中国神经科学论坛

 找回密码
 注册

扫一扫,访问微社区

QQ登录

只需一步,快速开始

123
返回列表 发新帖
楼主: thinker_jeff

[讨论]科学试验揭开时间感知之谜了吗?

[复制链接]
 楼主| thinker_jeff 发表于 2006-3-14 01:18:00 | 显示全部楼层

The following report is related with the action time domain.fficeffice" />

控制运动速度的神经细胞

作者:不详 | 来源:Nature          文章录入:bioguider

像行走或游泳这样的复杂运动,是由嵌入在脊索中的神经细胞网络产生的。对小鼠所做的一项新的研究工作,首次发现了这样的一个亚组的神经细胞,它们控制运动的速度。将遗传和电生理方法独特地结合起来所做的一项研究工作显示,这些细胞何以能够帮助确定脊索神经细胞的有节奏的活动。研究神经失调问题的科学家,应当对这项工作感兴趣。有趣的是,服务于这一功能的V1神经细胞,是在游泳和行走的脊椎动物之间保留下来的。

石悲 发表于 2006-3-14 20:52:00 | 显示全部楼层

在神经科学领域,有一个值得注意的倾向,就是把一些微观世界的发现,轻率地解释为我们的心理现象的原因。本帖顶用神经细胞与客观时间的对应关系来宣布的所谓科学揭开时间感知之谜,就是其中一例。这实际上反映了研究者的哲学观的缺陷。所以这里强调时间的客观性与主观性的差异,并不为过。光的问题同样如此,只是本帖以讨论时间为主题。

神经细胞能控制运动速度,这是不容怀疑的,但这不是时间的感知问题,感知应该是对事物的运动过程有意识地察觉。两者在层次上有很大的差异。

神经细胞对时间的客观存在是有反应的,生物钟、对个体的运动的控制、直到宏观的对日夜和年月的感觉,都可以归于此类。这些反应,表现为我们的神经系统可以客观地反映我们周围世界的事物运动过程。当神经系统(神经元、网络或各功能结构之间的关系)的功能发生异常时,那这种反应就会表现为异常。目前的神经科学所揭示的大脑对时间的反应,主要就局限于这些方面(包括楼主所提到的一些例子)。

但是,大脑对时间的主观感知问题则复杂得多。同样的客观时间,不同的人却会有不同的感觉。经历了一个小时的时间,有人会感觉过得特别慢,象有二个小时的过程,有人却会感觉过得特别快,好象只是十几分钟的时间。这就是时间的主观性问题。解决这个问题,光是考虑几个神经细胞或结构的生理(及病理)过程是不够的。

如果楼主对这样的讨论不太喜欢。那就此打住吧。

 楼主| thinker_jeff 发表于 2006-3-15 00:33:00 | 显示全部楼层

The Pharmaceutical Journal
Vol 275 No 7376 p644
19 November 2005fficeffice" />

Interactions emerge between biological clocks

Biological clocks, or circadian rhythms, control behaviour and essential life processes, including eating, sleeping, seasonal migrations and cell proliferation. Some sort of time keeping is part of the fabric of life, and regulatory clocks vary over a wide range of dimensions, from the millisecond operations of neuronal activity to the seasonal changes shifting the amount of daylight during the year and prompting variations in our habits.

Timekeeping mechanisms have hitherto been considered in isolation, but unexpected interactions between clocks have emerged. These have been examined by Martha Gillette of ffice:smarttags" />Illinois and Terence Sejnowski of California in an article in Science for 19 August.

Interesting questions about why life processes are subject to biological clocks involve genetic, cellular and molecular considerations. One that has been broadly studied is that of mitosis, regulating the dynamic process of eukaryotic cell division. Cells of different types and sizes are governed by different amounts of time in different parts of their cycle. Key proteins, the cyclins, undergo phosphorylation, proteolysis and spatial targeting as they progress.

Yeast cells show reductive and oxidative phases of metabolism, their replication being restricted to the reductive phase. It is not known whether their cell division and metabolic cycles are linked. Associated metabolic and mitotic oscillations have been observed in human cell cultures, so there may be similarities between the respective clocks. Moreover, yeast shows a high frequency oscillation synchronised with respiration phases.

Cycles of cell division and metabolism also appear to be co-ordinated with the familiar circadian pacemaker, an innate timekeeping mechanism governing the activity over roughly 24-hour intervals in an organism’s lifetime. In mammals the circadian clock is controlled by the suprachiasmic nucleus of the brain. Treatment of cultured mammalian cells with haem synchronises gene expression in the circadian clock — further evidence that this and the metabolic states are coupled in some way.

The most familiar timing system in organisms is the daily cycle of sleep and wakefulness. Studies of human sleep patterns and performance indicate that the sleep-wake cycle is regulated by dual brain mechanisms, the drive to sleep, increased with time spent awake and restorative during rest, and the circadian process in the suprachiasmic nucleus of the brain, which organises sleep and wakefulness in relation to night and day. Other brain regions may track time spent awake and also effects of food restriction. It is loss and restoration of brain energy stores that govern sleep homoeostasis, something attributable to gene regulation. Intensity of light plays a part in the cycle in many organisms.

There is a need to concentrate on the interrelationships between the many cyclical processes found in organisms and their interaction across a wide range of temporal and spatial scales, since natural clocks do not function in isolation.

victorfsh 发表于 2006-3-21 11:10:00 | 显示全部楼层
生物鐘或者類似的節拍裝置在腦内甚至皮質水平存在似乎已经是一個事實了。時間無論是作爲個體内省的客體,還是學術研究的對象,也早已不需要爭論。從Kant到Descartes到Bergson,從Mach到James,從Newton到Einstein,这些争论早就摆在眼前了。但似乎都不影响我们对它的研究。
可泽 发表于 2006-4-4 11:32:00 | 显示全部楼层

“生物鐘或者類似的節拍裝置在腦内甚至皮質水平存在似乎已经是一個事實了。時間無論是作爲個體内省的客體,還是學術研究的對象,也早已不需要爭論。”

你认为生物钟与时间感有关系吗?

您需要登录后才可以回帖 登录 | 注册

本版积分规则

小黑屋|手机版|Archiver|生物行[生物导航网] ( 沪ICP备05001519号 )

GMT+8, 2024-3-28 20:28 , Processed in 0.087956 second(s), 14 queries .

Powered by Discuz! X3.4

© 2001-2023 Discuz! Team.

快速回复 返回顶部 返回列表