Poizner_slds

Poizner_slds - Motor Disorders Howard Poizner Institute for...

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Unformatted text preview: Motor Disorders Howard Poizner Institute for Neural Computation & Cognitive Science Department UCSD • Sensory versus Motor Systems • Reason we have a brain • Breakdown of motor control following failure of sensory or motor systems • Deafferentation [peripheral] •Parkinson’s disease [central] I Cortical Motor Areas Thalamus Basal Ganglia Cerebellum Brain Stem II Spinal Cord III Muscle Contraction & Movement Final Common Path Sensory Receptors Parkinson’s Disease • Reliance on external cues • Basal Ganglia are important for the internal guidance of movement • Point to remembered 3D locations without vision Sensorimotor Mapping Problem • How to control joint angles of arm given knowledge of coordinates of target in external space SUBJECTS • 11 PD Patients (mild to moderate) • Studied OFF medication • 8 Age-Matched Controls • Right handed, right hand used Conclusions for Experiment 1 • With vision only of the initial hand position and target, mild to moderate PD patients have normal 3D pointing accuracy • Thus, PD patients are able to construct spatial maps of the target and of their moving limb and coordinate the two • Certain dimensions of performance are impaired • Challenging integration of vision and proprioception may induce large spatial errors Modes of Target Presentation 1. No-Vision 2. Finger-Vision 3. Target-Vision • No required transformations across sensory modalities: Finger-Vision • Required transformations across modalities: No-Vision Target-Vision Hypothesis: Deficits in Conditions 1 & 3, but not in 2. SUBJECTS • 9 PD Patients (mild to moderate) • Studied OFF Medication • 9 Age-Matched Controls Conclusions • PD patients show large 3D reaching errors when forced to extract critical information from proprioception to map onto a spatial target • This deficit may in part underlie PD patients’ reliance on external cues • Turn to mappings learning new sensorimotor Immersive 3D Virtual Reality Environment Virtual Head-Mounted Display Virtual Technologies 3D electromagnetic tracking Ascension Technology Visuomotor multistage learning task Visuomotor Task phases 3. Reverse discordance (RD) x - 10 cm & y - 10 cm 10 1. Baseline (B) 1. 4. AfterEffect (A) 2. Initial discordance (ID) x + 10 cm & y + 10 cm 10 * Biaxial Distortion Z X Virtual targets Real target Y SUBJECTS • 8 PD Patients (mild to moderate) • Studied OFF Medication • Minimal or No Tremor or Dyskinesias • 10 Age-Matched Controls • 10 Young Adult Controls Horizontal Errors Horizontal Errors Vertical Errors Vertical Errors 20 20 15 15 5 * IL 10 B RL 5 10 20 30 50 40 -10 * -15 -30 cm) 10 -5 -10 -15 20 30 * -25 Trial Number B– IL RL A- Baseline Initial Learning Reversal Learning AfterEffect -30 40 * -20 -20 -25 60 A RL B 0 0 -5 IL 10 A Trial Number Young Elderly Parkinson 50 ** 6 PD Subjects are impaired in reversal learning PD learning 35 2D Errors (cm) 30 25 Young Elderly Parkinson RL 20 15 B 10 A IL 5 0 5 15 25 35 45 Trial number 55 65 75 CONCLUSIONS • PD subjects show an endpoint elevation depression at baseline • The ability to adapt to a sudden biaxial visuomotor distortion applied in 3D space declines in normal aging and Parkinson disease • The Basal ganglia contribute to visuomotor learning, particularly when the task requires a rapid reconfiguration of newly learned visuomotor coordinations Deafferented Subjects ...
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This note was uploaded on 09/07/2011 for the course COGS 1 taught by Professor Lewis during the Spring '08 term at UCSD.

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