A COMMON CORTICAL METRIC FOR SPATIAL,
TEMPORAL, AND SOCIAL DISTANCE
A Journal of Neuroscience publication by Carolyn Parkinson, Shari
Liu, and Thalia Wheatley of Dartmouth College.
P R E S E N T E D BY N I CCO R E G G E N T E O N 4 / 1 0 / 1 4 AT
NEUROIMAGING+ JOURNAL CLUB
MOTIVATION
• Does distance carry a common psychological meaning?
• Spatial: Franz is “closer” to Gonda than it is to SaMo beach.
• Temporal: This moment is “closer” to HBM than it is to SfN.
• Social: Tessa is “closer” to Rachel than she is to R. Kelly.
• Construal Level Theory (CLT) says that distance in any domain
signifies a common meaning: distance from current first-hand
experience. Conceptual Metaphor theory(CMT) says that we use
spatial language because we actually “plot” information spatially.
• Does distance’s ubiquity across domains of thought serve a
computationally efficient purpose in the brain?
STIMULI/PARADIGM
In scanner:
“Yes” or “No”
Response to Probe
STIMULI/PARADIGM
Outside Scanner:
For soon/close/familiar 
For late/far/familiar  (-1 * (opposite_metric))
BEHAVIORAL METHODS
• Formation of a behavioral representational dissimilarity
matrices(bRDM)
• Closer/more familiar should be more similar than
closer/less familiar.
SUPPORT VECTOR MACHINE “BAIT & SWITCH”
• Train on Closer vs. Farther Trials
• Test on Sooner vs. Later Trials & More vs. Less Familiar
• “Apply Trained Classifier”/”Use the same decision boundary” in
a pairwise fashion
RSA
• Formation of neural representation dissimilarity matrices
(nRDM)
• In a pairwise fashion, calculate (1-Pearson’s r) for each
trial type
…
BRDM AND NRDM RSA
• Correlate the BRDM and NRDM in an attempt to see the
degree to which all pairs of experimental conditions are
dissimilar to one another in accordance with both fMRI
responses and behavioral ratings.

Spearman’s r

SEARCHLIGHT

• Conduct both Support Vector Machine “bait and switch”
and RSA of BRDM and NRDM in a searchlight mapping
fashion (9mm/3voxel radius).
Classify or correlate
STATISTICS
• For the SVM bait and switch to be considered significant…
• Classification values (arcsine transformed(y = arcsin( x ))) were submitted to a twotailed, one-sample t-test against 50% correct.
• Conjunction analysis of 6 t-test statistical maps(each possible training and testing
scheme) with FDR correction and p <.05.
• Clusters > 10 voxels
• For the BRDM and NRDM RSA to be considered significant...
• Shuffle BRDM scores and correlate with actual NRDM. 1000 permutations.
• Actual BRDM and actual NRDM compared to this pseudo-population to yield zscores.
• One-sample t-test(against 0) on the z-scores at the group-level and p<.05 FDR
corrected
• Clusters>10 voxels
BAIT AND SWITCH RESULTS
• Regions in which psychological distance could be decoded
across all distance domains.
BRDM AND NRDM RSA RESULTS
• Population codes within searchlights centered in these areas
contain representations that reflect subjective perceptions of
egocentric distance.
INTERPRETATIONS/DISCUSSION
• Right IPL/ Right TPJ is part of the frontoparietal control
network(FPCN)
• FPCN is thought to selectively recruit the Default Mode
Network(DMN) and the Dorsal Attention Network(DAN)
• DMN – internally directed cognition
• “proximal”/concrete/detailed information manipulation?
• DAN – externally directed cognition
• “distal” / decontexualized / abstract information manipulation?
• IPL would be perfectly positioned to fulfill this role and serve as
a “flexible hub” that has a common cortical metric /
parsimonious coding scheme for the guidance of information
processing….
INTERPRETATIONS/DISCUSSION
INTERPRETATIONS/DISCUSSION
INTERPRETATIONS/DISCUSSION
INTERPRETATIONS/DISCUSSION
• Right IPL/ Right TPJ has been shown to:
• Encode egocentric space
• Support self-other distinctions
• Lesions to Right IPL/ Right TPJ results in:
• Deficits in representing space
• Deficits in representing events along a mental timeline.
• IPL circuitry is thought to have been originally devoted to
sensorimotor transformations and representing one’s own
body in space and was “recycled” to operate analogously
on increasingly abstract contents via evolution.
INTERPRETATIONS/DISCUSSION
• Medial occipital has been previously associated with
mental imagery during relative distance comparisons
• SMA/IFG are involved in retrieving spatial locations from
memory and may be similarly involved in accessing
temporal and social frames of reference….
INTERPRETATIONS/DISCUSSION
“It would be inefficient for the brain to represent spatial, social,
and temporal distances entirely separately if they carry a
common psychological meaning.”