(C) 2008 Elsevier Ltd. All rights reserved.”
“The pattern of brain atrophy find more in semantic dementia and its associated cognitive effects have attracted a considerable body of research, but the nature of core impairments remains disputed. A key issue is whether the disease encompasses one neurocognitive network (semantics) or two (language and semantics). In order to address these conflicting perspectives,we conducted a longitudinal investigation of two semantic dementia patients, in which behavioural
performance across a range of measures of language and semantic performance was assessed and interpreted in the context of annually acquired MRI scans. Our results indicated a core semantic impairment in early stages of the disease, associated with atrophy of the inferior, anterior temporal cortex. Linguistic impairments emerged later, and were contingent on atrophy having spread into areas widely believed to subserve core language processes (left posterior perisylvian, inferior frontal and insular cortex). We claim, therefore, that phonological, syntactic and morphological processing deficits in semantic dementia reflect damage to core language areas. Further, we propose that much of the current controversy over the nature of deficits in semantic dementia reflect a tendency in the literature to adopt a static perspective
on what is a progressive disease. An approach in which the relationship between progressive neural changes and behavioural Blasticidin S concentration change over time is carefully mapped, offers a more constraining data-set from which to draw inferences about the relationship between language,
semantics and the brain. (C) 2008 Elsevier Ltd. All rights reserved.”
“Attention and awareness are intimately related concepts. Nevertheless, the two phenomena are empirically dissociable: visuo-spatial attention can act in the absence of visual awareness. We used magnetoencephalography (MEG) to record cortical neural activity from hemianopic patient GY while he performed a peripheral tetracosactide orientation-discrimination task in the context of an attention-cueing paradigm. The luminance contrast of target stimuli was set at GY’s threshold for reports of awareness (a feeling “”that something happened”" in his blind visual field). GY’s accuracy was significantly greater than chance and comparable, with or without awareness. GY was significantly faster to respond correctly on valid-cue versus invalid-cue trials, even in the absence of awareness, confirming the action of visuo-spatial attention in the absence of awareness. Time-frequency analysis of spectral power in the gamma frequency range (30-90 Hz), averaged over left parieto-occipital sensors, revealed effects of cue-validity independent of reported awareness, and effects of awareness independent of cue-validity.