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Text 1
Postmortem with Strings
by Anita Kunz
What eventually led to the premature
death of Mozart? Centuries after his demise, an unusual
clinical pathology conference was held in Maryland to
diagnose the genius' death, at which Professor Faith
Fitzgerald presented her peculiar diagnosis. How unusual
was the conference? How did Professor Fitzgerald conduct
the postmortem? The following article will get these
puzzles clear.
Down on the brick floor
of the University of Maryland's Davidge Hall, a noted
professor of medicine is about to perform a most unusual
postmortem. Although this domed amphitheater with its
steeply rising seats has hosted medical lectures and
demonstrations for more than 200 years, today's offering
is exceptional, for the deceased's remains are nowhere
in sight. And at the conclusion of the autopsy,
a string quarter will present a program of 18th-century
music. The occasion is the university's sixth annual
historical clinical pathology conference.
Each year the university's medical school invites a
physician to diagnose the mysterious maladies of historical
figures ranging from Edgar Allan Poe to Alexander the
Great. This year's patient is a 35-year-old male who
died in Vienna after a two-week illness. His body was
consigned to a common grave, but his genius still resounds
in concert halls the world over.
"We are disquieted when
extraordinary people die of ordinary things," begins
Faith Fitzgerald, an internist and professor of medicine
at the University of California, Davis School of Medicine.
Her introduction sounds a cautionary note for those
who would haste to interpret the synopsis that follows.
At the height of his creative powers, and while enjoying
a spell of good health, the subject fell suddenly and
ferociously ill, succumbing to high fever, headaches,
profuse sweating, and swelling of his hands and feet.
Within a few days the swelling of his hand spread to
his whole body—a condition known as anasarca. The bedridden
victim also developed a rash on his chest and belly;
after a week of illness, he complained of generalized
aches and pains and endured bouts of vomiting and diarrhea.
He remained conscious and alert until the night of December
4, 1791, when he became delirious, lapsed into a coma,
and died just after midnight.
Controversy has surrounded
this particular case history, Fitzgerald explains, because
of the deceased's celebrity status: Wolfgang Amadeus
Mozart's death "wouldn't have been mysterious at all
if Wolfgang Amadeus Muller had died that December night."
Strastruck physicians have since ascribed Mozart's death
to more than 100 causes. "Each of these [diagnoses]
is argued with a passion disproportionate to the data,"
Fitzgerald points out. "And of course, Mozart died of
syphilis as well as everything else, because
every great man dies of syphilis."
The physicians who attended
the sickly composer weren't much help, either. Their
succor amounted to a blood-letting and a few cold compresses.
No autopsy was performed on the body. According to musicologist
Neal Zaslaw of Cornell University, who sketches a brief
Mozart biography, the death and burial entries in two
church registers list the cause of death as "severe
miliary fever," a generic descriptor at the time for
any syndrome marked by a seedlike rash. Press reports
of his passing supplied such colorful and sinister diagnosis
as poisoning, venereal disease, and dropsy of the heart,
the 18th-century term for fluid retention and severe
swelling.
Even some learned men who
examined Mozart as a child had formulated their own
opinions about his eventual demise. "They believed that
each individual is born with a finite store of vital
essence and when that essence was consumed with the
intensity they perceived in the young Mozart," says
Zaslaw, "it was likely to be exhausted prematurely,
it leads to an early death."
Thus, overweight imaginations
and the sands of time have turned tragedy into a medical
mystery aching to be solved. That's just the sort of
material that appeals to the school's vice chair of
medicine, Philip Mackowiak, who launched the conference
six years ago after reading an account in a Maryland
historical magazine of Edgar Allan Poe's final days.
He hired an actor to play Poe and asked his colleague
Michael Benitez to review the writer's medical history.
The diagnosis—death by rabies—was
topped off, appropriately enough, with a monologue from
Poe's story "The Black Cat." The rabies theory attracted
enough attention to become a question on the TV game
show Jeopardy.
Since then, conferees have
taken on Alexander the Great, Beethoven, and the Athenian
military and political leader Pericles. So far, the
diagnoses made by Mackowiak's medics tend to be familiar,
if not mundane—and that's part of what makes the conference
not just interesting but useful to the doctors-in-training
who attend. There's a thoroughness to the historical
diagnostic procedure that is sometimes lost in contemporary
clinical practice, says Paul Sehdev, an M.D. in his
final year of training in infectious diseases. "Once
you get past your internship and residency, you tend
to make automatic diagnoses, without going through all
the possibilities," he says.
