Cortical representations of brief, static stimuli become more invariant to identity-preserving transformations along the ventral stream. Likewise, increased invariance along the visual hierarchy should imply greater temporal persistence of temporally structured dynamic stimuli, possibly complemented by temporal broadening of neuronal receptive fields. However, such stimuli could engage adaptive and predictive processes, whose impact on neural coding dynamics is unknown. By probing the rat analog of the ventral stream with movies, we uncovered a hierarchy of temporal scales, with deeper areas encoding visual information more persistently. Furthermore, the impact of intrinsic dynamics on the stability of stimulus representations grew gradually along the hierarchy. A database of recordings from mouse showed similar trends, additionally revealing dependencies on the behavioral state. Overall, these findings show that visual representations become progressively more stable along rodent visual processing hierarchies, with an important contribution provided by intrinsic processing.

No abstract

Along the ventral stream, cortical representations of brief, static stimuli become gradually more invariant to identity-preserving transformations. In the presence of long, ethologically relevant dynamic stimuli, higher invariance should imply temporally persistent representations at the top of this functional hierarchy. However, such stimuli could engage adaptive and predictive processes, whose impact on neural coding dynamics is unknown. More generally, coding dynamics in the presence of temporally structured stimuli are not understood. By probing the rodent analogue of the ventral stream with movies, we uncovered a hierarchy of temporal scales along this pathway, with deeper areas encoding visual information more persistently. Furthermore, the impact of intrinsic dynamics on the stability of stimulus representations gradually grows along the hierarchy. These results suggest that feedforward computations in the cortical hierarchy build up invariance even for dynamic, temporally structured stimuli, and that intrinsic processing contributes to the stabilization of representations in noisy, changing environments.

Thalamoreticular circuitry is central to sensory processing, attention, and sleep, and is implicated in numerous brain disorders, but the cellular and synaptic mechanisms remain intractable. Therefore, we developed the first detailed microcircuit model of mouse thalamus and thalamic reticular nucleus that captures morphological and biophysical properties of ~14,000 neurons connected via ~6M synapses, and recreates biological synaptic and gap junction connectivity. Realistic spontaneous and evoked activity during wakefulness and sleep emerge allowing dissection of cellular and synaptic contributions. Computer simulations suggest that reticular inhibition shapes thalamic responses and cortex can drive frequency-selective thalamic enhancement during wakefulness, whereas in sleep, reticular inhibition and cortical UP-states can trigger thalamic bursts and spindles. Gap junctions and short-term synaptic plasticity underlie spindle properties such as waxing and waning, and neuromodulation influences the occurrence of spindles. The model is openly available to support testing hypotheses of thalamoreticular circuitry in normal brain function and in disease.