title: Motion integration deficits are independent of magnocellular impairment in Parkinson's disease.
abstract: Motion processing involves multiple hierarchical steps, from the magnocellular pathway, sensitive to high temporal frequency modulations, to subsequent motion integration within the visual cortical dorsal stream. We have tested whether motion integration deficits in mild Parkinson disease (PD) can be explained by visual deficits in earlier processing nodes. Contrast sensitivity deficits in the magnocellular pathway, were compared with speed discrimination of local dots moving in random directions, speed and direction discrimination of moving surfaces and motion integration as measured by 2D coherence thresholds (n=27). We have found that low-level magnocellular impairment in PD does not explain deficits in subsequent steps in motion processing. High-level performance was abnormal in particular for tasks requiring perception of coherently moving surfaces. Motion coherence deficits were predictive of visuomotor impairment, corroborating a previous magnetic stimulation study in normal subjects. We conclude that dorsal stream deficits in PD have a high-level visual cortical basis independent of low-level magnocellular damage.
authors.affiliation: Visual Neuroscience Laboratory, IBILI, Faculty of Medicine, 3000-458 Coimbra, Portugal. mcbranco@ibili.uc.pt
authors.forename: Miguel
authors.initials: M
authors.lastname: Castelo-Branco
authors.forename: Mafalda
authors.initials: M
authors.lastname: Mendes
authors.forename: Fatima
authors.initials: F
authors.lastname: Silva
authors.forename: João
authors.initials: J
authors.lastname: Massano
authors.forename: Gustavo
authors.initials: G
authors.lastname: Januário
authors.forename: Cristina
authors.initials: C
authors.lastname: Januário
authors.forename: António
authors.initials: A
authors.lastname: Freire
mesh_terms: D020532:Basal Nucleus of Meynert / Q000473:pathology*; D003072:Cognition Disorders / Q000209:etiology / Q000503:physiopathology* / Q000523:psychology*; D015350:Contrast Sensitivity / Q000502:physiology; D003627:Data Interpretation, Statistical; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009039:Motion Perception / Q000502:physiology*; D010300:Parkinson Disease / Q000150:complications / Q000473:pathology / Q000523:psychology*; D010775:Photic Stimulation; D011597:Psychomotor Performance / Q000502:physiology; D012684:Sensory Thresholds / Q000502:physiology; D014795:Visual Pathways / Q000503:physiopathology