Research

Spoken Production Processing and Related Deficits

Research in the lab addresses the relationship between phonological, phonetic, and motor-based processes in spoken language production. In particular, we are interested in understanding how these levels differ and how they interact with one another. This work focuses on both the underlying neurocognitive processing system, as well as addressing the basis of differential diagnosis for individuals with acquired aphasia and apraxia of speech. We explore issues by examining articulation (using ultrasound imaging), acoustics, and more traditional psycholinguistic methods. The studies involve individuals with acquired impairment subsequent to neurological damage as well as unimpaired speakers.

Identifying and understanding levels of processing (and their related deficits)

This area of research is at the intersection of theoretical and applied interests. With respect to theoretical accounts of language production, this work uses data from neurologically-damaged and neurologically-intact individuals to identify different levels of linguistic processing, including identifying a level that operates over segment-sized units (Buchwald, Rapp & Stone, 2007) and identifying a processing level that treats sound structure sequences differently based on their underlying structural representations (Buchwald, 2009; Buchwald & Miozzo, 2011; Miozzo & Buchwald, 2013). At the same time, this work indicates that errors following neurological impairment may arise at multiple stages, and we have proposed criteria for identifying the level at which an error arises, which enhances our understanding of the taxonomy of acquired phonological and motor speech disorders (Buchwald & Miozzo, 2012).

Promoting learning and re-learning in the domain of speech production 

Individuals whose errors can be identified as arising in motor-based processing may be able to be helped by intervention that supports motor learning more generally (e.g., limb motor learning). In Buchwald and Miozzo (2012), we found that individuals with motor-based errors may benefit from repetition tasks which are structured to promote motor learning, even in the absence of feedback. Current follow-up work has replicated this finding with additional participants (Buchwald & Miozzo, 2015).

In addition, we have begun using non-invasive neuromodulation to enhance speech motor learning in both impaired and unimpaired speakers. In this line of research sponsored by the NIH, we use transcranial direct current stimulation (tDCS) (anode placed over left M1, cathode over right supraorbital region) to facilitate speech motor learning. Unimpaired individuals are trained to produce non-native consonant sequences (e.g., word-initial /fn/) whereas impaired individuals are treated for production of native consonant sequences (e.g., word-initial /sn/) that they have difficulty producing. This work follows the logic of the work on different error types, but the training involves both structured practice and feedback.

Written Language Production

Research on written language production in the Psycholinguistics and Aphasia Lab focuses on the cognitive and neural processes involved in spelling, and the relationship between orthographic processing and phonological processing. Previous research focusing on individuals with acquired dysgraphia has focused on the nature of consonant and vowel representations in orthography (Buchwald & Rapp, 2006) and in the differences between long-term memory and working memory representations of spelling (Buchwald & Rapp, 2009). More recent work has addressed the activation dynamics of lexical selection and letter processing in written word production (Buchwald & Falconer, 2014; Falconer & Buchwald, 2013).