First, rather than the global probability with which a cue is predicted by a practiced performer,
the current conceptualisation emphasises the uncertainty of the detection process as a function of trial sequence, a concept perhaps more akin to the response bias in signal detection theory. Second, it is not the neuromodulatory component that signals the level of predicted uncertainty (see below for a discussion of neuromodulatory effects); Docetaxel concentration rather, it is solely the cholinergic transient that affects the certainty of detection. Third, the cholinergic transient does not merely signal the degree of predicted uncertainty in incongruently cued trials; instead it reduces such uncertainty. In other words, the presence of a cholinergic transient shifts
the performer toward adopting a riskier detection criterion, thereby enhancing the probability that detection occurs in cued trials that follow non-cued trials. Reducing uncertainty of detection does not tap purely perceptual or purely behavioral operations; rather, it concerns the integration of the two, as captured by the definition of detection (detailed above) in Posner et al. (1980). Therefore, a neuronal mechanism that is designed to reduce detection uncertainty must be closely connected to, and to a degree depend on, the actual perceptual mechanisms. The finding that the generation of a cholinergic transient depends upon thalamic glutamatergic input, that is relayed to the SPTLC1 prefrontal cortex by all cues that yield hits, reflects selleck screening library this close connection between perceptual and decisional mechanisms. Moreover, as illustrated
rather drastically by the ability of artificially generated cholinergic transients to force hits on nonsignal trials (above), a cholinergic transient appears to be capable of overriding perception and triggering a decision to report a cue even in its absence. What then would be the costs of cholinergic transients if evoked on consecutively-cued trials? What would be the costs of further reducing detection uncertainty when the perceptual process already established that a cue was present, as indicated by the finding that glutamatergic transients reliably predict hits (Fig. 1B)? We speculate that the presence of cholinergic transients during consecutively cued hits would nearly completely abolish any residual detection uncertainty and thereby strongly bias performance to the reporting of signals. As a consequence, the ability to respond accurately to subsequent nonsignal trials could be impaired. In other words, cholinergic transients during consecutively-cued trials would reduce the flexibility to accurately perform a task that presents cued and non-cued trials at equal probability. Certainly, manipulating such probability will be an important experimental means of further testing our hypothesis.