Marker identification and mental rotation in automatic conditions

A basic finding of mental rotation research is that the time required to discriminate an asymmetrical visual stimulus from its reflected or backward version typically varies systematically with the angular departure of the probe stimulus from its normal upright (or expected) position within the picture plane. This regular dependence of reaction time (RT) on the rotational position (orientation) of the probe stimulus was interpreted by assuming an internal process working as a kind of mental analog of an external physical rotation and being carried out to bring the internal representations of the stimuli into congruence with each other before a decision is made. The present study was designed to investigate whether the dependence of RT on orientation also holds true in the case of a probe that can be identified on the basis of a single distinctive feature. In addition, it was examined whether the efficiency of the underlying processes could be improved by training. Results showed that the dependence of RT on orientation (RT function) does not occur if the presented visual probes differ with regard to a simple feature as, for example, an easily detectable angular difference. A change of the RT function, which would have indicated a change in the speed of the underlying processes, did not occur despite an "automatization" training.     

Important points of neuropsychology with reference to Luria's study procedures

The results presented by A. R. Luria receive special attention in this presentation of three principle directions of current neuropsychological research: the problem of attributing aspects of mental performance to specific regions of the brain, psychometric approaches to brain function measurement, and model approaches to neuropsychological therapy. More recent knowledge pertaining to activity and personality centres diagnosis and efficiency measurements should receive closer consideration. Attention is drawn to the inclusion of learning and concentration training in therapeutic schemes.     

Does Structural Complexity Necessarily Imply Processing Difficulty?

Our goal is to establish a link between the time needed to plan a sentence containing an embedded clause and the structure of this sentence. Contrary to a traditional monolithic conception of subordination, three types of embeddings were considered, depending on their degree of syntactic integration: subcategorized, modifier and pseudo-embedded clauses. We hypothesized that in the case of subcategorization, fewer pauses should occur between the matrix and the subordinate clause since the latter is required by the lexical properties of verbs. By contrast, pseudo-embedded clauses are the less integrated. Hence, they should exhibit planning characteristics similar to the ones of simple sentences, the matrix clause and the subordinate clauses being planned in two steps. Twenty texts produced by French speaking adults were recorded. Pauses were characterized according to their duration and position. Globally, both predictions were confirmed. We conclude that supposedly complex sentences are not necessarily difficult to process.     

Speaking with a single cerebral hemisphere: fMRI language organization after hemispherectomy in childhood

Speech-related fMRI activation was examined in six hemispherectomy patients (three left LX, three right RX, four with congenital and two with late-acquired hemiplegia) operated in childhood for the relief of drug-resistant epilepsy. Although the temporal and sensorimotor pattern of activation was similar to that found in neurologically intact control participants, activation in Broca's area and its right homolog varied greatly. Involvement of pars triangularis and orbitalis was found in the three cases with best outcome (two RX, one LX), whereas pars opercularis alone was activated in the two remaining LX patients. The results suggest that distinct subregions of Broca's area and their right homologs can subserve speech and language, and that this variability may determine functional outcome.     

Segmenting the body into parts: evidence from biases in tactile perception

How do we individuate body parts? Here, we investigated the effect of body segmentation between hand and arm in tactile and visual perception. In a first experiment, we showed that two tactile stimuli felt farther away when they were applied across the wrist than when they were applied within a single body part (palm or forearm), indicating a "category boundary effect". In the following experiments, we excluded two hypotheses, which attributed tactile segmentation to other, nontactile factors. In Experiment 2, we showed that the boundary effect does not arise from motor cues. The effect was reduced during a motor task involving flexion and extension movements of the wrist joint. Action brings body parts together into functional units, instead of pulling them apart. In Experiments 3 and 4, we showed that the effect does not arise from perceptual cues of visual discontinuities. We did not find any segmentation effect for the visual percept of the body in Experiment 3, nor for a neutral shape in Experiment 4. We suggest that the mental representation of the body is structured in categorical body parts delineated by joints, and that this categorical representation modulates tactile spatial perception.     

Hemispheric differences in the time-course of semantic priming processes: evidence from event-related potentials (ERPs)

To investigate hemispheric differences in the timing of word priming, the modulation of event-related potentials by semantic word relationships was examined in each cerebral hemisphere. Primes and targets, either categorically (silk-wool) or associatively (needle-sewing) related, were presented to the left or right visual field in a go/no-go lexical decision task. The results revealed significant reaction-time and physiological differences in both visual fields only for associatively related word pairs, but an electrophysiological difference also tended to reach significance for categorically related words when presented in the left visual field. ERP waveforms showed a different time-course of associative priming effects according to the field of presentation. In the right visual field/left hemisphere, both N400 and Late Positive Component (LPC/P600) were modulated by semantic relatedness, while only a late effect was present in the left visual field/ right hemisphere.