Line bisection and cerebellar damage.

BACKGROUND: The cerebellum plays a role in higher-order cognitive processes, although the evidence concerning spatial cognition is not definite. OBJECTIVE: To investigate the role of the cerebellum in setting the midpoint of a horizontal line and to assess the role of visual monitoring of the movement of the upper limb. METHODS: Twelve patients, 6 with left-sided and 6 with right-sided cerebellar damage, and 12 control participants, marked the midpoint of horizontal lines with their left or right hand, under conditions of present versus absent visual control of the movement of the upper limb. RESULTS: When visual feedback was available, the patients' accuracy was comparable to that of control participants with a minor leftward bias. Without visual feedback, controls and right-sided cerebellar patients exhibited a rightward bias. Conversely, left-sided cerebellar patients still showed a leftward bias. CONCLUSIONS: The leftward bias may be related to the visual monitoring of the movement of the upper limb, being reversed when this is not available. Under these conditions, kinesthetic information becomes more relevant, and may contribute to the rightward bias. This effect is not shown by left cerebellar patients, possibly due to the disconnection between the left cerebellum and the right hemisphere, involved in spatial cognition.

Noun-verb dissociation in aphasia: the role of imageability and functional locus of the lesion.

Aphasic patients occasionally manifest a dissociated naming ability between objects and actions: this phenomenon has been interpreted as evidence of a separate organization for nouns and verbs in the mental lexicon. Nevertheless Bird et al. [Bird, H., Howard, D., Franklin, S. (2000). Why is a verb like an inanimate object? Grammatical category and semantic category deficits. BrainandLanguage, 72, 246-309], suggested that the damage underlying noun-verb dissociation affects the corresponding semantic concepts and not the lexical representation of words; moreover, they claimed that many dissociations reported in literature are caused merely by a strong imageability effect. In fact, most authors used a picture-naming task to assess patients' naming ability, and due to the fact that this test involves the use of pictures to represent actions and objects, nouns were frequently more imageable than verbs [Luzzatti, C., & Chierchia, G. (2002). On the nature of selective deficit involving nouns and verbs. RivistadiLinguistica, 14, 43-71]. In order to overcome this drawback, we devised a new task - nouns and verbs retrieval in a sentence context (NVR-SC) - in which nouns and verbs have the same imageability rate. Patients' performance on this task is compared with that obtained by the same patients on a standard picture-naming task. Of the 16 aphasic patients with a selective verb deficit, as revealed by the picture-naming task, two continued to show dissociation in the NVR-SC task, while 14 did not. The data indicate that at least some patients have an imageability-independent lexical deficit for verbs. The functional locus/i of the damage is also considered, with particular reference to the lemma/lexeme dichotomy suggested by Levelt et al. [Levelt, W. J. M., Roelofs, A., & Meyer, A. S. (1999). A theory of lexical access in speech production. BehavioralandBrainSciences, 22, 1-75].