Keynote Address

The Keynote Address is an invited lecture delivered by a prominent colleague whose contributions to neuroscience are widely acknowledged. NCM provides the opportunity for members to suggest colleagues who would be suitable candidates to deliver a Keynote Address at the Annual Meeting. Individuals and topics outside the normal NCM community are encouraged.

Keynote Address

The Keynote Address is an invited lecture delivered by a prominent colleague whose contributions to neuroscience are widely acknowledged. NCM provides the opportunity for members to suggest colleagues who would be suitable candidates to deliver a Keynote Address at the Annual Meeting. Individuals and topics outside the normal NCM community are encouraged.

2017 Keynote Speaker

Roger Lemon PhD FMedSci

Roger Lemon PhD FMedSci

UCL Institute of Neurology, Queen Square

Primate Specific Features of Corticospinal Control

Biography

Roger Lemon is Sobell Professor of Neurophysiology at the UCL Institute of Neurology, Queen Square. He is a Fellow and past Council Member of the Academy of Medical Science. He was awarded the Fyssen Prize in 2015. His main research interest is the control of skilled hand movements by the brain and is prompted by the need to understand why hand and finger movements are particularly affected by damage to the cortex, and its major descending pathways, for instance as a result of stroke, spinal injury or motor neurone disease. His experiments involve the use of purpose-bred non-human primates, since these provide the best available model for the human sensorimotor system controlling the hand. He has carried out parallel studies in normal human volunteers and has sought to apply the knowledge gained from his work in monkeys to the effects of stroke on hand function in patients, to understand the process of recovery and to investigate therapies that might enhance recovery. He is actively engaged in the public dialogue on the responsible use of animals in biomedical research, and particularly the importance of using non-human primates as models of complex neurological and neurodegenerative disease.

 

Abstract

Primate Specific Features of Corticospinal Control

Roger Lemon (UCL, London)

Although the corticospinal tract is a feature of all mammalian brains, there are major species differences in the organisation of the corticospinal (CS) projection, and these are reflected in the different functions mediated by the CS tract.

I will discuss various interrelated CS features, all of which impact on its function. First, the size distribution of CS fibres. The non-human primate exhibits a similar CS fibre size spectrum to that of the human: there is a small but significant population of large, fast-conducting (> 50m/s) fibres. These fast fibres are not found in the rodent CS. Fast-conducting fibres might reflect activity levels in CS fibres, but are more likely important in reducing conduction delays in large-bodied primates. For technical reasons, most of our neurophysiological knowledge of the primate CS system is confined to this fast-conducting population. In the macaque this amounts to only 3% of the total number of fibres in the pyramidal tract, but this still represents some 18,000 fibres. A definitive role or roles for the much more numerous population of very thin fibres (axon diameter 1 µm or less) has yet to be found.

Second, the duration of CS action potentials. When recording from identified CS neurons in macaque motor cortex, activity is dominated by action potentials from large CS neurons. Most of these neurons (~80 %) have very brief spikes (<400 µs), with some as short as 150-200 µs. Brief spikes are also found in other M1 pyramidal neurons with projections to different subcortical targets. This is in contrast to the rodent motor cortex, where pyramidal neurons have much broader spikes (typically around 900 µs).

Third, I will consider membrane expression of the Kv3.1a K+ channel protein. Kv3.1a is rarely found in rat pyramidal neurons, while in the macaque most of these neurons show very clear expression. Since Kv3.1a channels likely contribute to the rapid repolarisation of the action potential, this is consistent with brief spike durations in monkey pyramidal neurons.

The final feature I shall discuss is the presence of CS fibres with direct cortico-motoneuronal (CM) connections. These are found in all dexterous primates, and are particularly well developed in humans. They are not present in rodents and carnivores. The monkey CM system is particularly active during dexterous movements, including tool use, while damage to the CS system has devastating immediate effects on skilled hand use. Although we do not know the exact proportion of the CS system that gives rise to CM connections, recent quantitative anatomical studies suggest that CM projections to motoneuron pools are numerous and amount to around one-third of the projections to the spinal intermediate zone. Clinically this system may be important in stroke and spinal injury, while in amyotrophic lateral sclerosis (ALS), the pattern of muscle weakness and wasting closely follows the distribution of CM projections, confirming that ALS is a primate specific disease that may spread through CM connections.

I will discuss how models of motor control might take into account these important features of the CS system.

Nomination and Selection

Board members nominate candidates for consideration. Members are invited to suggest candidates to the Board (any member) or directly to both the President and Program Chair. The deadline for nominations each year is in November. When submitting your Keynote Address suggestion, please include the proposed candidate’s name, title, major scientific contributions and their email address and phone number.

Past Keynotes

19th Annual Meeting (2009)
G. Melvill Jones
How do we steer ourselves where we want to go? Insights gleaned from 6 decades of messing around in labs on Earth and beyond.

22nd Annual Meeting (2012)
Emilio Bizzi

23rd Annual Meeting (2013)
Tom Jessell
Sifting Circuits for Motor Control

24th Annual Meeting (2014)
David S. Zee
Effects of MRI machine magnetic fields on the brain: Studies in normal humans, vestibular patients, mice and zebra fish

25th Annual Meeting (2015)
Peter Strick
Old and New M1: A tale of two motor areas

26th Annual Meeting (2016)
Eckart Altenmüller
Functional and dysfunctional plasticity in motor systems of music