Suboptimal Integration of Reward Magnitude and Prior Reward Likelihood in Categorical Decisions by Monkeys

Sensory decisions may be influenced by non-sensory information regarding reward magnitude or reward likelihood. Given identical sensory information, it is more optimal to choose an option if it is a priori more likely to be correct and hence rewarded (prior reward likelihood bias), or if it yields a larger reward, given that it is the correct choice (reward magnitude bias). Here, we investigated the ability of macaque monkeys to integrate reward magnitude and prior reward likelihood information into a categorical decision about stimuli with high signal strength but variable decision uncertainty. In the asymmetric reward magnitude condition, monkeys over-adjusted their decision criterion such that they chose the highly rewarded alternative far more often than was optimal; in contrast, monkeys did not adjust their decision criterion in response to asymmetric reward likelihood. This finding shows that in this setting, monkeys did not adjust their decision criterion based on the product of reward likelihood and reward magnitude as has been reported to be the case in value-based decisions that do not involve decision uncertainty due to stimulus categorization

Rapid switching between transdermal fentanyl and methadone in cancer patients

Purpose The aim of this study was to examine the clinical effects of switching from transdermal (TTS)fentanyl to methadone, or vice versa, in patients with a poor response to the previous opioid. Patients and Methods A prospective study was carried out on 31 patients who switched from TTS fentanyl to oral methadone, or vice versa, because of poor opioid response. A fixed conversion ratio of fentanyl to methadone of 1:20 was started and assisted by rescue doses of opioids, and then doses were changed according to clinical response. Pain and symptom intensity, expressed as distress score, were recorded before switching doses of the two opioids and after subsequent doses. The number of changes of the daily doses, time to achieve stabilization, and hospital stay were also recorded. Results Eighteen patients were switched from TTS fentanyl to methadone, and seven patients were switched from methadone to TTS fentanyl. A significant decrease in pain and symptom intensity, expressed as symptom distress score, was found within 24 hours after switching took place in both directions. Unsuccessful switching occurred in six patients, who were subsequently treated with an alternative therapy. Conclusion A rapid switching using an initial fixed ratio of fentanyl to methadone of 1:20 is an effective method to improve the balance between analgesia and adverse effects in cancer patients with poor response to the previous opioid. No relationship between the final opioid dose and the dose of the previous opioid has been found

The use of opioids in the last week of life in an acute palliative care unit.

The aim of this survey was to assess the opioid use in the last week of life of cancer patients admitted at an acute palliative care unit. From a consecutive sample of patients surveyed for a period of one year, patients who died in the unit were selected. Type of opioid, route of administration, and doses were recorded one week before death (or at admission time if the interval admission-death was less than one week) (-7), and on the day of death (Tend). Seventy-seven patients died in the unit in the period taken into consideration (12.4%). Oral morphine equivalents were 170 mg/day and 262 mg/day at -7 and Tend, respectively. Patients were receiving transdermal drugs or intravenous morphine at Tend, with a trend in the use of intravenous morphine at Tend (p=0.07). Intravenous morphine was more frequently used in sedated patients at Tend (p=0.015).No differences in age, gender, opioid doses, and OEI were found among opioids used. In patients who were sedated doses of opioids were significantly increased (p=0.012). In the last week of life intravenous morphine is the preferred modality to deliver opioids in an acute palliative care unit. Doses increases prevalently observed in sedated patients were performed before starting sedation with the purpose to treat concomitant distressing symptoms, such as dyspnoea

Opioid-induced or pain relief-reduced symptoms in advanced cancer patients?

Background: While opioids in increasing doses may produce adverse effects, the same adverse effects may be associated with poor pain control. Moreover, in the clinical setting symptomatic treatment and illness may balance the outcome of opioid titration. Some adverse effects may tend to disappear continuing the treatment in a long-term period. Aims: The aim of this study was to monitor the effects of a rapid opioid titration combined with symptomatic treatment in patients with poor relief and to monitor these changes in the following period of 20 days. Methods: A consecutive sample of 35 patients admitted to an acute Pain Relief and Palliative Care Unit were titrated with opioids, according to a department policy, allowing administration of parenteral opioids to assist opioid titration with oral or transdermal opioids. Results: Thirty-three patients were followed up for the period of the study. Pain was adequately controlled and doses were opioid doses were stable after a mean of 40 h. Opioid escalation index (OEI) was extremely high initially, and then progressively declined at the following study intervals. Weakness and nausea and vomiting did not change, as well as confusion and appetite. Drowsiness, constipation and dry mouth significantly increased and then did not change, although a significant decrease in drowsiness was subsequently observed. Well-being improved some weeks after opioid stabilization. In multivariate analysis, drowsiness and dry mouth were correlated to opioid doses. Conclusion: The effects reported were often due to multiple causes. A rapid decrease in pain intensity induced by rapid opioid titration does not produce changes in weakness, nausea and vomiting, appetite. While constipation appears the most relevant problem,resistant to common symptomatic treatment, drowsiness initially produced by acute opioid dose increase and the achievement of pain relief, tends to spontaneously decrease, probably as the result of late tolerance. Improved well-being may be the late positive effect of pain relief, also influenced by the setting of home care

Orienting of Attention to Gaze Direction Cues in Rhesus Macaques: Species-Specificity, and Effects of Cue Motion and Reward Predictiveness

Primates live in complex social groups and rely on social cues to direct their attention. For example, primates react faster to an unpredictable stimulus after seeing a conspecific looking in the direction of that stimulus. In the current study we tested the specificity of facial cues (gaze direction) for orienting attention and their interaction with other cues that are known to guide attention. In particular, we tested whether macaque monkeys only respond to gaze cues from conspecifics or if the effect generalizes across species. We found an attentional advantage of conspecific faces over human and cartoon faces. Because gaze cues are often conveyed by gesture, we also explored the effect of image motion (a simulated glance) on the orienting of attention in monkeys. We found that the simulated glance did not significantly enhance the speed of orienting for monkey-face stimuli, but had a significant effect for images of human faces. Finally, because gaze cues presumably guide attention toward relevant or rewarding stimuli, we explored whether orienting of attention was modulated by reward predictiveness. When the cue predicted reward location, face, and non-face cues were effective in speeding responses toward the cued location. This effect was strongest for conspecific faces. In sum, our results suggest that while conspecific gaze cues activate an intrinsic process that reflexively directs spatial attention, its effect is relatively small in comparison to other features including motion and reward predictiveness. It is possible that gaze cues are more important for decision-making and voluntary orienting than for reflexive orienting

Opioid-induced hyperalgesia after rapid titration with intravenous morphine: Switching and re-titration to intravenous methadone

Rapid titration with intravenous morphine (IV-MO) provides fast and efficient pain relief in cancer patients with severe-excruciating pain. However, some patients, after an initially favourable response, can develop an hyperexcitated state unrelieved or worsened by further dose increments

100 Gbps PON L-band downstream transmission using IQ-MZM CD digital pre-compensation and DD ONU receiver

We propose a downstream direct-detection 100G-PON solution aided by chromatic dispersion digital pre-compensation using an IQ-MZM, allowing L-band operation and 29 dB power budget with low ONU complexity and without requiring single-sideband modulation