It was found that the distribution of preferred directions of a very large population of cells in area 7a studied during eye and/or hand movement was highly anisotropic and favoured the representation of the contralateral space (Fig. 5). Interestingly,
this anisotropy was not observed in the memory epoch, when the animal kept in working memory the location of the target toward which, after a go-signal, an eye and/or a hand movement had to be made. Therefore, this anisotropy in the representation of motor space in IPL is of a dynamic nature, as it emerges only at the moment when all necessary information is available to transform the motor plan into action. It Talazoparib is our hypothesis that the loss of this representation and the difficulty in continuously combining and updating
all the spatial information necessary to select the direction of visually-guided movement lies at the core of directional hypokynesia. In this respect, it is noteworthy that network models of neglect mostly rest on anisotropy of spatial representations (Pouget & Sejnowski, 1997; Pouget & Driver, 2000). The assumption is that selleck chemicals llc a gradient of spatial representation is embedded in the activity of neurons in the left and right IPL, such that lesions in one hemisphere primarily disrupt information concerning the contralesional space. Therefore the data illustrated and discussed above offer a neurophysiological underpinning for understanding the motor impairments following parietal damage and provide new data to constrain future theoretical models of neglect. Apraxia in general has been defined as the ‘inability to perform certain subjectively purposive movements or movement
complexes Terminal deoxynucleotidyl transferase with conservation of motility, of sensation and of coordination’ (Wilson, 1909). Apraxia is typically the result of parietal lobe damage, and several types have been identified, including ideational, ideomotor and constructional apraxia. In ideational apraxia (Liepmann, 1920) there is a failure to perform a complex series of actions, such as an inability to perform the sequence movements needed to fold a piece of paper and place it inside an envelope. In ideomotor apraxia (Liepmann, 1920) the patient cannot execute a familiar action on verbal command or by imitation. In constructional apraxia there is a disturbance ‘in formative activities such as assembling, building and drawing, in which the spatial form of the product proves to be unsuccessful, without there being an apraxia for single movements’ (Kleist, 1934). There is a basic difference between ideational and ideomotor apraxia on one hand and constructional apraxia on the other; namely, in the first two forms the patients have difficulty in reproducing previously well learned motor tasks, whereas in constructional apraxia the difficulty is with reproducing visual figures or constructing a complex object made by different parts.