Illustrations: (Suzuki) Joe McKendry; (brain) ShutterStock
早在神經科學家成為我的志願之前，我夢想的是成為百老匯巨星。但儘管早年一心想進入演藝圈，後來卻很快在不知不覺間成為一個愛好科學的書呆子，並循着對科學的抱負，進入了家族的母校加州大學柏克萊分校就讀。
話說，我來自一個非常嚴肅的日裔美籍家庭，我們總是親切客氣，彬彬有禮，但從不過度展現情感。你可以把我們想像成是日裔美人版的《唐頓莊園》，只是沒有英國腔、僕人或不動產。這就是我們。因此，時候一到，爸媽便把我打包上車，送去學校，然後《唐頓莊園》再度上演。我們沒有擁抱，只是揮手道別。
上了大學後不久，我就為自己這一身科學異秉找到完美的出口。那是一門叫作「大腦及其潛能」的課，由瑪麗安．戴孟德教授執教。頭一天上課，戴孟德教授帶來一只帽盒，只見她緩緩打開蓋子，小心翼翼取出一顆貨真價實的人腦。那是我這輩子看到的第一顆人腦。
她告訴我們，捧在她手裏的東西是人類所知最複雜的結構，界定了我們的個性和創造力，讓我們能上一秒還在笑，下一秒就轉成哭。她說大腦最教人驚奇的事之一就是可以因應環境的變化，這項特性稱為大腦可塑性。就在那一瞬間，我明白了我想當神經科學家。
在投身神經學的職涯中，我專攻日常大腦可塑性形式之一的長期記憶，成為在與長期記憶關係重大之腦部區塊的解剖、生理和功能方面的專家，並且對單一經驗能在我們腦中留存六十、七十，甚至八十年之久，深感着迷。
然而，在紐約大學成立自己的研究實驗室之後，有天我在報上讀到一篇格外令人辛酸的文章，講述一對父子於人生後期才開始建立起親密關係，讓我察覺自己雖是記憶專家，卻從沒花過多少時間思索有關記憶的個人層面，也就是我們的記憶到底有多珍貴，而它又如何形塑了我們。
看過那篇文章之後，有次母親來電告訴我爸身體不適。不僅如此，她還說爸記不得怎麼開車去每天早上買咖啡三十年如一日的那家7-Eleven。
這消息讓我很害怕，因此立刻採取行動，致電史丹佛大學的同僚，就我能力所及為他找了個最傑出的神經科醫師。後來爸病情好轉，但記憶卻沒恢復。
至於我，我只覺得內疚。如果連幫爸恢復記憶這點小事都辦不到，我這個記憶專家還有什麼用？
隨着年歲增長，我和父母間的關係益發緊密，每逢週日，我都會打電話跟他們聊天。但在爸的記憶出了問題之後，我知道自己開始想把彼此的關係轉往新的方向。
爸媽很愛哥和我，這一點無庸置疑，實則打從成年起，我們從未對彼此說過「我愛你」。我決心要開始對爸媽說這幾個字。但由於我們先前從未說過，我不能突如其來就這麼對他們說。我得先徵得他們的同意才行。
撥這通電話讓我感到不自在，但我明白箇中原因不在提出請求所產生的尷尬，而在擔心他們可能拒絕。
但只有一種方法能知道答案，因此在某個週日，我鼓足勇氣，撥了電話。我當晚的宗旨是在不經意間輕鬆提起這個問題。我說：「你們好嗎？我這星期這樣這樣，你們這星期過得如何？」對話過程中，我說：「啊，媽，你知道嗎？我們從來沒說過『我愛你』。如果從現在開始，我們每次講話都說這句話，你覺得怎麼樣？」
她不接話，沉默良久，讓我的胃一路翻攪到喉頭。接着她才說：「我想這個主意不錯。」
謝天謝地，她答應了！我對自己說。但為了不偏離宗旨，我說：「好極了！」然後兩人繼續聊天。
接着壓力又開始上升。答應說「我愛你」是一回事，但真正說出口又另當別論 。
因為是我提出的要求，所以我勇敢面對挑戰。我說：「好囉」──換言之就是：媽，準備好囉。「我愛你！」接着她說：「我也愛你！」我們就此大功告成。
接着輪到爸。我知道因為我已經過了媽這一關，爸就容易了。因此我問爸，他說好。父女倆笨拙地說了「我愛你」，提出大哉問的夜晚也宣告結束。
我得意洋洋，可是一掛斷電話，就忍不住淚流滿面。我不僅頭一次以成年人身分向雙親說出「我愛你」，也明白那晚我改變了我們家的文化，而且是永遠地改變。
隔週，我一如往常地打電話回家，各位一定很高興聽到我對媽說「我愛你」時不再那麼彆扭。接着輪到和爸講話。我知道他可能記不得這個我們上週做成的協議，因此準備提醒他。但那天晚上他卻教我大吃一驚，因為在當晚和之後的每一個週日，他都先說「我愛你」。
這廂你可得記住，有時我爸不大記得我去看他們的時間是感恩節還是耶誕節，可是不知怎的，他卻能一直記住說「我愛你」這回事。
而我知道原因。身為神經科學家，我知道情感的共鳴能協助我們記憶，會將新記憶推入長期記憶的範疇。
所以，當女兒問他能否對他說「我愛你」時，他因而感受到的愛、甚至是驕傲戰勝了失智，讓他形成新的長期記憶。諸位可以確定我這輩子都會保留這段記憶。
而這就是我研究記憶的原因。
Why I Study Memory
Long Before I Ever wanted to be a neuroscientist, I wanted to be a Broadway star. But despite my early showbiz dreams, I quickly and easily fell into a life of total science geekdom, and I followed those scientific aspirations to the University of California, Berkeley, my family’s alma mater.
