Assessment of spatial attention and neglect with a virtual wheelchair navigation task

A total of 9 participants with right-hemisphere stroke performed a new virtual reality (VR) wheelchair navigation test of lateralized spatial attention and neglect. The test consists of a virtual path along which participants navigate (or are navigated) as they name virtual objects encountered. There are 4 VR conditions, obtained by crossing the factors array complexity and driver. Participants performed the VR task, a real-life wheelchair navigation task, and a battery of attention and neglect tests. The VR test showed sensitivity to both array complexity and driver, exhibited strong correlations with the wheelchair navigation test, and detected lateralized attention deficits in mild patients. The VR task thus shows promise as a sensitive, efficient measure of real-life navigation.     

Neuroeconomics: a view from neuroscience

All choices are economic decisions, and this is true because mobile organisms run on batteries. For them the clock is always ticking and their battery draining so every moment represents a choice of how to invest a bit of energy. From this perspective, all choices - those made and those not made - engender costs and yield variable future returns. There is no more fundamental stricture for an organism than to behave so as to recharge their batteries; consequently, each moment of existence is attended by the need to value that moment and its near-term future quickly and accurately. The central issue of neuroeconomics is valuation - the way the brain values literally everything from internal mental states to experienced time (the neuroscience part), and why it should do so one way and not another (the normative economics part). All these valuations have now begun to be probed in experiments by pairing quantitative behavioral and computational modeling with neuroimaging or neurophysiological experiments.     

Case of the month: Dislodged tracheo-oesophageal valve: importance of rapid replacement or stenting

Dislodgement of a tracheo‐oesophageal prosthesis needs prompt action to ensure patency and prevent aspiration in patients with total laryngectomy. Failure to do so may lead to an unnecessary repeat tracheo‐oesophageal puncture. This case report is about a patient who needed a repeat procedure under general anaesthetic. It highlights the need for emergency physicians to be aware of this not uncommon event in a patient with a laryngectomy and to refer them immediately for ENT review.     

When things are better or worse than expected: the medial frontal cortex and the allocation of processing resources

Access to limited-capacity neural systems of cognitive control must be restricted to the most relevant information. How the brain identifies and selects items for preferential processing is not fully understood. Anatomical models often place the selection mechanism in the medial frontal cortex (MFC), and one computational model proposes that the mesotelencephalic dopamine (DA) system, via its reward prediction properties, provides a "gate" through which information gains access to limited-capacity systems. There is a medial frontal event-related potential (ERP) index of attention selection, the anterior positivity (P2a), associated with DA reward system input to the MFC for the identification of task-relevant perceptual representations. The P2a has a similar spatio-temporal distribution as the medial frontal negativity (MFN), elicited to error responses or choices resulting in monetary loss. The MFN has also been linked to DA projections to the MFC but for action monitoring rather than attention selection. This study proposes that the P2a and the MFN reflect the same MFC evaluation function and use a passive reward prediction design containing neither instructed attention nor response to demonstrate that the ERP over medial frontal leads at the P2a/MFN latency is consistent with activity of midbrain DA neurons, positive to unpredicted rewards and negative when a predicted reward is withheld. This result suggests that MFC activity is regulated by DA reward system input and may function to identify items or actions that exceed or fail to meet motivational prediction.