Dichotic listening: expanded norms and clinical application

Archives of Clinical Neuropsychology 17 (2002) 79 – 90 Dichotic listening: expanded norms and clinical application John E. Meyersa,*, Richard J. Robertsb, John D. Baylessc, Kurt Volkerta, Paul E. Evittsd a Mercy Rehabilitation Clinic, 500 Jackson Street, Ste 340, Sioux City, IA 51101, USA b VA Medical Center, Iowa City, IA, USA c Department of Psychiatry, University of Iowa, Iowa City, IA, USA d University of Northern Iowa, Cedar Falls, IA, USA Accepted 29 September 2000 Abstract The object of this study was to provide an expanded normative base for the Dichotic Word Listening Test (DWLT), with particular emphasis on the performance of older individuals. The normative study consisted of 336 community living volunteers. These new norms were used to compare several groups of neurologically impaired patient groups. DWLT was found to be sensitive to the presence of brain injury, and also to the degree of acute injury as measured by loss of consciousness. The results of the short form version of the DWLT test showed 100% specificity and 60% sensitivity for mildly brain-injured patients to 80% sensitivity for more severely brain-injured patients. The respective sensitivities for Left CVA and Right CVA were 55% and 88%. The present findings suggest that the DWLT is a valid and easy to use clinical tool. D 2001 National Academy of Neuropsychology. Published by Elsevier Science Ltd. Keywords: Dichotic listening; Neuropsychology; Adult; Brain injury Numerous studies have demonstrated that experimental dichotic listening procedures are sensitive to cerebral dysfunction due to various types of neurologic disease processes and different forms of brain injury. Briefly, dichotic word listening is assessed by presenting a single word to a subject’s ear through stereo headphones, while simultaneously presenting a different word (usually matched for syllable length) to the other ear; the subject is asked to try to repeat both words. In their group of patients with lateralized lesions, Sparks, Goodglass, and Nickel (1970) found the ‘‘lesion effect’’ in which there was a loss of relative listening * Corresponding author. Tel.: +1-712-279-5718. 0887-6177/01/$ – see front matter D 2001 National Academy of Neuropsychology. 0887-6177(00)00105-0 Downloaded PII: from Shttps://academic.oup.com/acn/article-abstract/17/1/79/2181 by guest on 17 June 2018 80 J.E. Meyers et al. / Archives of Clinical Neuropsychology 17 (2002) 79–90 effectiveness in the contralateral ear. That is, their group of patients with right hemisphere lesions produced left ear extinctions on double simultaneous presentation of auditory stimuli. However, left hemisphere lesions produced ipsilateral (that is, ‘‘paradoxical’’) as well as contralateral ear extinctions. This ipsilateral effect was explained by a model in which information presented to the right ear is more directly routed to left hemisphere language areas, but information presented to the left ear is routed first to the right temporal lobe, then to the left hemisphere via anterior commissural fibers. Left-sided lesions affecting these fibers could thus produce a relative left ear extinction. Anatomical localization was elucidated by Rubens, Johnson, and Speaks (1978) who found that such left hemisphere lesions ‘‘must extend deeply into left central or parietal white matter’’ (p. 396). Further anatomical refinement was provided by Damasio and Damasio (1979), who indicated that ‘‘the pathway leaves the auditory cortex traveling backward and upward to arch around the lateral ventricles and joins the callosum in its posterior region’’ (p. 644). They noted that ‘‘damage to any portion of the interhemispheric auditory pathway produces left ear extinction if the subject has left hemisphere speech dominance’’ (p. 644). Rubens, Froehling, Slater, and Anderson (1985) frequently observed left ear suppressions in their group of patients with multiple sclerosis. This deficit was presumably due to degradation of auditory pathways through demyelinization, although such demyelinization did not have to be severe for the dichotic suppression to occur. They noted that their consonant–vowel combinations made the task difficult, and were concerned that tasks using high contrast, real word pairs might decrease score variability in normals at the cost of reduced sensitivity to cerebral dysfunction. More recently, dichotic listening effects have been noted in aphasia (Bouma & Ansink, 1988), demyelinating disorders (Rao et al., 1989), primary degenerative dementia (Mohr, Cox, Williams, Chase, & Fedio, 1990), seizures (Roberts, Varney, Paulsen, & Richardson, 1990), and closed head injury (Levin et al., 1989). Roberts and colleagues developed norms for an abbreviated form of the Damasio stimulus tape, and recommended its use for standard clinical assessment. For example Roberts et al. (1990), Springer, Garvey, Varney, & Roberts (1991), and Verduyn, Hilt, Roberts, and Roberts (1992) illustrated the use of dichotic listening as a marker for subtle electrophysiological dysfunction in persons with brain injury. Richardson, Springer, Varney, Struchen, and Roberts (1994) suggested its routine use in evaluation for closed head trauma. Subsequently, Roberts et al. (1994) standardized a dichotic listening procedure suitable for everyday neuropsychological practice, the Dichotic Word Listening Test (DWLT; Auditec of St. Louis, 1991). It was their purpose to detect more ‘‘robust’’ deficits in bilateral and unilateral central auditory processing secondary to cerebral dysfunction, rather than subtle ear advantages resulting from lateralization of language processing. The task requires no special equipment apart from a portable stereo cassette player (CD format is also available) with headphones. Twenty unilaterally presented practice items allow the subject to adjust volume for optimal levels, ensure proper headphone placement, and provide a screening for potentially confounding hearing loss/impairment in speech discrimination. All items are common, fourth grade level English words. The 60 dichotic word pairs comprise the long form, with the first 30 pairs used as the short form version; short and long forms were found to be comparable. J.E. Meyers et al. / Archives of Clinical Neuropsychology 17 (2002) 79–90 81 The DWLT yields three index scores; the Left Index and Right Index scores are the overall number of words correctly repeated in respective single ears. The Both Ear Index is the total number of items in which both words of the dichotic pair are correctly repeated. It is important to differentiate defective performance in the Both Ear Index from bilateral suppression, which occurs when both the Left and Right ear Indices are in the defective range. Norms for university students were provided, as well as for urban/rural adults and children. Canadian norms were also collected to provide cross-cultural information. DWLT performances of a brain-injured sample were presented as well. In (...truncated)