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| Authors | Methods | Results |
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| (1) Behavioral studies in normal subjects and brain-damaged patients |
| Whitehouse [31] | Explored in R and LBD patients aspects of pictorial and verbal encoding in two forced-choice recognition memory experiments. | Left hemisphere injury selectively impaired verbal memory coding, whereas right hemisphere damage preferentially impaired pictorial coding. |
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| Grossman and Wilson [32] | Asked right and left BD patients and normal controls to evaluate perceptual and conceptual stimuli for their degree of category membership. | The left-hemisphere patients showed anomalies in categorizing the conceptual but not the perceptual items, while the reverse was true for the right hemisphere patients. |
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| Nieto et al. [34] | Carried out two lateral tachistoscopic experiments in normal subjects, to test semantic capabilities of the left and right cerebral hemispheres, through categorization tasks with verbal and pictorial presentation. | Right visual field advantages were obtained for verbal presentations in both category-membership and category-matching tasks. However, no significant visual field differences were found for any pictorial presentations. |
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Gainotti
et al. [33] | Constructed two very similar tasks of verbal and pictorial memory and administered them to control subjects and patients with R and L hemispheric lesions. | Word recognition was selectively impaired by left and picture recognition by right brain injury, but the difference between R and LBD patients was significant only on the test of verbal memory, whereas the trend in the opposite direction observed on the test of pictorial memory was nonsignificant. |
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| Shibahara and Lucero-Wagoner [35] | Used a semantic priming paradigm to examine whether perceptual or conceptual properties of word meanings would be associated with the left or right hemisphere. | The results indicated that perceptual information is available only in the right hemisphere while conceptual information is available in both hemispheres. |
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| (2) Neuroimaging investigations in normal subjects and brain-damaged patients |
| Thierry et al. [36] | Used functional neuroimaging in normal subjects to compare semantic processing of spoken words to equivalent processing of environmental sounds, after controlling for low-level perceptual differences. | Words enhanced activation in left temporal (LT) regions while environmental sounds enhanced activation in the right temporal (RT) areas. The LT involvement in comprehending words was more extensive than the RT involvement in processing non-verbal sounds. |
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| Thierry and Price [37] | Developed these studies, comparing conceptual processing of verbal and non-verbal stimuli in both visual and auditory modalities. | They found that left temporal regions were more involved in comprehending words (heard or read), whereas the right temporal cortex was more involved in making sense of environmental sounds and images. |
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| Acres et al. [39] | Administered four verbal and non-verbal tasks (including words and pictures categorization) to patients with R and L temporal lesions and correlated their behavioural scores with voxel-based measures of neuronal integrity. | Performance on the verbal tasks correlated with the lesion of left inferior and anterior temporal regions, while performance on the non-verbal tasks correlated with the lesion of analogous right temporal areas. The L temporal lobe was more involved in word categorization than the right in pictures categorization. |
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| Butler et al. [40] | Used voxel-based morphometry to correlate performance on verbal and nonverbal versions of a semantic association task in patients with neurodegenerative diseases. | They found material-specific correlations, greater for verbal stimuli in left temporal regions than for nonverbal stimuli in the right fusiform gyrus. |
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| Hocking and Price [38] | Presented subjects simultaneously with one visual and one auditory stimulus and instructed them to decide whether these stimuli referred to the same object or not. Verbal stimuli consisted of spoken and written object names, whereas non-verbal stimuli consisted of pictures of objects and naturally occurring object sounds. | Verbal matching increased activation in the left temporal lobe, whereas non-verbal matching increased activation in the right fusiform region. |
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| (3) TMS experiments in normal subjects |
| Pobric et al. [41] | Used offline, low-frequency, and repetitive transcranial magnetic stimulation (rTMS) to disrupt neural processing temporarily in the left or right temporal poles. During the induced refractory period, subjects made judgements of semantic association for verbal and pictorial stimuli. | They found that rTMS applied to the left or right temporal poles disrupted semantic processing for words and pictures to the same degree. |
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