Single-Trajectory Multiple-Target Deep Brain Stimulation for Parkinsonian Mobility and Cognition.

BACKGROUND: Deep brain stimulation (DBS) of the nucleus basalis of Meynert (NBM) is an emerging target to potentially treat cognitive dysfunction. OBJECTIVES: The aim of this study is to achieve feasibility and safety of globus pallidus pars interna (GPi) and NBM DBS in advanced PD with cognitive impairment. METHODS: We performed a phase-II double-blind crossover pilot trial in six participants to assess safety and cognitive measures, the acute effect of NBM stimulation on attention, motor and neuropsychological data at one year, and neuroimaging biomarkers of NBM stimulation. RESULTS: NBM DBS was well tolerated but did not improve cognition. GPi DBS improved dyskinesia and motor fluctuations (P = 0.04) at one year. NBM stimulation was associated with reduced right frontal and parietal glucose metabolism (P < 0.01) and increased low- and high-frequency power and functional connectivity. Volume of tissue activated in the left NBM was associated with stable cognition (P < 0.05). CONCLUSIONS: Simultaneous GPi and NBM stimulation is safe and improves motor complications. NBM stimulation altered neuroimaging biomarkers but without lasting cognitive improvement. © 2021 International Parkinson and Movement Disorder Society.

Aging, pattern separation, and categorical perception of faces.

Categorical perception (CP) is the phenomenon by which observers view linear changes that occur across a continuum as distinct categories. Although categorical perception is a perceptual phenomenon, it may be subserved by mnemonic processes such as pattern separation. To examine this hypothesis, following standard CP tasks, we assessed younger and older participants' abilities to identify and discriminate between members of pairs of famous or non-famous faces. We hypothesized that if CP is dependent upon neural pattern separation, which declines with aging, discrimination ability as indexed by CP would be compromised in older adults, as was found in our study. Since familiarity promotes pattern separation, CP should be enhanced for famous, as compared to non-famous faces, even in older adults. We found that all participants benefited from familiarity, but younger adults outperformed older adults overall. We next examined the effects of face inversion on CP for both famous and non-famous faces. If pattern separation, and CP, is determined solely by the similarity across physical features, then CP should be similar for upright and inverted faces since these features are perceptually invariant across orientation. If, however, pattern separation, and CP, depends on how stimuli are represented, then orientation may matter as upright and inverted faces are represented holistically or part-based, respectively. We found that inversion disrupted CP in younger adults whereas older adults performed similarly across both conditions, suggesting that face-representation is more part-based in older adults.

Increases in the autistic trait of attention to detail are associated with decreased multisensory temporal adaptation.

Recent empirical evidence suggests that autistic individuals perceive the world differently than their typically-developed peers. One theoretical account, the predictive coding hypothesis, posits that autistic individuals show a decreased reliance on previous perceptual experiences, which may relate to autism symptomatology. We tested this through a well-characterized, audiovisual statistical-learning paradigm in which typically-developed participants were first adapted to consistent temporal relationships between audiovisual stimulus pairs (audio-leading, synchronous, visual-leading) and then performed a simultaneity judgement task with audiovisual stimulus pairs varying in temporal offset from auditory-leading to visual-leading. Following exposure to the visual-leading adaptation phase, participants' perception of synchrony was biased towards visual-leading presentations, reflecting the statistical regularities of their previously experienced environment. Importantly, the strength of adaptation was significantly related to the level of autistic traits that the participant exhibited, measured by the Autism Quotient (AQ). This was specific to the Attention to Detail subscale of the AQ that assesses the perceptual propensity to focus on fine-grain aspects of sensory input at the expense of more integrative perceptions. More severe Attention to Detail was related to weaker adaptation. These results support the predictive coding framework, and suggest that changes in sensory perception commonly reported in autism may contribute to autistic symptomatology.