Daily Archives: July 10, 2008

Encoding reward information in the pre-frontal cortex

Science Daily reports on research by Lee et. al. of Yale University:

Good things may come to those who wait, but research has proven that humans and animals actually prefer an immediate rather than a delayed reward. Now, a study published in the July 10 issue of the journal Neuron reveals how a decision-making region of the brain encodes information associated with the magnitude and delay of rewards.

The preference for immediate reward is called temporal discounting, and the value of reward depreciated according to its delay is referred to as temporally discounted value. Previous animal studies aimed at studying the neural signals associated with the impact of reward magnitude and delay on choice behavior have been difficult to interpret. “Despite the fundamental role of time in decision making, how the brain encodes the temporally discounted values to guide the animal’s choice during intertemporal choice remains poorly understood,” says lead author Dr. Daeyeol Lee from Yale University School of Medicine.

Dr. Lee and colleagues examined whether the dorsolateral prefrontal cortex (DLPFC), a part of the brain implicated in decision making and contextual control of behaviors, is involved in temporal discounting and intertemporal choice. The researchers studied the brains and behaviors of animals trained in an intertemporal choice task where reward delays were indicated by clocks. Importantly, the positions of targets associated with small or large rewards and their corresponding delays were randomly varied.

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Working memory: declarative vs. semantic?

Psychologists typically classify memory as declarative (facts and figures), procedural (um – procedures), or semantic (abstract/symbolic).  The latest issue of the journal Neuron has published a study by Montojo & Courtney that examines the nature of working memory (WM).  The authors’ abstract reads as follows:

Establishing what information is actively maintained in working memory (WM) and how it is represented and controlled is essential to understanding how such information guides future behavior. WM has traditionally been investigated in terms of the maintenance of stimulus-specific information, such as locations or words. More recently, investigators have emphasized the importance of rules that establish relationships between those stimuli and the pending response. The current study used a mental arithmetic task with fMRI to test whether updating of numbers (i.e., stimuli) and updating of mathematical operations (i.e., rules) in WM relies on the same neural system. Results indicate that, while a common network is activated by both types of updating, rule updating preferentially activates prefrontal cortex while number updating preferentially activates parietal cortex. The results suggest that both numbers and rules are maintained in WM but that they are different types of information that are controlled independently.

Hands in visual field = closer inspection of objects?

Science Daily reports on research by researchers at Washington University (St. Louis, MO):

[The study by Abrams et. al.] demonstrates that humans more thoroughly inspect objects when their hands are near the object rather than farther away from it. This reflexive, non-conscious difference in information processing exists, they posit, because humans need to be able to analyze objects near their hands, to figure out how to handle the objects or to provide protection against them.

Recognizing that the location of your hands influences what you see is a new insight into the wiring of the brain, one that could lead to rethinking current rehabilitative therapy techniques and prosthetic design.

For a stroke victim trying to regain use of a paralyzed hand, just placing the good hand next to the desired object could help the injured hand grasp it.

Likewise, prosthetics could be redesigned to include additional information flow from the hand to the brain, rather than just the brain controlling the spatial location of the prosthetic, as with today’s artificial limb technology.

The findings also may lend scientific support for recently enacted California legislation barring the use of hand-held cell phones while driving.