The Neural Substrates of Biological Motion
Perception: an fMRI Study

Philip Ser vos1, Rieko Osu2, Andrea Santi1 and Mitsuo Kawato2
1

Department of Psychology, Wilfrid Laurier University,
Waterloo, Canada and 2ATR Human Information Processing
Research Labs, Kyoto, Japan

Humans are very good at perceiving the movements performedby others. They can readily recognize an actor’s movements evenfrom a display consisting only of the motion of point lights
corresponding to the joints of the actor — this has been termed‘biological motion’ (Johansson, 1973). Each individual static
frame looks like a meaningless scatter of dots, but once theframes are animated, observers immediately perceive the action
performed by the actor. In addition, with the same limited
information people can make more specific categorizations suchas male or female, friend or stranger (Cutting and Kozlowski,
1977; Mather and West, 1993). Behavioral studies also suggest
the existence of highly sensitive and f lexible mechanisms for the
analysis of biological motion (Neri et al., 1998). However, thespecific neural substrate for the analysis of biological motion isstill an unanswered question.
Oram and Perrett reported neurons in the anterior section of
the superior temporal polysensory area (STPa) in the monkey
that responded selectively to such biological motion (Oramand Perrett, 1994). It has been suggested that processing ofvisual information in primates follows two pathways: the ventral‘form’, or ‘what’, pathway and the dorsal ‘motion’, or ‘where/
how’, pathway (Ungerleider and Mishkin, 1982; Goodale andMilner, 1992). Area STPa receives inputs from both the ventral
and dorsal pathways (Felleman and Van Essen, 1991). Thus, it has

been suggested that outputs from the dorsal pathway (e.g. areas
MT and MST) which deal with motion information, and outputs
from the ventral pathway (e.g. area IT) which deal with form
information, are integrated in the STPa cells and contribute to
the perception of biological motion. Several human neuroimaging studies have reported activation in the posterior
superior temporal sulcus/superior temporal gyrus (STS/STG; aregion possibly encompassing the human homologue of area
STPa) during the observation of biological motion (Bonda et al.,
1996; Howard et al., 1996).
Human neuropsychological research suggests that a separate
site from STPa is involved in biological motion perception.
Patient AF with damage to occipitoparietal cortex and patient
LM with damage to dorsal occipitotemporal cortex both show
specific deficits in many early aspects of motion analysis but
normal biological motion processing (Vaina et al., 1990; McLeod
et al., 1996). Presumably, area MT and associated motionprocessing areas were damaged in these two patients; thus,
inputs from the dorsal motion pathway to the human homologue
of area STPa would no longer exist in these two patients. Thisevidence suggests the existence of a separate motion pathway,specialized for the perception of biological motion, that may not
require processing within the STS. In contrast to these twopatients, patient AL cannot recognize form-from-motion,although she performs like normals on low-level motion tasks.
That is, AL can detect speed differences and the direction of
motion, but is impaired at recognizing two- or three-dimensional
form generated by motion (including Johansson figures).
Damage to the fusiform and lingual gyri that extends to lateroventral areas of the temporal lobe are most likely the source ofAL’s perceptual inabilities (Cowey and Vaina, 2000). Based onthese patient findings, the ventral pathway and not the dorsal
pathway appears critical for form-from-motion perception.
Consistent with this neuropsychological evidence, Zeki has
proposed that area V3 is a dynamic-form area on the basis ofneural connections within the occipital lobe (Zeki, 1993).
Motion information projects to MT from V1 and V2 and thenre-enters these visual areas diffusely, including areas which
project to V3; an area that contains form-sensitive neurons.
Additionally, the magnocellular layers of V1 and V2 project
directly to V3. Thus, both the direct and re-entry connections
provide a mechanism for form and motion to be integrated in V3,
making it a likely site in generating form-from-motion. Interestingly, previous neuroimaging studies have placed little emphasison the role of V3 in the computation of biological motion. For
example, Howard et al. (Howard et al., 1996) obser ved activation in V3 and Bonda et al. (Bonda et al., 1996) foundactivation within prestriate cortex which likely included V3,
however these obser vations were overshadowed by the STS
activation also obser ved in these studies.
The suggestion that two separate regions mediate biological© Oxford University Press 2002. All rights reserved.

