Refractory semantic access dysphasia resulting from resection of a left frontal glioma.

The existence of semantic access disorders is now well established, however the precise cognitive and anatomical underpinnings are still debated. Here we describe the case of a patient that became aphasic after the resection of a left frontal glioma. Detailed lesion reconstruction indicates that the lesion was mostly restricted to the left dorsal and ventral prefrontal cortices and the underlying white matter, but sparing temporal lobes.

Right posterior cortical functions in a tumour patient series.

It is standardly believed that the localisation of cognitive function by means of impairments arising from cortical tumour is not possible as the functional defects that result are mild and unspecific. These assumptions were not supported in an investigation of four processes generally sensitive to right posterior cortical lesions, when patients with parieto-occipital lesions were compared with prefrontal ones. In three of the tests loading on the individual processes - Reaching Accuracy, Star Cancellation, Fragmented Letters and Cube Analysis - parieto-occipital impairments were found in the basic groups analysis and this was so in the right-hemisphere group.

Two qualitatively different impairments in making rotation operations.

It is widely recognized that mental rotation is a cognitive process which engages a distributed cortical network including the frontal, premotor and parietal regions. Like other visual-spatial transformations it could require operations on both metric and categorical spatial representations. Previous reports have implicated respectively the right hemisphere being involved in the metric processing and the left hemisphere in the categorical processing.

A left basal ganglia case of dynamic aphasia or impairment of extra-language cognitive processes?

We report the case of OTM who presented with dynamic aphasia following a stroke that occurred in the left basal ganglia. He showed drastically reduced spontaneous speech in the context of well preserved naming, repetition and comprehension skills. OTM was particularly impaired in generating words, sentences and phrases when cued by a stimulus allowing many response options.

The neural basis of temporal preparation: Insights from brain tumor patients.

When foreperiods (FPs) of different duration vary on a trial-by-trial basis equiprobably but randomly, the RT is faster as the FP increases (variable FP effect), and becomes slower as the FP on the preceding trial gets longer (sequential effects). It is unclear whether the two effects are due to a common mechanism or to two different ones. Patients with lesions on the right lateral prefrontal cortex do not show the typical FP effect, suggesting a deficit in monitoring the FP adequately [Stuss, D.