Acute temporal lesions are associated with phonological word verification errors

Within the dual stream model for language, the bilateral dorsal superior temporal gyrus (STG) is associated with spectro-temporal analysis while the mid-post superior temporal sulcus is associated with processing of higher-level phonological codes. However, the true lateralization of functions needed for phonological discrimination at the word level remains unsettled. The aim of the present work was to determine if individuals with acute stroke primarily involving the left STG and middle temporal gyrus (MTG) demonstrated poorer discrimination (d') between phonologically related words in a word-picture verification task than those with left hemisphere lesions outside the temporal lobe and compared to those with right hemisphere stroke. The latter would support a left bias and provide an estimate of the magnitude.

One hundred fourteen individuals with acute stroke completed both acute magnetic resonance imaging and a word-picture verification task with phonological and semantic foils. Eighty-nine participants had left hemisphere stroke (51 included the temporal lobe). Twenty participants had right hemisphere stroke (14 included the temporal lobe). Five participants with bilateral stroke were included (3 included the bilateral temporal lobes). Quantile regression was performed controlling for overall lesion volume, age, and sex.

While more than half of patients performed the task well, patients with left temporal lobe lesions were more likely to perform poorly.

These results confirm a role for the left superior temporal lobe, including the STG, in phonological processing during word recognition, and indicate that a subset of individuals (<50%) have varying degrees of left bias in discrimination of phonologically similar words in the STG.