An experiment conducted by a clinical neuropsychologist at the
University of Pennsylvania, with Hell For Leather present, has used
Magnetic Resonance Imaging to demonstrate that viewing pictures of
motorcycles activates a portion of the brain associated with seeking
rewards such as sex, drugs and monetary reward. The results suggest
motorcycles fulfill an appetitive need, activating an important node in
the dopamine reward system.

The experiment was conducted by James Loughead, a doctor of clinical neuropsychology by day and the proprietor of Hammarhead Industries by night using a motorcycle-riding member of his team as the subject.

Above you'll find an image of brain activity as recorded by the fMRI machine and below you'll find a copy of the video played during the experiment. Note that it excludes the human faces used in the experiment as releases could not be obtained for our use.

Here's the summary of the experiment, written by James:

Background and Results
Viewing faces activates a very specific part of the human brain referred to as the fusiform face area (FFA).  Some individuals with damage to this brain region are unable to identify faces but have no problem using voice or body features to figure out a person's identity. Neuroimaging research has supported the dissociation of face identification and object processing.  However, evidence has emerged suggesting that the FFA is sensitive to any homogeneous group of objects that one has expertise in identifying (We are all experts in faces, some of us are expert with birds and others can identifying the rare and elusive 1952 Triumph TRW Mk1). For example, an early case report featured a bird watcher with damage to fusiform gyrus who subsequently could not discern different species of birds. Similarly, a car expert with fusiform damage could no longer identify the make and model of cars.  These reports sparked a series of neuroimaging experiments that have generally supported this broader role for the (so called) fusiform face area.  In our laboratory at the University of Pennsylvania we have used functional magnetic resonance imaging (fMRI) to map the FFA and have examined the effect of different emotional facial expressions on brain function in this early part of the visual system.  For the demonstration brain scan reported here, we used a similar mapping task but added the appropriate category to match the expertise of the volunteer: motorcycle.

Most fMRI data is averaged over several individuals (16-24 participants) in order to increase the power and reliability of the signal.  Single-subject results such as this demonstration scan are prone to false positive error.  However, new technologies such as increased magnetic field strength (3 Tesla) and more sensitive instrumentation (32 channel head coil) allow for interesting findings in a single subject.  The brain images shown in the figure highlight two aspects of the demonstration scan.  The first panel overlays brain response to faces (red areas) and motorcycles (green areas) with household objects subtracted out.   As expected, a portion of the fusiform gyrus is activated by both faces and motorcycles (yellow area is overlap).  Additionally, a very interesting effect was seen when directly contrasting the brain response to faces and motorcycles.  In this comparison, we saw bilateral activation of an important node in the dopamine reward system: the caudate nucleus.  This brain region showed greater activation to  motorcycles compared to faces. The caudate nucleus has been associated with the seeking aspect of appetitive behaviors such as eating, drinking and sex (i.e. seeking rewarding stimuli).  The caudate nucleus is part of a broader brain system that responds to reward stimuli such as sex, drugs and monetary reward.  This is an interesting observation that should be viewed cautiously as it is derived from a single demonstration scan, not a research study.

Methods and Materials
Participant: For this demonstration fMRI session we scanned a 31-year-old volunteer with 15 years riding experience and a lifelong interest in motorcycles. All procedures were approved by the University of Pennsylvania Institutional Review Board.

Task: The participant viewed pictures of faces, motorcycles and household objects while brain signal was measured with fMRI. Pictures were presented in 30-second blocks of similar items.  Each image was shown for 1 second (see movie for abbreviated demo task) followed by a simple fixation.

fMRI Acquisition: Blood oxygen level dependent (BOLD) fMRI was acquired with a Siemens Trio 3T (Erlangen, Germany) scanner using a whole-brain, single-shot gradient-echo (GE) echoplanar (EPI) sequence with the following parameters: TR/TE=3000/30 ms, FOV=220 mm, matrix= 64 X 64, slice thickness/gap=3/0mm, 40 slices, effective voxel resolution of 3 x 3 x 3 mm. RF transmission utilized a quadrature body-coil and reception used an 32-channel head coil.

Analysis:  BOLD fMRI signal was analyzed using standard image analysis procedures including: brain extraction, slice time-correction, motion correction, high pass filtering, spatially smoothing, and mean-based intensity normalization. Signal was then correlated (using general linear model procedures) with a predicted BOLD signal model.  Colored areas represent brain regions with signal that was significant explained by our hypothesized model.  We used the standard statistical threshold of p 0.05 (corrected) to create the display images.

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