Courtesy of Dr Paul Hoffman and Dr Alexa Morcom, this image shows activation likelihood maps generated by comparing contrasts of interest from young and older adults in a meta-analysis of 47 functional neuroimaging studies (PET and fMRI data). Contrasts of interest for this meta-analysis were computed from tasks that involved two experimental conditions in which one placed a greater demand on semantic cognition. Semantic cognition is the use of semantic knowledge, such as the meanings of words or sentences and knowledge relating to meaningful images. It is an important domain for research on neurocognitive ageing, as it has been thought to remain stable into older age unlike many other domains of cognition.
Functional neuroimaging studies of young adults have shown that semantic cognition is associated with activation of brain networks relatively lateralised to the left hemisphere, including inferior prefrontal, posterior temporal and inferior parietal cortex. This image shows direct comparisons of young and older adults, using an activation likelihood estimation (ALE) meta-analysis to investigate age-related differences in the neural basis of semantic cognition. Green regions are areas in which older adults were found to reliably exhibit more activation than young adults, and red regions are areas in which activation was reliably greater in young adults. Reduced activation in older adults was observed in a range of left-hemisphere regions linked with semantic processing, and also in left hippocampus and bilateral occipital cortex. In contrast, older adults showed increased activation in right frontal and parietal regions. This pattern of results indicates a shift from the neurally specialised left-lateralised semantic network in later life, with greater recruitment of domain-general neural resources.
The image is taken from a recent study published in Neuroscience & Biobehavioral Reviews:
Hoffman P & Morcom AM. Age-related changes in the neural networks supporting semantic cognition: A meta-analysis of 47 functional neuroimaging studies. Neuroscience & Biobehavioral Reviews 2018; 84:134-150.