Pathomechanisms and compensatory efforts related to Parkinsonian speech

Abstract

Voice and speech in Parkinson's disease (PD) patients are classically affected by a hypophonia, dysprosody, and dysarthria. The underlying pathomechanisms of these disabling symptoms are not well understood. To identify functional anomalies related to pathophysiology and compensation we compared speech-related brain activity and effective connectivity in early PD patients who did not yet develop voice or speech symptoms and matched controls. During fMRI 20 PD patients ON and OFF levodopa and 20 control participants read 75 sentences covertly, overtly with neutral, or with happy intonation. A cue-target reading paradigm allowed for dissociating task preparation from execution. We found pathologically reduced striato-prefrontal preparatory effective connectivity in early PD patients associated with subcortical (OFF state) or cortical (ON state) compensatory networks. While speaking, PD patients showed signs of diminished monitoring of external auditory feedback. During generation of affective prosody, a reduced functional coupling between the ventral and dorsal striatum was observed. Our results suggest three pathomechanisms affecting speech in PD: While diminished energization on the basis of striato-prefrontal hypo-connectivity together with dysfunctional self-monitoring mechanisms could underlie hypophonia, dysarthria may result from fading speech motor representations given that they are not sufficiently well updated by external auditory feedback. A pathological interplay between the limbic and sensorimotor striatum could interfere with affective modulation of speech routines, which affects emotional prosody generation. However, early PD patients show compensatory mechanisms that could help improve future speech therapies.

Sensorimotor control of vocal pitch and formant frequencies in Parkinson's disease

“…This function may be impaired in PD, resulting in a failure to filter and modulate the sensory input to cortical and subcortical areas (Haslinger et al, 2001; Liotti et al, 2003). The present results suggest a reduction in inhibition, yielding heightened sensory input to motor areas for F0 consistent with the observation of increased activity in the left superior parietal area reported in PD associated with prosodic pitch modulations (Arnold et al, 2014). Overall, these findings at the cortical level are consistent with our findings of increased compensatory responses to pitch perturbations.…”

Speaking-related changes in cortical functional connectivity associated with assisted and spontaneous recovery from developmental stuttering

“…The PPI analyses were performed similarly as in our previous reports on overt reading Pichon & Kell, 2013). In particular, we investigated group differences in functional connectivity between the selected seed volumes in the left hemisphere by testing for a significant speaking-related modulation (overt vs. covert reading) at p<0.05, FWE corrected on the voxel level within the 10 mm spheres around group coordinates that already served for seed identification (Arnold, Gehrig, Gispert, Seifried, & Kell, 2013). The results are not additionally corrected for the number of studied connections.…”

Autophonic loudness perception in Parkinson's disease

“…Schmidt, 1975). Dysfunction of motor planning, sensory feedback, or their integration may differentially impact speakers' perception, moreover (Arnold et al, 2014;Tatton et al, 1984).…”