Cerebral Cortex Jul 2002;12:772–782; 1047–3211/02/$4.00

We used fMRI to identify the brain areas related to the perception of
biological motion (4 T EPI; whole brain). In experiment 1, 10 subjects
viewed biological motion (a human figure jumping up and down,
composed of 21 dots), alternating with a control stimulus created byapplying autoregressive models to the biological motion stimulus(such that the dots’ speeds and amplitudes were preserved whereas
their linking structure was not). The lengths of the stimulus bouts
varied, and therefore the transitions between biological motion andcontrol stimuli were unpredictable. Subjects had to indicate with abutton press when each transition occurred. In a related biologicalmotion task, subjects detected short (1 s) disturbances within these
displays. We also examined the neural substrates of motion andshape perception, as well as motor imagery, to determine whether
or not the cortical regions involved in these processes are also
recruited during biological motion perception. Subjects viewed linear
motion displays alternating with static dots and a series of common
objects alternating with band-limited white noise patterns. Subjects
also generated imagery of their own arm movements alternatingwith visual imagery of common objects. Biological motion specific
BOLD signal was found within regions of the lingual gyrus at the
cuneus border, showing little overlap with object recognition, linear
motion or motion imagery areas. The lingual gyrus activation was
replicated in a second experiment that also mapped retinotopic
visual areas in three subjects. The results suggest that a region of
the lingual gyrus within VP is involved in higher-order processing of
motion information.

Introduction

motion perception parallel findings from face perception
research. Face-sensitive neurons are found not only in monkey
IT (Gross et al., 1972) and in human ventral occipitotemporal
cortex (fusiform face area) (Kanwisher et al., 1997) but also inmonkey and human STS (Perrett et al., 1991; Puce et al., 1998).
Monkey IT and human fusiform gyrus are sensitive to theinvariant aspects of faces that are required for face identification(Hasselmo et al., 1989; Hoffman and Haxby, 2000). In contrast,
human and monkey STS tend to respond to variant aspects of theface (e.g. gaze and mouth movements) that communicate social
intentions or meaning (Perrett et al., 1991; Puce et al., 1998;
Hoffman and Haxby, 2000). Given that such biological stimuli as
faces may be processed by more than one region, it is possiblethat the perception of biological motion is also subserved bymultiple regions.
Consensus has not yet been reached about which brain
regions are critical for biological motion perception. Using fMRI,
Howard et al. found bilateral activation both in the MT/MST
complex and in the STG anterior to it during the observation of
biological motion compared with random motion (Howard et al.,1996). On the other hand, Bonda et al. found activation mainlyin the right STS and limbic structures such as the amygdala, but
did not find activation in MT/MST (Bonda et al., 1996). One
reason for these discrepancies might be the difficulty of generating good control stimuli which have local motion characteristics
highly similar to biological motion but lack global structure.
However, a recent fMRI study has succeeded at creating such
perceptually appropriate controls (Grossman et al., 2000). In
this study, biological motion was found to activate primarily theposterior STS and also somewhat area MT. A further strength of
this study was their use of an active task (one-back task)
throughout the experiment. Although the STS region located by
Grossman et al. (Grossman et al., 2000) and Bonda et al. (Bonda
et al., 1996) are fairly similar, Howard et al. (Howard et al.,1996) located a more superior, anterior, and medial region
compared to the regions located by these other two studies.
Therefore, there is still ambiguity surrounding the specific locale
within the STS/STG that is involved in biological motion
perception. Moreover, it is unclear whether regions in addition
to the STS are also involved in biological motion.
A nother question of interest is whether the mechanisms
responsible for the perception of biological motion overlap withthose involved in motor execution and/or motor imagery. Motor
imager y has been shown to activate many areas involved in
motor execution, such as supplementary motor area, superiorpremotor cortex, inferior premotor cortex (Brodmann’s areas
44/45), superior and inferior parietal regions and cerebellum(Parsons et al., 1995). In addition, a PET study has revealed thatthe observation of meaningful action also activates inferior premotor cortex (Grèzes et al., 1998). Apparent motion of human
movements is also found to activate motor and parietal cortex inhumans (Stevens et al., 2000). In contrast, Bonda et al. (Bonda etal., 1996) did not find activation in motor-related areas duringobservation of whole-body point-light movements, although theyfound activation in parietal cortex during obser vation ofpoint-light hand movements.
In the present fMRI study, we investigated the cortical activation patterns of subjects observing biological motion in comparison with control stimuli. We also used three control tasks todetermine if the cortical region(s) sensitive to biological motion
can be dissociated from regions involved in linear motion
perception, object perception, and motor imagery.

