Inside the magnet room

Scanning and presenting stimuli

Acquisition schemes

Stimulus presentation

FMRI Facility: Scanning and presenting stimuli

Scans are controlled by a Varian Inova console. The operator sits at the host Sun SPARCStation Ultra computer which is running Varian's VNMR program for image acquisition and processing. The host computer is connected to an acquisition computer via a dedicated fast ethernet (100 Base-T) line, which in turn controls the various circuitry and amplifiers that drive the RF and gradient coils. Under VNMR, pulse sequences are compiled from C language routines. VNMR's structure is such that almost any conceivable MRI sequence can be programmed. After image acquisitions are completed, image data are saved directly to a RAID server across an internal network for post-processing.

For fMRI scans various stimuli can be presented to a subject in the magnet. The stimulus presentation devices are controlled by personal computers connected to the scanner by dedicated control (TTL) lines. Short, low voltage electrical pulses instruct the peripheral computers when to present a particular stimulus. This allows extremely accurate synchronization of stimulus presentations and image acquisitions. Visual, acoustic and olfactory stimuli are most commonly used in the BIC.

Whenever a response from a subject is required to acknowledge an instruction, or to answer a problem, the subject pushes buttons on a response box that is connected to the computer presenting the stimuli. In this way the entire experiment is very well synchronized. Some of the stimulus presentation equipment was purchased by a generous donation by Vincent J. Coates, Chairman of the Board, Nanometrics, Inc.