It's instructive, too,
to watch another physician work through a case without
the benefit of modern technology, says Sehdev. In
Mozart's example, the most compelling symptom—anasarca—has three
common causes: liver disease, kidney disease, and congestive
heart failure. Lacking modern lab techniques, Fitzgerald
must use deductive reasoning. Her first step is to discount
liver disease because there was no evidence of jaundice.
Some medical historians
have implicated kidney disease because of Mozart's malformed
ear. Ears and kidneys develop at about the same time
in the human embryo; hence, a malformed ear may indicate
problems with the kidneys as well. But Mozart had no
history of renal dysfunction6, Fitzgerald
says. And advanced kidney disease produces delirium
earlier in the course of illness.
So Fitzgerald settles at
last on congestive heart failure, which can cause anasarca
if the heart can't pump enough blood through the kidneys
to eliminate fluid-retaining salts. Heart troubles would
be easy to confirm with any one of the stethoscopes
that adorn audience members at Davidge Hall. "Unfortunately,"
says Fitzgerald, "Mozart died more than a quarter of
a century before the invention of stethoscopy. And there
was no description of his doctor's leaning an ear against
his heart to listen to it. If I were facing a really
swollen, febrile, rashy, sweaty guy, I might not want
to put my ear on his chest either."
Fitzgerald notes, however,
that at the time of Mozart's death an epidemic of rheumatic
fever is said to have besieged Vienna. Rheumatic fever
is triggered by an invading bacterium that elicits antibodies
from the immune system. The antibodies attack the bacterium,
but they can also attack tissue in a vulnerable host's
own heart, skin, joints, and brain. This reaction can
cause congestive heart failure, Fitzgerald points out,
as well as the rest of Mozart's physical symptoms. And
chorea, the neurological consequence of rheumatic fever,
could account for Mozart's final delirium, as well as
the puzzling change of character that prompted him to
drive his pet canary out of the sickroom days before
his passing.
"One could say that the
epidemic was immaterial to his death, that it was coincidental,"
she says. "But I think it's bit of arrogance to dismiss
it." Applying the principle of Occam's razor—which states
that the simplest explanation for a phenomenon is the
most probable—Fitzgerald formalizes her diagnosis: congestive
heart failure brought on by rheumatic fever.
The audience seems calm
and deeply satisfied, as if absorbing a eulogy for a
departed friend. Sandwiches are passed around, the string
quartet warms up, and as the first note is struck, Wolfgang
Amadeus Mozart lives again.
(1 187 words)
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课文一
尸检和弦乐
安尼塔·昆茨
是什么最终导致了莫扎特的早逝？他死了数百年后，在马里兰州召开了一次不同寻常的临床病理学会议，以诊断这位天才的死因，会上，费思·菲茨杰拉德教授提出了其独到的诊断意见。这次会议如何不同寻常？菲茨杰拉德教授又是如何进行尸检的？下面的文章将会澄清这些疑团。
