Learning abilities

Occlusal acuity and bite force in young adults

Occlusal tactile acuity (OTA) and bite force are essential components of the sensorimotor control of oral behaviors. While these variables have been studied independently, it has not yet been revealed whether compressive force impacts the occlusal perception mediated by the mechanoreceptive afferents in the periodontal ligament. The present study examined the effect of repetition and maximum bite force on OTA by testing nine aluminum foils of different thicknesses together with a sham test with no foil, three times each, in randomized order in 36 healthy individuals. In addition, the 40 μm foil was tested three more times at the start of each session to evaluate possible short-term effects. This test session was repeated with and without an interspersed maximum bite force task in between. The results demonstrated that repeated measurements increased OTA significantly (p = 0.033); a change mainly driven by the 40 μm thickness, whereas maximum bite force tests did not affect OTA (p = 0.097). Collectively, the results suggest that the enhanced OTA may be attributed to repetition-mediated learning and neuroplasticity within the pathways related to OTA. Furthermore, the compressive bite force may have induced a short-term change that lasted seconds and was not detected by the subsequent OTA measurements or may have altogether inhibited the facilitatory effect of repeated OTA. This underscores the potential for future research to explore the implications of compressive force and pain on OTA in patient populations, which could provide valuable insights into the adaptive mechanisms of the sensorimotor system in pathological conditions.

Bridging perspectives - A review and synthesis of 53 theoretical models of delusions

The degree to which numerous existing models of delusion formation disagree or propose common mechanisms remains unclear. To achieve a comprehensive understanding of delusion aetiology, we summarised 53 theoretical models of delusions extracted from a systematic literature search. We identified central aspects and unique or overarching features of five core perspectives: cognitive (n = 22), associative learning (n = 4), social (n = 6), neurobiological (n = 6), and Bayesian inference (n = 15). These perspectives differ in foci and mechanistic explanations. Whereas some postulate delusions to result from associative and operant learning, others assume a disbalance in the integration of prior beliefs and sensory input or emphasise the relevance of information processing biases. Postulated moderators range from maladaptive generalised beliefs over neurocognitive impairment to dopamine, stress, and affective dysregulation. The models also differ in whether they attempt to explain delusion formation in general or the delusional content (i.e., persecutory). Finally, some models postulate functional aspects of delusions, such as insight relief. Despite their differences, the perspectives converge on the idea that delusions form as an explanation for an experienced ambiguity. Building on this common ground, we propose an integrative framework incorporating essential mechanistic explanations from each perspective and discuss its implications for research and clinical practice.

Evaluating peripheral neuromuscular function with brief movement-evoked pain

Movement-evoked pain is an understudied manifestation of musculoskeletal conditions that contributes to disability, yet little is known about how the neuromuscular system responds to movement-evoked pain. The present study examined whether movement-evoked pain impacts force production, electromyographic (EMG) muscle activity, and the rate of force development (RFD) during submaximal muscle contractions. Fifteen healthy adults (9 males; age = 30.3 ± 10.2 yr, range = 22-59 yr) performed submaximal isometric first finger abduction contractions without pain (baseline) and with movement-evoked pain induced by laser stimulation to the dorsum of the hand. Normalized force (% maximal voluntary contraction) and RFD decreased by 11% (P < 0.001) and 15% (P = 0.003), respectively, with movement-evoked pain, without any change in normalized peak EMG (P = 0.77). Early contractile RFD, force impulse, and corresponding EMG amplitude computed within time segments of 50, 100, 150, and 200 ms relative to the onset of movement were also unaffected by movement-evoked pain (P > 0.05). Our results demonstrate that movement-evoked pain impairs peak characteristics and not early measures of submaximal force production and RFD, without affecting EMG activity (peak and early). Possible explanations for the stability in EMG with reduced force include antagonist coactivation and a reorganization of motoneuronal activation strategy, which is discussed here.NEW & NOTEWORTHY We provide neurophysiological evidence to indicate that peak force and rate of force development are reduced by movement-evoked pain despite a lack of change in EMG and early rapid force development in the first dorsal interosseous muscle. Additional evidence suggests that these findings may coexist with a reorganization in motoneuronal activation strategy.

Visual communication via the design of food and beverage packaging

A rapidly growing body of empirical research has recently started to emerge highlighting the connotative and/or semiotic meanings that consumers typically associate with specific abstract visual design features, such as colours (either when presented individually or in combination), simple shapes/curvilinearity, and the orientation and relative position of those design elements on product packaging. While certain of our affective responses to such basic visual design features appear almost innate, the majority are likely established via the internalization of the statistical regularities of the food and beverage marketplace (i.e. as a result of associative learning), as in the case of round typeface and sweet-tasting products. Researchers continue to document the wide range of crossmodal correspondences that underpin the links between individual visual packaging design features and specific properties of food and drink products (such as their taste, flavour, or healthfulness), and the ways in which marketers are now capitalizing on such understanding to increase sales. This narrative review highlights the further research that is still needed to establish the connotative or symbolic/semiotic meaning(s) of particular combinations of design features (such as coloured stripes in a specific orientation), as opposed to individual cues in national food markets and also, increasingly, cross-culturally in the case of international brands.