DOI: 10.5061/dryad.mgqnk98x8
title: The organizational principles of de-differentiated topographic maps - Data

description: Topographic maps are a fundamental feature of cortex architecture in the
 mammalian brain. One common theory is that the de-differentiation of
 topographic maps links to impairments in everyday behavior due to less
 precise functional map readouts. Here, we tested this theory by
 characterizing de-differentiated topographic maps in primary somatosensory
 cortex (SI) of younger and older adults by means of ultra-high resolution
 functional magnetic resonance imaging together with perceptual finger
 individuation and hand dexterity. Older adults’ SI maps showed similar
 amplitude, size, and levels of stimulus-related noise than younger adults’
 SI maps, but presented with less representational similarity between
 distant fingers. Larger population receptive field sizes in older adults’
 maps did not correlate with behavior, whereas reduced cortical distances
 related to better hand dexterity. Our data uncover the drawbacks of a
 simple de-differentiation model of topographic map function, and motivate
 the introduction of a feature-based model of cortical reorganization.
description: Behavioral motor tests, a tactile finger discrimination task, and
 7 Tesla functional magnetic resonance imaging (7T-fMRI) data of younger
 and older adults were collected to describe cortical de-differentiation in
 the primary somatosensory cortex and its relation to sensorimotor
 behavior. Data collection and data processing is described in the
 readme.txt files that are associated to each dataset, and in the main text
 of the submitted manuscript. In brief, a group of
 younger adults (21-29 years) and a group of older adults (65-78 years)
 were invited to two appointments. There was one appointment for behavioral
 tests (Purdue Pegboard Test, Grooved Pegboard Test, O'Connor
 Dexterity Test, Digit confusion test, data uploaded in the folder
 "Behavior"), and one appointment for a 7T-fMRI session. During
 the 7T-fMRI session, participants underwent 6 blocks were the fingers of
 their right hand were stimulated using an automated Piezo-driven
 stimulator. Fingers were either stimulated in a Fourier-design (2 blocks,
 D1-&gt;D5 and D5-&gt;D1), in a blocked design (2 blocks, random
 stimulation), or in an HRF design (2 blocks). Finally, a 5-minute resting
 state scan was measured (eyes open). Functional data resolution was 1x1x1
 mm (see Materials and Methods: fMRI task for more details).
 Data were preprocessed and analysed, and the following parameters
 were calcualted: Cortical distances between finger representations (data
 uploaded in the folder "Finger_distances"), significant
 phase-encoded finger maps (data uploaded in the folder
 "Fourier"), map dispersion of finger maps across each age group
 (data uploaded in the folder "MapDispersion"), population
 receptive field sizes of each participant (data uploaded in the folder
 "pRF"), representational similarity between finger
 representations across runs (data uploaded in the folder
 "Representational_similarity"), and resting state signal
 correlations between finger areas (data uploaded in the folder
 "RestingState"). Each folder contains a readme.txt file where
 more information on the data are provided, and links to the respective
 section in the manuscript are given. Due to reasons of
 data protection, no raw MRI data are provided that could be used to
 identify the subject, but the statistical outputs of the analyses are
 uploaded.
description: Data collection and data processing is described in the
 readme.txt files that are associated to each dataset, and in the main text
 of the manuscript.