Preserved use of spatial cues for sound segregation in a case of spatial deafness

Auditory spatial deficits following hemispheric lesions: Dissociation of explicit and implicit processing

“…The use of spatial eues for parsing the sound mixture, such as demonstrated with SRM tasks, can occur implicitly, i.e., without the explicit awareness of the positions of the target and masker. This was reported in two patients, one with a right inferior collicular lesion (Litovsky, Fligor, & Tramo, 2002) and the other with a large right hemispheric lesion (Thiran & Clarke, 2003). The latter patient, MN, presented spatial deafness, being totally unable to localise sounds or to compare their positions in free-field or in tasks using interaural time (ITD) or intensity differences (IID); despite her profound inability to use explicitly auditory spatial information, she did it implicitly, benefiting fully from spatial eues in SRM tasks.…”

“…For sound motion the perception of the direction of the moving sound was assessed. Auditory spatial abilities were assessed using sound lateralisation paradigms with ITD (as in Adriani, Bellmann et al, 2003;Adriani, Maeder et al, 2003;Altman, et al, 1979;Clarke, Adriani, & Bellmann, 1998;Clarke et al, 2000;Cusack, Carlyon, & Robertson, 2001;Clarke, et al, 2002;Griffiths et al, 1996;Rey et al, 2007;Spierer, Bellmann-Thiran et al, 2009;Spierer, Meulî, & Clarke, 2007;Tanaka, Hachisuka, & Ogata, 1999;Thiran & Clarke, 2003) or IID (as in Bisiach, Rusconi, Peretti, & Vallar, 1994;Spierer, Bellmann-Thiran et al, 2009;Sterzi, Piacentini, Polimeni, Liverani, & Bisiach, 1996). For each test, the volume was set at a level judged comfortable by the subject (75-85 dB SPL; CESV A SC-L; www.cesva.com).…”

“…First, they contribute to overt sound localisation, which allows us to identify explicitly the position of a sound source, to point to it (Makous & Middlebrooks, 1990) or to discriminate two successive sound positions (Mills, 1958). Patients who are unable to explicitly localise sounds typically report difficulties in crossing the street; they fail to follow the position of vehicles by auditory eues and often compensate by repeated visual checking (Thiran & Clarke, 2003). Another frequently reported difficulty resides in identifying the speaker within a group of unknown people; unable to determine where the voice cornes from, patients proceed then by checking whose lips are moving.…”

Where sound position influences sound object representations: A 7-T fMRI study

“…1990; Yost, 1991) or 'cocktail party effect' (Cherry, 1953). These roles can be partially dissociated, as indicated by evidence from brain damaged patients, suggesting that auditory spatial information may influence directly sound object representations (Thiran and Clarke, 2003). The interdependence of spatial and non-spatial information is furthermore suggested by facilitative interactions in near threshold discrimination tasks (Tardif et al, 2008).…”

Roaring lions and chirruping lemurs: How the brain encodes sound objects in space

“…conversely, lesions centered on the right parietal convexity are associated with auditory spatial deficits but not with sound recognition deficits (Clarke et al 2000;Adriani et al 2003a;Thiran and Clarke 2003;Ducommun et al 2004;Rey et al 2007;Spierer et al 2009). It is important to note that these specific deficits are likely not the result of postlesional reorganization.…”