Experiment l
Materials and Methods
Subjects
Ten neurologically intact adult volunteers (five males and seven females,mean age 25 years) participated in the study. Informed consent was
obtained from all the subjects prior to the experiment. The protocol ofthe present study was in accordance with the ethical guidelines of the
Robarts Research Institute (London, ON, Canada).
General Procedure
Subjects participated in five functional runs two of which consisted of
biological motion stimuli and three of which consisted of linear motion
stimuli, object perception stimuli, and motor imagery. Each functional
run lasted 360 s and consisted of six 60 s stimulus–control cycles. All
stimuli were presented in MATLAB, using the extensions provided by thehigh-level Psychophysics Toolbox (Brainard, 1997) and low-level Video
Toolbox (Pelli, 1997). In the biological motion, linear motion and object
perception experiments, subjects were instructed to fixate in the centerof the stimulus display.
Generation of Biological Motion Stimuli and Control Stimuli
Point-light displays of biological motion stimuli were generated byrecording sequences of whole-body jumping movements, using the
Optotrak, an optoelectronic imaging system. Twenty-one light-points
were attached to major joints of the body (head, neck, torso, and bothshoulders, elbows, wrists, hands, hips, knees, ankles, heels, and toes).
The control stimuli were created by applying autoregressive models to the
biological motion stimuli using TIMSAC (Akaike et al., 1979; Kitagawa
and Akaike, 1981) such that the dots’ positions, speeds and amplitudes
were preser ved whereas their linking structure was not. First, threedimensional joint position data acquired by the Optotrak were projected
onto a plane. A univariate autoregressive (A R) model was applied
separately to the x and y coordinates of each joint position’s 8 s data set
sampled at 60 Hz. Coefficients of each A R model and covariance ofinnovation (system noise input) were estimated using the least squareerror method (UNIVAR program in TIMSAC). The order of the AR models
ranged from 3 to 50. Control stimuli were then produced by applying
artificially generated Gaussian white noise as input to the noise
component of each model. Both stimuli were centered in the display andoccupied a 8.0° by 8.0° area.
Figure 1 shows a portion of the biological motion and control stimulus
sequences presented to the subjects. Figure 2 shows mean position,
amplitude and velocity of each joint, and mean rate of change of thelink length between each pair of joints. Larger changes in the relative
positions of joints in the control stimuli, compared to those in the
biological motion stimuli, suggest that the linking structures were destroyed. However, little overall difference in the properties of individual
joints suggests similar basic attributes for the two types of stimuli. Figure
3 shows examples of position–velocity plots for individual joints in the xand y-planes. The overlap between the dashed and solid curves found ineach panel also suggests the similarity in basic attributes of the two typesof stimuli. By sequentially adding biological motion stimuli and control
stimuli with a smoothly changing weight, smooth transitions between
biological motion stimuli and control stimuli were generated for the first
biological motion task. Using the procedure that was used to generate thecontrol stimuli, small disturbances were inserted during biologicalmotion and control stimuli for the second biological motion task (1 srandom motions for biological motion stimuli, and 1 s sinusoidal motions
for control stimuli).
The Tasks
Biological Motion Perception with Detection of Gradual Transitions.
Because the lengths of the stimulus bouts varied (20, 25, 30, 35 or 40 s),
the transitions between biological motion and control stimuli were
unpredictable. Subjects had to indicate the transitions with a right buttonpress.
Biological Motion Perception with Detection of Disturbances.
Stimulus bouts of constant length were used. During presentation of

