Receptive amusia: evidence for cross-hemispheric neural networks underlying music processing strategies

Abstract

Perceptual musical functions were investigated in patients suffering from unilateral cerebrovascular cortical lesions. Using MIDI (Musical Instrument Digital Interface) technique, a standardized short test battery was established that covers local (analytical) as well as global perceptual mechanisms. These represent the principal cognitive strategies in melodic and temporal musical information processing (local, interval and rhythm; global, contour and metre). Of the participating brain-damaged patients, a total of 69% presented with post-lesional impairments in music perception. Left-hemisphere-damaged patients showed significant deficits in the discrimination of local as well as global structures in both melodic and temporal information processing. Right-hemisphere-damaged patients also revealed an overall impairment of music perception, reaching significance in the temporal conditions. Detailed analysis outlined a hierarchical organization, with an initial right-hemisphere recognition of contour and metre followed by identification of interval and rhythm via left-hemisphere subsystems. Patterns of dissociated and associated melodic and temporal deficits indicate autonomous, yet partially integrated neural subsystems underlying the processing of melodic and temporal stimuli. In conclusion, these data contradict a strong hemispheric specificity for music perception, but indicate cross-hemisphere, fragmented neural substrates underlying local and global musical information processing in the melodic and temporal dimensions. Due to the diverse profiles of neuropsychological deficits revealed in earlier investigations as well as in this study, individual aspects of musicality and musical behaviour very likely contribute to the definite formation of these widely distributed neural networks.

How does the brain process music?

“…In a temporal lobectomy series, Liegeois-Chauvel et al found metrical impairments following left and right anterior temporal lobe resections. 16 Neither Ayotte et al 11 nor Peretz 3 found stroke patients with heterogeneous left and right hemisphere strokes to be impaired relative to neurologically normal control subjects, while Schuppert et al 17 found that both left and right hemispheric stroke patients were impaired relative to controls.…”

“…The validity of this model continues to be examined. 16,17 However, the model underlines the importance of cooperation between the cerebral hemispheres in music processing: music is not the province of either hemisphere exclusively, rather the two hemispheres are relatively more or less involved in particular aspects of music analysis.…”

“…Impaired detection of rhythmic changes has been described in left temporoparietal stroke and left hippocampal sclerosis, 18 while other studies have not demonstrated laterality differences. 3,17 However, functional imaging studies have demonstrated activity in the lateral cerebellum and basal ganglia during the reproduction of a rhythm, and there may be distinct representations for sequences with time intervals in integer ratios (more common in music) compared with non-integer ratios. 19 The observed activation of motor structures suggests that the perception and production of rhythm may share brain circuitry, though this is likely to apply to rhythm in other auditory and visual domains as well as music.…”

Deficit in automatic sound-change detection may underlie some music perception deficits after acute hemispheric stroke

“…Because of the wide variability in terms of music education and listening habits, however, music perception deficits might have been overlooked in clinical practice. In fact, in a recent study we could demonstrate in a group of 20 unselected patients that suffered from their first ischemic hemispheric stroke that music perception deficits are quite common and are due to the disturbance of widely distributed networks [18]. For this study, a new test battery was designed to assess different aspects of music perception: lower-level auditory information processing by testing discrimination of pitch, auditory memory function by testing recognition of familiar songs, local (sequential) auditory information processing by testing discrimination of interval-violated melodies and rhythm-violated musical stimuli, global (parallel) auditory information processing by testing discrimination of contour-violated melodies and metre.…”

“…While it is clear that very specific music processing deficits, e.g. pertaining to the hedonic qualities of music, can occur in the absence of a disturbance in the functions mentioned above, the processes addressed by the battery can be argued to form the basic building blocks of music perception [15,18].…”