Computer-controlled stimulation for functional magnetic resonance imaging studies of the neonatal olfactory system.
Bottom Line: The system was used to present the odour of infant formula milk in a validation group of seven neonatal subjects at term equivalent postmenstrual age (median age 40 weeks).A safe, reliable and reproducible pattern of stimulation was delivered leading to well-localized positive BOLD functional responses in the piriform cortex, amygdala, thalamus, insular cortex and cerebellum.The described system is therefore suitable for detailed studies of the ontology of olfactory sensation and perception during early human brain development.
Affiliation: Centre for the Developing Brain, Division of Imaging Sciences & Biomedical Engineering, Kings College London, St. Thomas' Hospital, London, UK.Show MeSH
Related in: MedlinePlus
Mentions: The odour-sourcing subsystem (b) consists of three disposable odour chambers made using single-use mucous specimen traps (Pennine Healthcare, Derby, UK), each containing 3 mL of liquid odorant (see Fig. 2). To prevent possible contamination of the control unit and minimize between-subject infective risk, an anaesthetic grade ventilator circuit breathing filter (Clear-Guard II; Intersurgical Ltd., Wokingham, UK) was fitted to the inlet of each odour chamber. In addition, the use of medical grade air from the hospital wall supply has the important advantage that the airflow has already been filtered for particulate and chemical contamination. Air flow into each of the odour chambers was controlled via separate on/off pneumatic valves, with timed opening and closing achieved via the user interface and DAQ. The system was designed such that the third of the three odour chambers could contain a control odour (sterile water), with the valve to this chamber remaining continuously open between periods of stimulation. During periods of stimulation, the control valve is closed and the selected odorant is presented by simultaneous opening of the appropriate valve. The delivery apparatus (c) is fitted to the subject prior to image acquisition and consists of appropriately sized soft-tip curved nasal cannulae (Flexicare Medical Ltd., Mountain Ash, UK) connected to a manifold containing three one-way valves, which prevent odour mixing (Bio-orb, Reef-One, Norwich UK). Each of these valves is then connected via 6 m lengths of PVC bubble tubing (Flexicare Medical Ltd., Mountain Ash, UK) to the individual odour chambers. To prevent any subject discomfort and maximize patient safety, the system has several means of monitoring and limiting the possible airflow: firstly through the flow control valve; secondly through the stimulus control software which allows only one of the solenoid valves to be opened at a time; thirdly through the stimulus control interface on which a visual feedback graph displays airflow in real time during an experiment; and lastly through two emergency stop switches (one on the device itself and the other on the computer interface), which can immediately close all three of the solenoid valves if required.
Affiliation: Centre for the Developing Brain, Division of Imaging Sciences & Biomedical Engineering, Kings College London, St. Thomas' Hospital, London, UK.