The Role of Higher Visual Cortices in Texture Discrimination
Corey Ziemba, Robbe Goris, Gabriel Stine, Richard Perez, Eero Simoncelli, and Anthony Movshon
(see article e0349242024)
As visual information about our external environment is carried from the eye up the visual cortical hierarchy, its complexity grows with each processing stage. However, how distinct neuron populations in visual cortices process information about our environments remains unclear. To broaden our understanding, Ziemba et al. examined whether the selectivity of neurons in macaque monkey primary (V1) and secondary (V2) visual cortices could be differentiated as they made discriminatory choices about texture. Two male macaques learned a continuum of textures and then judged which extreme on this continuum a sample texture resembled. While V2 neurons seemed more sensitive to the visual features on which the behavior was based, the results for each monkey were oppositional: both V1 and V2 neuron firing could predict choices in one monkey, but neither neuron population could predict the choices of the other monkey. The findings of this study reveal stable and distinct visual selectivity in V1 and V2 neuronal populations but suggest that the relationship between neural responses and behavior varies across observers and tasks. Thus, neural responses with a more direct link to behavior likely exist. The complex and shifting relationship between neural and perceptual sensitivity observed in this study is informative for neuroscientists across many fields relating brain and behavior.
Rethinking Aperiodic Activity during Sleep Stages
Janna Lendner, Jack Lin, Pål Larsson, and Randolph Helfrich
(see article e0171242024)
As we slumber, our brains drift through many stages of consciousness. Recent studies have revealed that sleep stages can be distinguished through aperiodic activity. The scientific definition of aperiodic activity has long been understood as the spectral slope of the 1/frequency decay function of the electrophysiological power spectrum, but this definition is now under scrutiny as scientists probe whether several decay processes, with different timescales, may better represent aperiodic activity and stages of consciousness during sleep. Lendner et al. explored the relationship between different brain states and the spectral slope using human intracranial encephalography to record from the brains of nearly 50 participants across three independent studies. The authors used a new approach to estimate aperiodic activity and identified intrinsic timescales that could predict physiological and functional neural interactions. Their approach allowed them to make estimations about decay processes describing the signal from different brain regions in different brain states. This work puts to rest contradictions on aperiodic activity during different stages of consciousness in sleep by demonstrating that there is not a single decay process but rather a composition of decay processes that reflect what is happening electrophysiologically through our stages of sleep.
Electrode placement in the medial temporal lobe and prefrontal cortex. Recordings showed nonuniform distribution of electrophysiological aperiodic activity during sleep. See Lendner et al. for more information.
Footnotes
This Week in The Journal was written by Paige McKeon
