EN
Individual memories are thought to be stored by ensembles of neurons that are reactivated during recall. While these memory ensembles can now be labelled and manipulated in the rodent brain, they are difficult to measure in humans using non-invasive methods. Here, by adopting a multifaceted approach, I will show how indirect measures of memory ensembles can be obtained from the human brain. Data from ultra-high field MR spectroscopy, fMRI and transcranial direct current stimulation (tDCS) will be presented to demonstrate how these techniques can be combined to investigate storage of associative memories. By measuring and manipulating neocortical GABA in the human brain I will then show evidence to suggest that associative memories are stored in balanced excitatory-inhibitory ensembles. The inhibitory component of memory ensemble ensures that memories lie dormant unless neocortical excitability is modulated but also appears to play a critical role in protecting overlapping memories from interference. FINANCIAL SUPPORT: Medical Research Council, Wellcome Trust, John Fell Fund, Merton College.