Inference of causality
A better understanding of various cognitive processes and their relationship with activity patterns recorded with human neuroimaging techniques such as functional magnetic resonance imaging (fMRI) can be gained by using the same fMRI approach in other species, such as macaque monkeys. In macaques, fMRI recording can also be combined with non invasive approaches such as Transcranial Focused Ultrasound Stimulation (TUS) to establish the causal importance of the brain area for a cognitive process.
The following work uses this combination of fMRI and TUS.
Using fMRI, we found different patterns of activity co-varying with values of counterfactual choices in a circuit spanning hippocampus, anterior lateral prefrontal cortex, and anterior cingulate cortex (ACC). ACC activity also reflected whether the internal value representations would be translated into actual behavioral change. To establish the causal importance of ACC for this translation process, we used a novel technique, Transcranial Ultrasound Stimulation to reversibly alter ACC activity.
Transcranial focused ultrasound stimulation (TUS) was applied to a deep cortical region, anterior cingulate cortex (ACC, experiment 1) and a subcortical brain structure, the amygdala (experiment 2) in macaques. The impact of TUS was measured by examining functional connectivity patterns between activity in each brain area and in the rest of the brain using functional magnetic resonance imaging (fMRI). Dissociable and spatially focal effects were found in both cases.