Enlighten Knowledge; Major approaches to human cognition and techniques used to study the brain

One of the most dramatic changes within cognitive psychology in recent decades has been the huge increase in the number of weapons available to cognitive psychologists.

Forty years ago, most cognitive psychologists carried out laboratory studies on healthy individuals. Nowadays, in contrast, many cognitive psychologists study brain-damaged individuals, others construct elaborate computer- based models of human cognition, and still others use numerous brain-imaging techniques.

Four major approaches to human cognition have now been developed:

• Experimental cognitive psychology:

This is the traditional approach and involves carrying out experiments on healthy individuals, typically under laboratory conditions.

• Cognitive neuropsychology:

This approach involves studying patterns of cognitive impairment shown by brain-damaged patients to provide valuable information about normal human cognition.

• Computational cognitive science:

Comparative cognitive science approach involves developing computational models to further our understanding of human cognition.

• Cognitive neuroscience

Cognitive neuroscience approach (which has become of major importance within the last 15 years) involves using numerous brain-imaging techniques to study aspects of brain functioning and structure relevant to human cognition.

Note that the term “cognitive neuroscience” is often used in a broader sense to indicate an approach to understanding human cognition based on considering evidence about brain functioning as well as about behaviour, and about how brain functioning influences behaviour.

What is common to both definitions is the importance attached to the use of brain-imaging techniques.

Major techniques used to study the brain

Single-unit recording:

This technique involves inserting a micro-electrode one 10,000th of a millimetre in diameter into the brain to study activity in single neurons. This is a very sensitive technique.

Event-related potentials (ERPs):

The same stimulus is presented repeatedly, and the pattern of electrical brain activity recorded by several scalp electrodes is averaged to produce a single waveform. This technique allows us to work out the timing of various cognitive processes.

Positron emission tomography (PET):

This technique involves the detection of positrons, which are the atomic particles emitted from some radioactive substances. PET has reasonable spatial resolution but poor temporal resolution, and it only provides an indirect measure of neural activity.

Functional magnetic resonance imaging (fMRI):

This technique involves the detection of magnetic changes in the brain. fMRI has superior spatial and temporal resolution to PET, but provides only an indirect measure of neural activity.

Magneto-encephalography (MEG):

This technique measures the magnetic fields produced by electrical brain activity. It provides fairly detailed information at the millisecond level about the time course of cognitive processes. Its spatial resolution is reasonably good.

Transcranial magnetic stimulation (TMS):

This is a technique in which a coil is placed close to the participant’s head and a large, very brief pulse of current is run through it. This produces a short-lived magnetic field, inhibiting processing in the brain area affected. This technique has (jokingly!) been compared to hitting someone’s brain with a hammer (Johannes Zanker, personal communication).

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