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Is optical imaging spectroscopy a viable measurement technique for the investigation of the negative BOLD phenomenon? A concurrent optical imaging spectroscopy and fMRI study at high field (7 T).

Kennerley AJ, Mayhew JE, Boorman L, Zheng Y, Berwick J - Neuroimage (2012)

Bottom Line: Often accompanying positive BOLD fMRI signal changes are sustained negative signal changes.These experiments suggested that the negative BOLD signal in response to whisker stimulation was a result of an increase in deoxy-haemoglobin and reduced multi-unit activity in the deep cortical layers.Furthermore their study utilised a homogeneous tissue model in which is predominantly sensitive to haemodynamic changes in more superficial layers.

View Article: PubMed Central - PubMed

Affiliation: Centre for Signal Processing in Neuroimaging and Systems Neuroscience (SPiNSN), Department of Psychology, University of Sheffield, Western Bank, Sheffield S10 2TN, UK. A.J.Kennerley@shef.ac.uk

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Schematic diagrams of apparatus including a) the magnet capsule containing a heating blanket and temperature probe to maintain the body temperature of the subject whist in the MRI scanner. A large birdcage coil is used for RF transmission. A circular RF receiver coil on top of the subject's cranium is attached to a simple tuning circuit consisting of three non-magnetic variable capacitors. The animal is held still within the magnet using b) a Perspex head-stage. The head-stage consists of the well attached to the subject's cranium (with integrated surface coil). This is screwed onto the holding bridge of the magnet capsule to reduce movement artefacts during the experiment. The endoscope banjo can then be lowered onto the locking screws to position it above the brain. Foam gaskets are used as required because the well is filled with D2O to reduce air-tissue susceptibility artefacts and ensure good optical contact for c) the endoscope. The non-magnetic endoscope used for concurrent fMRI and 2D-OIS consisting of a 50 K fibre optic bundle and a series of lenses and prisms to allow perpendicular imaging within the small bore 7 Tesla magnet.
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f0005: Schematic diagrams of apparatus including a) the magnet capsule containing a heating blanket and temperature probe to maintain the body temperature of the subject whist in the MRI scanner. A large birdcage coil is used for RF transmission. A circular RF receiver coil on top of the subject's cranium is attached to a simple tuning circuit consisting of three non-magnetic variable capacitors. The animal is held still within the magnet using b) a Perspex head-stage. The head-stage consists of the well attached to the subject's cranium (with integrated surface coil). This is screwed onto the holding bridge of the magnet capsule to reduce movement artefacts during the experiment. The endoscope banjo can then be lowered onto the locking screws to position it above the brain. Foam gaskets are used as required because the well is filled with D2O to reduce air-tissue susceptibility artefacts and ensure good optical contact for c) the endoscope. The non-magnetic endoscope used for concurrent fMRI and 2D-OIS consisting of a 50 K fibre optic bundle and a series of lenses and prisms to allow perpendicular imaging within the small bore 7 Tesla magnet.

Mentions: Upon completion of the coil attachment procedure the animal was secured within the magnet-compatible holding capsule (Fig. 1a). Inside the capsule an electrically filtered and isolated heating blanket (Harvard Apparatus Inc. USA) and rectal probe, maintained the temperature of the animal. The animal was artificially ventilated (Zoovent Ltd, UK) and blood pressure monitored throughout using a pressure transducer attached to the arterial cannulae (CWE systems Inc. USA). A pressure sensitive pad was placed under the animal to monitor breathing patterns whilst inside the magnet bore (SAII, USA — Model 1025L Monitoring and Gating System). The surface coil was locked to a holding bridge, using a screw on locking ring, thus suspending the head of the animal in the approximate centre of the holding capsule and thus magnet centre following insertion. A non-magnetic endoscope (see below), inserted into a protective Perspex banjo, was subsequently positioned over the surface coil and held in place with locking screws (Fig. 1b). This formed a well which was filled with Deuterium oxide (D2O) having a similar refractive index to saline. This reduced optical specularities from the skull surface for 2D-OIS and air-tissue susceptibility artefacts (around the thinned cranial window) for high field fMRI whilst not being excited by the 300 MHz RF pulses and consequently avoiding magnetic resonance. The RF feeder cables for the surface coil were attached to the tuning circuit.


