Two Double-Dissociations in How the Brain Encodes Rules – Different Regions Encode (1) Rule Identity vs Rule Order, and (2) Rules Requiring Where- vs What-Responses
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1
Charité Univertitätsmedizin Berlin, BCCN, Germany
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2
Università Milano - Bicocca, Department of Psychology, Italy
Conditional rules of the form ”If X then Y” are of vital importance in our everyday life. Recently, researchers have started to uncover the neural substrate underlying cognitive control and conditional rule processing (Reverberi, 2011; Bunge, 2008).
Here, we present results from two studies that investigated two critical, so far largely neglected, aspects of rule processing:
(1) Which vs When: Do different regions encode rule identity and rule order? What are the brain regions encoding rule order?
(2) Where vs What: Does the brain encode rules differently for different types of responses?
To investigate this, we recorded fMRI while participants performed a cued task-switching paradigm, in which participants had to retrieve, maintain, and apply two rules in a fixed order, such as “Check first: If there is an X, do Y. Check second: If there is a V, do W”. Using multivariate searchlight decoding (Kriegeskorte, 2006; Haynes, 2007), we found neural double dissociations for both questions:
(1) Regions representing which rule to use (i.e. rule A vs. rule B) differed from regions representing when to use which rule (i.e. rule A before rule B), and
(2) Regions encoding rules that used (spatial) where responses (e.g. “If X, press left”) differed from rules using (symbolic) what responses (e.g. “If X, press where an 'A' appears”).
More specifically, rules requiring where/what-responses were encoded in lateral parietal/lateral temporal areas, respectively, reminiscent of the classical dichotomy between the dorsal “where” and ventral “what” pathway. Only right dorso-lateral PFC encoded rule identity in both conditions. Still different regions were found to encode when (i.e. in which order) rules should be applied, including both cortical (e.g. premotor areas) and subcortical structures (e.g. Putamen and Hippocampus).
Our finding that what-response rules are not represented in parietal cortex challenges the current view that rule processing in general depends on a fronto-parietal network. Rather, it suggests that the frequently observed parietal involvement may be due to the need of spatial processing.
In conclusion, we were able to extend previous research on rule representation by (a) identifying the neural code underlying the order with which rules are to be applied; (b) finding a double dissociation that suggests that the brain handles two important features of tasks sets, namely rule identity and rule order, differently; and (c) showing that neural representations of rules differ depending on the required response type. More generally, this work demonstrates that neural representations of multiple features of task sets can be decoded from patterns of human brain activity.
Acknowledgements
We thank the BMBF (“Förderkennzeichen” 01GQ1001B & 01GQ1001C) and the GRK1589/1 for financial support.
References
Reverberi, C., Görgen, K., & Haynes, J.-D. (2011). Neural representation of conditional rules: Compositionality of the neural code. Cerebral Cortex, doi: 10.1093/cercor/bhr200
Bunge, S. A., & Wallis, J. D. (2008). Neuroscience of rule-guided behavior. Oxford University Press, USA.
Kriegeskorte, N., Goebel, R., & Bandettini, P. (2006). Information-based functional brain mapping. PNAS USA, 103(10), 3863–3868.
Haynes, J.-D., Sakai, K., Rees, G., Gilbert, S., Frith, C., & Passingham, R. E. (2007). Reading Hidden Intentions in the Human Brain. Current Biology, 17(4), 323–328.
Keywords:
Decoding,
fMRI,
multi-variate pattern analysis,
rule order,
rule priority,
task-set,
what-pathway
Conference:
BC11 : Computational Neuroscience & Neurotechnology Bernstein Conference & Neurex Annual Meeting 2011, Freiburg, Germany, 4 Oct - 6 Oct, 2011.
Presentation Type:
Poster
Topic:
neural encoding and decoding (please use "neural coding and decoding" as keyword)
Citation:
Görgen
K,
Reverberi
C and
Haynes
J
(2011). Two Double-Dissociations in How the Brain Encodes Rules – Different Regions Encode (1) Rule Identity vs Rule Order, and (2) Rules Requiring Where- vs What-Responses.
Front. Comput. Neurosci.
Conference Abstract:
BC11 : Computational Neuroscience & Neurotechnology Bernstein Conference & Neurex Annual Meeting 2011.
doi: 10.3389/conf.fncom.2011.53.00229
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Received:
04 Aug 2011;
Published Online:
04 Oct 2011.
*
Correspondence:
Mr. Kai Görgen, Charité Univertitätsmedizin Berlin, BCCN, Berlin, 10115, Germany, kai.goergen@bccn-berlin.de