Cerebral Cortex Jul 2002, V 12 N 7 773

Figure 1. Example segments of the biological motion and control motion sequences presented to the subjects. Note that dashed lines connecting joints (links) were not visible tothe subjects. Only the joints indicated by circles were shown (white dots on a black background).
biological or control stimuli, subjects had to detect (with a right buttonpress) short (1 s) disturbances within the biological or control stimuli.
Each bout had zero, one or two disturbances.
Linear Motion Perception. Subjects observed 200 randomly moving
dots (mean velocity of 4°/s). As control stimuli, individual frames
randomly selected from the linear motion sequence were presented for
500 ms and alternated with 500 ms presentations of a blank screen withthe same mean luminance. The stimuli subtended 12.6° by 12.6°.
Common Object Perception. Subjects observed images of common
objects alternating with band-limited white noise patterns (Fig. 4A). Each
image was presented for 2 s, and subjects passively obser ved the images.
The stimuli subtended 6.4° by 5.6°.
Motor Imagery. Subjects were asked to generate imager y of theirarm(s) performing various tasks alternating with a visual imagery task
requiring size judgements. During the motor imagery period, sentencessuch as ‘scratch back with left hand’ were presented (Fig. 4B). During thevisual imagery period, sentences such as ‘which larger: airplane or truck’
were presented. Each sentence were presented for 2 s, followed by a 4 s
gray screen during which subjects generated imagery.

MRI Acquisition
Images were collected with a 4.0 T, whole-body MRI system (Varian,
Palo A lto, CA; Siemens, Erlangen, Germany) at the Robarts ResearchInstitute (London, ON, Canada), using a quadrature head coil. The
field of view was 20.0 × 20.0 × 14.4 cm, with an in-plane matrix of
64 × 64 pixels and 24 contiguous axial slices, resulting in a voxel size of
3.125 × 3.125 × 6 mm. Each volume (24 slices) was sampled once every
5 s. Slices were obtained to encompass the entire cerebral cortex andthe upper half of cerebellum. Functional data were collected using
T2*-weighted segmented gradient echo-planar imaging (TE = 15 ms,
TR = 1.2338 s, four shots, f lip angle = 60°, navigator-corrected) for
BOLD-based imaging. Functional activation data were superimposed onto
high-resolution T1-weighted anatomical images.

774 Biological Motion Perception • Servos et al.

MRI Analysis
A ll functional images were temporally filtered by a low-pass Gaussian
filter (FWHM = 2). Time courses within each voxel (72 time points) werecorrected for linear drift. All functional imaging data were preprocessed
and analyzed using Brain Voyager 3.9. Correlation maps were generated
for each subject by cross-correlating the BOLD response for a given taskwith a reference time course corresponding to the conditions within thattask. Reference time courses were corrected according to thehemodynamic response function. Individual high-resolution volume
anatomies (0.75 × 0.75 × 1.5 mm) were transformed into the Talairach
coordinate system (Talairach and Tournoux, 1988). The resulting
transformation was applied to the functional volumes. Finally, a generallinear model multi-subject analysis (non-separate predictor for eachsubject) was performed for each of the five experiments to generategroup-average maps.

