Abstract
The relevance of human primary motor cortex (M1) for motor actions has long been established. However, it is still unknown how motor actions are represented, and whether M1 contains an ordered somatotopy at the mesoscopic level. In the current study we show that a detailed within-limb somatotopy can be obtained in M1 during finger movements using Gaussian population Receptive Field (pRF) models. Similar organizations were also obtained for primary somatosensory cortex (S1), showing that individual finger representations are interconnected throughout sensorimotor cortex. The current study additionally estimates receptive field sizes of neuronal populations, showing differences between finger digit representations, between M1 and S1, and additionally between finger digit flexion and extension. Using the Gaussian pRF approach, the detailed somatotopic organization of M1 can be obtained including underlying characteristics, allowing for the in-depth investigation of cortical motor representation and sensorimotor integration.
Highlights
Cortical sensorimotor areas in the human brain have been shown to exhibit somatotopic organizations at least at the macroscopic level between limbs
The current study investigates whether a detailed, yet complex, somatotopic organization of cortical area M1 can be obtained through the implementation of a Gaussian population Receptive Field (pRF) approach during finger movements
We developed a Gaussian pRF model that predicted the timeseries for finger digit flexion and finger digit extension
Summary
Cortical sensorimotor areas in the human brain have been shown to exhibit somatotopic organizations at least at the macroscopic level between limbs. It has even been argued that M1 explicitly does not have an orderly somatotopic organization on the mesoscopic ‘within limb’ level (Sanes and Schieber, 2001; Schieber, 2001). It is argued that the human ability for acquiring new motor skills could require the brain to maintain a flexible attitude towards cortical motor organization. This poses several challenging questions, how movement of body parts is represented within the human brain, and how sensorimotor integration is accomplished if M1 is not somatotopically organized and could change its organization over time depending on newly acquired motor skills
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