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).
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.
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.ukShow MeSH
Related in: MedlinePlus
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.
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