Multi-modal brain imaging studies of mnemonic control processes

The ability to flexibly retrieve information regarding our personal past from memory is an essential aspect of healthy everyday functioning. Over the course of our lives, an enormous amount of information is stored in memory - in effect, the record of our lives. Different situations require us to selectively retrieve information relevant to the situation or task at hand from this record without being inundated with a flood of task-irrelevant information that is also stored in memory. The fact that we are able to do this indicates that we exert a significant degree of control over what is and is not retrieved from memory. This research proposal is concerned with understanding both the functional nature of these memory control processes (i.e. what are they, and what do they do?), as well as identifying the brain regions that are associated with these processes. Understanding how memory control processes operate in healthy individuals will provide insight into the reasons why ageing and various patient populations (such as those suffering from dementia or Alzheimer's Disease) experience memory problems. These impairments are often specific to the retrieval of task-relevant information from memory, in that these populations are often either unable to retrieve information when needed, or are unable to filter out the retrieval of irrelevant information. Some evidence exists to suggest that these problems can be reduced if appropriate retrieval strategies are provided, which suggests that the locus of these memory impairments is not necessarily the ability to remember information, but rather the ability to spontaneously adopt appropriate retrieval strategies (i.e. the ability to control retrieval). Refining our understanding of how these processes operate in healthy participants - and the brain regions involved - will permit greater understanding of memory impairments in other populations. This research programme will employ a variety of brain imaging methods to explore these issues. This is because no imaging method provides all the information needed to understand the brain basis of behaviour fully. Some methods, such as EEG and MEG, give detailed information regarding the timecourse of brain activity and the frequencies involved. Others, such as fMRI, give much more detailed anatomical information (i.e. specifically which brain regions are associated with the processes of interest). Employing a variety of methods in this research programme will not only permit a greater understanding of the neural basis of memory control processes, but will also provide insight into how brain imaging data collected using each of these techniques relate to each other.

Recollecting task-relevant contextual information from episodic memory requires a great deal of cognitive control, as this information must be selectively and successfully retrieved without triggering the involuntary recollection of large amounts of irrelevant information. Recent research employing a variety of brain imaging techniques have provided initial evidence that these mnemonic control process operate pre-retrieval, during retrieval attempts, and post-retrieval. This research programme is concerned with investigating these issues further, and will assess the boundary conditions governing controlled episodic retrieval as well as identifying the functional characteristics and neural correlates of core mnemonic control processes. This research programme will take a convergent methods approach, incorporating EEG, MEG and fMRI brain imaging techniques to identify the neural correlates and functional characteristics of mnemonic control processes. It is anticipated that these processes are likely predominantly located in prefrontal cortex, a region of the brain that is highly functionally heterogeneous. Although EEG data will provide important information regarding the temporal characteristics of mnemonic control processes, and is a cost-effective method of assessing the impact of various factors on previously identified neural correlates of interest, it is likely that event-related fMRI and MEG methods will be required to obtain detailed information regarding anatomical localisation and functional connectivity.