The relation between MRI neuroactivation changes and response rate on a word-fluency task.

Area of Science:

• Neuroscience
• Cognitive Neuroscience
• Psycholinguistics

Background:

• The left premotor cortex, specifically areas 44 and 6, is implicated in language processing.
• Its precise role in word generation, whether in speech production or lexical search, remains debated.

Purpose of the Study:

• To investigate the functional magnetic resonance imaging (fMRI) response of the left premotor cortex during a word-fluency task.
• To determine if this region is more involved in the motor planning of speech output or the cognitive search for words.

Main Methods:

• fMRI was used to measure brain activity in ten participants performing a word-fluency task.
• Participants were presented with letters varying in word-generational frequency.
• Neuroactivation changes were correlated with magnetic resonance signal changes in the left premotor cortex (Brodmann's areas 44 and 6).

Main Results:

• Significant differences in neuroactivation were observed between letters associated with high and low overt frequencies (p = .05).
• Activation in the region crossing Brodmann's areas 44 and 6 showed a bias toward output, increasing with more words generated.
• This pattern supports the hypothesis that this cortical region is involved in motor planning of speech.

Conclusions:

• The findings support the hypothesis that Brodmann's areas 44 and 6 are critical for the motor planning of speech during word generation.
• This suggests a role in speech production rather than the lexical search component of word fluency.