中年失忆不必担心?


  【24drs.com】一篇新的影像学研究认为,中年失忆反映的可能是脑部在形成记忆和检索记忆时的某种信息类型转变,而不是认知功能下降。
  
  加拿大蒙特娄McGill大学Douglas脑部影像中心研究人员发现,记忆任务中,青壮年的视觉皮层活化比中老年人增加;相对的,中老年人的前额叶皮层比较活化。
  
  主要研究者、Douglas脑部影像中心主任Natasha Rajah博士表示,当你首次遇见某人,年轻人会注意在何时何地遇到这个人,他们可以记住这个信息。
  
  Rajah博士指出,但是,中老年人会比较注意他们遇到的人的社会情感关联─他们愉快吗,他们是否提到他们认识的其它人等等─有关注意的重点上的这个差异,对他们记住更多客观特征造成负面影响。
  
  这篇研究在线发表于6月12日NeuroImage期刊。
  
  众多研究显示,与失智有关的脑部变化在症状发生的几十年前就开始,因此,当前记忆研究的一个关键问题是,关注哪里些变化是正常的,哪里些不是。
  
  Rajah博士在一份新闻稿中表示,我们对健康老化之中年人的改变、这些改变对老年生活的关联所知有限,我们的研究目标即是在于解决这个议题。
  
  此次研究,研究人员共招募了112名19-76岁成人,这些研究对象没有神经或心理疾病史,也没有阿兹海默氏症家族史。
  
  共两次测试,第一次时,参与者完成了多个神经心理学评估,包括迷你国际神经精神会谈工具以及贝克忧郁量表。接著,参与者在一系列的实验性操作期间进行功能性MRI (fMRI),他们在这些操作时必须编码和检索脸部的空间和时间详情。
  
  在检索时,参与者被要求回忆某一特定的脸部出现在屏幕上的位置─左或右─或它何时出现—最近一次或近期最少。接著用fMRI扫描分析以确认,在回忆脸部详情时,脑中的哪里个区域被活化。
  
  fMRI扫描的分析发现,当年轻人完成回忆任务时,他们的视觉皮层被活化。
  
  Rajah博士表示,这表示,青壮年真正注意使他们决定的感性细节。
  
  当进行相同的回忆任务时,中老年研究对象并没有相同程度的视觉皮层活化,而是在编码时,内侧前额叶皮质有较多的活动;检索时,海马旁皮质较多活动,这些区域涉及处理与反思活动更相关的讯息。
  
  Rajah博士表示,换句话说,青壮年和年长者在空间与时间处理上的差异,可能反映出不同年龄层的成年人在判断哪里些是重要信息上的差异。
  
  这种解释获得一个事实支持,编码任务过程中,参与者被要求,不仅要以客观的方式进行外部信息编码,还要记住这些脸孔出现时是愉悦的还是中性的。
  
  Rajah博士表示,我们认为,中年人和老年人可能比较会涉及作出愉悦感之判断,这些判断可能会在记忆任务中业已拟定,即使我们明确指示参与者,记忆任务只和脸部的空间与时间关联信息有关。
  
  Rajah博士也认为,透过学习更专注于过程中出现的外部客观信息,年长者也许可以提高他们的回忆能力。
  
  例如,曾有文献提出,正念可改善认知功能,因为它教人活在当下且顾及经验的客观性质,而非反覆思考与局限于自己的内心。
  
  现在,需要一篇纵向研究,以确认中年和老年人的大脑编码和检索回忆观察到的差异,是否反映脑部功能衰退,或是反映年长者在任何经验类型的注意重点。
  
  资料来源:http://www.24drs.com/
  
  Native link:Midlife Memory Lapses No Cause for Concern?

Midlife Memory Lapses No Cause for Concern?

By Pam Harrison
Medscape Medical News

Midlife memory lapses may reflect a shift in the type of information the brain focuses on during memory formation and retrieval, rather than a decline in cognitive function, a new imaging study suggests.

Investigators at Douglas Brain Imaging Centre, McGill University, Montreal, Canada, found that during a memory task, activation of the visual cortex was increased in young adults in comparison with middle-aged and older adults.

In contrast, in middle-aged and older adults, activation was greater in the prefrontal cortex.

"When you meet someone for the first time, it is likely that young adults are paying attention to where and when they met this person, and they can remember this information," principal investigator Natasha Rajah, PhD, director, Douglas Brain Imaging Centre, told Medscape Medical News.

"But middle-aged and older adults focus more on the social-emotional relevance of the person they met ─ were they pleasant, whether they reminded them of other people they know, and so on ─ and this change in focus negatively impacts their ability to remember more objective features," Dr Rajah added.

The study was published online June 12 in NeuroImage.

What's Normal, What's Not?

Numerous studies have shown that brain changes associated with dementia begin decades before the onset of symptoms. Therefore, a key question in current memory research concerns which changes are normal and which are not.

"We know little about what happens at midlife in healthy aging and how this relates to findings in late life. Our research was aimed at addressing this issue," Dr Rajah said in a release.

For the study, investigators recruited 112 adults aged 19 to 76 years. The participants had no history of neurologic or psychological illness, nor did they have a family history of Alzheimer's disease.

During the first of two test sessions, participants completed multiple neuropsychological assessments, including the Mini-International Neuropsychiatric Interview and the Beck Depression Inventory.

Participants then underwent functional MRI (fMRI) during a series of experimental runs in which they had to encode and retrieve spatial and temporal details of faces.

During retrieval, participants were asked to recall where a particular face appeared on a screen ─ left or right ─ or when it appeared — most recently or least recently. fMRI scans were then analyzed to identify which areas of the brain were activated during recall of facial details.

Analyses of the fMRI scans revealed that the visual cortex was activated in young adults as they completed the recall task.

"This suggests that young adults are really paying attention to perceptual details to make their decisions," said Dr Rajah.

Mindfulness May Help

Middle-aged and older participants did not exhibit the same level of visual cortex activation when engaged in the same recall task but rather showed more activity in the medial prefrontal cortex during encoding and in the parahippocampal cortex during retrieval. These regions are involved in processing information that has more to do with introspective activity.

In other words, the differences in spatial and temporal processing observed between young adults and older participants may reflect a difference in what adults judge to be important information as they age, said Dr Rajah.

This interpretation is supported by the fact that during the encoding task, participants were asked not only to encode external information in an objective way but also to register whether the face being presented was pleasant or neutral.

"We think middle-aged and older adults may be more engaged in making 'pleasantness' judgments, and these judgments may have been elaborated upon during the memory task, even though we explicitly instructed participants that the memory task was only about spatial and temporal contextual information of the faces," said Dr Rajah.

Dr Rajah also suggested that older adults might be able to improve their recall abilities by learning to focus more on external objective information during encounters.

It has been suggested, for example, that mindfulness may improve cognitive function because it teaches individuals to be "present in the moment" and to attend to the objective nature of the experience instead of ruminating and being caught up in their own inner world.

A longitudinal study is now needed to determine whether the observed differences in the way middle-aged and older brains encode and retrieve memories is a reflection of functional brain decline or a reflection of what older adults pay attention to during any type of experience.

Dr Rajah has disclosed no relevant financial relationships.

Neuroimage. Published online June 12, 2016.

    
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