4 research outputs found
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A Neural Dissociation Within Language: Evidence that the Mental Dictionary is Part of Declarative Memory, and that Grammatical Rules are Processed by the Procedural System
Language comprises a lexicon for storing words and a grammar for generating rule-governed forms. Evidence is presented that the lexicon is part of a temporal-parietalhnedial-temporal “declarative memory” system and that granlmatical rules are processed by a frontamasal-ganglia “procedural” system. Patients produced past tenses of regular and novel verbs (looked and plagged), which require an -ed-suffixation rule, and irregular verbs (dug), which are retrieved from memory. Word-finding difficulties in posterior aphasia, and the general declarative memory impairment in Alzheimer's disease, led to more errors with irregular than regular and novel verbs. Grammatical difficulties in anterior aphasia, and the general impairment of procedures in Parkinson's disease, led to the opposite pattern. In contrast to the Parkinson's patients, who showed suppressed motor activity and rule use, Huntington's disease patients showed excess motor activity and rule use, underscoring a role for the basal ganglia in grammatical processing.Psycholog
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Monitoring Motor Fluctuations in Patients With Parkinson’s Disease Using Wearable Sensors
This paper presents the results of a pilot study to
assess the feasibility of using accelerometer data to estimate the
severity of symptoms and motor complications in patients with
Parkinson’s disease. A support vector machine (SVM) classifier
was implemented to estimate the severity of tremor, bradykinesia
and dyskinesia from accelerometer data features. SVM-based
estimates were compared with clinical scores derived via visual inspection
of video recordings taken while patients performed a series
of standardized motor tasks. The analysis of the video recordings
was performed by clinicians trained in the use of scales for the
assessment of the severity of Parkinsonian symptoms and motor
complications. Results derived from the accelerometer time series
were analyzed to assess the effect on the estimation of clinical scores
of the duration of the window utilized to derive segments (to eventually
compute data features) from the accelerometer data, the use
of different SVM kernels and misclassification cost values, and the
use of data features derived from different motor tasks. Results
were also analyzed to assess which combinations of data features
carried enough information to reliably assess the severity of symptoms
andmotor complications.Combinations of data features were
compared taking into consideration the computational cost associated
with estimating each data feature on the nodes of a body
sensor network and the effect of using such data features on the
reliability of SVM-based estimates of the severity of Parkinsonian
symptoms and motor complications.Engineering and Applied Science
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The Cortical Signature of Alzheimer's Disease: Regionally Specific Cortical Thinning Relates to Symptom Severity in Very Mild to Mild AD Dementia and is Detectable in Asymptomatic Amyloid-Positive Individuals
Alzheimer's disease (AD) is associated with neurodegeneration in vulnerable limbic and heteromodal regions of the cerebral cortex, detectable in vivo using magnetic resonance imaging. It is not clear whether abnormalities of cortical anatomy in AD can be reliably measured across different subject samples, how closely they track symptoms, and whether they are detectable prior to symptoms. An exploratory map of cortical thinning in mild AD was used to define regions of interest that were applied in a hypothesis-driven fashion to other subject samples. Results demonstrate a reliably quantifiable in vivo signature of abnormal cortical anatomy in AD, which parallels known regional vulnerability to AD neuropathology. Thinning in vulnerable cortical regions relates to symptom severity even in the earliest stages of clinical symptoms. Furthermore, subtle thinning is present in asymptomatic older controls with brain amyloid binding as detected with amyloid imaging. The reliability and clinical validity of AD-related cortical thinning suggests potential utility as an imaging biomarker. This “disease signature” approach to cortical morphometry, in which disease effects are mapped across the cortical mantle and then used to define ROIs for hypothesis-driven analyses, may provide a powerful methodological framework for studies of neuropsychiatric diseases.Psycholog