IELTS Academic Reading Practice Test 373

Before the twentieth century, surgeons who opened the human skull had little idea what any particular fold of the brain's surface did. The organ has no pain receptors of its own, so an operation could in principle be carried out while the patient was awake and able to talk. Epilepsy was among the conditions that most often brought patients to a surgeon, and it was the attempt to treat it that produced some of the earliest detailed maps of the human cortex.

Wilder Graves Penfield was born in Spokane in 1891, and went east to Princeton University as an undergraduate. He won a Rhodes scholarship and sailed to England in 1914 to study physiology at Oxford, where he worked in the laboratory of Charles Sherrington, whose experiments on the nervous system shaped the young American's thinking about the brain. The First World War interrupted his studies; he served with the American Red Cross in France, and after returning to complete his degree he took a medical qualification at Johns Hopkins University in 1918. A period in Madrid followed, where he learned from the Spanish histologist Pío del Río Hortega how to stain nervous tissue.

He then trained as a neurosurgeon in the United States and worked for a time with the German surgeon Otfrid Foerster, whose operations on conscious patients made a deep impression on him, before accepting a post at McGill University in Montreal in 1928. There he found a hospital willing to support his research and a colleague, the neurologist Herbert Jasper, who shared his interest in epilepsy. In 1934 the Montreal Neurological Institute opened, with Penfield as its first director, and it became one of the most influential centres for the study and treatment of the condition.

The surgical problem was to remove the damaged tissue that was generating seizures without destroying the neighbouring cortex on which the patient's speech or movement depended. The two kinds of tissue look very similar, and in an unconscious patient the surgeon has no way of knowing whether a particular point on the surface is essential. Penfield's solution was to keep the patient awake.

Because the brain itself feels no pain, the scalp and the membranes covering it can be numbed with a local anaesthetic while the patient remains alert. Once the skull has been opened, an electrical probe is applied to points along the exposed surface and a small current is passed through it. Stimulation of the motor cortex produces a twitch in a part of the body; stimulation of the sensory cortex produces a described feeling, such as tingling in the thumb. If the current halts the patient's speech, the surgeon knows that the tissue beneath the probe must be left in place.

Penfield labelled the stimulated points with small numbered tickets and recorded each response on a sketch of the brain, so that after the operation he and his colleagues possessed a detailed chart of each patient's cortex. Patients sometimes reported more than simple sensations. When the electrode touched the temporal lobe, a minority described complete experiences — a recalled scene, a piece of music, a familiar room — which the patient seemed to live through again. Penfield called these experiential responses and believed they showed that the temporal cortex stores records of past experience, though later researchers have pointed out that such responses also occur in people who do not have epilepsy, and the interpretation remains disputed.

From hundreds of such observations came the map for which Penfield is best remembered. He and his colleagues found that the body is represented along a strip of cortex running across the top of the brain, but that the representation is wildly out of proportion. The hands, lips and tongue, which make fine movements and receive rich sensation, occupy far more of the strip than the whole of the back or the thigh. The resulting diagram, published with the surgeon Edwin Boldrey in 1937 and drawn in later books as a distorted figure stretched along the brain's surface, became known as the cortical homunculus, or 'little man'.

The work had limitations. The patients were not healthy volunteers but people with epilepsy, some of whom had tumours or scars that had distorted the normal anatomy, and the surface of the brain is folded so tightly that an electrode on the crown of a fold may stimulate tissue hidden in a crease. Stimulation also forces groups of cells to fire at once, which is not how the brain behaves in ordinary life. Penfield himself was cautious about his charts, describing them as approximations rather than exact photographs.

Penfield gave up surgery in 1960. His later writing turned to philosophy, and in The Mystery of the Mind, published in 1975, he argued that the brain and the mind are distinct, a position few of his neuroscientific colleagues shared. He died in Montreal in 1976.

His influence nevertheless persists. Modern imaging techniques show activity in the living brain without opening the skull, and they have largely confirmed the broad outlines of his maps while revealing that the boundaries between regions are less clear-cut than they seemed. In epilepsy surgery, direct stimulation remains a standard method of protecting speech and movement. The questions Penfield asked at his operating table are still being pursued.

