Functional neuroimaging

Functional neuroimaging is the use of neuroimaging technology to measure an aspect of brain function, often with a view to understanding the relationship between activity in certain brain areas and specific mental functions. It is primarily used as a research tool in cognitive neuroscience and neuropsychology.



Common methods include Positron Emission Tomography (PET), Functional Magnetic Resonance Imaging (fMRI), and Near Infrared Spectroscopic Imaging (NIRSI). These methods are used to measure localized changes in cerebral bloodflow related to neural activity. These changes are referred to as "activations". Regions of the brain which are activated when a subject performs a particular task may play a role in the neural computations which contribute to the behaviour. For instance, widespread activation of the occipital lobe is typically seen in tasks which involve visual stimulation (compared with tasks that do not). This part of the brain receives signals from the retina and is believed to play a role in visual perception.

Traditional "activation studies" focus on determining distributed patterns of brain activity associated with specific tasks. However, we are able to more thoroughly understand brain function by studying the interaction of distinct brain regions, as a great deal of neural processing is performed by an integrated network of several regions of the brain. An active area of neuroimaging research involves examining the functional connectivity of spatially remote brain regions. Functional connectivity analyses allow the characterization of interregional neural interactions during particular cognitive or motor tasks or merely from spontaneous activity during rest. fMRI and PET enable us to create functional connectivity maps of distinct spatial distributions of temporally correlated brain regions called functional networks.

However, interpretation of the results of functional neuroimaging studies is fraught with difficulty. It depends on careful experimental design and statistical analysis (often using a technique called statistical parametric mapping) so that the different sources of activation within the brain can be distinguished from one another. This can be particularly challenging when considering processes which are difficult to conceptualise or have no easily definable task associated with them (for example belief and consciousness).

Functional neuroimaging draws on data from many areas other than cognitive neuroscience, including biological sciences (such as neuroanatomy and neurophysiology) and fields such as physics and maths, to further develop and refine the technology.