Assessment of agnosias often combines both neuropsychological testing and brain imaging. A basic neurological examination is designed to determine: intellectual status, memory function, linguistic competence, and to assess sensory-perceptual processing in the affected modality (Bauer, 2006). Brain imaging tends to be utilized for identifying more subtle forms of agnosias and determining the cause of cerebral lesions (e.g. MRI, CT).
A. Rule Out Alternative Explanations
A variety of cognitive and neurological conditions can cause disturbances in recognition abilities. For this reason, it is critical to assess for these conditions in order to rule them out as explanations for an individual's recognition disturbances. The following table presents some strategies for achieving this purpose. An assessment of an individual's language ability is also important to conduct in order to understand the role that linguistic factors may have on the recognition defects. Language ability includes: naming, comprehension, fluency, repetition, writing, and reading (Bauer, 2006).
Assessments used to help rule out alternative explanations for disturbances in recognition (Bauer, 2006)
B. Determine the Scope and Nature of the Recognition Disturbance
Further testing may be completed to further determine the precise nature of the individual's recognition defects. For instance, distinction between apperceptive and associative agnosias can be done. This can be accomplished by allowing the individual with agnosia to complete copying and matching tasks.
Individuals with apperceptive agnosias WILL NOT be able to match two identical stimuli: written words or pictures (visual), words or sounds (auditory), and objects (somosthetic). For instance, individuals with an apperceptive agnosia will not be able to match an object to a drawing or copy it (visual) or repeat a word or imitate a sound (auditory). In contrast, individuals with associative agnosias will be able to perform the above tasks normally in the modality tested but WILL NOT be able to match different examples of stimulus. For example, for visual agnosia, the individual would not be able to match a mechanical pencil and a wood pencil, a closed to an open umbrella, or a script to a printed word (Damasio,Tranel, & Rizzo, 2000). In auditory agnosia, an individual would not be able to match two different doorbell sounds, baby cries, or a man and woman saying the same word. In the tactile modality, the individual would not be able to match a large and small cube by touch. It is important to remember that individuals with associative agnosia may be not able to name the stimulus through vision, hearing, or touch, but he or she would still be able to do so through the unaffected modalities.