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Dr Julia Pitcher

The Developmental Neuromotor Physiology group was established in 2004 to study the fetal and early life developmental programming of human movement (motor) physiology and function, how it is perturbed by adverse intrauterine and perinatal events such as growth restriction and obstetric interventions, and how we might minimise any negative long term impact these perturbations might have on the individual in later life. We study motor control in children, adolescents and adults. We also pursue research questions in basic human motor control, particularly in relation to cortical plasticity, neuromuscular fatigue and motor skill learning. It is a multidisciplinary team including neurophysiologists, obstetricians, neonatologists and clinical epidemiologists.

Postgraduate students:

Ms Alexandra Robertson

Collaborators:

• Professor Timothy Miles (Physiology)
• Dr. Michael Ridding (Physiology)
• Dr. Vivienne Moore (Public Health)
• Professor Caroline Crowther ( Maternal & Perinatal Clinical Trials Unit, WCH)
• Assoc. Prof. Ross Haslam (Neonatal Medicine, WCH

Current projects:

Neuromotor outcomes of fetal growth restriction.

Pitcher JB, Robertson AL, Moore VM, Cockington R & Miles TS.

We have been studying corticospinal function, fine motor skills, strength and sensorimotor integration in a cohort of young adults whose birth characteristics were recorded in detail. We are interested to know if size and weight at birth, relative to gestational age, influences these neuromotor functions later in life.

Corticospinal function and neuromotor outcomes in children after prenatal corticosteroid administration.

Pitcher JB, Haslam RR, Crowther CA & Robinson JS.

Despite widespread clinical use, evidence supported by findings from animal studies suggests that repeat doses of prenatal corticosteroids, given to accelerate infant lung maturity in women at risk of premature delivery, might adversely affect (among other outcomes) infant birthweight, brain weight, myelination and neurological development postnatally. The longer-term neurological consequences of prenatal steroid treatment are unknown. We are trying to determine the effect, if any, of single and repeat prenatal doses of corticosteroids on corticospinal and motor function in children born prematurely who are now 8-10 years of age. These motor outcomes are being compared with matched control children whose mothers were not given antenatal corticosteroids. The overall aim is to determine which specific aspects (if any) of corticospinal development and corticospinal function are perturbed by antenatal corticosteroid administration and persist into childhood.

Mechanisms of homeostatic plasticity in human motor cortex

We have recently shown for the first time that the human motor cortex is capable of bi-directional plasticity by stimulating nerves in the body periphery. Its excitability can be induced to either increase or decrease, depending on the stimulus parameters. One of these parameters is stimulus frequency; low frequency stimulation induces depression, while high frequency stimulation. However, homeostatic mechanisms may limit the degree to which these changes can occur, to prevent neural assemblies either saturating or failing to respond to incoming stimuli. In addition, there may be distinct time windows during which any repeat of the novel stimulation (for example) may 'undo' the changes in synaptic strength induced by the original stimulation. We are now examining the frequency and temporal characteristics of repeated stimulation to determine how these homeostatic mechanisms work in awake, performing humans. Longer term, these findings may help in the development of therapies in which different types of plasticity are induced to overcome aberrant motor function acquired perinatally, or help reinstate motor function lost due to illnesses such as stroke and Parkinson's Disease.

The functional significance of post-exercise depression of motor cortex excitability

Following a strong 'fatiguing' muscle contraction, the excitability of the motor cortex area of the human brain is depressed for up to an hour or more. While this originates partly in the fatigued muscle, this reduced excitability is only evident in the motor cortex, is not associated with a reduced ability of the muscle to produce force. However, the functional significance of this depression is unknown. Is it a manifestation of 'central fatigue', often associated with an increased sense of effort when performing a task? Is it confined to the motor cortex, or is the excitability of other brain areas involved in producing voluntary movements also affected? Or is it related to changes in synaptic strength associated with the learning and memory of motor skills? We have recently shown that it does not appear to significantly affect the strength of the input to the motor cortex from those areas of the brain responsible for the storage and generation of internal representations of movement.

Recent Publications

Pitcher JB, Henderson-Smart DS & Robinson JS (2005). Prenatal programming of human motor function. In: Early Life Origins of Health and Disease . Eds. M. Coghlan-Wintour and JA Owens. Landes Bioscience (In press).

Pitcher JB, Robertson AL, Miles TS, Cockington RA & Moore VM (2004). The influence of birthweight on neuromotor outcomes in adult humans. Proceedings of the 31 st Annual Meeting Fetal & Neonatal Physiological Society , Tuscany, Italy.

Pitcher JB, Moore VM, Robertson AL, Cockington RA & Miles TS (2004). Birthweight, gestational age and neuromotor outcomes in adult humans. XVIII th National Workshop on Fetal and Neonatal Physiology , Sydney, Australia.

Pitcher JB, Robertson AL, Clover EC & Jaberzadeh S (2004). Facilitation of cortically evoked potentials with motor imagery during post-exercise depression of motor cortex excitability. Experimental Brain Research (In press).

Pitcher JB, Ridding MC & Miles TS (2003). Bidirectional, frequency-dependent plasticity in the adult human motor cortex. Clinical Neurophysiology 114(7): 1265-1271.

Pitcher JB, Ogsten KM & Miles TS (2003). Age and sex differences in human motor cortex input-output characteristics. Journal of Physiology (London) 546(2): 605 - 613.