Cellular mechanisms of brain state–dependent gain modulation in visual cortex

Abstract

During locomotion, visual cortical neurons fire at higher rates to visual stimuli than during immobility while maintaining orientation selectivity. The mechanisms underlying this change in gain are not understood. We performed whole cell recordings from layer 2/3 and layer 4 visual cortical excitatory neurons as well as from parvalbumin-positive and somatostatin-positive inhibitory neurons in mice free to rest or run on a spherical treadmill. We found that the membrane potential of all cell types became more depolarized and (with the exception of somatostatin-positive interneurons) less variable during locomotion. Cholinergic input was essential for maintaining the unimodal membrane potential distribution during immobility, while noradrenergic input was necessary for the tonic depolarization associated with locomotion. Our results provide a mechanism for how neuromodulation controls the gain and signal-to-noise ratio of visual cortical neurons during changes in the state of vigilance.

Decision-related pupil dilation reflects upcoming choice and individual bias

“…Neuromodulators such as noradrenaline seem to boost the gain of neural interactions in the cortex (5,7,26). It is tempting to speculate that such a transient boost in gain during decision formation enables conservative subjects to overcome their bias against responding "yes."…”

“…These neuromodulatory systems also activate briefly ("phasically") during perceptual decisions, such as visual target detection (5,(20)(21)(22)(23)(24), likely mediated via feedback connections from the prefrontal cortex (5,25). The modulatory neurotransmitters released from the projections of these brainstem systems, in turn, shape the internal state of cortical networks, for instance, by boosting the gain of neural interactions (5,7,26). Thus, these brainstem systems might also shape decision computations in cortical networks-provided that they are activated already during decision formation.…”

Top-down modulation in human visual cortex predicts the stability of a perceptual illusion

“…Finally, neuromodulatory brain stem systems are in a position to stabilize the perceptual dynamics because they can dynamically alter key cortical circuit parameters in profound ways. In particular, neuromodulators suppress cortical variability (Polack et al 2013) and may amplify inhibitory interactions in cortical circuits (Haider et al 2013). In competitive networks underlying multistable perception (Braun and Mattia 2010;Moreno-Bote et al 2007), a transient boost of mutual inhibition is equivalent into the deepening of valleys shown in Fig.…”

Extraction of Synaptic Input Properties in Vivo

“…All traces (n = 8) were 90 seconds long and contained at least 10 seconds of movement. Locomotion modulates subthreshold and spiking activity in a large number of brain regions (Dombeck, Graziano, and Tank, 2009;Polack, Friedman, and Golshani, 2013;Schiemann et al, 2015). In cerebellar interneurons, locomotion is associated with increased excitatory input drive, Fig.…”