Thursday, July 3, 2014

Broca's area: a dessert topping or a floor wax? It may help you decide.

Broca's area seems to be involved in everything.

  • Speech articulation
  • Sentence comprehension
  • Working memory
  • Cognitive control
  • Sequencing
  • Hierarchical processing
  • Manual gesture execution
  • Speech perception
  • Gestural action understanding
to name a few of the top of my head.  One thing in common with many tasks, including those that activate Broca's area is that the subjects in these studies must make a decision.  A recent study by Greg Reckless et al. has added to the list of functions ascribed to Broca's area by showing that activation in this hyperactive region is modulated by changes in decision bias in a picture-based perceptual decision-making task (abstract below).  This is quite consistent with findings from Jon Venezia's study in my lab lab here at UC Irvine showing that motor speech-related areas are modulated by response bias. See here for a discussion of that work.  

These studies seriously complicate claims that Broca's area does [pick your favorite from the list above] because it could simply be a function of the decision process.  

1000 points to whoever can figure out what Broca's area is REALLY doing.

The left inferior frontal gyrus is involved in adjusting response bias during a perceptual decision-making task



Changing the way we make decisions from one environment to another allows us to maintain optimal decision-making. One way decision-making may change is how biased one is toward one option or another. Identifying the regions of the brain that underlie the change in bias will allow for a better understanding of flexible decision-making.


An event-related, perceptual decision-making task where participants had to detect a picture of an animal amongst distractors was used during functional magnetic resonance imaging. Positive and negative financial motivation were used to affect a change in response bias, and changes in decision-making behavior were quantified using signal detection theory.


Response bias became relatively more liberal during both positive and negative motivated trials compared to neutral trials. For both motivational conditions, the larger the liberal shift in bias, the greater the left inferior frontal gyrus (IFG) activity. There was no relationship between individuals' belief that they used a different strategy and their actual change in response bias.


The present findings suggest that the left IFG plays a role in adjusting response bias across different decision environments. This suggests a potential role for the left IFG in flexible decision-making.

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