TY - JOUR TI - State-dependent geometry of population activity in rat auditory cortex AU - Kobak, Dmitry AU - Pardo-Vazquez, Jose L AU - Valente, Mafalda AU - Machens, Christian K AU - Renart, Alfonso A2 - Salinas, Emilio A2 - Marder, Eve A2 - Goodman, Dan FM VL - 8 PY - 2019 DA - 2019/04/10 SP - e44526 C1 - eLife 2019;8:e44526 DO - 10.7554/eLife.44526 UR - https://doi.org/10.7554/eLife.44526 AB - The accuracy of the neural code depends on the relative embedding of signal and noise in the activity of neural populations. Despite a wealth of theoretical work on population codes, there are few empirical characterizations of the high-dimensional signal and noise subspaces. We studied the geometry of population codes in the rat auditory cortex across brain states along the activation-inactivation continuum, using sounds varying in difference and mean level across the ears. As the cortex becomes more activated, single-hemisphere populations go from preferring contralateral loud sounds to a symmetric preference across lateralizations and intensities, gain-modulation effectively disappears, and the signal and noise subspaces become approximately orthogonal to each other and to the direction corresponding to global activity modulations. Level-invariant decoding of sound lateralization also becomes possible in the active state. Our results provide an empirical foundation for the geometry and state-dependence of cortical population codes. KW - auditory cortex KW - population activity KW - cortical state JF - eLife SN - 2050-084X PB - eLife Sciences Publications, Ltd ER -