The paper reviewed here is ‘The Anterior Temporal Lobes and the Functional Architecture of Semantic Memory’ by Simmons and Martin. The authors review the evidence for three competing theories of the role of the Anterior Temporal Lobes (ATL) in semantic memory. There is no stated methodology for this review article but instead it appears to represent a review of the literature guided by the expertise of the authors in this area. This topic is potentially important for diseases such as semantic dementia. In the introduction, the authors outline three competing theories for the function of the ATL’s in semantic memory
1. The ATL links together areas in the brain containing semantic information
2.The ATL contains information about unique objects
3. The ATL stores ‘social conceptual information’
They then go on to explain some of the subtleties within these classifications including the neat idea that the temporal lobe might not actually store the information itself but could point to this information elsewhere – in effect acting as a signpost. They alos highlight the possible roles for the ATL’s in storing broad or narrow categories of objects and specific objects or broader categories of objects.
The authors then go onto look at the some of the neuropsychological evidence for the role of the ATM in semantic memory. They comment on studies with transcranial magnetic stimulation in which the lateral surface of the ATL is targetted and where there is an impairment in object naming response. However they note that the TMS can have effects areas other than those directly targetted and so it is difficult to confirm a simple causal relationship between the two. There are similar arguments with other types of study and they also outline some of the counterarguments that have been developed.
The authors then look at neuroimaging data particularly fMRI studies. There is a focus on the conclusions of these studies rather than the methodologies and so this would be a useful starting point for further reading. The results cited included
- ATL activation on viewing familiar faces
- ATL activation on viewing famous faces
- ATL activation on inferring mental states and emotions in others
- Right ATL activated on ‘viewing photgraphs depicting scens with moral connotations…versus nonmoral control scens’
- Right ATL activated in relation to ‘socal abstract concepts such as courage or generosity’
as well as a number of other findings. They comment that there are no direct comparisons of all three competing theories in a single neuroimaging study. In their conclusions, the authors suggest that comparisons of the different theories could be tested within the same study and also comment on the possibility of using alternative methodologies to test the theories. One suggestion which I thought was particularly interesting was the use of cortical surface recording. This has already proved useful in investigating the role of the speech and language areas and perhaps it might be useful in asnwering these types of questions.
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