Here we highlight some 2014 messages from the Motor Impairment team. They focus on some new physiology reported during the year and hopefully illustrate how the body functions.
In the coming days we will post additional highlights from 2014 dealing with other aspects of Motor Impairment and motor performance.
MUSCLE STUFF
Muscle growth: how to make your muscles grow longer. This study, highlighted in a previous Motor Impairment blog post, examined how different types of eccentric exercise can lead to longitudinal muscle growth.
Muscle contraction: A review of new work on the key role played by the regulatory protein triadin in excitation-contraction coupling.
Muscles, motoneurones and speed: There is a specific molecular signal that makes some motoneurones ‘fast’.
SYNAPSES
Synapses: These studies published in Nature reveal a new role for astrocytes and their phagocytic paths in synapse elimination and remodelling in the developing and adult brain.
OUTPUT TO MUSCLES
Maps of spinal motor output in humans during walking forward, backward, on tiptoe and uphill. Reconstructed spinal maps from 26 leg muscle EMGs revealed that all these walking tasks have many similarities in their temporal spinal activation profiles.
Standing up: the lateral gastrocnemius muscle is surprisingly inactive during quiet stance. New data on the human ankle plantarflexor muscles, highlighted here on the Motor Impairment blog.
Muscle synergies: The operation of a limited number of muscle synergies was explored in the arm during a reach. It reveals how they can produce force accurately. For important prior work in 2013 see here.
Hand-to-mouth and other motor synergies. It is claimed that they are built into the human motor cortex. However, there may be subcortical controllers too! Nonetheless, the work provides insight into the organization and development of motor functions in primates.
Control of reaching. There is a vital role for one class of propriospinal neurones in reaching. This is revealed in elegant studies in the mouse.
Grasping an object with both hands: a special parietal cortical area (the right anterior intra-parietal sulcus) is important for bimanual tasks.
The use of transcranial magnets and batteries to activate motor cortical circuits. Helpful review from Di Lazzaro and Rothwell.
Sensorimotor cortex: How the primary sensory cortex may bombard the primary motor cortex.
Spinal reflexes: This review highlights a broad body of evidence on plasticity and operant conditioning of spinal reflexes. This has potential clinical usefulness.
EXERCISE
Exercise limitations: Is heart rate the major limit to exercise capacity in trained humans? New work using cardiac pacing during cycling. This will likely remain a controversial area.
Exercise: How is heart rate controlled by the autonomic nervous system during dynamic exercise? New view on parasympathetic – sympathetic balance. A message to beware the simplistic explanation!
Exercise and the brain: How does exercise control the state of your cerebral cortex? New studies have focused on the brainstem path from the mesencephalic locomotor region to the cortex in mice.
SENSES
Sensory discrimination: Staggering evidence that the nose ‘wins’. It far outperforms the other senses.
Touch sensation: How do we sense it? New data on how mechanical events are sensed. The Piezo2 channel in the skin is critical for the Merkel cell–neurite complex to act as a touch receptor (mechanotransducer) that encodes fine details of objects
Proprioception: Further evidence that position sense is not stable – it ‘drifts’. This is predominantly due to adaptation in the firing of muscle spindles.
Pain and nociception: There are complexities in coding sensory inputs especially at peripheral nociceptors. Great new set of symposium reviews.
OTHER
Your 24-hour body clock: A major new clock gene found called ‘Chronos’. It is affected by stress. This is an important development for understanding how a cellular clock that ultimately affects our sleep–wake cycle is built.
Memory failing? How many types of memory are there? New work suggests it is more complicated than we used to think – so not just semantic and episodic memory.
Free will perhaps? New data plus a new interpretation of Libet’s classic experiment on free will and decision making.