Tone Discrimination in Patients with Temporal Lobe Lesions

Within the framework of working memory, subsidiary systems have been investigated for the retention of verbal and nonverbal material. While the majority of this research has been concerned with the verbal short-term store (see Baddeley 1986 for a review), the storage of nonverbal material has also been investigated with different types of stimuli. A visual — spatial short-term store was proposed for maintaining simple visual stimuli and complex spatial material (Phillips and Christie 1977; Baddeley and Lieberman 1980; Logie 1986). This temporary store was found to be susceptible to disruption by concurrent spatial processing. Eye movements were assumed to serve as control processes rehearsing and maintaining the visual image. Nonverbal auditory material, such as tones, has mostly been investigated in the form of sequences either at a perceptual level in terms of pitch discrimination (Moore and Rosen 1979; Patterson et al. 1983) or with respect to the cognitive representation of tonal relationships (Deutsch 1984; Dowling and Harwood 1986). Little neuropsychological work has been done on the storage and rehearsal of these auditory stimuli. Early studies (Kimura 1961a,b; Shankweiler 1966) reported a double dissociation for the site of lesion (left or right temporal) and type of material (digits or melodies). Patients with left epileptogenic lesions showed more errors on the dichotic digits test and patients with similar right-sided lesions were impaired in the recognition of melodies.