The findings suggest that gains in naming accuracy obtained through picture-naming therapy may generalize to naming of the same items in more linguistically and cognitively demanding connected speech tasks. Demonstrating this generalization is methodologically challenging and the method utilized in this study may serve as one starting point for gathering a larger database in order to answer the question posed by this paper more robustly.

A long history of neuropsychology and neuroimaging has implicated the angular gyrus (AG) with a myriad of cognitive functions. We investigated the functional engagement of AG by three forms of memory: 1) episodic/autobiographical memory 2) object semantic-memory, and 3) event-semantic processing using the previously under-examined naturalistic task of propositional speech production. We conducted an ALE meta-analysis of imaging studies of propositional speech, followed by an fMRI study in which we conducted direct cross-domain comparisons. The results from the meta-analysis suggest that the AG is only engaged as part of the propositional speech network when the task carries an autobiographical component. This conclusion was strongly supported by the results from the fMRI study. The key fMRI findings were: 1) AG was positively engaged during autobiographical memory retrieval. 2) The AG was strongly deactivated for definitions of object semantics and non-propositional speech. 3) The level of AG activation increased with the degree to which the event descriptions relied on input from the episodic memory system. 4) Critically, the AG showed a very different pattern to that of known semantic representation regions (the anterior temporal lobe; ATL) - whilst AG activation increased with the autobiographical nature of the task, the ATL was equally responsive to all conditions. These results provide clear evidence that the AG is not acting as a semantic hub. In contrast, the AG activation profile directly mirrored that found in the wider autobiographical retrieval network. We propose that information stored elsewhere in the episodic system is temporally buffered online in the AG during autobiographical retrieval/memory construction.

Accumulating, converging evidence indicates that the anterior temporal lobe (ATL) appears to be the transmodal hub for semantic representation. A series of repetitive transcranial magnetic stimulation (rTMS) investigations utilizing the 'virtual lesion' approach have established the brain-behavioural relationship between the ATL and semantic processing by demonstrating that inhibitory rTMS over the ATL induced impairments in semantic performance in healthy individuals. However, a growing body of rTMS studies suggest that rTMS might also be a tool for cognitive enhancement and rehabilitation, though there has been no previous exploration in semantic cognition. Here, we explored a potential role of rTMS in enhancing and inhibiting semantic performance with contrastive rTMS protocols (1Hz vs. 20Hz) by controlling practice effects. Our results demonstrated that it is possible to modulate semantic performance positively or negatively depending on the ATL stimulation frequency: 20Hz rTMS was optimal for facilitating cortical processing (faster RT in a semantic task) contrasting with diminished semantic performance after 1Hz rTMS. In addition to cementing the importance of the ATL to semantic representation, our findings suggest that 20Hz rTMS leads to semantic enhancement in healthy individuals and potentially could be used for patients with semantic impairments as a therapeutic tool.

ObjectiveThe objective assessment of socially inappropriate behaviour in patients with frontotemporal lobar degeneration (FTLD) is difficult and hampered by its elusive cognitive basis. Neuropsychological tests of social cognition such as complex theory- of-mind tasks are unlikely to be helpful for early differential diagnosis in the future, because patients with non-neurological disorders show impairments on these tasks and they are confounded with general executive abilities. Here, we used a newly developed test of the knowledge of the consequences of social behaviour to investigate whether this can be impaired in patients with FTLD relative to a previously developed test of social conceptual knowledge.MethodWe included 19 consecutive patients with features of bvFTD or SD. Based on their background neuropsychological tests and neuroimaging features, we classified patients into those with primary neurodegeneration of the anterior temporal lobes (ATL group, n=12), those with primary neurodegeneration outside the ATL (non-ATL group, n=5) and those with global impairment or atrophy (n=2).ResultsAs predicted, we found conceptual knowledge of social behaviour to be impaired in the primary ATL group whilst knowledge of its long-term consequences was relatively preserved compared with the non-ATL group. In contrast, the non-ATL group showed impaired performance on the task probing knowledge of long-term consequences with relatively better conceptual social knowledge compared with the ATL group.ConclusionsThis shows that conceptual and sequential knowledge of social behaviour are dissociable and are likely to independently contribute to socially inappropriate behaviour. Short versions of these social conceptual and sequential knowledge tests are therefore promising tools for improvement of differential diagnosis when added to standard test batteries.