在马里兰州立大学戴威基大厅里的砖铺地面上，一位著名的医学教授正准备进行一次最为不同寻常的尸检。虽然两百多年来，这座前后座椅间坡度很大的带圆顶的圆形剧场举办了各种医学讲座及演示，今天提供的内容却不同一般，因为根本见不到死者的遗体。尸解结束时，一个弦乐四重奏乐队将奉献十八世纪的音乐节目。这儿正在举行的是该校第六次历史临床病理学年会。每年，该大学的医学院会邀请一位医生就一些历史人物——从艾德加·爱伦·坡到亚历山大大帝——所患的神秘疾病作出诊断。今年的病人是一位三十五岁的男性，患病两周后死于维也纳。他的遗体被安葬在一个普通的墓地里，但他那才华横溢的音乐至今仍在世界各地的音乐厅中回荡。
费思·菲茨杰拉德是内科医生，加利福尼亚大学戴维斯医学院教授。她首先提出：“当一些杰出人物死于普通疾病时，我们就会感到不安。”她的开场白给那些急于解释随后的研究的人提了个醒。当事人当时正处于创作的颠峰期，且那一阵健康状况很好，突然一病不起，发高烧、头疼、盗汗、手脚浮肿。几天之内，浮肿就扩散到了身体各处——也就是我们所说的全身性水肿。这位受害者卧病在床，胸部和腹部还出了疹子。病了一周时间之后，他诉说全身疼痛，遭受了阵阵呕吐和痢疾的折磨。他神智仍一直清醒和警觉，但到1791年12月4日晚，出现谵妄症状，陷入昏迷，午夜过后便病逝。
费思·菲茨杰拉德解释说，围绕着这一特殊病历的争议，是因为死者名人身份：沃尔夫冈·阿马戴乌斯·莫扎特的去世“一点儿都不会神秘至今，如果那个十二月的晚上死去的是沃尔夫冈·阿马戴乌斯·穆勒的话。”此后，被名人效应左右的医生们归结了一百多种使莫扎特死亡的病因。菲茨杰拉德指出，“这些[诊断]的每一种，争论时的热情要远大于对数据的关注。”“当然，莫扎特死于梅毒，死因怎么说都行——因为每个伟人都死于梅毒。”
曾给生病的作曲家看病的医生们同样也帮不上什么忙。他们的救助方法就是放血或用冷敷布降温。当时没有对尸体进行尸检。康奈尔大学音乐理论家尼尔·扎斯罗简述了莫扎特生平，据他所说，莫扎特死亡与安葬时，两座教堂载明的死因都是“严重的粟疹热”，在当时这是对出现籽状疹症候群的一种通用描述。报纸上登载的关于其死亡的诊断则有声有色，不怀好意，认为是一种有毒的性病，还有心脏浮肿——这在十八世纪用来指体液潴留及严重水肿。
甚至一些在莫扎特小时侯给他检查过身体、颇有学识的人士，对他最终的死因也形成自己的看法。扎斯罗说，“他们认为，每个个体生来就存储有限的生命要素，当这种生命要素以他们认为的在年轻的莫扎特体内的强度消耗时，这种要素就可能提前耗尽，导致早逝。”
就这样，过多的想象以及时间的流逝，使悲剧演变成一个亟待解决的医学之谜。对于该医学院副院长菲利普·迈考威艾克来说，这正是他所感兴趣的材料。六年前，他在一本马里兰州的历史杂志上读到一篇关于艾德加·爱伦·坡临终情况的叙述，然后便发起组织了这个会议。他雇了一个演员扮演坡，还邀请他的同事迈克尔·本尼特斯重新审查这位作家的病史。用选自坡所著的故事《黑猫》中的一段独白，恰如其分地最终得出诊断结果：死于狂犬病。死于狂犬病的说法吸引了相当多的注意力，以致成为电视益智问答节目《危险》中的一个问题。
从那以后，参加会议的人探讨过亚历山大大帝、贝多芬以及雅典军事和政治领袖培里克利斯的死因。到目前为止，迈考威艾克的医学同行们所作出的诊断，要是不算平庸的话，也是比较常见的——这使得会议不仅有趣，而且对于与会的受训医生来说也很实用。医学博士保罗·萨赫戴夫正在传染病研究领域接受最后一年培训，他说，给历史人物会诊过程中体现一种彻底性，而当前临床实践有时就缺乏这一点。“一旦你过了见习期及住院实习期，你就容易不假思索地作出一些诊断，而不仔细考虑所有的可能性。”
萨赫戴夫说，通过没有现代科技帮助的一个病例考察另一种医疗工作，也具有启发性。在莫扎特这个例子中，最显著的病症——全身水肿一般有三个成因：肝脏疾病、肾脏疾病以及充血性心力衰竭。没有现代的实验技术，菲茨杰拉德必须运用演绎推理。她第一步是排除肝脏疾病，因为并没有出现黄疸症状。
一些医学史家曾暗示是肾脏疾病，因为莫扎特的耳朵有些畸形。耳朵和肾脏几乎在人类胚胎阶段同时发育；因此，畸形的耳朵也可以表明肾脏有问题。但是菲茨杰拉德说，莫扎特并没有肾脏机能不良的病史。而且，严重的肾脏病在发病过程中产生谵妄症状时间要早。
因此，最后菲茨杰拉德转向了充血性心力衰竭。如果心脏不能泵压足够的血液通过肾脏以排出存在于体液中的盐分，也可能会导致全身水肿。用戴威基大厅配备的听诊器，在场的任何一位听众都会很容易确诊心脏疾病。“不幸的是，”菲茨杰拉德说，“在莫扎特死后二十五六年才发明听诊检查。而且也没有记录表明，他的医生曾经把耳朵贴在胸部听心跳。如果我真得面对一个出疹、发烧、盗汗、浮肿的家伙，我大概也不会想要把耳朵靠在他的胸部。”
但是，菲茨杰拉德注意到，据说在莫扎特去世时，维也纳正遭受一场流行性风湿热的侵扰。风湿热的形成是由于某种细菌入侵诱发免疫系统产生抗体。抗体袭击细菌，但它们也可能会袭击体质虚弱的寄主的心脏、皮肤、关节和大脑。菲茨杰拉德指出，这种反应会引发产生在莫扎特身上的其它病症，也会导致充血性心力衰竭。由风湿热引起的神经系统的舞蹈症，可以用来解释莫扎特临终时的谵妄症状，也可以解释其令人困惑的性格变化——在去世前几天，这种变化导致他把自己最宠爱的金丝雀从病房中赶了出去。
她说：“人们可以说那场流行病对他的死因并不重要，那只是巧合而已。但我认为，要是对此不加以考虑，则有些自大。”菲茨杰拉德运用奥卡姆剃刀原则——即对某一现象最简单的解释可能性最大——作出了诊断：由风湿热引起的充血性心力衰竭。
听众们显得平静，而且深感满意，就好像沉浸在对一位亡友的颂扬之中。人们分发着三明治，弦乐四重奏乐队正在做演出准备，当第一个音符奏响的时候，沃尔夫冈·阿马戴乌斯·莫扎特又重获生命。
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Text 2
Pay Attention， Rover
by Amy Davis Mozdy
8:15 a.m. A flight lands at Melbourne's
Tulamarine International Airport. Several hundred pieces
of baggage are rushed from the plane onto a conveyor
belt in the baggage reclaim annex. Over the sound of
roaring engines, rushing air vents, and grinding generators,
a dog barks, Florence, a sleek black Labrador, wags
her tail.
