Perceptual bias for affective and nonaffective information in asymmetric Parkinson's disease.
OBJECTIVE
To relate lateralized impairments of visual perception in Parkinson's disease to asymmetries in the severity of motor symptoms.


METHODS
Ten patients with worse left-sided motor symptoms (LPD), 15 with worse right-sided (RPD), and 13 healthy age-matched controls (all right-handed) viewed mirror-imaged pairs of emotional chimeric faces, (left side smiling, right neutral, and vice versa), of greyscales (strips whose luminance varied smoothly from black on the left to white on the right, and vice versa) and of gender chimeric faces (left side male, right female, and vice versa). Participants signaled which stimulus appeared happier, brighter, or more feminine, respectively, so showing which side received more attention.


RESULTS
For emotional chimeras, controls and LPD showed little bias, whereas RPD showed a strong bias to left hemispace (p = .018, r = .45). Across all patients, this bias was associated with severity of right-sided motor impairment (p = .018, r = .49). The bias was much weaker and insignificant for greyscales (p = .72, r = .14). For gender chimeras, RPD again showed a significantly greater left hemispace bias than did LPD (p = .037, r = .47), although neither patient group differed significantly from controls. Across all patients, this bias correlated with ratio of right-to-left symptom severity (p = .044, r = .48).


CONCLUSIONS
The left hemispace bias in RPD is greater for facial than for luminance judgments, and is amplified for emotional judgments. Asymmetrical degeneration of the striatum, particularly involving the left side, appears to underlie this deficit in visual processing.
Smith
Jared G
JG
School of Psychology and Clinical Language Sciences, University of Reading, Reading, United Kingdom.
Harris
John P
JP
Khan
Saleem
S
Atkinson
Elizabeth A
EA
Fowler
M Susan
MS
Gregory
Ralph P
RP
D000368:Aged; D015982:Bias; D016022:Case-Control Studies; D005260:Female; D007839:Functional Laterality / Q000502:physiology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D019964:Mood Disorders / Q000209:etiology*; D009483:Neuropsychological Tests; D010300:Parkinson Disease / Q000150:complications*; D010364:Pattern Recognition, Visual / Q000502:physiology; D010468:Perceptual Disorders / Q000209:etiology*; D010775:Photic Stimulation / Q000379:methods