Implicit memory is critical for many complex human behaviors. Some implicit tests, such as visual word fragment completion, reflect perceptual processes and do not transfer from auditory to visual modalities whereas other tests, such as visual stem completion, involve more abstract processes and do transfer across perceptual modality.
The neural regions that support implicit memory depend on the specific processing demands of the test. For example, visual perceptual implicit tests rely on early visual regions. Although it has been suggested that visual perceptual implicit memory might rely preferentially on the right hemisphere, lesion studies have shown normal implicit memory in patients with extensive right hemisphere lesions, indicating the implicit memory is not lateralized to the right hemisphere.