Among the cavalcade of
luggage passing beneath Florence's all-smelling nose
is a nondescript hardback suitcase. Inside the case,
within Styrofoam casing, packed in loose pepper and
coffee, wrapped in freezer paper, and heat-sealed in
plastic, are 18 kilograms of hashish7.
The cleverly concealed
drugs don't fool supersniffer Florence, and her persistent
scratching at the case alerts her handler. Florence
is one of a truly new breed: the product of what is
perhaps the only project in the world dedicated to breeding
dogs solely to detect drugs. Ordinary dogs have a 0.1
percent chance of making it in drug detection. The new
breeding programme, run by the Australian Customs Service,
is so successful that more than 50 percent of its dogs
make the grade.
And what began as a wholly
practical exercise in keeping illegal drugs out of Australia
may end up playing a role in an entirely different sphere—the
comparatively esoteric world of neurobiology. It turns
out that it's not Florence's nose that makes her a top
drug dog, but her unswerving concentration, plus a few
other essential traits. Florence and her relatives could
help neurobiologists to understand both what they call
"attentional processing", the brain mechanisms that
determine what a person pays attention to and for how
long, and its flip side8, problems such as
attention deficit/hyperactivity disorder.
The Australian Customs
Service has used dogs to find drugs since 1969. Traditionally,
the animals came from pounds and private breeders. But
in 1993, fed up with the poor success rate of finding
good dogs this way, John Vandeloo, senior instructor
with the detector dog unit, joined forces with Kath
Champness, then a doctoral student at the University
of Melbourne, and set up a breeding
programme.
Champness, now with the
Royal Guide Dogs Association of Australia, began by
defining six traits that make a detector dog. "First,
every good detector dog must love praise," she says,
because this is the only tool the trainers have at their
disposal. Then the dog needs a strong hunting instinct,
and the strength to keep sniffing at the taxing rate
of around 300 times per minute. The ideal detector is
also fearless enough to deal with jam-packed airport
crowds, and the roaring engine rooms of cargo ships.
Ivan the terrible
The remaining two
traits are closely related and cognitive in nature.
A good detector must be capable of focusing on the task
of searching for drugs, despite the circus of distractions
in any airport or dockside. This is what neurobiologists
call "selective attention". And finally, with potentially
tens of thousands of hiding places for drugs, the dog
must persevere and maintain focus for hours at a time.
Neurobiologists call this "sustained attention".
To create the supersniffer,
Champness selected for these traits over three generations
of dogs. She also discovered that of the six traits,
selective attention was the most heritable. This finding,
which Champness intends to publish later this year,
shows that genes account for about 25 percent of the
difference between dogs in their ability to pay attention.
That's about as heritable as it gets for a complex behaviour
in animals, according to Robert Plomin, deputy director
of the Social, Genetic and Developmental Psychiatry
Research Centre at the Institute of Psychiatry in London.
After only three generations,
"the success of the breeding programme jumped way beyond
our expectations," says Champness. "We hoped that 30
percent of the pups from the programme would become
detector dogs, but the actual success rate consistently
exceeds 50 percent."
Vandeloo and Champness
assess the dog's abilities to concentrate by marking
them on a scale between one and five according to how
well they remain focused on a toy tossed into a patch
of tall grass. Ivan scores a feeble one. He follows
the toy, gets halfway there, then becomes distracted
by places where other dogs have peed or by flowers in
the pad dock. Rowena, on the other
hand, has phenomenal concentration: some might even
consider her obsessive. When Vandeloo tosses the toy,
nothing can distract her from the searching, not other
dogs, not food. And even if no one is around to encourage
her, she keeps looking just the same. Rowena gets a
five.
