More thoughts on the neurobiological account for working memory

Central executive and attention control
The memory system is generally thought to be composed of two elements, short-term memory and long-term memory. Baddeley and Hitch (1974) developed "working memory" model from the short-term memory system, refering to short-term memory system that is involved in a temporary storage of information and processing (Gastherole & Baddeley, p. 2). The working memory system sublines human cognitive activities, such as "reasoning, language comprehension, long-term learning and mental arithmetic"(p.2). The WM system has three main componants that Baddeley use for explaning relationship between language and memory-with 'central executive' as center componant'; phonological loop', and 'sketchpad'serving as "slave systems" to central executive. The central executive involves in regulating information flow, and retrieval of information from long-term memory. Baddeley also quoted other people's studies in the book that the executive might be involved in planning, task coordination, and consious awareness, and selection and control of action. The concept comes from Shallice's (1988) model of the "attentional control of action." Shallice (quote) reported a paradoxical phenomanon of frontal lobe damage patients. Due to the impairment to the central executive (SAS, "Supervisory Attentional System), the patient can't selectively intervene the activated schemas for apporpriate actions. That is, the patient either have difficulty in inhibiting other distracting schemas, or show perseverance of an already activated schema.

Working memory cells
Coming from neurophysiological point of view, Fuster (2003) looks at memories as cortical networks. The formation of memory is through "the modulation of transmission of information acorss synapses, the neural elements anatomically associating cells with one another" (p. 113). Therefore, memorys are associative with one another. Working memory under such sense is what Fuster called "attention focused on the internal representation of a recent event for a pending action" (p.155). The main propoerties of working memory is not to form a new memory, but to hold active at the need of processing a new action. Thus it's components can be both new items such as sensory inputs, associations; and old, past experience (long-term memory).

The most notable neuronal evidence for this sustained attention is found in monkeys performing a "delayed-response task" (todo:elaboration). Cells in monkeys' prefrontal cortex were found to maintain discharged at a higher level in delayed period (i.e. when the stimulus is obsent from the environment) than in periods between trials. These cells are later called "memory cells". The characteristics of the finding are, first, the delayed-period activation was dependent on the impending need to perform an act "that's contingent on the signal in memory". Second, it was not dependent on the expectation of reward. Third, the accuracy is correlated with the monkey's ability to remember the signal. Forth, the performance could be attenuated when the animal was distracted. (p. 156). In short, these cells discharge selectively to the retention of a stimulus, and they can be distracted by other stimulus concommitently.

Physiologically, single neuron recordings (Goldman-Rakic et al.,1996) reveal neurons in prefrontal cortex firing specifically to the same one or a few locations in a two-dimentional visual field when the animal was performing visual delayed response tasks. According to Fuster, the significance of Goldman-Rakic and collegues' work is that they dissociate two subareas of cortex that's specialized in working memory function: neurons engaged in the memory of the object predominate in the ventral aspect of lateral prefrontal cortex, whereas the neurons for memory of special information predominate in the dorsal apspect. This examplifies that the nature of working memory is not a single unit or localization, but more a distributed network(p.158).

Other studies involving tasks during a state of attention, so called "working memory" tasks also found "memory cells" not limited to prefrontal areas. For example, visual memory were found in the inferior temporal cortex (quote) (Fuster & Jervey, 1981; Miller et al., 1993), spatial memory cells in posterior parietal cortex (quote) (Andersen et al., 1990), and tactile memory cells in somatosensory cortex (quote) (Zhou & Fuster, 1996). In human visual cortex, increased activity was found when the stimuli was obsent but the subject was attending a specific visual field (Kastner et al., 1999).

The inferences can be drown from these findings, according to Fuster (2003) are that, working memory consists of a large cognitive network (perceptual and executive memory), and the selective attention during a task of working memory consists of the sustained and selective activation of this network.



Dopamine projection

Dopamine in the prefrontal cortex:
In the study of Goldman-Rakic et al.(1996), they pointed out that pyramidal neurons and non-pyramidal neurons in prefrontal cortex is critical for the formation of a "memory field" found in the area. Dopamine has inhibitory and excitatory effect on the prefronal cells. Prefrontal cortex is also known as the richest in dopamine than any other cortical areas. Tus the role of dopamine projection to prefrontal area and its effect on working memory tasks worths further discussion.

