  Sensory stimuli can be recognized more rapidly when they are expected. This
phenomenon depends on expectation affecting the cortical processing of sensory
information. However, virtually nothing is known on the mechanisms responsible
for the effects of expectation on sensory networks. Here, we report a novel
computational mechanism underlying the expectation-dependent acceleration of
coding observed in the gustatory cortex (GC) of alert rats. We use a recurrent
spiking network model with a clustered architecture capturing essential
features of cortical activity, including the metastable activity observed in GC
before and after gustatory stimulation. Relying both on network theory and
computer simulations, we propose that expectation exerts its function by
modulating the intrinsically generated dynamics preceding taste delivery. Our
model, whose predictions are confirmed in the experimental data, demonstrates
how the modulation of intrinsic metastable activity can shape sensory coding
and mediate cognitive processes such as the expectation of relevant events.
Altogether, these results provide a biologically plausible theory of
expectation and ascribe a new functional role to intrinsically generated,
metastable activity.
