Academic Reading: 1

The Discovery of Neuroplasticity

For much of the twentieth century, most neuroscientists assumed the adult brain was essentially fixed after childhood, unable to rewire its structure. Textbooks stated that damaged neurons could not regenerate and that neural connections, once formed, remained permanent. This "fixed brain" doctrine led many physicians to assume stroke patients had little hope of recovering lost functions beyond a brief initial period.

A series of later studies undermined this assumption. Some stroke patients receiving intensive rehabilitation regained abilities that had seemingly been lost, suggesting other brain regions could partly take over functions handled by damaged tissue. One influential study examined the hippocampi of London taxi drivers, whose training in memorising the city's complex streets was linked to a measurably larger hippocampus, a region tied to spatial memory, than in non-drivers. Researchers concluded that sustained mental practice could physically reshape brain structure, not merely alter behaviour.

At the cellular level, this capacity for change, called neuroplasticity, rests on the strengthening or weakening of synaptic connections between neurons, depending on how often they fire together. Repeated activation strengthens a pathway, making a thought or movement easier to perform later, whereas unused pathways tend to weaken over time. Plasticity declines somewhat with age, but most researchers agree meaningful reorganisation remains possible throughout life.

This understanding has reshaped rehabilitation for stroke patients, now encouraged to repeat specific movements intensively, since this may help surviving regions compensate for damaged ones. Some neuroscientists nonetheless caution against overstating the brain's flexibility, since popular accounts occasionally imply neuroplasticity can overcome almost any impairment given sufficient willpower, an interpretation the research does not fully support. Recovery, researchers stress, typically remains partial and depends heavily on the extent of the original damage.

練習問題

  1. According to the passage, what did the "doctrine of a fixed brain" claim about the adult brain?

    • That it was essentially unable to substantially rewire its own structure after childhood
    • That it grew new connections mainly during sleep
    • That it could regenerate neurons faster than a child's brain
    • That it was more flexible than a child's brain in most respects

  2. According to the passage, what did studies of stroke patients receiving intensive rehabilitation suggest?

    • That lost functions could never be recovered under any circumstances
    • That only young stroke patients could show any improvement
    • That rehabilitation therapy had no measurable effect on recovery
    • That other brain regions could, to some degree, take over functions previously handled by damaged tissue

  3. According to the passage, what was found regarding the hippocampi of London taxi drivers?

    • Their hippocampi shrank the longer they worked as drivers
    • Their hippocampi showed no measurable difference from non-drivers
    • Their hippocampi were smaller than those of non-drivers
    • Their hippocampi were measurably larger, and this correlated with years of navigational experience

  4. According to the passage, what tends to happen to neural pathways that go unused over time?

    • They are immediately replaced by entirely new pathways
    • They remain exactly the same regardless of use
    • They gradually weaken over time
    • They strengthen automatically to compensate for disuse

  5. According to the final paragraph, why do some neuroscientists caution against certain popular accounts of neuroplasticity?

    • Because those accounts correctly describe how recovery always works
    • Because those accounts imply recovery is impossible in any case
    • Because those accounts focus only on childhood brain development
    • Because those accounts overstate the brain's flexibility, whereas recovery is typically only partial and depends on factors such as the extent of damage

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