Dual effects of ‘losses disguised as wins’ and near-misses in a slot machine game

Individually, both near-misses and losses disguised as wins (LDWs) have been seen to exert pro-motivational effects on gambling. However, it is not clear whether both structural characteristics are effective within the same game. Participants (n = 40) played a slot machine simulation. The simulation delivered near-misses, wins and ‘full-misses’. Half the participants also received LDWs that occurred independently of the outcomes on the payline. Valence and motivation ratings were collected after each round. Results showed that the LDW group reported increased valence ratings compared to the no-LDW group. Within the LDW group, trials with LDWs also resulted in increased enjoyment compared to trials without LDWs. We distinguished near-misses falling either side of the payline. Near-misses before the payline (NMB) were rated as more motivational than near-misses after the payline (NMA), whereas NMAs were rated as more aversive than NMBs. These differences between the two near-miss types were exacerbated by LDWs. Results demonstrate LDWs increase the trial-by-trial enjoyment of non-win outcomes. The motivational and hedonic effects of near-misses differed for events either side of the payline, and these differences were exaggerated by the presence of LDWs. Thus, near-misses can retain their effectiveness in complex forms of gambling that also deliver LDWs

Ketamine effects on memory reconsolidation favor a learning model of delusions.

Delusions are the persistent and often bizarre beliefs that characterise psychosis. Previous studies have suggested that their emergence may be explained by disturbances in prediction error-dependent learning. Here we set up complementary studies in order to examine whether such a disturbance also modulates memory reconsolidation and hence explains their remarkable persistence. First, we quantified individual brain responses to prediction error in a causal learning task in 18 human subjects (8 female). Next, a placebo-controlled within-subjects study of the impact of ketamine was set up on the same individuals. We determined the influence of this NMDA receptor antagonist (previously shown to induce aberrant prediction error signal and lead to transient alterations in perception and belief) on the evolution of a fear memory over a 72 hour period: they initially underwent Pavlovian fear conditioning; 24 hours later, during ketamine or placebo administration, the conditioned stimulus (CS) was presented once, without reinforcement; memory strength was then tested again 24 hours later. Re-presentation of the CS under ketamine led to a stronger subsequent memory than under placebo. Moreover, the degree of strengthening correlated with individual vulnerability to ketamine's psychotogenic effects and with prediction error brain signal. This finding was partially replicated in an independent sample with an appetitive learning procedure (in 8 human subjects, 4 female). These results suggest a link between altered prediction error, memory strength and psychosis. They point to a core disruption that may explain not only the emergence of delusional beliefs but also their persistence

A comprehensive overview of radioguided surgery using gamma detection probe technology

The concept of radioguided surgery, which was first developed some 60 years ago, involves the use of a radiation detection probe system for the intraoperative detection of radionuclides. The use of gamma detection probe technology in radioguided surgery has tremendously expanded and has evolved into what is now considered an established discipline within the practice of surgery, revolutionizing the surgical management of many malignancies, including breast cancer, melanoma, and colorectal cancer, as well as the surgical management of parathyroid disease. The impact of radioguided surgery on the surgical management of cancer patients includes providing vital and real-time information to the surgeon regarding the location and extent of disease, as well as regarding the assessment of surgical resection margins. Additionally, it has allowed the surgeon to minimize the surgical invasiveness of many diagnostic and therapeutic procedures, while still maintaining maximum benefit to the cancer patient. In the current review, we have attempted to comprehensively evaluate the history, technical aspects, and clinical applications of radioguided surgery using gamma detection probe technology

A re-examination of responding on ratio and regulated-probability interval schedules.

The higher response rates observed on ratio than on matched interval reward schedules has been attributed to the differential reinforcement of longer inter-response times (IRTs) on the interval contingency. Some data, however, seem to contradict this hypothesis, showing that the difference is still observed when the role of IRT reinforcement is neutralized by using a regulated-probability interval schedule (RPI). Given the mixed evidence for these predictions, we re-examined this hypothesis by training three groups of rats to lever press under ratio, interval and RPI schedules across two phases while matching reward rates within triads. At the end of the first phase, the master ratio and RPI groups responded at similar rates. In the second phase, an interval group yoked to the same master ratio group of the first phase responded at a lower rate than the RPI group. Post-hoc analysis showed comparable reward rates for master and yoked schedules. The experienced response-outcome rate correlations were likewise similar and approached zero as training progressed. We discuss these results in terms of a contemporary dual-system model of instrumental conditioning

Risk-avoidant decision making increased by threat of electric shock.

Threat cues elicit defensive reactions mediated by limbic brain circuitry that is also implicated in risk-sensitive decision making. Building upon research looking at stress effects on decision making, a gambling task was administered to 65 healthy adults, comparing decision making on trials on which a red screen background signalled threat of shocks against trials when shocks could not occur. The threat cues elicited increased electrodermal activity and a sustained decrease in heart rate, consistent with defensive vigilance. The threat condition was associated with risk-avoidant choices, on trials where the risky option involved moderate losses and when choosing between options involving only losses. These effects were not explained by changes in latency. Threat exerts immediate effects on decision making and physiological arousal, biasing subjects towards safer alternatives, potentially through a magnified processing of loss information