A person's ability to pay
attention, like a dog's, depends on a number of overlapping
cognitive behaviours, including memory and learning—the
neurobiologists' attentional processing.
Attention in humans can
be tested by asking subjects to spot colours on a screen
while ignoring shapes, or to spot sounds while ignoring
visual cues, or to take a "vigilance test". Sitting
a vigilance test is like being a military radar operator.
Blips appear on a cluttered monitor infrequently, and
at irregular intervals. Rapid detection of all blips
earns a high score. Within about five minutes, one in
ten subjects will start to miss the majority of the
blips, one in ten will still be able to spot nearly
all of them, and the rest will come somewhere in-between.
Vigilance tasks push the
limits of attention by providing signals that are infrequent
and unpredictable—which is exactly what is expected
of the detector dogs when they are asked to notice just
a few odour molecules in the air, and then to home in
on the source. During a routine mail screen that can
take hours, the dogs stay so focused that not even a
postcard lined with 0.5 grams of heroin and hidden in
a bulging sack of letters escapes detection.
Dogged focus
By combining attention tests with
brain scanning techniques in normal people, and in people
with brain damage due to strokes and bullets, neurobiologists
have identified which bits of the brain are activated
when a person pays attention. Others have investigated
what happens to the ability of a rodent or a monkey
to focus when parts of their brains are lesioned, or
when they are given drugs that block or enhance the
effect of different neurotransmitters.
Gradually a coherent picture
is emerging. Several areas in the brain's prefrontal
cortex9 are especially important for attentional
processing. Trevor Robins, an experiment psychologist
at the University of Cambridge, explains that in humans
"when a task gets difficult, the anterior cingulate
gyrus [in the frontal lobe of the brain]
seems to work overtime". The prefrontal cortex receives
and sends inputs to most of the rest of the cortex which,
among other tasks, processes visual and auditory information
and language. But the prefrontal cortex alone is responsible
for "executive" functions such as strategic planning
and the allocation of cognitive resources.
The prefrontal cortex may
even be able to boost the supply of stimulatory chemicals
that reach the cortex during prolonged periods of concentration,
by calling on parts of the brainstem and
the basal forebrain, two areas that house the body's
arousal centres and are located below the cortex. The
prefrontal cortex provides the lion's share of the brain's
neuronal input to these areas, and the whole cortex
receives a lot of stimulation from the brainstem and
the basal forebrain via neurons that feed its neurotransmitters
like noradrenaline and acetylcholine. As Robbins says,
through such mechanisms the prefrontal cortex is in
a position to regulate the activity of the cortex—"it
may turn the volume up and down".
Although the prefrontal
cortex is obviously vital to an animal's ability to
focus its attention, researchers are divided over the
exact nature of its role. Neuroscientists like Raja
Parasuraman argue that there are discrete control centres
for attentional processing that reside in the prefrontal
cortex. Parasuraman says that the prefrontal cortex
decides what needs to be attended to next and what must
be ignored.
Others, like Robbins, envisage
a more democratic mechanism. They argue that attentional
processing is the sum of a multitude of different mental
processes including, say, moving to focus the eyes or
ears on a target, and feeling enthusiastic or indifferent
about a topic. Rather than a central control, they envisage
an integrated network of processing carried out by different
brain regions that, in addition to the cortex, include
the amygdala, which plays a role in emotional responses,
and the basal ganglia, which govern voluntary movement.
"Memory [also] plays an
absolutely critical and essential role in guiding attention,
" says Robert Desimone, who studies the link between
memory and attention, and has helped champion the idea
that the attentional processing control centre lies
in the prefrontal cortex.
Take the example of someone
looking for a lost of keys, he says. The search begins
in the prefrontal cortex, where neurons process the
goal "find keys". These neurons make connection with
the visual cortex at the back of the brain, activating
a mental image of keys. In order to stay focused on
the task at hand, the key image must have priority over
all other images already stored in the memory. Desmone's
work on monkeys suggests that the activity in the prefrontal
and visual cortex which creates the image of keys also
inhibits other neuronal connections that would conjure
up distracting images.
"The end result is conscious
perceptual awareness of the thing that is important
right then, and unawareness of the things that aren't
important," says Desimone.
Although most people have
a degree of conscious control over how much attention
they will pay to a given object or task, it constantly
risks being hijacked by environmental stimuli. The search
for lost keys, for example, is driven by the goal of
finding the keys, or "top-down" voluntary control. But
a cue from the environment, a knock at the door or the
phone ringing, is likely to steer attention
toward the door and away from the search. Such "bottom-up"
effects are based solely on the properties of the stimulus
itself and the brain's involuntary, instinctive response,
and has nothing to do with attaining a goal.