More evidence has been made between the dopamine dysregulation in prefrontal cortex in dschizophrenia(Goldman-Rakic et al. 2004). Working memory deficits have been postulated to be "underlying the myriad impairment of disorders" in schizophrenia (p. 4). In Diamond (1989) young infants still can't perform without errors in working memory plus inhibition tasks due to late developmental maturity of human dorsal lateral prefronal cortex.

Thoughts on working memory (for self record)

man, I think I picked the hard topic to look at...
If I were to give the definition of "working memory", I would end up burying myself in the literatures of working memory, but still couldn't give out a clear model of definition for it without confusing myself to death. This is how I have been feeling whenever I found any study talking about this topic.
I gradually learned (still not very skillfuly) to first identify which camp they are coming from:

1. Second language acuqistion camp: these people are langauge educators, applied linguists, and people who like to borrow psychological concepts and studies. The implication of WM for them is the predictor for learning a second/foreign language. Intuitively everybody would think that if you can remember a sequence of foreign sounds and be able to repeat promptly, that means you have some kinda "talent" for learning languages.
But knowing this and to prove it doesn't solve my question. What's working meomry in a neurobiological sense?

2. Psychology camp: they are the people who first brought up the idea of working memory from the concept of short-term memory, including Baddaley himself. Since they made up the term, their studies are being quoted by others all the time, but only at the introduction. After that they just go on whatever directions they like to talk about this term.
3. Neurolinguistic people: looks like these people like fMRI very much. A lot of them believe in UG and language area it seems like. The attempt is to find out the location of working memory, which is prefronal cortex, along with some other regions like temporal gyrus, parietal areas being found in those imaging studies.
Sometimes these localization studies or ROI ("region of interest") look cool but couldn't explain what's going on underneath the cortex. When parietal cortex and cingulate both light up, what does it tell us about the brain?

4. Neuroscientist: Fuster, Goldman-Rakic et al...
These are the people whom I think have cool ideas about working memory. Fuster has this "cognit" neuronetwork explaning cognition in the cortex. He discovered the memory cells when monkeys doing delayed response task. Same kinda cells are found in different regions of the brain when doing other tasks such as tonal, visual-spatial, color, etc. Goldman-Rakic found cells firing at certain "memory field" when monkeys doing delayed response tasks through single cell recordings. Another way to understand WM and the relationship with prefrontal area might be through pathological studies, like autism or schizophrenia. For example, "autism" (though this term needs clear definitions too!) subjects tend to have working memory deficits, same as schizophrenia patients, WM integrity can even predict whether they can reintegrate socially or replase. Some studies connect these deficits to dopamine projection dysfunction in prefrontal cortex, which I am still trying to figure out. I got the feeling this might the direction I want to go just to avoid the endless debate on what working memory does and what it actually is.

近況; 人腦與其他

我跟Nick現在住在距離學校約20分鐘車程的一個公寓裡。目前家裡還是一團混亂，一堆之前搬家的箱子有很多還散在各處沒開箱。學校已經開學三週了。我還剩下這個學期和春季學期，六月就會畢業，目前打算先工作再想博士班的事情。這學期少了婚禮的忙碌，可是還是一樣的忙。(我好像從開始念研究所就一直很忙的樣子) 這學期我修了兩門課，一門是補大學的預修(語音學)，一門是腦神經解剖學(neuroanatomy)。會修腦解剖學有很多原因。一來是因為我的論文是作語言、記憶、跟大腦之間的關係，二來是因為這個老師開課的機會非常難得。老師是個MD，已經八十四歲了，教這門課已經有半世紀了。(我是聽說他就是那個發現insula的那個人，還有研究pyramidal cell成名的)總之…我常很驚訝一個八十幾歲的人頭腦可以這麼清楚，尤其是神經系統的學問是這麼複雜。上課的時候很像在聽Discovery Channel，聽老師娓娓道來。不過以非醫學或生物背景的我們去修這堂課，而且還是研究所的程度，很多時候是完全聽不懂老師在講什麼，連筆記都抄不起來。還好我們教授跟他有協議，讓我們的考試跟醫學院的人分開，我們不用跑檯，也不用考切片。不過讀起來還是滿有壓力的，我的生物只有國中程度，連細胞裡有什麼都搞不清楚。不過這堂課讓我們每個星期可以用真的人腦。老師不知道哪裡弄來了十二顆人腦，每四五個人分到一顆，就這麼裝在水桶裡，戴著手套捉出來放在墊好餐巾紙的餐盤上。
我們的同學都是醫工、生物、認知科學的研究生。有些人還是去年被當掉重修的…

