Overconfidence in visual perception in Parkinson’s disease

Abstract

BackgroundIncreased dependence on visual cues in Parkinson’s disease (PD) can unbalance the perception-action loop, impair multisensory integration, and affect everyday function of PD patients. It is currently unknown why PD patients seem to be more reliant on their visual cues.ObjectivesWe hypothesized that PD patients may be overconfident in the reliability (precision) of their visual cues. In this study we tested coherent visual motion perception in PD, and probed subjective (self-reported) confidence in their visual motion perception.Methods20 patients with idiopathic PD, 21 healthy aged-matched controls and 20 healthy young adult participants were presented with visual stimuli of moving dots (random dot kinematograms). They were asked to report: (1) whether the aggregate motion of dots was to the left or to the right, and (2) how confident they were that their perceptual discrimination was correct.ResultsVisual motion discrimination thresholds were similar (unimpaired) in PD compared to the other groups. By contrast, PD patients were significantly overconfident in their visual perceptual decisions (p=0.002 and p<0.001 vs. the age-matched and young adult groups, respectively).ConclusionsThese results suggest intact visual motion perception, but overestimation of visual cue reliability, in PD. Overconfidence in visual (vs. other, e.g., somatosensory) cues could underlie accounts of increased visual dependence and impaired multisensory integration in PD, and could contribute to gait and balance impairments. Future work should investigate PD confidence in somatosensory function. A better understanding of altered sensory reliance in PD might open up new avenues to treat debilitating symptoms.

A neurocomputational view of the effects of Parkinson’s disease on speech production

“…Though not as directly linked to motor activity as proprioception, tactile feedback from mechanoreceptors in the skin also depends heavily on selfgenerated movement for its interpretation; e.g., contact between the tongue and palate is expected if the tongue muscles have positioned it against the palate, but is indicative of a movement error if it occurs when the tongue has been commanded to a position that should not involve palatal contact. Indeed, somatosensory deficits have been well documented in PD across a number of nonspeech effectors (Konczak et al, 2009;Conte et al, 2013;Lee et al, 2018;Halperin et al, 2021) as well as along the vocal tract, including the airway (Hammer et al, 2013;Troche et al, 2014;Hegland et al, 2019), larynx (Hammer, 2009;Hammer and Barlow, 2010), jaw (Schneider et al, 1986), and tongue (Chen and Watson, 2017). Changes in vocal tract somatosensation have been shown to correlate with functional measures of speech, 10.3389/fnhum.…”