Many psychiatric illnesses lead to alterations in mood, perception and memory. How activity in the brain leads to accurate perception and memory recall is a critical basic question in neuroscience that has been difficult to address directly. In this grant we develop an approach in mice that allows the genetic alteration of neurons based on their activity in response to a natural environmental stimulus or learning paradigm. We use this to introduce either the hM3Dq DREADD receptor or a variant of channelrhodopsin (ChEF) to allow the electrical stimulation of the labeled neurons either chemically or with light. In this way we can directly stimulate the ensemble of neurons activated naturally in response to a stimulus in the behaving animal to investigate the parameters required to produce a perception or memory. In preliminary studies we show that anatomically dispersed, and internally generated neural activity can be integrated into new memory. This is consistent with the idea that new memory does not form de novo but integrates with pre-existing schemas or relevant internal representations that may be active at the time of learning. Using ChEF we found that light stimulation of neurons in the retrosplenial cortex that were activated naturally with fear conditioning could produce a freezing response. This suggests that we are directly recruiting a component of the memory trace through the artificial stimulation of the correct pattern of neurons. We will extend these studies to investigate the parameters that control the integration of neural activity into new and existing memories during consolidation and reconsolidation. In addition, we will use local stimulation to directly test the optimal conditions (number of neurons, firing frequency) required for recruiting memory recall. These studies will provide the first direct test of the role of spatial and temporal patterns of neural activity in th generation of perceptions and memories. The data generated should advance our understanding of psychiatric disorders and aid in the creation of animal models in which to test treatments.
This grant addresses the fundamental question of how the activity of nerve cells in the brain lead to the perception of the world and memory of past experience. Many psychiatric illnesses are characterized by a disruption of these functions. The information we get from these studies would help in our understanding of these disorders and in creating new animal models in which to test treatments.
|Sanders, Jeff; Mayford, Mark (2016) Chronic fluoxetine dissociates contextual from auditory fear memory. Neurosci Lett 632:152-6|
|Cai, Denise J; Aharoni, Daniel; Shuman, Tristan et al. (2016) A shared neural ensemble links distinct contextual memories encoded close in time. Nature 534:115-8|
|Mayford, Mark (2014) The search for a hippocampal engram. Philos Trans R Soc Lond B Biol Sci 369:20130161|
|Drane, Laurel; Ainsley, Joshua A; Mayford, Mark R et al. (2014) A transgenic mouse line for collecting ribosome-bound mRNA using the tetracycline transactivator system. Front Mol Neurosci 7:82|
|Cowansage, Kiriana K; Shuman, Tristan; Dillingham, Blythe C et al. (2014) Direct reactivation of a coherent neocortical memory of context. Neuron 84:432-41|
|Sanders, Jeff; Mayford, Mark; Jeste, Dilip (2013) Empathic fear responses in mice are triggered by recognition of a shared experience. PLoS One 8:e74609|
|Garner, Aleena R; Rowland, David C; Hwang, Sang Youl et al. (2012) Generation of a synthetic memory trace. Science 335:1513-6|
|Sanders, Jeff; Cowansage, Kiriana; Baumgartel, Karsten et al. (2012) Elimination of dendritic spines with long-term memory is specific to active circuits. J Neurosci 32:12570-8|
|Bibb, James A; Mayford, Mark R; Tsien, Joe Z et al. (2010) Cognition enhancement strategies. J Neurosci 30:14987-92|
|Matsuo, Naoki; Reijmers, Leon; Mayford, Mark (2008) Spine-type-specific recruitment of newly synthesized AMPA receptors with learning. Science 319:1104-7|
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