SSVEP Changes in Response to Olfactory Stimulation

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Sensory Neuroscience Laboratory Centre for
Biomedical Instrumentation
COOPERATIVE RESEARCH CENTRE FOR INTERNATIONAL FOOD
MANUFACTURE AND PACKAGING SCIENCE
John Patterson Caroline Owen
Sensory Neuroscience Laboratory
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Introduction

• Do specific patterns of brain electrical activity
  reveal differences in brain function associated
  with an odour stimulus?
• Research developing a technique to monitor
  changes in electrical brain activity associated
  with olfactory processing during normal
  respiration

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Aim

• To monitor changes in patterns of brain
  electrical activity in response to odours
• To investigate the relationship of brain
  electrical activity to subjective odour detection
  responses
• To provide a system which is
• objective and quantitative
• language experience independent

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EEG and EPs

• EEG activity from the cerebral cortex
• Spontaneous EEG cortical activity
• Sensory or an event-related potential generated
  over a number of discrete trials

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Previous researchOlfactory modulation of steady
state visual evoked potential topography

• Impose continuously varying stimulus to stimulate
  known frequency of brain electrical activity
• If cortical processing is altered by the
  presence of the odour stimulus, odour induced
  changes will appear as altered levels of probe
  signal
• size of signal (amplitude)
• timing of signal (latency)

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Equipment - helmet

electrodes
stimulus goggles
facemask
amplifiers
pneumotachograph
Sensory Neuroscience Laboratory
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Sensory Neuroscience Laboratory
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Directions

• As the brain is the seat of preference, it is
  logical that preference-related signals will be
  evident in brain activity
• The next step is to determine the relationship
  between preferences and specific brain electrical
  patterns
• During acute (brief) exposure to odours using the
  CRO
• During chronic (long) exposure to odours using an
  oxygen therapy hood system.

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Continuous Respiration Olfactometer
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Oxygen Therapy Hood System
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Correlation of preference responses for odours
with changes in brain activity

• Subject panel profiled to establish
• Basic olfactory ability
• Subjective preference responses
• 40 odours
• Pleasant and unpleasant
• Familiar and unfamiliar
• Sub-group selected for use in pilot study
• Matched for age, olfactory ability, handedness,
  smoking status
• Selected for responses to four odours
• Acetaldehyde ? Butyric acid
• Isovaleric acid ? Vanillin

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Brain electrical activity to odours
Sections
Quadrants
Left hemisphere vs right hemisphere
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Brain electrical activity to odours acetaldehyde
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Brain electrical activity to odours Sections
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Brain electrical activity to odours Sections
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Brain electrical activity to odours Sections
Power Spectrum
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Brain electrical activity to odours Sections
Power Spectrum
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Conclusions

• Physiological responses independent of
  subjective detection
• Significant amplitude latency changes in brain
  activity with odour cf air
• Regional and temporal alterations in cortical
  responses to an odour