“Liking” as an early and editable draft of long-run affective value

Psychological and neural distinctions between the technical concepts of “liking” and “wanting” pose important problems for motivated choice for goods. Why could we “want” something that we do not “like,” or “like” something but be unwilling to exert effort to acquire it? Here, we suggest a framework for answering these questions through the medium of reinforcement learning. We consider “liking” to provide immediate, but preliminary and ultimately cancellable, information about the true, long-run worth of a good. Such initial estimates, viewed through the lens of what is known as potential-based shaping, help solve the temporally complex learning problems faced by animals.

What is the distinction between ’liking’ and ’wanting’? Why could we ’want’ something that we do not ’like,’ or ’like’ something but be unwilling to exert effort to acquire it? This Essay argues that the primary hedonic phenomenon called ’liking’ might solve the temporal credit assignment problem for learning that arises when true reinforcement values are available slowly or late.     

Optimism and pessimism in optimised replay

The replay of task-relevant trajectories is known to contribute to memory consolidation and improved task performance. A wide variety of experimental data show that the content of replayed sequences is highly specific and can be modulated by reward as well as other prominent task variables. However, the rules governing the choice of sequences to be replayed still remain poorly understood. One recent theoretical suggestion is that the prioritization of replay experiences in decision-making problems is based on their effect on the choice of action. We show that this implies that subjects should replay sub-optimal actions that they dysfunctionally choose rather than optimal ones, when, by being forgetful, they experience large amounts of uncertainty in their internal models of the world. We use this to account for recent experimental data demonstrating exactly pessimal replay, fitting model parameters to the individual subjects’ choices.     

Convergence in morphological patterns and community organization between Old and New World rodent guilds

We studied morphological relationships within three guilds of gerbillid rodents in Israel. We found a nonrandom pattern of overdispersed means (community-wide character displacement) for upper incisor widths among the species in these three guilds. Upper tooth-row lengths, condylo-basal skull lengths, and tooth-row surfaces displayed similar patterns. We also studied seed-size selection by two well-studied gerbil species, which have previously been found to compete, in order to test whether specializing on husking seeds of different sizes as a mechanism of coexistence may underlie the morphological patterns. The seed-size selection experiments took place in two large aviaries with artificial lighting simulating full-moon nights, which is when predation risk is perceived as high. Seeds of different sizes (commercial seeds in one experiment and husked wheat particles in the other) mixed with sand were offered in trays. The larger Gerbillus pyramidum took significantly larger commercial seeds and marginally larger wheat particles than the smaller Gerbillus allenbyi. The patterns attest to ecomorphological convergence at the guild level; we previously demonstrated size structuring in several North American heteromyid rodent guilds, and we now report similar size structuring among Israeli gerbillid guilds. The occurrence of convergent community structure strongly indicates general rules governing ecological communities or guilds.     

Phytotoxicity and volatile constituents from leaves of Callicarpa japonica Thunb

The essential oil from the leaves of Callicarpa japonica was analyzed by GC-MS, and 84 compounds were identified. The main constituents of the essential oil were spathulenol (18.1%), germacrene B (13.0%), bicyclogermacrene (11.0%), globulol (3.3%), viridiflorol (2.6%), alpha-guaiene (2.3%), and gamma-elemene (2.0%). The essential oil constituents of C. japonica were significantly different from those found in our previous work on Callicarpa americana. The oil of C. japonica was selectively phytotoxic to bentgrass compared to lettuce seeds, with 80-100% growth reduction observed at 0.3 mg/ml.     

The inhibitory activity of natural products on plant p-hydroxyphenylpyruvate dioxygenase

The inhibitory activity of 34 natural products of various structural classes on hydroxyphenylpyruvate dioxygenase (HPPD), the target site for triketone herbicides, and the mode of interaction of selected natural products were investigated. Recombinant HPPD from arabidopsis is sensitive to several classes of natural compounds including, in decreasing order of sensitivity, triketones, benzoquinones, naphthoquinones and anthraquinones. The triketone natural products acted as competitive tight-binding inhibitors, whereas the benzoquinones and naphthoquinones did not appear to bind tightly to HPPD. While these natural products may not have optimal structural features required for in vivo herbicidal activity, the differences in their kinetic behavior suggest that novel classes of HPPD inhibitors may be developed based on their structural backbones.     