Now, I come from a very serious Japanese American family. We are always pleasant and very polite but never overly affectionate. You can think of us as a Japanese American version of Downton Abbey, without the accent, the servants or the real estate. That’s us. So when the time came, Mom and Dad packed me up in the car and drove me there and – again, Downton Abbey – we didn’t hug. We just waved goodbye.
Soon after arriving at the university, I found the perfect outlet for my science geekiness: a class called The Brain and Its Potential, taught by Professor Marian Diamond. On the first day of class, she slowly opened the lid of the hatbox she had brought and very carefully pulled out a real human brain, the first one I had ever seen.
She told us that what she was holding in her hands was the most complex structure known to humankind; it defined our personalities and creativity and allowed us to go from laughing to crying from one second to the next. She said that one of the most amazing things about the brain is that it can change in response to the environment, a trait called brain plasticity. It was at that moment I realised I wanted to be a neuroscientist.
For my career in neuroscience, I studied a form of everyday brain plasticity: long-term memory. I became an expert in the anatomy, physiology and function of the brain areas important for long-term memory, fascinated with how a single experience could live on in our brains for 60, 70, even 80 years.
But one day, after I had started my own research lab at New York University, a particularly poignant newspaper article about the bond between a father and son that had been formed late in life made me realise that despite the fact I was a memory expert, I spent very little time thinking about the personal aspects of memory – that is, how precious our memories are and how they define us.
Some time after I read that article, my mother called to tell me that Dad wasn’t feeling well. Not only that, she said he couldn’t remember how to drive to the 7‑Eleven where he had bought his morning coffee for the past 30 years.
Now, that was scary. I jumped into action and called my colleagues at Stanford University to find him the best neurologist I could find. Dad got better, but his memory didn’t recover.
Me, I just felt guilty. What good was being an expert on memory if I couldn’t do one little thing to help my father get his memory back?
As I had got older, my relationship with my parents had grown closer, and I would call them every Sunday to chat. But after my Dad’s memory problem developed, I knew I wanted to start to shift our relationship in a new direction.
While there was never any question that my parents loved my brother and me, the fact was, we never said “I love you” to each other as adults. I decided that I wanted to start saying those words to my parents. But because we had never said it before, I couldn’t just start saying it to them out of the blue. I would have to ask permission.
I was feeling uncomfortable about making this call, but I realised it wasn’t because of the awkwardness of making the request. It was because I was afraid they might say no.
But there was only one way to know their answer, so one Sunday, I gathered up all my courage and called. My theme that night was keep it light. I said, “How you doing? Here’s my week. How was your week?” And sometime during the conversation, I said, “Hey, Mom. You know, we never say ‘I love you.’ What do you think about the idea of starting to say that when we talk to each other?”
She paused. There was a long silence, and my stomach went all the way up to my throat. Then she said, “I think that’s a great idea.”
Thank goodness she said yes! I said to myself. But keeping with my theme, I said, “That’s great!” and we continued our conversation.
Then the tension started rising again. It’s one thing to agree to say “I love you,” but it’s another thing to actually say it.
It had been my request, so I took the bull by the horns. I said, “Okay” – in other words, Get ready, Mom. “I love you!” And she said, “I love you too!” And we had done it.
Then it was Dad’s turn. I knew because I made it through with Mom, Dad would be easy. So I asked my Dad. He said yes. We said our awkward “I love yous”, and the night of the Big Ask was over.
I was triumphant, but as soon as I got off the phone, I broke down in tears. Not only had I said “I love you” to my parents for the first time as an adult, I realised that night I had changed the culture of our family. Forever.
The next week, I called as usual, and you’ll be happy to know that my “I love you” with my mom was much less awkward. Then it was time to talk to Dad. I realised that he might not remember we had made this agreement last week, so I was ready to remind him. But that night he surprised me. Because that night and every Sunday since, he has said “I love you” first.
Now, you have to remember that sometimes my dad can’t quite remember whether I’m visiting for Thanksgiving or Christmas. But somehow, he was able to make this memory stick.
And I know why. As a neuroscientist, I know that emotional resonance helps us to remember, it pushes new memories into the long term.
So the love or maybe even the pride he felt because his daughter asked whether she could say “I love you” to him – it beat dementia and allowed him to form a new long-term memory. You can be sure that I will keep that memory for the rest of my life.
And now that is why I study memory.