@article {4099, title = {Neural Interactions Underlying Visuomotor Associations in the Human Brain}, journal = {Cerebral Cortex}, volume = {1{\textendash}17}, year = {2018}, month = {12/2018}, abstract = {

Rapid andflexible learning during behavioral choices is critical to our daily endeavors and constitutes a hallmark ofdynamic reasoning. An important paradigm to examineflexible behavior involves learning new arbitrary associationsmapping visual inputs to motor outputs. We conjectured that visuomotor rules are instantiated by translating visual signalsinto actions through dynamic interactions between visual, frontal and motor cortex. We evaluated the neuralrepresentation of such visuomotor rules by performing intracranialfield potential recordings in epilepsy subjects during arule-learning delayed match-to-behavior task. Learning new visuomotor mappings led to the emergence of specificresponses associating visual signals with motor outputs in 3 anatomical clusters in frontal, anteroventral temporal andposterior parietal cortex. After learning, mapping selective signals during the delay period showed interactions with visualand motor signals. These observations provide initial steps towards elucidating the dynamic circuits underlyingflexiblebehavior and how communication between subregions of frontal, temporal, and parietal cortex leads to rapid learning oftask-relevant choices.

}, keywords = {frontal cortex, human neurophysiology, reinforcement learning, visual cortex}, issn = {1047-3211}, doi = {10.1093/cercor/bhy333}, url = {http://klab.tch.harvard.edu/publications/PDFs/gk7766.pdf}, author = {Radhika Madhavan and Bansal, Arjun K and Joseph Madsen and Golby, Alexandra J and Travis S Tierney and Emad Eskandar and WS Anderson and Gabriel Kreiman} } @article {1155, title = {Decrease in gamma-band activity tracks sequence learning}, journal = {Frontiers in Systems Neuroscience}, volume = {8}, year = {2015}, month = {01/21/2015}, abstract = {

Learning novel sequences constitutes an example of declarative memory formation, involving conscious recall of temporal events. Performance in sequence learning tasks improves with repetition and involves forming temporal associations over scales of seconds to minutes. To further understand the neural circuits underlying declarative sequence learning over trials, we tracked changes in intracranial field potentials (IFPs) recorded from 1142 electrodes implanted throughout temporal and frontal cortical areas in 14 human subjects, while they learned the temporal-order of multiple sequences of images over trials through repeated recall. We observed an increase in power in the gamma frequency band (30{\textendash}100 Hz) in the recall phase, particularly in areas within the temporal lobe including the parahippocampal gyrus. The degree of this gamma power enhancement decreased over trials with improved sequence recall. Modulation of gamma power was directly correlated with the improvement in recall performance. When presenting new sequences, gamma power was reset to high values and decreased again after learning. These observations suggest that signals in the gamma frequency band may play a more prominent role during the early steps of the learning process rather than during the maintenance of memory traces.

}, doi = {10.3389/fnsys.2014.00222}, url = {http://journal.frontiersin.org/article/10.3389/fnsys.2014.00222/abstract}, author = {Radhika Madhavan and Daniel Millman and Hanlin Tang and NE Crone and Fredrick A. Lenz and Travis S Tierney and Joseph Madsen and Gabriel Kreiman and WS Anderson} } @article {1134, title = {Neural Dynamics Underlying Target Detection in the Human Brain}, journal = {Journal of Neuroscience}, volume = {34}, year = {2014}, chapter = {3042}, author = {Bansal, A and Radhika Madhavan and Agam, Y and Golby, A and Joseph Madsen and Gabriel Kreiman} } @article {217, title = {Spatiotemporal Dynamics Underlying Object Completion in Human Ventral Visual Cortex}, journal = {Neuron}, volume = {83}, year = {2014}, month = {08/06/2014}, pages = {736 - 748}, abstract = {

Natural vision often involves recognizing objects from partial information. Recognition of objects from parts presents a significant challenge for theories of vision because it requires spatial integration and extrapolation from prior knowledge. Here we recorded intracranial field potentials of 113 visually selective electrodes from epilepsy patients in response to whole and partial objects. Responses along the ventral visual stream, particularly the Inferior Occipital and Fusiform Gyri, remained selective despite showing only 9-25\% of the object areas. However, these visually selective signals emerged ~100 ms later for partial versus whole objects. These processing delays were particularly pronounced in higher visual areas within the ventral stream. This latency difference persisted when controlling for changes in contrast, signal amplitude, and the strength of selectivity. These results argue against a purely feed-forward explanation of recognition from partial information, and provide spatiotemporal constraints on theories of object recognition that involve recurrent processing.

}, keywords = {Circuits for Intelligence, vision}, issn = {08966273}, doi = {10.1016/j.neuron.2014.06.017}, url = {http://linkinghub.elsevier.com/retrieve/pii/S089662731400539Xhttp://api.elsevier.com/content/article/PII:S089662731400539X?httpAccept=text/xmlhttp://api.elsevier.com/content/article/PII:S089662731400539X?httpAccept=text/plain}, author = {Hanlin Tang and Buia, Calin and Radhika Madhavan and NE Crone and Joseph Madsen and WS Anderson and Gabriel Kreiman} }