Results

Biological Motion Perception
Figure 5A shows the regions activated at the P < 0.001 (all P
values uncorrected) level of significance by the two biologicalmotion tasks, overlaid on the anatomical image of one subject(which has been transformed into the Talairach coordinate
system). Significant activation was found only in the lingual
gyrus at the cuneus border (see Table 1). The high degree ofoverlap between the regions responsive to the two biologicalmotion tasks indicates the reliability of the contribution of theseareas to biological motion perception. A lthough the group
analyses did not demonstrate significant activation in the STG,
individual analyses showed that five subjects displayed STG
activation in the biological motion experiment involving gradualtransitions (P < 0.001) and three subjects showed STG activationin the biological motion with disturbances experiment (P <

Figure 2. Properties of biological and non-biological motion stimuli. Mean position, amplitude, and velocity of each joint, and mean rate of change of the link length between eachpair of joints are shown. Black bars denote biological motion stimuli and gray bars denote control stimuli generated with an autoregressive model. Error bars show SD.

0.001). Group analyses revealed no significant activation in
MT/MST.
During both active tasks, performance was more than 90%
accurate for both biological motion and control sequences,indicating that subjects were attending to the stimuli.
Linear Motion Perception
Figure 5B shows the regions activated by linear motion
perception in comparison to static dots (P < 0.00001). As manyothers have found (Zeki et al., 1991; Watson et al., 1993; Dupont
et al., 1994; Tootell et al., 1995; Rees et al., 2000), we foundbilateral activation in lateral temporal–occipital–parietal cortex(the human homologue of MT/MST, see Table 1).
Common Object Perception
Figure 5C shows the regions activated by object perception incomparison to white noise patterns (P < 0.00001). Bilateral
activations were found in the fusiform gyrus (see Table 1),
consistent with previous work showing activation in this region
during object and face perception (Kanwisher et al., 1996, 1997).
Motor Imagery
Figure 5D shows the regions activated by motor imager y incomparison to visual object imagery (P < 0.0001). Activations

were found in the left precentral gyrus and the left inferiorparietal lobe (see Table 1), both of which are involved in motor
execution (see Table 1). In our motor imagery task, 19 commands out of 30 involved right-hand movements, while seveninvolved the left hand, and four involved both hands. Therefore,
it is reasonable that we found higher left-hemisphere activationin this task.
Overlap Between Biological Motion Perception and the Other
Tasks
We did not find overlap between the areas sensitive to biologicalmotion and the areas involved in the perception of motion andshape, or the generation of motor imagery. This conclusion heldeven when we lowered the significance levels of these threetasks to that used for the biological motion tasks (i.e. P < 0.001).
Discussion
Our results show that the biological motion stimuli activated the
lingual gyrus at the cuneus border, whereas previous neuroimaging studies have reported the involvement of inferior,
middle and superior temporal regions as well as parietal andlateral occipital regions. On the other hand, our finding complements observations in patient AL (Cowey and Vaina, 2000). As

Cerebral Cortex Jul 2002, V 12 N 7 775

Table 1
Activation foci in each condition of experiment 1
Condition

Brain region

Brodmann’s Talairach coordinates
area
x
y

z

Biological motion

R lingual gyrus
Cuneus
L middle temporal gyrus
R middle temporal gyrus
L fusiform gyrus
R fusiform gyrus
L precentral gyrus
L inferior parietal lobe

30/18/19
18
37
37
37
37
6
40

8
8
0
1
–17
–18
55
55

Linear motion
Common objects
Motor imagery

5
0
–41
41
–32
30
–28
–38

–68
–80
–69
–68
–43
–44
–11
–49

mean age 25 years) participated in the experiment. Informed consent was
obtained from all the subjects prior to the experiment. The protocol ofthe present study was in accordance with the ethical guidelines of the
Robarts Research Institute (London, ON, Canada).
General Procedure
Subjects participated in two functional runs. One run consisted of
biological motion stimuli and the other run consisted of polar angle
stimuli. The biological motion and polar angle runs lasted 360 s (six 60 s
stimulus–control cycles) and 288 s (six 48 s periods), respectively. In bothruns, subjects were instructed to fixate in the center of the stimulus
display.
The Tasks
Biological Motion Perception with Detection of Disturbances. See
experiment 1 methods.

