Delayed auditory feedback simulates features of nonfluent primary progressive aphasia

Abstract

The pathophysiology of nonfluent primary progressive aphasia (nfvPPA) remains poorly understood. Here, we compared quantitatively speech parameters in patients with nfvPPA versus healthy older individuals under altered auditory feedback, which has been shown to modulate normal speech output. Patients (n = 15) and healthy volunteers (n = 17) were recorded while reading aloud under delayed auditory feedback [DAF] with latency 0, 50 or 200 ms and under DAF at 200 ms plus 0.5 octave upward pitch shift. DAF in healthy older individuals was associated with reduced speech rate and emergence of speech sound errors, particularly at latency 200 ms. Up to a third of the healthy older group under DAF showed speech slowing and frequency of speech sound errors within the range of the nfvPPA cohort. Our findings suggest that (in addition to any anterior, primary language output disorder) these key features of nfvPPA may reflect distorted speech input signal processing, as simulated by DAF. DAF may constitute a novel candidate pathophysiological model of posterior dorsal cortical language pathway dysfunction in nfvPPA.

Music Perception in Dementia

“…The musical phenotype was more severe in the PNFA group here; the involvement of pitch pattern analysis in this syndrome is in line with previous work [32] and suggests a putative mechanism linking generic mechanisms of dynamic auditory encoding with speech production via the dorsal auditory cortical pathway, extending over a range of timescales relevant to processing of individual and sequential speech sounds [9,77,[90][91][92], Marked involvement of musical perceptual mechanisms might be anticipated from the severe and focal involvement of auditory association areas in the progressive aphasias [9,11]. Although we did not demonstrate a correlation of musical measures with standard measures of verbal encoding, pitch processing mechanisms are likely to be more relevant to prosody (a crucial non-linguistic attribute of speech signals) than phonemic sequencing, at least for non-tonal languages.…”

Functional neuroanatomy of speech signal decoding in primary progressive aphasias

“…Only the nfvPPA group showed a profile of activation to sound that differed significantly from healthy controls: this is in keeping with emerging evidence for deficits of early auditory perceptual processing in nfvPPA that may distinguish it from other PPA syndromes (Goll et al., 2010, Goll et al., 2011, Grube et al., 2016, Maruta et al., 2014). …”

Behavioural and neuroanatomical correlates of auditory speech analysis in primary progressive aphasias

“…In addition to any deficit of motor speech planning, impaired tuning, monitoring and rehearsal of own speech output might contribute to impaired production of lexical stress and prosody in patients with nfvPPA [ 12 , 24 , 32 ]. Supplementary motor cortex mediates the tracking and integration of prosodic and syntactical rhythms in the healthy brain [ 33 ]; it has been proposed that speech apraxia in nfvPPA may at least in part reflect dysfunctional integration of temporal perceptual and speech output processes [ 12 , 24 , 34 ]. An additional correlate of temporal regularity processing was identified here in the caudate nucleus, consistent with previous work implicating the striatum in tracking of speech and other stimuli with extended temporal structures [ 35 ].…”