Information processing with population codes

Information is encoded in the brain by populations or clusters of cells, rather than by single cells. This encoding strategy is known as population coding. Here we review the standard use of population codes for encoding and decoding information, and consider how population codes can be used to support neural computations such as noise removal and nonlinear mapping. More radical ideas about how population codes may directly represent information about stimulus uncertainty are also discussed.     

9,10-Anthraquinone Reduces the Photosynthetic Efficiency of Oscillatoria perornata and Modifies Cellular Inclusions

The natural compound 9,10-anthraquinone was found to inhibit the growth of the musty odor-producing cyanobacterium Oscillatoria perornata at a low concentration (1 μM) in previous laboratory studies. In this study, the mode of action of 9,10-anthraquinone was investigated by observing ultrastructural changes in O. perornata and by monitoring chlorophyll fluorescence as an indicator of photosynthetic efficiency. Results indicate that 9,10-anthraquinone inhibits photosynthetic electron transport, probably at PSII, and thereby affects growth. Moreover, 9,10-anthraquinone treatment caused thylakoid disorganization and reduced the number of ribosomes in O. perornata. The thylakoid disorganization is identical to reported modification in a cyanobacterium treated with simazine, a PSII inhibitor.     

Simple Plans or Sophisticated Habits? State,Transition and Learning Interactions in the Two-Step Task

The recently developed ‘two-step’ behavioural task promises to differentiate model-based from model-free reinforcement learning, while generating neurophysiologically-friendly decision datasets with parametric variation of decision variables. These desirable features have prompted its widespread adoption. Here, we analyse the interactions between a range of different strategies and the structure of transitions and outcomes in order to examine constraints on what can be learned from behavioural performance. The task involves a trade-off between the need for stochasticity, to allow strategies to be discriminated, and a need for determinism, so that it is worth subjects’ investment of effort to exploit the contingencies optimally. We show through simulation that under certain conditions model-free strategies can masquerade as being model-based. We first show that seemingly innocuous modifications to the task structure can induce correlations between action values at the start of the trial and the subsequent trial events in such a way that analysis based on comparing successive trials can lead to erroneous conclusions. We confirm the power of a suggested correction to the analysis that can alleviate this problem. We then consider model-free reinforcement learning strategies that exploit correlations between where rewards are obtained and which actions have high expected value. These generate behaviour that appears model-based under these, and also more sophisticated, analyses. Exploiting the full potential of the two-step task as a tool for behavioural neuroscience requires an understanding of these issues.     

Insights into the role of components of the tumor microenvironment in oral carcinoma call for new therapeutic approaches

The research on oral cancer has focused mainly on the cancer cells, their genetic changes and consequent phenotypic modifications. However, it is increasingly clear that the tumor microenvironment (TME) has been shown to be in a dynamic state of inter-relations with the cancer cells. The TME contains a variety of components including the non-cancerous cells (i.e., immune cells, resident fibroblasts and angiogenic vascular cells) and the ECM milieu [including fibers (mainly collagen and fibronectin) and soluble factors (i.e., enzymes, growth factors, cytokines and chemokines)]. Thus, it is currently assumed that TME is considered a part of the cancerous tissue and the functionality of its key components constitutes the setting on which the hallmarks of the cancer cells can evolve. Therefore, in terms of controlling a malignancy, one should control the growth, invasion and spread of the cancer cells through modifications in the TME components. This mini review focuses on the TME as a diagnostic approach and reports the recent insights into the role of different TME key components [such as carcinoma-associated fibroblasts (CAFs) and inflammation (CAI) cells, angiogenesis, stromal matrix molecules and proteases] in the molecular biology of oral carcinoma. Furthermore, the impact of TME components on clinical outcomes and the concomitant need for development of new therapeutic approaches will be discussed.