allocations of gray and white matter tissue. Dopamine Recent studies have found that adults who stutter have elevated levels of the neurotransmitter dopamine, and have thus found dopamine antagonists that reduce stuttering (see anti-stuttering medication below). Overactivity of the midbrain has been found at the level of the substantia nigra extended to the red nucleus and subthalamic nucleus, which all contribute to the production of dopamine. However, increased dopamine does not imply increased excitatory function since dopamine's effect can be both excitatory or inhibitory depending upon which dopamine receptors (labelled D1–D5) have been stimulated. Diagnosis Some characteristics of stuttered speech are not as easy for listeners to detect. As a result, diagnosing stuttering requires the skills of a certified speech–language pathologist (SLP). Diagnosis of stuttering employs information both from direct observation of the individual and information about the individual's background, through a case history. Information from both sources should consider things such as age, the various times it has occurred, and other impediments. The SLP may collect a case history on the individual through a detailed interview or conversation with the parents (if client is a child). They may also observe parent-child interactions and observe the speech patterns of the child's parents. The overall goal of assessment for the SLP will be (1) to determine whether a speech disfluency exists, and (2) assess if its severity warrants concern for further treatment. During direct observation of the client, the SLP will observe various aspects of the individual's speech behaviors. In particular, the therapist might test for factors including the types of disfluencies present (using a test such as the Disfluency Type Index (DTI)), their frequency and duration (number of iterations, percentage of syllables stuttered (%SS)), and speaking rate (syllables per minute (SPM), words per minute (WPM)). They may also test for naturalness and fluency in speaking (naturalness rating scale (NAT), test of childhood stuttering (TOCS)) and physical concomitants during speech (Riley's Stuttering Severity Instrument Fourth Edition (SSI-4)). They might also employ a test to evaluate the severity of the stuttering and predictions for its course. One such test includes the stuttering prediction instrument for young children (SPI), which analyzes the child's case history, part-word repetitions and prolongations, and stuttering frequency in order to determine the severity of the disfluency and its prognosis for chronicity for the future. Stuttering is a multifaceted, complex disorder that can impact an individual's life in a