Toward a Cognitive Neurobiological Account of Free Association

Free association has been central to psychoanalytic theory and practice for over a century, yet its physiology has largely been ignored. When viewed from a cognitive neurobiological perspective, the process resembles a minimally constrained executive task, one that might engage the left dorsolateral prefrontal cortex. To test this hypothesis, we used functional magnetic resonance imaging to detect neural activity while subjects performed overt, vocal free association in the scanner. Twelve healthy subjects performed three active tasks—vocal free association, orthographic (letter) fluency, and semantic (category) fluency—alternating with a baseline condition, word repetition. Stimulus administration and overt response performance occurred during periods of scanner silence. Each subject was scanned three times, the order of conditions counterbalanced across scans. Statistical parametric mapping was used to perform a mixed-effects analysis of those images acquired. We found that, in common with both verbal fluency tasks, free association was accompanied by activation of the left dorsolateral prefrontal cortex. Indeed, it elicited significantly greater activation in adjacent areas. The main effect of “task,” common to all three active conditions, revealed an extensive network of activation within executive brain regions (including bilateral dorsolateral prefrontal and anterior cingulate cortices). While free association has been considered a probe of the “unconscious,” these data suggest that, early on in the process, under experiment conditions, this behavior engages components of the prefrontal executive (specifically, on the left). This finding points to a possible congruence between psychological accounts of “ego” function and neuropsychological accounts of a cognitive executive instantiated in prefrontal systems.