The human brain runs on electricity. When a neuron fires, charged particles cross its membrane and produce a tiny voltage that lasts a few thousandths of a second. A single neuron's signal is far too small to detect through the skull, but when millions of cells in a patch of cortex fire in step, the combined voltage reaches the scalp, where it can be picked up by flat metal discs attached to the skin. The technique, electroencephalography, or EEG, was first applied to a human being by the German psychiatrist Hans Berger, who recorded the brain's activity in the mid-1920s and published his results in 1929.

The voltages involved are minute. A typical scalp recording is measured in tens of microvolts, a fraction of the voltage of a small torch battery, and the signal must be amplified many thousands of times before it can be displayed on a screen. Electrodes are usually filled with a conductive paste or gel. Its purpose is to reduce the resistance between the metal and the skin, because a poor connection allows electrical interference from the room — mains wiring, lights and computers — to swamp the brain's signal. The amplified signal then passes through filters that remove unwanted frequencies and is converted into digital form for storage and analysis.

Placement follows an international convention known as the 10–20 system, introduced in the 1950s, in which electrodes are spaced at intervals of ten or twenty per cent of standard distances measured across the skull. Each position has a name: F for frontal, C for central, O for occipital, with odd numbers on the left side and even numbers on the right. The result is a grid that allows recordings from different laboratories to be compared directly, and it is one of the reasons why an EEG made in one country can be read in another. A routine clinical recording uses about twenty electrodes; research systems may use sixty or more, and dense arrays of well over a hundred are now built for laboratory work.

The trace that appears on the screen is not a picture of thought but a record of rhythm. Groups of neurons tend to oscillate together, and the frequency of these oscillations tells clinicians and researchers something about the state of the person being recorded. In an adult who is awake and relaxed with the eyes closed, a prominent oscillation of roughly eight to thirteen cycles per second appears over the back of the head. Berger noticed that this rhythm faded when the subject opened their eyes. It is now called the alpha rhythm, and the various bands of frequency — delta, theta, alpha and beta — have become standard vocabulary. Faster beta activity tends to appear when a person is alert or concentrating, while the slow delta waves of deep sleep look quite different again.

Real recordings are never clean. Blinking, swallowing and the constant activity of the jaw and neck muscles generate voltages far larger than those from the cortex, and a restless patient can produce a trace in which the brain's activity is barely visible. Electrodes that come loose, or sweat beneath a cap, create their own patterns of interference. An experienced reader learns to distinguish these artefacts from genuine brain activity, and software now removes some of them automatically, though not always reliably; an inexperienced one may mistake them for signs of disease.

In hospitals, EEG has four main uses. In epilepsy, it can reveal the abnormal discharges that accompany seizures, and a recording made over several days may capture an event that happens only occasionally; it also helps to classify the type of epilepsy, which guides treatment. In sleep medicine, the changing pattern of frequencies allows each stage of sleep to be scored without watching the patient all night. During an operation, the depth of anaesthesia can be estimated from the trace. In intensive care, an EEG can show whether any cortical activity remains, which may support, though never by itself establish, a diagnosis of brain death.

The method's great weakness is its poor spatial resolution. Because the skull and scalp conduct electricity, a burst of activity in one small region spreads across the surface before it reaches the electrodes, and the recording cannot say precisely where it began. Deep structures such as the hippocampus and the amygdala lie far from the scalp and contribute little to the trace. Magnetoencephalography, which records the tiny magnetic fields produced by neural currents, avoids some of this smearing, because magnetic fields pass through bone almost unchanged, but the equipment is expensive and must be kept at extremely low temperatures.

When more precise information is needed, electrodes are placed directly on or inside the brain. Before surgery for epilepsy, patients may have a grid of electrodes laid on the exposed cortex, or thin depth electrodes inserted through the skull, and stay in hospital for a week or more while their seizures are recorded. Because the electrodes are close to the source, the signal is far larger and its location far clearer, at the cost of an operation and a small risk of bleeding or infection. The same approach, known as electrocorticography, is used in research that maps the cortex during surgery for tumours as well as epilepsy.

