Temporal specificity in Pavlovian-to-instrumental transfer

Cognition of Time and Thinking Beyond

A common research protocol in cognitive neuroscience is to train subjects to perform deliberately designed experiments while recording brain activity, with the aim of understanding the brain mechanisms underlying cognition. However, how the results of this protocol of research can be applied in technology is seldom discussed. Here, I review the studies on time processing of the brain as examples of this research protocol, as well as two main application areas of neuroscience (neuroengineering and brain-inspired artificial intelligence). Time processing is a fundamental dimension of cognition, and time is also an indispensable dimension of any real-world signal to be processed in technology. Therefore, one may expect that the studies of time processing in cognition profoundly influence brain-related technology. Surprisingly, I found that the results from cognitive studies on timing processing are hardly helpful in solving practical problems. This awkward situation may be due to the lack of generalizability of the results of cognitive studies, which are under well-controlled laboratory conditions, to real-life situations. This lack of generalizability may be rooted in the fundamental unknowability of the world (including cognition). Overall, this paper questions and criticizes the usefulness and prospect of the abovementioned research protocol of cognitive neuroscience. I then give three suggestions for future research. First, to improve the generalizability of research, it is better to study brain activity under real-life conditions instead of in well-controlled laboratory experiments. Second, to overcome the unknowability of the world, we can engineer an easily accessible surrogate of the object under investigation, so that we can predict the behavior of the object under investigation by experimenting on the surrogate. Third, the paper calls for technology-oriented research, with the aim of technology creation instead of knowledge discovery.

Flexible control of Pavlovian-instrumental transfer based on expected reward value

The Pavlovian-instrumental transfer (PIT) paradigm is widely used to assay the motivational influence of reward-predictive cues, reflected by their ability to invigorate instrumental behavior. Leading theories assume that a cue's motivational properties are tied to predicted reward value. We outline an alternative view that recognizes that reward-predictive cues may suppress rather than motivate instrumental behavior under certain conditions, an effect termed positive conditioned suppression. We posit that cues signaling imminent reward delivery tend to inhibit instrumental behavior, which is exploratory by nature, in order to facilitate efficient retrieval of the expected reward. According to this view, the motivation to engage in instrumental behavior during a cue should be inversely related to the value of the predicted reward, since there is more to lose by failing to secure a high-value reward than a low-value reward. We tested this hypothesis in rats using a PIT protocol known to induce positive conditioned suppression. In Experiment 1, cues signaling different reward magnitudes elicited distinct response patterns. Whereas the one-pellet cue increased instrumental behavior, cues signaling three or nine pellets suppressed instrumental behavior and elicited high levels of food-port activity. Experiment 2 found that reward-predictive cues suppressed instrumental behavior and increased food-port activity in a flexible manner that was disrupted by post-training reward devaluation. Further analyses suggest that these findings were not driven by overt competition between the instrumental and food-port responses. We discuss how the PIT task may provide a useful tool for studying cognitive control over cue-motivated behavior in rodents. (PsycInfo Database Record (c) 2023 APA, all rights reserved).

Quantitative properties of the creation and activation of a cell-intrinsic duration-encoding engram

The engram encoding the interval between the conditional stimulus (CS) and the unconditional stimulus (US) in eyeblink conditioning resides within a small population of cerebellar Purkinje cells. CSs activate this engram to produce a pause in the spontaneous firing rate of the cell, which times the CS-conditional blink. We developed a Bayesian algorithm that finds pause onsets and offsets in the records from individual CS-alone trials. We find that the pause consists of a single unusually long interspike interval. Its onset and offset latencies and their trial-to-trial variability are proportional to the CS-US interval. The coefficient of variation (CoV = σ/μ) are comparable to the CoVs for the conditional eye blink. The average trial-to-trial correlation between the onset latencies and the offset latencies is close to 0, implying that the onsets and offsets are mediated by two stochastically independent readings of the engram. The onset of the pause is step-like; there is no decline in firing rate between the onset of the CS and the onset of the pause. A single presynaptic spike volley suffices to trigger the reading of the engram; and the pause parameters are unaffected by subsequent volleys. The Fano factors for trial-to-trial variations in the distribution of interspike intervals within the intertrial intervals indicate pronounced non-stationarity in the endogenous spontaneous spiking rate, on which the CS-triggered firing pause supervenes. These properties of the spontaneous firing and of the engram read out may prove useful in finding the cell-intrinsic, molecular-level structure that encodes the CS-US interval.

Neuroplastic Changes in the Superior Colliculus and Hippocampus in Self-rewarding Paradigm: Importance of Visual Cues

Coincident excitation via different sensory modalities encoding objects of positive salience is known to facilitate learning and memory. With a view to dissect the contribution of visual cues in inducing adaptive neural changes, we monitored the lever press activity of a rat conditioned to self-administer sweet food pellets in the presence/absence of light cues. Application of light cues facilitated learning and consolidation of long-term memory. The superior colliculus (SC) of rats trained on light cue showed increased neuronal activity, dendritic branching, and brain-derived neurotrophic factor (BDNF) protein and mRNA expression. Concomitantly, the hippocampus showed augmented neurogenesis as well as BDNF protein and mRNA expression. While intra-SC administration of U0126 (inhibitor of ERK 1/2 and long-term memory) impaired memory formation, lidocaine (local anaesthetic) hindered memory recall. The light cue-dependent sweet food pellet self-administration was coupled with increased efflux of dopamine (DA) and 3,4-dihydroxyphenylacetic acid (DOPAC) in the nucleus accumbens shell (AcbSh). In conditioned rats, pharmacological inhibition of glutamatergic signalling in dentate gyrus (DG) reduced lever press activity, as well as DA and DOPAC secretion in the AcbSh. We suggest that the neuroplastic changes in the SC and hippocampus might represent memory engrams sculpted by visual cues encoding reward information.