Faculty Bibliography

Probability and risk are important factors for value-based decision making and optimal foraging. In order to survive in an unpredictable world, organisms must be able to assess the probability and risk attached to future events and use this information to generate adaptive behavior. Recent studies in non-human primates and rats have shown that both probability and risk are processed in a distributed fashion throughout the brain at the level of single neurons. Reward probability has mainly been shown to be coded by phasic increases and decreases in firing rates in neurons in the basal ganglia, midbrain, parietal, and frontal cortex. Reward variance is represented in orbitofrontal and posterior cingulate cortex and through a sustained response of dopaminergic midbrain neurons.

This article reviews the role of imaging in the management of trauma patients. First the trauma series is reviewed, principally the chest, pelvis and cervical spine radiographs along with an approach to their interpretation. The role of computed tomography in trauma imaging is then discussed.

The importance of cranial computed tomography in the diagnosis and follow up of intracranial pathology cannot be underestimated. Clinicians at every level should have a basic understanding of this technique. This second part discusses the practical use of computed tomography in the clinical setting.

Individuals can learn by interacting with the environment and experiencing a difference between predicted and obtained outcomes (prediction error). However, many species also learn by observing the actions and outcomes of others. In contrast to individual learning, observational learning cannot be based on directly experienced outcome prediction errors. Accordingly, the behavioral and neural mechanisms of learning through observation remain elusive. Here we propose that human observational learning can be explained by two previously uncharacterized forms of prediction error, observational action prediction errors (the actual minus the predicted choice of others) and observational outcome prediction errors (the actual minus predicted outcome received by others). In a functional MRI experiment, we found that brain activity in the dorsolateral prefrontal cortex and the ventromedial prefrontal cortex respectively corresponded to these two distinct observational learning signals.

The importance of cranial computed tomography in the diagnosis and follow up of intracranial pathology cannot be underestimated. Clinicians at every level should have a basic understanding of this technique. This first of two articles looks at the technical strengths and weaknesses of cranial computed tomography, and cranial anatomy.

Non-fatal stroke has significant social and financial implications, and the use of appropriate imaging is essential for early diagnosis and treatment to prevent permanent disability. This article discusses the pivotal role radiological imaging plays in the management of stroke and transient ischaemic attack.

Preoperative positron emission tomography (PET) scanning of three patients with lung cancer revealed increased unilateral focal activity in a parotid gland. Further investigation with ultrasound and core biopsy confirmed benign parotid neoplasm in all three cases. The phenomenon of imaging-related incidentaloma is increasingly recognized and further investigation of these lesions remains controversial. This article discusses PET incidentaloma in the parotid, why tracer uptake may occur and how these lesions may be managed with changes in patient management that ensue.

Like other species, humans are sensitive to the decisions and actions of conspecifics, which can lead to herd behavior and undesirable outcomes such as stock market bubbles and bank runs. However, how the brain processes this socially derived influence is only poorly understood. Using functional magnetic resonance imaging (fMRI), we scanned participants as they made decisions on whether to buy stocks after observing others' buying decisions. We demonstrate that activity in the ventral striatum, an area heavily implicated in reward processing, tracked the degree of influence on participants' decisions arising from the observation of other peoples' decisions. The signal did not track non-human, non-social control decisions. These findings lend weight to the notion that the ventral striatum is involved in the processing of complex social aspects of decision making and identify a possible neural basis for herd behavior.

A decade ago, the detection of the first transiting extrasolar planet provided a direct constraint on its composition and opened the door to spectroscopic investigations of extrasolar planetary atmospheres. Because such characterization studies are feasible only for transiting systems that are both nearby and for which the planet-to-star radius ratio is relatively large, nearby small stars have been surveyed intensively. Doppler studies and microlensing have uncovered a population of planets with minimum masses of 1.9-10 times the Earth's mass (M[symbol:see text]), called super-Earths. The first constraint on the bulk composition of this novel class of planets was afforded by CoRoT-7b (refs 8, 9), but the distance and size of its star preclude atmospheric studies in the foreseeable future. Here we report observations of the transiting planet GJ 1214b, which has a mass of 6.55M[symbol:see text]), and a radius 2.68 times Earth's radius (R[symbol:see text]), indicating that it is intermediate in stature between Earth and the ice giants of the Solar System. We find that the planetary mass and radius are consistent with a composition of primarily water enshrouded by a hydrogen-helium envelope that is only 0.05% of the mass of the planet. The atmosphere is probably escaping hydrodynamically, indicating that it has undergone significant evolution during its history. The star is small and only 13 parsecs away, so the planetary atmosphere is amenable to study with current observatories.