Studies of cognitive changes in PD have focused on patients without dementia and have mainly cited the involvement of the basal ganglia (16
), prefrontal cortex (21
), fronto-striatal regions (25
) or cortico-striatal (frontal and parietal) regions (28
). Aspects of cognition often associated with these regions in PD include executive function contributing to ADLs, attention, verbal recall, and visuospatial cognition. Cognitive differences between men and women with PD have been largely unexamined. One area of focus has been the comparison in quality of life and ADLs between men and women, functions that require intact cognitive abilities.
Riedel and colleagues (2008) tested 873 PD patients (33
). Women were more likely than men to be depressed but there was no mention of using depression as a covariate in analyzing cognitive performance. Participants were assessed with the Mini-Mental State Examination (MMSE) (34
), a brief measure of overall mental status; the Clock Drawing Test (CDT), and the Parkinson Neuropsychometric Dementia Assessment (PANDA) (35
), a measure including five subscales of cognition commonly affected in PD (word pair associate learning, alternating verbal fluency, visuospatial skills, working memory, and attention). Though there were no differences on the MMSE or PANDA total score, women attained significantly worse scores than men across stages of motor severity. Because the MMSE and PANDA-total were measures of overall cognitive status and the results were not compared to a control group, the investigators were limited in their interpretation of specific cognitive abilities.
Locascio and colleagues (2003), Clark and colleagues (2008), and Davidsdottir and colleagues (2005, 2008) have discussed cognitive impairment in PD more specifically, and reported gender differences. In a rare longitudinal study, Locascio et al. administered tests of memory, language, visuospatial and frontal-lobe function to healthy adults and PD patients over 10 years (36
). Gender differences across groups emerged on the Road Map Test of Direction Sense, a right-left discrimination task that requires egocentric mental rotation in space (men superior) (37
), and on a letter fluency test (women superior). In the PD group, men's performance declined faster across disease duration for this test as well as for the other verbal test, category fluency.
Davidsdottir et al. (2005) queried PD patients on visual and spatial symptoms (38
). The men and women did not differ in demographic characteristics or in duration of illness. Equal proportions of men and women endorsed at least one problem relating to visual or visuospatial functioning. There was an interaction of side of onset and gender on spatial performance, as men who had left-side onset of PD symptoms (LPD) reported more difficulty in estimating spatial relations than women with LPD; there were no male-female differences for the group who had right-side onset of symptoms (RPD). Side of motor symptom onset is an important consideration in the study of PD, as most patients initially present with symptoms on one side of the body, reflecting the loss of dopamine primarily in the contralateral hemisphere. The right hemisphere is more responsible than the left for many spatial abilities and failure to distinguish patients with LPD from RPD may mean that visuospatial deficits that contribute to functional decline are missed in patients with LPD.
In another study of spatial processing, Clark and colleagues (2008) found that PD patients were deficient in recognition of facial emotion, particularly for the emotions of anger and surprise, and men showed specific deficits in identifying fearful expressions (39
). The control group exhibited the opposite pattern: women were less accurate than men at identifying fearful expressions. In this group, women with PD reported more interpersonal problems than control women on a questionnaire assessing difficulties with self-assertion and over-accommodating behavior. These findings are consistent with those of previous studies that found that women with PD reported lower levels of quality of life, another index of social functioning (40
), and more depression than men (8
). An associated study of visual scanning in a subgroup of the same participants found that control women spent less time fixating on fearful expressions than control men did, but there was no male-female difference in fixation duration for the PD group (41
), making the point that for some perceptual or cognitive functions, PD may be associated with the disappearance of normal gender-based differences.
Davidsdottir and colleagues (2008) examined spatial navigation and visuospatial functioning, including measurement of veering during a navigation task, visual ability as assessed through acuity, contrast sensitivity and motion perception, and visuospatial function through tests of line bisection, optic flow perception, egocentric reference, and visual dependence (28
). LPD patients were generally more visually dependent than RPD patients, who in turn were more visually dependent than the control group. Gender differences were found in the navigation task, egocentric midline test, line bisection, and motion perception. The results of this study showed that both side of symptom onset and gender were important in understanding visuospatial and visual functioning and navigational veering in patients with PD.
Not all studies of visuospatial function in PD have found male-female differences in performance, including Cronin-Golomb and Braun (1997) (42
) on visuospatial problem solving using Raven's Coloured Progressive Matrices, a matching test of visual closure and spatial reasoning (43
); Amick and colleagues (2006) on mental rotation (30
); and Schendan and colleagues (2009) on hierarchical pattern perception, a test of global and local visual pattern processing (29
). The latter two studies reported LPD-RPD effects. Cronin-Golomb (2010) recently reviewed the side of onset literature, describing PD as a disconnection syndrome (31
). Taken together, the several studies suggest that gender differences pertain to some but not all visuospatial abilities, and may interact with side of disease onset. A number of the reported gender differences in clinical characteristics, functional status, and cognition are listed in .