Consonant and vowel discrimination by brain-damaged individuals: effects of phonological segmentation

Two ‘same–different’ discrimination tasks were conducted to explore consonant voicing and vowel discrimination abilities in groups of left- and right-hemisphere-damaged individuals and normal controls. Stimuli were manipulated such that for half of each set, segmentation of the syllable was required for a discrimination decision; for the other half of the stimuli, no phonological segmentation was required. Results revealed impaired consonant voicing and vowel discrimination in a group of left-hemisphere-damaged non-fluent aphasic participants. Discrimination accuracy for groups of fluent aphasic participants and right-hemisphere-damaged participants fell between those of the non-fluent aphasic participants and the normal controls on both tasks. The findings are suggestive of a role for left frontal lobe regions in phonological segmentation, but remain inconclusive on this issue. The results are considered in relation to models of the neural bases and cerebral lateralization of speech perception processes.