Pitch constancy, perceiving the same pitch from tones with differing spectral shapes, requires one to extract the fundamental frequency from two sets of harmonics and compare them. We previously showed this difficult task to be easier when tonal context is present, presumably because the context creates a tonal reference point from which to judge the test tone. The present study assessed the role of the right auditory cortex in using tonal context for pitch judgements. Thirty-six patients with focal brain excisions of the right or left anterior temporal lobe (RT, LT) and 12 matched control participants (NC) made pitch judgements on complex tones that could differ in fundamental frequency and/or spectral shape. This task was performed in isolation and within a melodic context. The RT group showed impairments both on trials in which extraction of pitch from differing spectral shapes was required (different-timbre trials) and when this was not required (same-timbre trials). All groups performed poorly in the isolated condition, but improved with melodic context. Degree of improvement varied in that the LT group performed normally, whereas the RT group was not able to obtain the same amount of facilitation from the melodic context. In particular, melodic context did not facilitate the RT group's performance on different-timbre trials. Excisions within Heschl's gyrus did not affect these results, suggesting that the impairments were due to the removal of the anterior temporal cortex. The results of this study therefore implicate right anterior auditory cortical areas in making pitch judgements relative to tones that were heard previously. We propose that auditory association areas located on the anterior portion of the superior temporal gyrus, an area with connections to frontal regions implicated in working memory, could be involved in holding and integrating tonal information.
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