposure (0.25 mg/kg per day for 2 weeks) in rats resulted in protracted working memory impairment [29]. The current studies attempt to show a temporal relationship between the DFP-induced impairment in performance of a spatial memory task and the protracted decrease in the expression of cholinergic receptors and acetylcholinesterase in specific brain regions. Cholinergic receptors labeled with the ligands [(3)H]epibatidine and [(3)H]AFDX-384 were affected to a much greater extent and for a longer period of time than were both acetylcholinesterase activities and cholinergic receptors labeled with [(3)H]QNB. Pre-testing administration of nicotine was shown to completely reverse this DFP-induced impairment in memory-related task performance. Additionally, prophylaxis with pyridostigmine bromide (PB) caused DFP-treated animals to exhibit near normal levels of memory-related task performance. These results are consistent with the development of a protracted phase of learning impairment to sub-acute DFP exposure, which may involve the loss of hippocampal nicotinic receptors, and may be prevented or reversed by PB or nicotine, respectively.     

Effects of ethanol on hippocampal place-cell and interneuron activity

Mounting evidence suggests that ethanol exerts effects on learning and memory by altering cellular activity in the hippocampus and related structures. However, little is actually known regarding ethanol's effects on hippocampal function in awake, freely-behaving animals. The present study examines the effects of ethanol on hippocampal place-cell and interneuron activity in freely-behaving rats. Signals from individual hippocampal neurons were isolated while subjects traversed a symmetric Y-maze for food reward. Following 15 min of baseline recording, subjects were injected with one of four doses of ethanol (0.0, 0.5, 1.0 and 1.5 g/kg), and cellular activity was monitored for a 1-h time period. Following sufficient time for recovery (minimum of 3 h post injection), cellular activity was monitored for an additional 15-min period. Both 1.0 and 1.5 g/kg ethanol potently suppressed the firing of hippocampal place-cells without altering place-field locations. Ethanol did not significantly suppress out-of-field firing rates, leading to a decrease in spatial specificity (i.e. the ratio of in-field/out-of-field firing rates). Interneuron activity was not altered by 1.0 g/kg ethanol, but was occasionally suppressed by 1.5 g/kg ethanol. Results are interpreted in light of recent behavioral and electrophysiological studies examining the effects of ethanol on hippocampal function.