The diagnosis of<unk>  requires multiple investigative tools all described in the Montreal Protocol for Identification of<unk> . This protocol has at its center the Montreal Battery of Evaluation of<unk>  (MBEA), which involves a series of tests that evaluate the use of musical characteristics known to contribute to the memory and perception of conventional music, but the protocol also allow for the ruling out of other conditions that can explain the clinical signs observed. The battery comprises six subtests which assess the ability to discriminate pitch contour, musical scales, pitch intervals, rhythm, meter, and memory. An individual is considered<unk>  if they perform two standard deviations below the mean obtained by musically-competent controls. This musical pitch disorder represents a phenotype that serves to identify the associated neuro-genetic factors. Both MRI-based brain structural analyses and electroencephalography (EEG) are common methods employed to uncover brain anomalies associated with<unk>  (See Neuroanatomy). Additionally, voxel-based morphometry (VBM) is used to detect anatomical differences between the MRIs of<unk>  brains and musically intact brains, specifically with respect increased and/or decreased amounts of white and grey matter. Classifications There are two general classifications of<unk> : congenital<unk>  and acquired<unk> . Congenital<unk>  Congenital<unk> , commonly known as tone deafness, refers to a musical disability that cannot be explained by prior brain lesion, hearing loss, cognitive defects, or lack of environmental stimulation, and it affects about 4% of the population. Individuals who suffer from congenital<unk>  seem to lack the musical predispositions with which most people are born. They are unable to recognize or hum familiar tunes even if they have normal audiometry and above-average intellectual and memory skills. Also, they do not show sensitivity to dissonant chords in a melodic context, which, as discussed earlier, is one of the musical predispositions exhibited by infants. The hallmark of congenital<unk>  is a deficit in fine-grained pitch discrimination, and this deficit is most apparent when congenital<unk> s are asked to pick out a wrong note in a given melody. If the distance between two successive pitches is small, congenital<unk> s are not able to detect a pitch change. As a result of this defect in pitch perception, a lifelong musical impairment may emerge due to a failure to internalize musical scales. A lack of fine-grained pitch discrimination makes it extremely difficult for<unk> s to enjoy and appreciate music, which consists largely of small pitch changes. Tone-deaf people seem to be disabled only when it comes to music as they can fully interpret the prosody or intonation of human speech. Tone deafness has a strong negative correlation with belonging to societies with tonal languages. This could be evidence that the ability to reproduce and distinguish between notes may be a learned skill; conversely, it may suggest that the genetic predisposition towards accurate pitch discrimination may influence the linguistic development of a population towards tonality. A correlation between allele frequencies and linguistic typological features has been recently discovered, supporting the latter hypothesis. Tone deafness is also associated with other musical-specific impairments such as the inability to keep time with music (beat deafness, or the lack of rhythm), or the inability to remember or recognize a song. These disabilities can appear separately, but some research shows that they are more likely to appear in tone-deaf people. Experienced musicians, such as W. A. Mathieu, have addressed tone deafness in adults as correctable with training. Acquired<unk>  Acquired<unk>  is a musical disability that shares the same characteristics as congenital<unk> , but rather than being inherited, it is the result of brain damage. It is also more common than congenital<unk> . While it has been suggested that music is processed by music-specific neural networks in the brain, this view has been broadened to show that music processing also encompasses generic cognitive functions, such as memory, attention, and executive processes. A study was published in 2009 which investigated the neural and cognitive mechanisms that underlie acquired<unk>  and contribute to its recovery. The study was performed on 53 stroke patients with a left or right hemisphere middle cerebral artery (MCA) infarction one week, three months, and six months after the stroke occurred.<unk>  subjects were identified one week following their stroke, and over the course of the study,<unk> s and non-amusics were compared in both brain lesion location and their performances on neuropsychological tests. Results showed that there was no significant difference in the distribution of left and right hemisphere lesions between<unk>  and non-amusic groups, but that the<unk>  group had a significantly higher number of lesions to the frontal lobe and auditory cortex. Temporal lobe lesions were also observed in patients with<unk> .<unk>  is a common occurrence following an ischemic MCA stroke, as evidenced by the 60% of patients who were found to be<unk>  at the one-week post-stroke stage. While significant recovery takes place over time,<unk>  can persist for long periods of time. Test results suggest that acquired<unk>  and its recovery in the post-stroke stage are associated with a variety of cognitive functions, particularly attention, executive functioning and working memory.
Amusia
Anotia
Mania
Somnophilia
Amaurosis fugax
Hypomimia
Dyssomnia
Distichia