Outside the clinic, EEG has moved into laboratories and even living rooms. Wireless caps with dozens of channels allow a volunteer to walk about while their brain is being recorded. Cheap headsets with a handful of dry electrodes can register a person's level of attention and are used in games and in research on brain–computer interfaces, in which a signal from the scalp is translated into a command that moves a cursor or a robotic arm. Such devices are impressive, but their signals are coarse and easily disturbed, and the claims made for them should be treated with caution.

A growing number of schools now ask their pupils to complete a short questionnaire about how they have been feeling. The exercise is called screening, and it is easily confused with diagnosis. Screening does not establish whether a young person has a disorder. It is an attempt to sort a large population into those who seem to be at risk and those who do not, so that the former can be offered a fuller assessment.

The appeal rests on a simple fact: almost every young person is at school. Mental health services reach only those who ask for help or are noticed by an adult, and many teenagers are reluctant to approach either. Schools also possess information that clinics lack — who has stopped attending, whose marks have fallen, who sits alone at break. Yet attendance registers and examination results reveal very little about how a pupil feels. A teacher may see a child every day for five years and still be unaware of distress at home.

Questionnaires can be completed by a whole year group in a single lesson and scored by software within minutes. Widely used instruments, such as the Strengths and Difficulties Questionnaire, have been translated into many languages and tested extensively with young people. Their purpose is to catch the suffering that never reaches the notice of an adult: the quiet pupil who is not disruptive, the pupil whose family does not use health services, the pupil who has learned to hide anxiety. In theory, then, screening finds the people who would otherwise be missed. For a school with limited resources, that is an attractive promise.

The theory has an established set of tests to satisfy. In 1968 the World Health Organization published principles of screening that remain a reference point. The condition must be serious; there must be an accepted form of treatment; facilities for diagnosis and treatment must be available; the test itself must be acceptable and reasonably accurate; and the cost must be justified. What strikes a reader today is how firmly the criteria subordinate detection to care. A screening programme is not judged by how many cases it finds but by whether the people it finds are helped.

That is where school programmes become vulnerable. Most adolescent mental health problems would not be identified by a single questionnaire on a single morning. Questionnaires are blunt instruments, and because serious disorders are, in statistical terms, uncommon among teenagers, even a good test will produce far more false alarms than genuine cases. A pupil who is flagged may simply have had a bad week, or may be answering carelessly. Some researchers also warn of labelling: once a young person has been described as at risk, teachers may interpret ordinary behaviour differently, and the pupil may begin to see themselves as fragile.

The more serious problem is what happens next. In many countries child mental health services are stretched, with waiting lists measured in months. A screening programme that generates referrals faster than clinics can absorb them does not obviously improve anyone's health; it may simply move a young person from unnoticed suffering to visible waiting. Even a well-funded service cannot create trained therapists overnight. Nor does it follow that every pupil identified needs a specialist. Much distress responds to ordinary support — a trusted adult, better sleep, help with a difficult situation at home, a place to talk.

There are also questions of consent. Teenagers can be asked about self-harm, eating and bullying only if they know what will happen to their answers and who will see them. A blanket promise of confidentiality is unwise, since a school has a duty to act on some disclosures; equally, a pupil who fears that every answer will be reported to parents may not answer honestly at all. Explaining the limits of confidentiality in advance, in plain language, is a precondition of trustworthy screening rather than an afterthought.

None of this means that schools should ignore the problem. A whole-school approach — teaching pupils to recognise distress, training staff to respond calmly, making space in the timetable for discussion — has a reasonable record and helps everyone, not only those who would be identified. Targeted screening of groups known to be at higher risk, such as pupils who have been persistently absent, may be a better use of scarce resources than a universal questionnaire. So may careful monitoring of the pupils teachers are already worried about, provided there is a system for acting on those worries. Such measures are less dramatic than a questionnaire, but they require no new labels and can be adjusted as circumstances change.

My own view is that universal screening is worth a trial only in schools that can guarantee a route from questionnaire to care. Where that route exists, the case for identifying hidden suffering is strong. Where it does not, a programme that labels a pupil as at risk and then offers nothing is a form of harm. A questionnaire that is cheap to administer can be extremely expensive in the expectations it raises, and any scheme should be evaluated honestly before it is extended to other schools.