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.

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->D5 and D5->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.

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.