Good detector dogs excel
at top-down control. Training takes advantage of that
and creates the goal by getting the dogs to associate
finding a toy that smells like cocaine, hash or heroin,
with praise from their trainers. Dogs like Ivan, on
the other hand, are all bottom up.
Ivan is a bit like a person
with attention deficit/hyperactivity disorder. Children
with ADHD are so distractable and their attention spans
are so short that they can't function normally or learn
properly. As many as 3 to 5 per cent of children are
thought to suffer from the disease in the US, where
the incidence is highest, although the diagnosis is
often controversial.
Wandering minds
In the past three years, ADHD researchers
have begun to look for genetic components to the disorder.
Plomin says that the studies "consistently and surprisingly
show very substantial genetic influences —in the order
of 60 per cent heritability". Behavioural traits in
humans typically show higher heritabilities than they
do in animals, perhaps because they can be characterised
more easily in humans. Nonetheless, a 60 per cent heritability
for ADHD is considered high because the disorder is
likely to be a range of different defects that come
under one umbrella diagnosis.
With the current interest
in attentional processing, as well as human diseases
that have an attention defect component, such as ADHD
and schizophrenia (sufferers appear to lose voluntary
control over where they focus their attention), Plomin
predicts that it is only a matter of time before the
super-sniffer dogs attract the attention of neurobiologists.
"At the behavioural level,"
says Plomin, "humans are much closer to dogs than to
[rodents]." Rats are one of the favourite animals in
which to study attentional processing. "Dogs are [also]
more trainable than [rodents]," he points out. With
their highly-heritable dynamo concentration, the Australian
drug detection dogs could even help to identify some
of the many genes that underlie attentional processing.
But so far, says Champness,
nobody has beaten down her door with requests for dogs
to study. Not that Melbourne's super-detector dogs aren't
still very useful. During their first year of operation,