就這樣，我又開始回復學校生活。只是突然覺得好累。也許有個婚禮當作目標還比較容易應付。現在要面對的是論文還有未來的道路，只覺得好難好難…

婚禮4

我覺得這場婚禮讓我看見我爸媽一些特別的地方，是我從來沒發現的，特別是我爸。

我的爸媽並不太會說英文。這對我們上一輩的人來說是很正常的，因為語言教育的關係，就連我們這一帶也可能只會讀而不能講。Nick的爸媽則是完全不會中文。雙方見面的前一天，Nick跟爸媽通電話，他媽媽叫nick到一旁偷偷的不要讓我爸媽發現，叫他念我爸媽的名字，教她講。我媽的名字是還好，我爸的名有個捲舌的/zh/音對英文為母語的人是特別難發音。Nick媽媽練了很久，每次念到"zh"這個音還是很小心翼翼，沒有很大信心。我們也討論了很久，到底要讓Nick的爸媽叫我爸媽什麼。台灣人叫“親家”但是與其教他們用台語叫，還不如用中文叫名字算了。我爸媽也是特別練習叫nick爸媽的英文名字好幾次。不過後來父母們真正見面，我發現雙方都避免叫對方的名字…


我爸展現了不可思議的融合力。他什麼都吃，什麼都覺得好吃。基本上我們只煮過兩次飯是有中式的炒青菜但是混合西式的作法。我讓他們吃早餐燕麥片加優格，喝我每天一定要喝的伯爵紅茶加豆乳，也帶爸媽吃墨西哥菜、吃古巴菜、吃漢堡三明治、甜甜圈，在Nick家吃火雞、吃起士。我媽倒是很容易因為桌上沒有青菜而抱怨不好吃不夠健康。

Nick的爸媽和我的爸媽必須要靠我們幾個人（nick、 我、lisa、claire、maymay）的翻譯才能溝通，其他時間都一直微笑。有一天早上起來，我赫然發現我爸跟nick他爸坐在起居室裡兩人不知在聊什麼天。還講得滿高興的。我後來問我爸，他們到底在講什麼，原來兩個人比手畫腳在講木工的東西。

我媽一直說其實我爸是不可小看的，因為他是聽得懂我們的英文對話的。在海關也是靠我爸讓難纏的海關放他們進來。雖然我真的不知道他是如何達成的。我爸很勇於嘗試並且試著跟nick的父母比手劃腳的溝通，相較起來，我媽就比較喜歡自己拿著相機到處東拍西拍，跟我的伴娘們走在一起講話，或是倚靠我們的翻譯。



喜宴上有一段是我跟Nick的獨舞，背景是路易斯阿姆斯壯的”a kiss to build a dream on”，接下來是nick跟他媽媽，我跟我爸在路易斯阿姆斯壯的”what a wonderful world”下起舞。我才發現原來爸爸還滿會跳舞的呢，頗讓人驚艷的。我一邊跳一邊問他到底哪裡學的，他笑得很得意的說，”我已經很久沒跳了啦，那是大學時候的事”。之後爸爸跟Nick的媽媽跳了一段，Nick的媽媽大讚他跳得比Nick爸爸還好（因為Nick的爹一點都不喜歡跳舞，所以特許Nick媽可以跟別的男士跳舞）。

