Immunohistochemical localization of Leu-M1 carbohydrate antigen in human oral squamous cell carcinoma

Twenty-six biopsy specimens of oral squamous cell carcinomas were examined by the avidin biotin peroxidase complex (ABC) method for the presence of an epithelial cell membrane bound lacto-N-fucopentaose III, known also as Leu-M1 or Lex antigen. In normal oral epithelium, Leu-M1 antigen was expressed on keratinizing epithelia in the stratum spinosum. In well-differentiated carcinomas the antigen was found on the cell membrane of nucleate cells in infiltrating epithelial islands. Such pattern in moderately well and in poorly differentiated carcinomas was minimally expressed and was associated with flattened squamous cells or otherwise recorded negative. Leu-M1 antigen immunoreactivity in normal oral epithelia and in carcinomas was comparable to that of blood group H-2 chain that were examined. It was concluded that the intensity of the reaction parallels the magnitude of differentiation of epithelia. Leu-M1 antigen can serve as a marker of differentiation in oral squamous epithelium.     

Dynamic gray matter changes within cortex and striatum after short motor skill training are associated with their increased functional interaction

Gray matter (GM) changes have been described after short learning tasks that lasted for 7 days or after external stimulation that lasted for 5 days. However, the early time course of training-dependent GM changes is still unknown. We investigated whether shorter motor training sessions (four times of 30 min training) would induce GM changes. Therefore, T1-weighted MRIs were acquired daily. Because reported GM changes were induced by learning, a close relationship was assumed between the functional activity and the GM changes. Therefore, fMRI was performed in addition to daily T1-weighted MRIs.At the end of the four training sessions (at time point “post”), the test results of the trained motor skill were associated with an increase of GM in secondary cortical motor areas (dPMC_right, dPMC_left, SMA_left and the right inferior parietal lobule, IPL_right). The earliest time point at which a GM change was detected was 1 day before in the right ventral striatum (by contrasting daily T1-weighted MRI vs. baseline). To analyze whether this very early GM change within the right ventral striatum is associated with those GM changes at time point post (which were associated with motor skill performance), their functional connectivity was investigated over the time period of motor skill training. This analysis revealed an increase of functional coupling between these regions (striatum and cortex) over the training days.The current data demonstrate training-induced short GM plasticity is paralleled by their temporally dynamical process of functional interaction between the cortex and the striatum in response to a motor skill training.     

Ventral and dorsal fiber systems for imagined and executed movement

Although motor imagery is an entirely cognitive process, it shows remarkable similarity to overt movement in behavioral and physiological studies. In concordance, brain imaging studies reported shared fronto-parietal sensorimotor networks commonly engaged by both tasks. However, differences in prefrontal and parietal regions point toward additional cognitive mechanisms in the context of imagery. Within the perspective of a general dichotomization into dorsal and ventral processing streams in the brain, the question arises whether motor imagery and overt movement could differentially involve the dorsal or ventral system. Therefore, we combined fMRI and DTI data of 20 healthy subjects to analyze the anatomical characteristics of connecting fronto-parietal association pathways of imagined and overt movements. We found a dichotomy of fiber pathways into dorsal and ventral systems: the superior longitudinal fascicle (SLF II-III) was found to connect frontal and parietal regions involved in both overt and imagined movements, whereas a ventral tract via the extreme/external capsule (EmC/EC) connects cortical regions specific for motor imagery that were situated more anteriorly and posteriorly. We suppose that motor imagery-related kinesthetic emulations are embedded into dorsal sensorimotor networks, and imagery-specific cognitive functions are implemented in the ventral system. These findings have implications for models of motor cognition.     

Neuroimaging the semantic system(s)

Background: The organisation of the semantic system is controversially discussed among cognitive scientists. Whereas some authors assume that semantic processing is amodal, others propose modality-specific semantic systems. The amodal account holds that there is a single semantic system independent of the modality of stimulus presentation and nature of the concept. The multi-modal account, on the other hand, postulates that semantic knowledge is represented in modality-specific, distinct semantic systems. Attempts to integrate both accounts resulted in a hybrid model of semantic processing. Although an amodal semantic network is assumed in this view, input-dependent semantic specialisation coexists. Aims: The purpose of this study was to examine contrasting theories of the representation of the semantic knowledge with functional magnetic resonance imaging (fMRI). Methods & Procedures: Nine healthy subjects performed a semantic judgement task on graphemic words and pictures in the experimental condition, as well as a visual identity judgement task on pseudoword and three-dimensional geometric objects in the control condition. Outcomes & Results: A common activation pattern for words and pictures was found in the left inferior frontal gyrus and in the left middle temporal gyrus. Word-specific effects occurred in the left superior parietal, the left inferior occipital, the left anterior cingulate gyrus, and the right inferior frontal gyrus as well as bilaterally in the anteriomedial temporal area. Picture-specific areas involved the left supramarginal gyrus and the left cingulate gyrus. Further activation was found in the right middle frontal gyrus and bilaterally in the fusiform and inferior occipital gyrus. Conclusions: The results can best be accommodated in the framework of an integrative, hybrid model of semantic representation combining features of the amodal and the modality-specific account.