The primary goals of this research are i) to establish how learning impacts the structure and function of the brain, and ii) to determine how learning can be modulated by factors such as feedback (positive or negative). Over the past year we have focused equally on both of these goals. 1) Impact of learning on brain structure and function (NCT00001360) Over the past few years, we have been conducting a long-term longitudinal study of participants learning different tasks (e.g. motor sequences, spatial layout) to determine how structural properties of the brain (gray matter, white matter) change over time. Over a period of four weeks, participants were trained in two different tasks and we collected extensive functional and structural MRI data over the course of training. While previous studies have identified structural changes associated with learning, even over the course of a couple of hours, our initial findings have highlighted a potential confound that needs to be accounted for in such studies. Specifically, we have found that the structural measures obtained with MRI fluctuate according to the time of day, with decreases in gray matter thickness and increases in ventricular volume. These fluctuations appear to be related to changes in cerebrospinal fluid in the brain and may reflect the impact of the daily circadian rhythm. Interestingly, these fluctuation appear to be modulated by training and we are trying to establish what additional structural and functional changes occur with training above and beyond these time-of-day effects. With the motor sequence task we find that, following training, sensorimotor networks show changes in their functional connectivity. In contrast, with the spatial layout task, hippocampal networks change. These findings suggest task-specific changes in particular networks underlie learning above and beyond any changes due to circadian fluctuations. 2) Impact of feedback on learning (NCT00001360) We are investigating the impact of feedback (positive, negative) on motor learning. Groups of participants were trained on one of two different motor tasks and either provided with positive, negative or neutral (uninformative) feedback. Training occurred in the MRI scanner and we measured fMRI activity before, during and after training. Behaviorally, we found that the impact of feedback is dependent on the task. While in a sequence learning task we find that punishment improves online performance, we observe the opposite effect in a purely motoric force-tracking task. In terms of brain activity, we found that punishment was more associated with changes in the medial temporal lobe and hippocampus, while reward was more associated with changes in the cerebellum. These findings suggest a dissociation of the neural mechanisms underlying the impact of reward and punishment that might be utilized to enhance training. Establishing the nature, degree and consequences of plasticity in the adult cortex provides important insights into the potential for rehabilitative brain therapies following injury or dysfunction in the nervous system.

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11
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2017
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U.S. National Institute of Mental Health
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Thomas, Cibu; Sadeghi, Neda; Nayak, Amrita et al. (2018) Impact of time-of-day on diffusivity measures of brain tissue derived from diffusion tensor imaging. Neuroimage 173:25-34
Silson, Edward H; Aleman, Tomas S; Willett, Aimee et al. (2018) Comparing Clinical Perimetry and Population Receptive Field Measures in Patients with Choroideremia. Invest Ophthalmol Vis Sci 59:3249-3258
Steel, Adam; Silson, Edward H; Stagg, Charlotte J et al. (2016) The impact of reward and punishment on skill learning depends on task demands. Sci Rep 6:36056
Trefler, Aaron; Sadeghi, Neda; Thomas, Adam G et al. (2016) Impact of time-of-day on brain morphometric measures derived from T1-weighted magnetic resonance imaging. Neuroimage 133:41-52
Ashtari, Manzar; Zhang, Hui; Cook, Philip A et al. (2015) Plasticity of the human visual system after retinal gene therapy in patients with Leber's congenital amaurosis. Sci Transl Med 7:296ra110
Burianová, Hana; Rich, Anina N; Williams, Mark et al. (2015) Long-term plasticity in adult somatosensory cortex: functional reorganization after surgical removal of an arteriovenous malformation. Neurocase 21:618-27
Thomas, Cibu; Avram, Alexandru; Pierpaoli, Carlo et al. (2015) Diffusion MRI properties of the human uncinate fasciculus correlate with the ability to learn visual associations. Cortex 72:65-78
Robertson, Caroline E; Thomas, Cibu; Kravitz, Dwight J et al. (2014) Global motion perception deficits in autism are reflected as early as primary visual cortex. Brain 137:2588-99
Thomas, Cibu; Baker, Chris I (2013) Teaching an adult brain new tricks: a critical review of evidence for training-dependent structural plasticity in humans. Neuroimage 73:225-36
Robertson, Caroline E; Kravitz, Dwight J; Freyberg, Jan et al. (2013) Slower rate of binocular rivalry in autism. J Neurosci 33:16983-91

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