(visual reinforced audiometry, VRA) a behavioural test of hearing for children aged approximately 6 to 30 months in which the subject sits between two calibrated loudspeakers. A sound is generated from one loudspeaker. Children who turn towards the sound are rewarded by brief illumination of a toy adjacent to the loudspeaker. Older children can be tested with headphones, rather than using the loudspeakers, to enable each ear to be tested separately. The test can be adapted for use with older subjects who have learning disabilities.
Stimulation of the retina of the EYE with light causes changes in the electrical activity of the cerebral cortex (see BRAIN). These changes can be measured from outside the skull and can give valuable information about the state of the visual pathway from the retinal ganglion cells to the occipital cortex. Not only can it determine that function is normal, it can also help to diagnose some causes of poor VISION.... visual evoked response
n. (in psychology) the strengthening of a conditioned reflex (see conditioning). In classical conditioning this takes place when a conditioned stimulus is presented at the same time as – or just before – the unconditioned stimulus. In operant conditioning it takes place when a pleasurable event (or reinforcer), such as a reward, follows immediately after some behaviour. The reinforcement schedule governs how often and when such behaviour is rewarded. Different schedules produce different effects on behaviour.... reinforcement
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