the dogs made 1 500 drug seizures, including one 5-tonne
load of cannabis in a shipping container and a smaller
load concealed in condoms inside a smuggler's stomach.
(2 050 words) TOP
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课文二
注意，三心二意者
艾米·戴维斯·墨兹第
上午八点十五分。一架航班降落在墨尔本图拉玛瑞那国际机场。几百件行李被匆忙地从飞机上运到行李申领处的传送带上。佛罗伦斯，这条皮毛柔滑光亮的黑色拉布拉多雌犬，摇着尾巴，汪汪地叫声盖过了轰鸣的引擎声、通风口的呼呼的气流声和刺耳的发电机声。
行李连续不断地从佛罗伦斯无所不闻的鼻子下通过，其中有一个毫不起眼的硬皮手提箱。在箱子里聚苯乙烯泡沫塑料的包装内，在散装的胡椒和咖啡中，有18公斤用冷藏纸包装，塑料加热封口的大麻制剂，。
巧妙隐藏的毒品并不能瞒过超级辑毒犬佛罗伦斯。她不停地抓挠着手提箱，引起了训犬员的警觉。佛罗伦斯完全是一个新犬种：她或许是世界上唯一专门培育辑毒犬种计划的产物。对于普通犬来说，使之成为辑毒犬的概率只有0.1%。由澳大利亚海关服务部负责的新犬培育计划极其成功，其培育出的狗超过50%达标。
开始时这完全是一种实用性的练习，把非法毒品拒之于澳大利亚国门之外，但结果可能会发挥作用的，是在在一个完全不同的领域——比较而言较为神秘的神经生物学领域。结果，使佛罗伦斯成为一条顶级辑毒犬的，不是她的鼻子，而是她不懈的专注，加上一些其它的基本特性。佛罗伦斯和她的亲戚们可以帮助神经生物学家了解他们所称的“注意力处理过程”——一种决定一个人会专注于什么以及多长时间的大脑机制——以及其相对面，如注意力缺乏/多动症（ADHD）这样的问题。
澳大利亚海关服务部自1969年起就用狗来查寻毒品。根据传统，狗是从走失犬监管处或私人养犬者那里挑选。但通过这种方法寻觅到优秀侦缉犬的成功率很低，侦探犬训练部高级教官约翰·凡德鲁对此无法忍受，于是在1993年，与凯斯·钱伯尼斯——当时她还是墨尔本大学的博士生——联手开展了一个培育计划。
钱伯尼斯现在为澳大利亚皇家导盲犬联合会工作，她首先界定侦缉犬的六种特性。她说，“首先，每一条优秀的侦缉犬必须喜欢受人夸奖，”因为这是训练者可以支配的唯一工具。接着它需要有敏锐的搜寻直觉，还要有体力，能胜任每分钟约300次的繁重的嗅查任务。理想的侦缉犬还能毫无畏惧地应对在机场内水泄不通的人群和货船轰鸣的轮机舱。
恐怖的伊凡
剩下的两种特性相互紧密联系，本质上是认知性的。无论机场或码头的喧嚣如何分心，一条出色的侦缉犬必须能专注搜寻毒品的任务。这就是神经生物学家所称的“选择性注意力”。最后，毒品可能有上万个潜在的隐匿之处，侦缉犬必须能连续使注意力保持数小时之久。神经生物学家称之为“持续性注意力”。
为了培育出超级辑毒犬，钱伯尼斯在三代侦缉犬中寻找具有这些特性。她也发现在这六种特性中，选择性注意力最可以遗传。钱伯尼斯打算今年晚些时候发表的发现报告显示，狗在集中注意的能力方面的个体差异，25%可以用基因来解释。据伦敦精神病研究所社会、遗传和发展精神病学研究中心副主任罗伯特·普罗明的说法，这是动物的一个复杂行为可以遗传的程度。
钱伯尼斯说：只过了三代，“该培育计划就突然获得意想不到的成功。”“我们原希望该计划培育的幼犬30%能成为侦缉犬，但实际的成功率往往超过50%。”
凡德鲁和钱伯尼斯在估测狗的专注能力时，把一个玩具扔入高草丛生的一块地里，根据它们对玩具保持的注意力把它们划分为一到五等。伊凡得了一个糟糕的分数。他跟着玩具，但半路上被其它狗撒尿的地方或被围场中的花朵分散了注意力。罗伊娜却相反，她具有罕见的专注力：有人甚至会认为她是着迷。当凡德鲁扔出玩具后，搜寻中没有任何东西能使她分心，没有别的狗能让她分心，食物也不能。即使没人在一边鼓励她，她照样会不停地寻找。罗伊娜得了五分。
和狗的专注力相仿，人的专注能力取决于一些相互重叠交叉的认知行为，包括记忆和学习——神经生物学家所说的注意力处理过程。
测试人类的注意力可以让试验对象辨识屏幕上的颜色而忽略形状，或者辨别声音而忽略视觉提示，或者进行“警觉测试”。做警觉测试就好像当一名操作雷达的军事人员。在一个有杂乱回波的监视器上会出现不多的光点，而且其间的间隔也不规则。能很快发现所有的光点就能得高分。约五分钟后，十分之一的试验对象会漏掉大部分光点，十分之一的仍能够发现几乎所有的光点，剩下的则介于二者之间。
通过找寻不经常出现而且无法预测的信号，警觉测试任务进一步锻炼了注意力。要侦缉犬在空气中嗅到很少的气味分子，然后就直奔源头，希望侦缉犬做的正是这一点。耗时数小时的例行邮件检查中，侦缉犬高度专注，在鼓鼓的一大麻袋信件中即使混有一封藏有0.5克海洛因的明信片也不会逃过检查。
不懈的注意力
