Sutherland Matthew T, Ross Thomas J, Shakleya Diaá M, Huestis Marilyn A, Stein Elliot A
Neuroimaging Research Branch, National Institute on Drug Abuse-Intramural Research Program, NIH/DHHS, 251 Bayview Blvd., Baltimore, MD 21224, USA.
Psychopharmacology (Berl). 2011 Jan;213(1):29-42. doi: 10.1007/s00213-010-2013-6. Epub 2010 Sep 23.
Beyond the amelioration of deprivation-induced impairments, and in contrast to effects on attentional processes, the cognitive-enhancing properties of nicotine on working memory (WM) operations remain unclear.
In an effort to elucidate potential enhancing effects, we explored the impact of transdermal nicotine on neural functioning in minimally deprived smokers and, in addition, assessed differences between smokers and non-smokers using a mixed block/event-related fMRI design that attempted to isolate specific central executive operations (attentional switch events) within general WM function (task blocks).
In task blocks, participants performed a continuous counting paradigm that required the simultaneous maintenance of, and frequent switching of attentional focus between, two running tallies in WM on some trials. Cigarette smokers (n = 30) were scanned twice, once each with a nicotine and placebo patch, while non-smokers (n = 27) were scanned twice with no patch.
Across both groups, task blocks were associated with bilateral activation, notably in medial and lateral prefrontal cortex (PFC), anterior insula, and parietal regions, whereas individual attentional switch trials were associated with activation in a similar, but predominantly left-lateralized network. Within the smoker group, although nicotine increased heart rate, altered performance and mood, and reduced tobacco cravings, no acute drug (state-like) effect on brain activity was detected for either the task or switch effects. However, relative to non-smokers, smokers showed greater tonic activation in medial superior frontal cortex, right anterior insula, and bilateral anterior PFC throughout task blocks (trait-like effect).
These data suggest smokers require recruitment of additional WM and supervisory control operations during task performance.
除了改善剥夺引起的损伤外,与对注意力过程的影响相反,尼古丁对工作记忆(WM)操作的认知增强特性仍不清楚。
为了阐明潜在的增强作用,我们探讨了经皮尼古丁对轻度剥夺吸烟者神经功能的影响,此外,使用混合块/事件相关功能磁共振成像设计评估吸烟者和非吸烟者之间的差异,该设计试图在一般WM功能(任务块)中分离特定的中央执行操作(注意力切换事件)。
在任务块中,参与者执行连续计数范式,在某些试验中,该范式要求在WM中同时维持两个正在进行的计数,并频繁在两者之间切换注意力焦点。吸烟者(n = 30)接受两次扫描,分别使用尼古丁贴片和安慰剂贴片,而非吸烟者(n = 27)不使用贴片接受两次扫描。
在两组中,任务块均与双侧激活相关,特别是在内侧和外侧前额叶皮质(PFC)、前岛叶和顶叶区域,而个体注意力切换试验与类似但主要为左侧化网络的激活相关。在吸烟者组中,尽管尼古丁增加了心率、改变了表现和情绪,并减少了对烟草的渴望,但未检测到药物对任务或切换效应的脑活动有急性(状态样)影响。然而,相对于非吸烟者,吸烟者在整个任务块中在内侧额上皮质、右前岛叶和双侧前额叶皮质表现出更大的紧张性激活(特质样效应)。
这些数据表明吸烟者在任务执行过程中需要调用额外的WM和监督控制操作。