Hands are things with which we act

Encoding manual dexterity through modulation of intrinsic alpha band connectivity

O. Maddaluno  S Della Penna , A. Pizzuti , M. Spezialetti , M. Corbetta , F. de Pasquale  V. Betti 

J Neurosci 2024 Mar 27:e1766232024

Using hands efficiently is central to our daily life. Importantly, however, individuals differ in manual dexterity. We study whether the brain's functional organization encodes variability in manual behavior. Using a large set of MEG data acquired during rest and a finger-tapping task, we investigated how hand movements change the intrinsic functional connectivity and network architecture. Specifically in the alpha band, we demonstrate that higher dexterity is associated with decreased connectivity, specifically in the motor cortex, increased segregation, and reduced nodal centrality. Low-dexterous individuals show opposite patterns. We concluded that manual dexterity influences how the motor system responds during movements. These findings yield high potential to understand how intrinsic connectivity retains relevant behavior and to develop neural biomarkers of pathological behavior.

The spatio-temporal architecture of everyday manual behavior.

Sili D, De Giorgi C, Pizzuti A, Spezialetti M, de Pasquale F, Betti V.

Sci Rep. 2023 Jun 9;13(1):9451. 

In everyday activities, humans move alike to manipulate objects. Prior works suggest that hand movements are built by a limited set of basic building blocks consisting of a set of common postures. However, how the low dimensionality of hand movements supports the adaptability and flexibility of natural behavior is unknown. Through a sensorized glove, we collected kinematics data from thirty-six participants preparing and having breakfast in naturalistic conditions. By means of an unbiased analysis, we identified a repertoire of hand states. Then, we tracked their transitions over time. We found that manual behavior can be described in space through a complex organization of basic configurations. These, even in an unconstrained experiment, recurred across subjects. A specific temporal structure, highly consistent within the sample, seems to integrate such identified hand shapes to realize skilled movements. These findings suggest that the simplification of the motor commands unravels in the temporal dimension more than in the spatial one.

Spontaneous Beta Band Rhythms in the Predictive Coding of Natural Stimuli.

Betti V, Della Penna S, de Pasquale F, Corbetta M.

Neuroscientist. 2021 Apr;27(2):184-201. 

The regularity of the physical world and the biomechanics of the human body movements generate distributions of highly probable states that are internalized by the brain in the course of a lifetime. In Bayesian terms, the brain exploits prior knowledge, especially under conditions when sensory input is unavailable or uncertain, to predictively anticipate the most likely outcome of upcoming stimuli and movements. These internal models, formed during development, yet still malleable in adults, continuously adapt through the learning of novel stimuli and movements.Traditionally, neural beta (β) oscillations are considered essential for maintaining sensorimotor and cognitive representations, and for temporal coding of expectations. However, recent findings show that fluctuations of β band power in the resting state strongly correlate between cortical association regions. Moreover, central (hub) regions form strong interactions over time with different brain regions/networks (dynamic core). β band centrality fluctuations of regions of the dynamic core predict global efficiency peaks suggesting a mechanism for network integration. Furthermore, this temporal architecture is surprisingly stable, both in topology and dynamics, during the observation of ecological natural visual scenes, whereas synthetic temporally scrambled stimuli modify it. We propose that spontaneous β rhythms may function as a long-term "prior" of frequent environmental stimuli and behaviors.