整個晚上，我爸的嘴都笑得合不起來，我想他真的很開心。

婚禮3

証婚牧師是Nick大學時的團契輔導，也是我們參加的教會的助理牧師，以前婚姻輔導。他最近才通過長老們的認可，開始主持証婚的事宜。我們是他的第二對。他一開始便抖出了一堆我們在輔導時告訴他的，發生在我們之間的糗事，Nick追求我的故事，還有我們在婚姻輔導時講過的話。全場笑聲連連，我們自己也覺得又好笑，又有點不好意思。但是他對我們婚姻的建言更是令我們難忘的。我們選了約翰福音十三章，耶穌為門徒洗腳來當作主題。牧師針對我跟Nick的性格，各自提醒我們在婚姻中需要彼此造就與勉勵的地方，特別切中我們關係中最需要的部分。這段經文是我跟Nick都很喜歡的經文，也是很匪夷所思的一段經文:一個比萬有都大的神變成人，成為卑微的僕人，而祂成為主人的最好模範，正是透過祂對門徒的服事。

到了交換誓言的部分，我才猛然想起，我們兩個還沒有選定誓言的版本!牧師之前給了我們幾個範例，但是我們實在太忙了。最後是上場前五分鐘，Nick跟牧師兩個人在後台溝通好其中一個版本，我們就這麼許下終生的約定了。整個過程是由牧師宣讀，我們輪流一句一句的覆述。輪到我的時候，牧師一時說成，”我在此立誓視nick為我的'妻子'＂，我正在覆述，馬上自己應變改口成為'丈夫'全部的人包括証婚牧師自己也笑了。之後大家一直開他玩笑說他差點幫兩個"妻子"証婚。

婚禮2

二點零五分：準備回到教堂。
我的裙子是A型裙，但是還是滿大的，上下車都是maymay幫我”塞”進後座，然後把門關上，她再從另一邊的車門上車。一下車，大大的澎裙掃過隔壁一台該死的銀色 HONDA，正好幫它骯髒的車身掃個乾淨，也把我前面的裙身給髒污了一片。混合著婚禮開始的緊張和不安，我開始發作了起來：「我還沒有走上紅毯就把衣服弄髒了！！」進了休息室，一堆人七手八腳的想幫我把衣服擦乾淨，但是似乎越弄越糟，髒污沾了水便擴散了開來。接下來是發現我忘了帶補妝包…好像沒一件對的。


最後我接受了眾人的安慰，開始相信衣服上的髒污看起來像衣服皺折處的陰影，還有借了大嫂的唇蜜，才覺得好一些，也才想起我還沒吃東西。為了不把妝弄壞，我媽還特地把三明治撕成小塊餵我吃。這一幕也被攝影師發現了，又是一陣閃光。教堂的wedding coordinator還送進來聖餐沒用完的餅和一些果汁給我們。因為我們每個女生都上了妝，吸管正是方便的喝水方式，因此一人拿了一罐開始喝。不一會兒，晴晴跑進來問我們有沒有看見聖餐的葡萄汁和餅…我們看了一下手上的飲料，正是葡萄口味的果汁，才發現我們居然把聖餐的酒給喝掉了！

二點三十分:距婚禮還有十五分鐘才開始
決定上個廁所。真是浩大的工程，需要一個人跟我一起進去拉裙子。是沒當過新娘的人不會了解的痛苦。沒當過那個拉裙子的伴娘的，也不會了解的。感謝Maymay真是我換帖的好姐妹。
二點四十五分:婚禮該開始了，不過大家還沒就定位。
二點五十分:wedding coordinator示意我們出去就定位。在邊廳裡，我突然感到非常緊張。maymay,claire和Lisa圍著我為我禱告。禱告快結束時，我感覺到門打開了，wedding coordinator示意要伴娘們先出場就定位。接下來的五分鐘我一個人在邊廳裡，突然回想起剛認識Nick的那個夏天，真理堂的學生宿舍…
三點整:我跟爸爸在門後就定位，"Largo" (from Xerces)樂聲響起，門一打開，牧師示意全体起立迎接我們進場。

