Unconscious determinants of free decisions in the human brain.
Soon CS, Brass M, Heinze HJ, Haynes JD.
Published in Nat Neurosci. 2008 May;11(5):543-5.
There has been a long controversy as to whether subjectively 'free' decisions are determined by brain activity ahead of time. We found that the outcome of a decision can be encoded in brain activity of prefrontal and parietal cortex up to 10 s before it enters awareness. This delay presumably reflects the operation of a network of high-level control areas that begin to prepare an upcoming decision long before it enters awareness.
Decoding sequential stages of task preparation in the human brain.
Bode S, Haynes JD.
Published in Neuroimage. 2009 Apr 1;45(2):606-13. Epub 2008 Dec 9.
The flow of information from sensory stimuli to motor responses in the human brain can be flexibly re-routed depending on task demands. However, it has remained unclear which sequence of processes is involved in preparing the brain for an upcoming task. Here, we used a combination of fMRI and multivariate pattern classification to decompose the information flow in a task-switching experiment. Specifically, we present a time-resolved decoding approach that allowed us to track the temporal buildup of task-related information. This approach also allowed us to distinguish encoding of the task from encoding of target stimuli and motor responses, thus separating between different components of information processing. We were able to decode from parietal and lateral prefrontal cortex which specific task-set a subject was currently holding. Importantly, this revealed that the intraparietal sulcus encoded task-set information before prefrontal cortex, and it was the only region to encode the specific task-set before the relevant target stimulus was presented. This suggests that task-related information in parietal cortex does not rely on input from prefrontal cortex as previously suggested. In contrast, our findings suggest that parietal cortex might play a role in establishing task-sets in prefrontal cortex.
Compositionality of Rule Representations in Human Prefrontal Cortex.
Reverberi C, Görgen K, Haynes JD.
Published in Cereb Cortex. 2011 Aug 4. [Epub ahead of print]
Rules are widely used in everyday life to organize actions and thoughts in accordance with our internal goals. At the simplest level, single rules can be used to link individual sensory stimuli to their appropriate responses. However, most tasks are more complex and require the concurrent application of multiple rules. Experiments on humans and monkeys have shown the involvement of a frontoparietal network in rule representation. Yet, a fundamental issue still needs to be clarified: Is the neural representation of multiple rules compositional, that is, built on the neural representation of their simple constituent rules? Subjects were asked to remember and apply either simple or compound rules. Multivariate decoding analyses were applied to functional magnetic resonance imaging data. Both ventrolateral frontal and lateral parietal cortex were involved in compound representation. Most importantly, we were able to decode the compound rules by training classifiers only on the simple rules they were composed of. This shows that the code used to store rule information in prefrontal cortex is compositional. Compositional coding in rule representation suggests that it might be possible to decode other complex action plans by learning the neural patterns of the known composing elements.
Tracking the unconscious generation of free decisions using ultra-high field fMRI.
Bode S, He AH, Soon CS, Trampel R, Turner R, Haynes JD.
Published in PLoS One. 2011;6(6):e21612.
Recently, we demonstrated using functional magnetic resonance imaging (fMRI) that the outcome of free decisions can be decoded from brain activity several seconds before reaching conscious awareness. Activity patterns in anterior frontopolar cortex (BA 10) were temporally the first to carry intention-related information and thus a candidate region for the unconscious generation of free decisions. In the present study, the original paradigm was replicated and multivariate pattern classification was applied to functional images of frontopolar cortex, acquired using ultra-high field fMRI at 7 Tesla. Here, we show that predictive activity patterns recorded before a decision was made became increasingly stable with increasing temporal proximity to the time point of the conscious decision. Furthermore, detailed questionnaires exploring subjects' thoughts before and during the decision confirmed that decisions were made spontaneously and subjects were unaware of the evolution of their decision outcomes. These results give further evidence that FPC stands at the top of the prefrontal executive hierarchy in the unconscious generation of free decisions.
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