通过对常人以及因中风或弹伤而脑部受损的病人同时进行注意力测试和脑扫描技术，神经生物学家辨别出了一个人集中注意力时，大脑的哪些部分会被激活。还有一些神经生物学家研究啮齿类动物或猴子的部分大脑受损时，或给它们注射麻醉剂以阻碍或增强不同神经传递素所产生的效果时，那么它们的专注能力会发生什么变化。
一幅清晰的图象逐渐地形成了。脑额叶前部皮层的一些区域对注意力处理过程至关重要。剑桥大学实验心理学家特雷弗·罗宾斯解释说，“当任务变得困难时，（位于脑额叶的）人的脑前扣带回看起来会超时工作。”脑额叶前部皮层接受并传送输入信号到脑皮层的其它部分，由它们处理视听觉信息及语言等任务。但是只有脑额叶前部皮层负责“执行”功能，如制订战略性计划和分配认知资源等。
通过唤起脑干和基底大脑额叶的部分区域——这两处是人体的兴奋中枢，位于脑皮层之下，脑额叶前部皮层甚至会促进一些刺激性化学物质的供给，该化学物质在持续集中注意力的过程中会抵达脑皮层。脑额叶前部皮层把绝大部分神经元输入信号传给脑干和基底大脑额叶的这些区域，而整个大脑皮层是从脑干和基前脑处通过神经元接受大量的刺激，神经元会为此产生如去甲肾上腺素和乙酰胆碱这样的神经传递素。正如罗宾斯所说的，通过这样的机制，脑额叶前部皮层也许能够调节脑皮层的活动——“它或许能调节活动量大小”。
尽管脑额叶前部皮层对动物的专注能力至关重要，研究人员对其作用的确切性质仍有分歧。拉贾·帕拉素拉曼这样的神经系统科学家认为，在脑额叶前部皮层中有分开的控制注意力处理过程的中枢。帕拉素拉曼说，脑额叶前部皮层决定下步该注意什么以及必须忽略什么。
其他科学家，如罗宾斯，设想的是一种更民主的机制。它们提出注意力处理过程结合了大量不同的脑处理过程，包括如使眼睛或耳朵的注意力集中在目标上，以及对某一话题充满热情或漠不关心等。他们不将这看成中心控制系统，而看成一个经过协调的处理网络，通过不同的大脑区域运转。这些大脑区域除了脑皮层，还包括脑扁桃核（它在情感回应中发挥作用）和控制随意运动的基底神经节。
罗伯特·戴西摩纳说：“记忆在引导注意力方面〔也〕绝对起着重要和关键的作用。”他研究的是记忆和注意力之间的联系，并支持注意力处理过程的控制中心位于脑额叶前部皮层的论点。
他说，例如一个人要找一套丢失的钥匙。寻找过程发端于脑额叶前部皮层，由这里的神经元处理“找钥匙”这个目标。这些神经元同位于大脑后部处理视觉信号的脑皮层取得联系，在脑中激活钥匙形象。为了能够把注意力集中到目前的任务上，钥匙这个形象对于已储存在记忆中的所有其它形象来说应具有优先权。戴西摩纳在猴子身上做的研究显示，脑额叶前部皮层与视觉处理皮层中的活动建立了钥匙这个形象，同时还阻止与会产生分散注意力的形象的神经元的其它联系。
戴西摩纳说：“其最终结果就是产生一种对当时重要的事情有意识的感知，而不重要的事情就无法意识到.”
虽然大多数人在某种程度上有意识地控制自己对某一特定的目标或任务需要集中多少注意力，但是，这种控制经常面临着会被多种环境刺激带走的危险。例如，驱动寻找失落的钥匙的，是找钥匙这样一个目标驱动，或者说，是一种“自上而下”的自行控制。但是来自环境的一个次要的刺激，敲门声或电话铃响声，就有可能使注意力从寻找转向房门。产生这种“自下而上”的颠倒效果的基础，仅仅是刺激物本身的性质和不受意识控制、本能的大脑反应，和达到某一目标毫无关系。
杰出的侦缉犬在“自上而下”的控制方面能力超群。训练就利用这一优势，让狗把寻找一个有可卡因、大麻或海洛因气味的玩具同训练员的夸奖联系起来，形成一个目标。相反，像伊万这样的狗完全是自下而上的。
伊万有点像是一个患注意力缺乏/多动症（ADHD）的病人。患有ADHD的孩子注意力很容易被分散，注意时间非常短暂，以致他们无法正常行使功能或很好地学习。在美国，有3%-5%的孩子被认为患有这种疾病，是病发率最高的国家，虽然这样的诊断经常有争议。
心不在焉
在过去的三年里，注意力缺失/过动症的研究人员开始寻找该病症的基因成分。普罗明说，研究的结果“一致且令人惊讶地表明，存在着非常实质性的基因影响，可遗传性方面有60%的概率”。人类行为特征的可遗传性与动物相比，通常要高得多，或许是因为行为特征在人类身上更容易体现出来。不过，对ADHD来说，60%的可遗传性仍相当高，因为该紊乱症只是一个综合性的诊断，其名下可能包括许多不同形式的缺陷。
随着人们对注意力处理过程以及一些伴有注意力缺陷因素的人类疾病——如注意力缺失/過動症和精神分裂症（患者似乎对他们关注的对象丧失了自主控制）的关注，普罗明预测，超级辑毒犬吸引神经生物学家的目光，这只是个时间问题。
普罗明说：“在行为这个层次上，人类和犬类要比人类和〔啮齿类动物〕更接近。”老鼠是人们在研究注意力处理过程中最喜欢使用的一种动物。但他指出:“犬类比〔啮齿类动物〕更容易训练。”澳大利亚的辑毒犬具有极易遗传的高度注意力，也许能帮助鉴别许多潜伏于注意力处理过程之下的基因。
但是钱伯尼斯说，到目前为止，还没有人敲她的门，提出用狗做研究。这并不是说墨尔本的这些超级侦缉犬不再很有用。在它们服务的第一年，就查获了1500例毒品案，包括藏在一个轮船集装箱内的5吨大麻，以及藏在避孕套中吞入走私者胃里的量小一些的毒品。
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