結果我太緊張隨便抓了邊廳的一束捧花便出場。結束後Nick媽拿了一束花來給我:「妳拿到的是婚宴上要丟的捧花，這才是真的新娘捧花。」


不過花商倒是很認真的做了每一束捧花，連丟出去的捧花都非常的漂亮。怪不得我一緊張根本分不出來

婚禮

實在很難相信，婚禮居然結束了。我們都有鬆一口氣的感覺，但是並不代表我們並不享受這場婚禮。婚禮的當天，我倒是覺得頗愉快，好像參加一場派對似的，但事實也正是一場我人生中最大的一場派對。只不過婚禮涉及太多的細節和人事物，加上我們兩個還在就學，又要寫論文。過去這三四個月的生活其實是充滿壓力的。每個詢問我們"wedding planning"怎麼樣的朋友，都會得到我們的苦笑。一直到婚禮的前一天，我們還在"planning"。


婚禮前一天晚上的rehearsal，所有跟婚禮當天有關的朋友都到了:牧師、伴娘伴郎、敬拜團、招待、雙方父母家人。我們兩個走進教堂做預演的時候，一個表情呆滯、一個面帶愁容。Nick因為好幾餐沒有吃什麼東西，有點注意力沒法集中在預演上，我則是覺得好忙好忙。還好預演晚宴過後，我們恢復了點体力，才又露出笑容。牧師走過來拍拍我們的肩膀，告訴我們: 「我希望你們明天走進禮堂的時候，是跟今天完全不一樣的表情。」他補充說，我們今天走進來時，一個看起來充滿殺氣(我啦)，一個看起來有點恍神 (nick)。 牧師說: 「我希望你們明天想著不是婚禮趕快過去，而是能享受這一個日子。」我一直記得他說的話，而我當天的確過得很享受，除了剛起床時有點焦慮。


星期五當天依照行程，八點半造型師便會出現在旅館為我們化妝。我其實很早就醒過來了。很多人之前一直問我緊不緊張，我總是回答一點也不，因為事情太多太忙根本沒時間想太多。但是那天早上，造型師為我上了髮捲，給我一個小時自由活動的時間，她繼續打點我媽和伴娘們的造型。我在旅館走廊頂著像藝妓般的頭，一直焦慮地在不同房間走來走去。一下子去大嫂的房間，一下子跑去伴娘的房間，一下子又回到爸媽的套房看造型師為我媽和伴娘們弄造型。這是我第一次覺得緊張的時刻。



10點50分Joyce開始為我上妝，攝影師也來了。一下子整間套房擠滿了人: 三個造型師、我媽、maymay、Claire、Lisa、我爸、大嫂、攝影師夫妻檔。不一會兒連nick爸爸和媽媽，Nick妹妹和她的先生也出現了。攝影師們基本上捕捉每一個婚禮的細節，包括像化妝這樣的事前工作。我爸媽和伴娘們也拿出相機到處拍。在這個數位的時代，記憶体真是個神奇的東西，不用擔心浪費這種小事。
12:00左右我開始準備穿上禮服，也順便讓攝影師捕捉伴娘們為我穿禮服的畫面。最後造型師為我夾上頭紗，十二點半我們下樓去，又在飯店大廰拍了幾個角度。之後便趕往San Gabriel Mission出外景。



傳統上新郎只能在婚禮時新娘走上紅毯時才能看到新娘的樣子和有白紗禮服。所以Nick一直沒有看過我禮服的樣子。但是婚禮是在下午，結束時大約四點，太陽下山後，光線也就沒了。為了照相我們只好破例。下午一點，Lisa開車載著maymay、我、claire，我們每個人都"盛裝"出現在這個觀光景點，吸引了路人的目光。有的人經過還會面帶微笑的說恭喜。到的時候新郎和伴郎們已經在那裡等候了。我跟Nick有個尷尬的第一次相會，(穿著禮服的第一次)，之後便開始覺得輕鬆了點。當男生真是容易。我說我八點半就開始做頭髮了，他居然睡得晚晚的，跟他的伴郎吃了早午餐，然後開車到教堂在停車場裡穿好衣服，對著照後鏡整理一下就出現了。