Effects of cortico-thalamic feedback on responses in mouse dLGN
Prof. Laura Busse
Department Biology II
Feed-forward sensory processing is a fundamental model of how the brain mediates visual perception. Using a largely feed-forward architecture, artificial neural networks can now carry out robust and dynamic operations as to rival human perception.
So why then, in the brain is feedback such a prominent and ubiquitous motif? As a model for feedback effects on sensory processing, the cortico-thalamic (CT) circuit has, for over half a century, sparked much interest. Despite these efforts, however, how CT feedback influences the representation of visual information remains poorly understood.
Here, we revisited the fundamental question of cortical feedback’s role in thalamic visual processing. We performed a series of experiments using optogenetic tools for circuit manipulations in awake mice. We found that CT feedback during spontaneous activity enhanced firing rates and reduced bursting, and, during processing of natural movie clips, reduced sparseness of dLGN responses. Hence, CT feedback seems crucial for promoting tonic firing mode in dLGN, potentially allowing a more linear transmission of incoming visual information.
Furthermore, our results indicate that CT feedback shapes spatial processing. Measuring tuning for stimulus size, we found that dLGN RFs in conditions with intact CT feedback were smaller and showed stronger surround suppression. Finally, we demonstrate that these effects on spatial integration might, at least partially, be mediated by neurons in the visual part of TRN, via which CT feedback can exert suppressive effects.
Together, our findings suggest that a function of CT feedback is to enhance responses to local visual signals and shape contextual modulations.
Im Neuenheimer Feld 306