Objective support for subjective reports of successful inner speech in two people with aphasia

Abstract

People with aphasia frequently report being able to say a word correctly in their heads, even if they are unable to say that word aloud. It is difficult to know what is meant by these reports of "successful inner speech". We probe the experience of successful inner speech in two people with aphasia. We show that these reports are associated with correct overt speech and phonologically related nonword errors, that they relate to word characteristics associated with ease of lexical access but not ease of production, and that they predict whether or not individual words are relearned during anomia treatment. These findings suggest that reports of successful inner speech are meaningful and may be useful to study self-monitoring in aphasia, to better understand anomia, and to predict treatment outcomes. Ultimately, the study of inner speech in people with aphasia could provide critical insights that inform our understanding of normal language.

Keywords: anomia; aphasia; inner speech; language; stroke.

Figures

Figure 1

A model of naming including IS. The upper, light grey box includes the lexical “access” stages. The lower, darker grey box includes the speech “output” stages. A report of successful IS requires successful access, but not correct overt production. Self-monitoring of IS occurs through an “inner loop” in which the phonological representation is compared to an auditory image via the speech perception and comprehension pathways in the temporal lobes.

Figure 2

Structural MRI of participants. Axial slices from high-resolution T1-weighted MRIs obtained at the time of testing: (a) YPR: 52-year-old left-handed male with right middle cerebral artery stroke; (b) ODH: 71-year-old right-handed female with left middle cerebral artery stroke.

Figure 3

Comparisons of characteristics of words that were reported as having successful IS vs. those having unsuccessful IS when overt speech was incorrect. (a) log10SUBTLEXus Word Frequency; (b) age of acquisition; (c) Phonological Neighbours; (d) Articulatory Complexity; (e) Triphone Probability (×104). *p < .05, **p < .01, ***p < .001, ****p < .0001

Figure 4

Comparisons of characteristics of words that were correct aloud vs. those that were incorrect aloud when IS was reported as successful. (a) log10SUBTLEXus word frequency; (b) age of acquisition; (c) phonological neighbours; (d) articulatory complexity, e) triphone probability (×104). *p < .05, **p < .01, ***p < .001, ****p < .0001

Figure 5

Percentage of items learned against the session in which they were learned. YPR and ODH learned more successful IS items than unsuccessful IS items (YPR: p = .0081; ODH: p = .043). YPR trended towards learning successful IS more quickly than unsuccessful IS (p = .087). ODH learned items reported as successful IS more quickly than items reported as unsuccessful IS (p