Biomedical subjects

Xintian Hu

Publications and source records attributed to Xintian Hu.

6 recordsLinked to original sources

PubMed2006

Saccade initiation and the reliability of motor signals involved in the generation of saccadic eye movements.

We examined the trial-by-trial relationship between the metrics of saccadic eye movements and the activity of individual putative premotor neurons in the paramedian pontine reticular formation (PPRF) of rhesus monkeys. The region of the pons containing these excitatory burst neurons (EBNs) extends for several millimetres. Motoneurons innervating extraocular muscles integrate the output of hundreds or even thousands of these neurons. Accordingly, there was no reason to expect that relatively small variations in the activity of a single pontine neuron would be related to variations in saccade amplitude or speed observed during repetitive eye movements to the same target. Nonetheless, we observed consistent relationships between variations in the number of spikes in the burst of pontine neurons and the amplitude of the saccade. Trial-to-trial variations in the instantaneous spike frequency during a burst are associated with variations in the velocity profile of the movement. Based on these data, we conclude that the activity of pontine burst neurons is not statistically independent and that simultaneous recordings from multiple cells will reveal a high degree of correlated activity.

Action Potentials↗

PubMed2005

Gender effect on the right-left discrimination task in a sample of heroin-dependent patients.

RATIONALE: Discriminating right from left is an everyday cognitive ability. Repeated exposure to certain drugs, such as heroin, can produce poor performance on many cognitive tasks. However, it is yet unclear whether drug abuse impairs the ability of right-left discrimination. OBJECTIVES: The aim of the present study is to examine whether the spatial ability measured by the right-left discrimination task can be affected by heroin abuse and whether such drug effect, if it exists, is gender related. METHODS: A paper-and-pen test was used. The test consists of line drawings of a person with no arm, one arm, or both arms crossing the vertical body axis of the figure. The line drawings are viewed from the back, from the front, or randomly alternating between the back and front drawings. The subjects' task is to mark which is the right or left hand in the figure as fast as possible. RESULTS: A main finding in this study was that the ability to discriminate between left and right in visual space was impaired in heroin-dependent patients. Especially, heroin-dependent females performed poorer than control females in all conditions but heroin-dependent males only performed poorly in part of conditions. CONCLUSIONS: Recent heroin abuse impairs the ability of right-left discrimination and such impairment is gender related: heroin-dependent females demonstrated greater performance deficits than males.

Adult↗

PubMed2005

Effects of extremely low-frequency electromagnetic fields on morphine-induced conditioned place preferences in rats.

In the present study, we examined the effects of extremely low-frequency (ELF) electromagnetic fields on morphine-induced conditioned place preferences in rats. During the conditioning phase (12 days), three groups of rats were placed in a sensory cue-defined environment paired with morphine (10mg/kg, i.p.) following exposure to either 20 Hz (1.80 mT) or 50 Hz (2.20 mT) or sham electromagnetic fields for 60 min/day, respectively, and were placed in another sensory cue-defined environment paired with physiological saline (1 ml/kg, i.p.) without exposure to electromagnetic fields. After finishing 12 days of conditioning, preference tests for the morphine-paired place were performed during a 10-day withdrawal period. The exposure to electromagnetic fields substantially potentiated morphine-induced place preferences in rodents, suggesting that ELF electromagnetic fields can increase the propensity for morphine-induced conditioned behaviors.

Analgesics, Opioid↗

PubMed2005

EEG activities in the orbitofrontal cortex and dorsolateral prefrontal cortex during the development of morphine dependence, tolerance and withdrawal in rhesus monkeys.

Investigating the activities of the prefrontal cortex (PFC) in the process of addiction is valuable for understanding the neural mechanism underlying the impairments of the PFC after drug abuse. However, limited data are obtained from primate animals and few studies analyze Electroencephalogram (EEG) in the gamma band, which plays an important role in cognitive functions. In addition, it is yet unclear whether drug abuse affects the orbitofrontal cortex (OFC) and dorsolateral PFC (DLPFC)--the two most important subregions of the PFC--in similar ways or not. The aim of this study is to address these issues. We recorded EEG in the OFC and DLPFC in three rhesus monkeys. All animals received a course of saline (NaCl 0.9%, 2 ml) injection (5 days) followed by 10 days of morphine injection (every 12 h), and then a further series of saline injection (7 days). A main finding in the present study was that morphine decreased EEG power in all frequency bands in a short period after injection in both the OFC and DLPFC in monkeys. And gamma power decreased not just in a short period after morphine injection but lasted to 12 h after injection. Moreover, we found that although the changes in EEG activities in the OFC and DLPFC at 30-35 min after injection were similar, the DLPFC was more sensitive to the effect of morphine than the OFC.

Analysis of Variance↗

PubMed2005

Gender related effects of heroin abuse on the simple reaction time task.

Accumulated studies have demonstrated that there are serious negative consequences of drug abuse, especially the impairment of central nervous system (CNS) function. The simple reaction time (SRT) is the simplest model of measuring the function of the CNS. The purpose of the present study is to examine whether the SRT is affected by heroin abuse and whether such drug effect, if exists, is gender related. We found significant slowing of the SRT in both male and female heroin dependent patients at 1-3 months from withdrawal. However, the SRT slowing remitted after 3 months of abstinence in heroin dependent males but not in females. Our results suggested that the SRT is slowed by heroin abuse and such slowing is gender related.

Adult↗

PubMed2002

The clothing effect: tactile neurons in the precentral gyrus do not respond to the touch of the familiar primate chair.

Neurons in a restricted zone in the precentral gyrus of macaque monkeys respond to tactile, visual, and auditory stimuli. The tactile receptive fields of these multimodal cells are usually located on the face, arm, or upper torso. In the present study, in awake monkeys sitting in a primate chair, the neurons responded to a tactile probe touching the skin within the tactile receptive field. However, the same neurons did not respond when the tactile receptive field was touched by the primate chair, to which the monkey was habituated.

Animals↗