Is optical imaging spectroscopy a viable measurement technique for the investigation of the negative BOLD phenomenon? A concurrent optical imaging spectroscopy and fMRI study at high field (7 T).

Kennerley AJ, Mayhew JE, Boorman L, Zheng Y, Berwick J - Neuroimage (2012)

Schematic diagrams of apparatus including a) the magnet capsule containing a heating blanket and temperature probe to maintain the body temperature of the subject whist in the MRI scanner. A large birdcage coil is used for RF transmission. A circular RF receiver coil on top of the subject's cranium is attached to a simple tuning circuit consisting of three non-magnetic variable capacitors. The animal is held still within the magnet using b) a Perspex head-stage. The head-stage consists of the well attached to the subject's cranium (with integrated surface coil). This is screwed onto the holding bridge of the magnet capsule to reduce movement artefacts during the experiment. The endoscope banjo can then be lowered onto the locking screws to position it above the brain. Foam gaskets are used as required because the well is filled with D2O to reduce air-tissue susceptibility artefacts and ensure good optical contact for c) the endoscope. The non-magnetic endoscope used for concurrent fMRI and 2D-OIS consisting of a 50 K fibre optic bundle and a series of lenses and prisms to allow perpendicular imaging within the small bore 7 Tesla magnet.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3368428&req=5

f0005: Schematic diagrams of apparatus including a) the magnet capsule containing a heating blanket and temperature probe to maintain the body temperature of the subject whist in the MRI scanner. A large birdcage coil is used for RF transmission. A circular RF receiver coil on top of the subject's cranium is attached to a simple tuning circuit consisting of three non-magnetic variable capacitors. The animal is held still within the magnet using b) a Perspex head-stage. The head-stage consists of the well attached to the subject's cranium (with integrated surface coil). This is screwed onto the holding bridge of the magnet capsule to reduce movement artefacts during the experiment. The endoscope banjo can then be lowered onto the locking screws to position it above the brain. Foam gaskets are used as required because the well is filled with D2O to reduce air-tissue susceptibility artefacts and ensure good optical contact for c) the endoscope. The non-magnetic endoscope used for concurrent fMRI and 2D-OIS consisting of a 50 K fibre optic bundle and a series of lenses and prisms to allow perpendicular imaging within the small bore 7 Tesla magnet.
Mentions: Upon completion of the coil attachment procedure the animal was secured within the magnet-compatible holding capsule (Fig. 1a). Inside the capsule an electrically filtered and isolated heating blanket (Harvard Apparatus Inc. USA) and rectal probe, maintained the temperature of the animal. The animal was artificially ventilated (Zoovent Ltd, UK) and blood pressure monitored throughout using a pressure transducer attached to the arterial cannulae (CWE systems Inc. USA). A pressure sensitive pad was placed under the animal to monitor breathing patterns whilst inside the magnet bore (SAII, USA — Model 1025L Monitoring and Gating System). The surface coil was locked to a holding bridge, using a screw on locking ring, thus suspending the head of the animal in the approximate centre of the holding capsule and thus magnet centre following insertion. A non-magnetic endoscope (see below), inserted into a protective Perspex banjo, was subsequently positioned over the surface coil and held in place with locking screws (Fig. 1b). This formed a well which was filled with Deuterium oxide (D2O) having a similar refractive index to saline. This reduced optical specularities from the skull surface for 2D-OIS and air-tissue susceptibility artefacts (around the thinned cranial window) for high field fMRI whilst not being excited by the 300 MHz RF pulses and consequently avoiding magnetic resonance. The RF feeder cables for the surface coil were attached to the tuning circuit.

Bottom Line: Often accompanying positive BOLD fMRI signal changes are sustained negative signal changes.These experiments suggested that the negative BOLD signal in response to whisker stimulation was a result of an increase in deoxy-haemoglobin and reduced multi-unit activity in the deep cortical layers.Furthermore their study utilised a homogeneous tissue model in which is predominantly sensitive to haemodynamic changes in more superficial layers.

View Article: PubMed Central - PubMed

Affiliation: Centre for Signal Processing in Neuroimaging and Systems Neuroscience (SPiNSN), Department of Psychology, University of Sheffield, Western Bank, Sheffield S10 2TN, UK. A.J.Kennerley@shef.ac.uk

Show MeSH
Related in: MedlinePlus