Why Are the Right and Left Hemisphere Conceptual Representations Different?
Table 2
Data obtained in investigations which contrasted performances obtained on verbal and non-verbal semantic tasks by patients with semantic dementia (SD) with prevalent right or left anterior temporal lobe (ATL) atrophy.
Administered to 15 SD patients, whose temporal lobe atrophy was more severe on the left or on the right side, tests of famous faces and names and the verbal and pictorial versions of the Pyramids and Palm Trees test (PPT).
Subjects with a predominance of left TL atrophy identified faces better than names and obtained better results on the pictorial than on the verbal version of the PPT test, whereas patients with a more severe right TL degeneration showed the opposite pattern.
Investigated if semantic dementia patients with prevalent left or right atrophy have different impairments of object recognition, as measured by the ability to classify two visually different tokens of an object as the same thing.
The impairment was greater for cases whose anterior temporal lobe atrophy was prevalent on the right than for those with a prevalence of left-sided atrophy.
Examined in SD the neural correlates of verbal and non-verbal semantic measures with FDG-PET. The semantic verbal task was picture naming, whereas the non-verbal semantic task was a pictorial version of the “Camel and Cactus test”. The authors performed an additional behavioural study on a wider cohort of patients with semantic dementia.
The left anterior fusiform activity predicted performance on the verbal semantic task whereas the right anterior fusiform metabolism predicted performance on the perceptual semantic task. The L temporal lobe was more involved in the verbal semantic tasks than the right in the non-verbal task. Patients with more extensive right temporal atrophy were significantly more impaired on the test of non-verbal semantics.
Studied the abnormalities of the N400 component of the ERP in a picture-probe matching task in patients with atrophy of the right and left ATL. Probes were semantically related and unrelated words and pictures.
A significant N400 potential was found in patients with atrophy of the left but not of the right ATL [46] only when the probe was a semantically unrelated but not a related word.
Reexamined performance of SD patients with predominantly right and left TL atrophy, not only on faces and names of famous people, but also on the pictorial and word versions of the PPT test. They based statistical comparisons on individual performance ranks.
Differences in rankings for face and name identification strongly distinguished the two SD subgroups, whereas comparisons between picture and word versions of the PPT tests only approached significance.
