Objective: Executive deficits are frequent sequelae of neurological and psychiatric disorders, but their adequate neuropsychological assessment is still a matter of contention, given that executive tasks draw on a multitude of cognitive processes that are often not sufficiently specified. In line with this, results on psychometric properties of the Tower of London, a task measuring planning ability as a prototypical executive function, are equivocal and furthermore lacking completely for adult clinical populations.
Methods: We used a structurally balanced item set implemented in the Tower of London (Freiburg version, TOL-F) that accounts for major determinants of problem difficulty beyond the commonly used minimum number of moves to solution.
The inferior frontal gyrus (IFG) is active during both goal-directed action and while observing the same motor act, leading to the idea that also the meaning of a motor act (action understanding) is represented in this "mirror neuron system" (MNS). However, in the dual-loop model, based on dorsal and ventral visual streams, the MNS is thought to be a function of the dorsal steam, projecting to pars opercularis (BA44) of IFG, while recent studies suggest that conceptual meaning and semantic analysis are a function of ventral connections, projecting mainly to pars triangularis (BA45) of IFG. To resolve this discrepancy, we investigated action observation (AO) and imitation (IMI) using fMRI in a large group of subjects.
View Article and Find Full Text PDFProcessing of multiple or bilateral conditions presented simultaneously in both hemifields reflects the natural mode of perception in our multi-target environment, but is not yet completely understood. While region-of-interest based studies in healthy subjects reported single cortical areas as the right inferior parietal lobe (IPL) or temporoparietal junction (TPJ) to process bilateral conditions, studies in extinction patients with reduced ability in this regard suggested the right superior temporal cortex to hold a key role. The present fMRI study on healthy subjects aimed at resolving these discrepancies by contrasting bilateral versus unilateral visual conditions in a paradigm similar to the bed-side test for patients with visual extinction on a whole brain level.
View Article and Find Full Text PDFThe current concept of a dual loop system of brain organization predicts a domain-general dual-pathway architecture involving dorsal and ventral fiber connections. We investigated if a similar dichotomy of brain network organization applies for pantomime (P) and imitation of meaningless gestures (I). Impairments of these tasks occur after left hemispheric brain lesions causing apraxia.
View Article and Find Full Text PDFApraxia is a cognitive disorder of skilled movements that characteristically affects the ability to imitate meaningless gestures, or to pantomime the use of tools. Despite substantial research, the neural underpinnings of imitation and pantomime have remained debated. An influential model states that higher motor functions are supported by different processing streams.
View Article and Find Full Text PDFThe cortical motor system follows a modular organization in which different features of executed movements are supported by distinct streams. Accordingly, different levels of action recognition, such as movement characteristics or action semantics may be processed within distinct networks. The present study aimed to differentiate areas related to the analysis of action features involving semantic knowledge from regions concerned with the evaluation of movement characteristics determined by structural object properties.
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