Microinjections of biocytin have been made in the granular layer of the rat cerebellar cortex in order to label the axonal projections of a localised population of granule cells. Light microscopic techniques were used to determine the lengths of the parallel fibres and to measure the spacing and size of the fibre varicosities. Fibres were longest in the superficial one-third of the molecular layer, where mean overall length was 4.7 mm, and mean length decreased to 4.2 mm in the lower one-third of the molecular layer. We found no very short fibres but a small population deep in the molecular layer had a branch length of about one-half the average. Mean intervaricosity interval and varicosity size varied with distance from proximal to distal along the fibres. Mean intervaricosity interval was 3.7 microns within 250 microns of the fibre bifurcation points and progressively increased towards the distal ends, where the mean interval was 7.4 microns. Mean varicosity size was 0.82 microns 2 in this proximal region and decreased to 0.47 microns 2 about 1.2 mm distally. Mean intervaricosity interval on the ascending axons of the granule cells was 4.0 microns. Electron microscopy revealed that a high proportion (89%) of the parallel fibre varicosities formed synaptic junctions. The majority of the synapses (91%) were formed on Purkinje cell dendritic spines. Some varicosities also formed simultaneous synaptic contacts or double synapses with two spines. These double synapses occurred more frequently in the proximal region of the fibres (11%) than on the distal ends (2%). The length of the postsynaptic density also differed according to the location of the varicosities and the mean length at the proximal parallel fibre synapses was 0.59 microns compared with 0.38 microns at the distal synapses. It is concluded that a beam or bundle of parallel fibres originating from cells in a focal region of the granular layer will exert a graded synaptic influence on its target Purkinje cells, with the most powerful influence occurring on cells located around the proximal region of the fibres where they bifurcate and the weakest action being exerted on cells located at the distal end of the fibres.

The validity of learning styles needs supports of additional objective evidence. The identification of learning styles using subjective evidence from VARK questionnaires (where V is visual, A is auditory, R is read/write, and K is kinesthetic) combined with objective evidence from visual event-related potential (vERP) studies has never been investigated. It is questionable whether picture superiority effects exist in V learners and R learners. Thus, the present study aimed to investigate whether vERP could show the relationship between vERP components and VARK learning styles and to identify the existence of picture superiority effects in V learners and R learners. Thirty medical students (15 V learners and 15 R learners) performed recognition tasks with vERP and an intermediate-term memory (ITM) test. The results of within-group comparisons showed that pictures elicited larger P200 amplitudes than words at the occipital 2 site (P < 0.05) in V learners and at the occipital 1 and 2 sites (P < 0.05) in R learners. The between-groups comparison showed that P200 amplitudes elicited by pictures in V learners were larger than those of R learners at the parietal 4 site (P < 0.05). The ITM test result showed that a picture set showed distinctively more correct responses than that of a word set for both V learners (P < 0.001) and R learners (P < 0.01). In conclusion, the result indicated that the P200 amplitude at the parietal 4 site could be used to objectively distinguish V learners from R learners. A lateralization existed to the right brain (occipital 2 site) in V learners. The ITM test demonstrated the existence of picture superiority effects in both learners. The results revealed the first objective electrophysiological evidence partially supporting the validity of the subjective psychological VARK questionnaire study.

It is generally agreed that cerebellar and lemniscal pathways project to largely separate areas of the thalamus and influence different functional areas of the cerebral cortex. Cerebellar afferents arise from neurones in the deep cerebellar nuclei and terminate in the ventral lateral group of thalamic nuclei or the "motor thalamus," whereas lemniscal afferents arise from the dorsal column nuclei and terminate in the adjacent ventral posterior group of thalamic nuclei or "sensory thalamus." However, it remains unclear whether or not these pathways converge onto thalamic neurones in the border zone between motor and sensory thalamus. The aim of this study was to compare directly the locations of cerebellar interposed and dorsal column nuclei terminals in the rat thalamus by using a double anterograde labelling technique. Microinjections of dextran-tetramethylrhodamine and dextran-fluorescein were made into the interposed and dorsal column nuclei, and labelled terminals in the thalamus were examined in the same sections. The labelled cerebellar and lemniscal terminals were located in separate areas throughout most of the ventral lateral and ventral posterior lateral nuclei, and there was only a limited region around the rostral border between these nuclei where the two groups of terminals came in close proximity to each other. In this common projection zone, however, cerebellar and lemniscal terminals seldom intermingled, and they mostly occupied separate, discreet areas. The results show that cerebellar and lemniscal fibres do indeed project to the border zone between the sensory and cerebellar thalamic nuclei, but they show practically no overlap in this region and are likely to influence separate thalamic neurones.

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