Figure 3. Examples of position–velocity plots of joints. Examples of position–velocity
plots of individual joints in the x- and y-planes (left wrist, right shoulder and right knee).
Solid curves indicate biological motion stimuli. Dashed curves indicate control stimuli.
Values are normalized such that the maximum height of the stimuli is 1.

discussed in the Introduction, AL is impaired at recognizing
form-from-motion as a result of a lesion in the lingual andfusiform gyri. Although AL’s perceptual inabilities could be due
to lingual gyrus inputs to biological motion specific regions
being disconnected, the present finding provides evidence thatthe lingual gyrus directly mediates biological motion perception.
Human neuroanatomical work suggests that the lower parts ofthe second (V2) and third (VP — the ventral component of V3)
visual areas lie on the lingual gyrus, whereas the analogue of themacaque’s fourth visual area probably lies on the fusiform gyrus(Clarke and Miklossy, 1990). It is possible that the region we
found lies within VP. Thus, our finding may provide support for
Zeki’s hypothesis concerning the role of V3 in form-from-motion
perception (Zeki, 1993). To determine whether the area lies
within V P, we conducted a second experiment that mapped
retinotopic visual areas. An additional purpose of the second
experiment was to replicate our biological motion finding, giventhat few studies have detected activation within the lingual
gyrus.

Experiment 2
Materials and Methods
Subjects
Three neurologically intact adult volunteers (one male and two females,

776 Biological Motion Perception • Servos et al.

Polar Angle Perception. Subjects fixated while a contrast-reversing(8 Hz) 45° black and white checkerboard wedge, presented on a uniform
gray field, rotated 360° about the fixation point. The viewing aperturewas 14.25°. This method is similar to previous retinotopic mapping
studies of visual cortex (Sereno et al., 1995; Engel et al., 1997).
MRI Acquisition
Images were collected with a 4.0 T, whole-body MRI system (Varian, Palo
Alto, CA; Siemens, Erlangen, Germany) at the Robarts Research Institute(London, ON, Canada), using a quadrature head coil. Functional data
were collected using T2*-weighted segmented gradient echo-planar
imaging. In the biological motion run, the field of view was
19.2 × 19.2 × 6.60 cm, with an in-plane matrix of 64 × 64 pixels and 11
pseudo-coronal slices, resulting in a voxel size of 3.0 × 3.0 × 6.0 mm (TE =15 ms, TR = 750 ms, two shots, f lip angle = 40°, navigator-corrected). In
the polar angle run, the field of view was 19.2 × 19.2 × 5.5 cm, with anin-plane matrix of 128 × 128 pixels and 11 pseudo-coronal slices, resulting
in a voxel size of 1.5 × 1.5 × 5.0 mm (TE = 15 ms, TR = 1000 ms, four shots,
f lip angle = 40°, navigator-corrected). The anatomies were sampled
pseudo-coronally in a 19.2 × 19.2 × 25.6 cm field of view at highresolution (voxel size: 0.75 × 0.75 × 1.00 mm).
MRI Analysis
The biological motion data were analyzed in the same way as inexperiment 1 (see experiment 1 methods), except that the GLM analysis
was conducted separately for each subject. Given that most biologicalmotion activation was medial with a slight right hemisphere bias,
retinotopic analysis was restricted to the right hemisphere.
The polar angle data were first processed to remove any slow drift
trends and then cross-correlated with six phase delays to a referencefunction of 6, 48 s cycles (4 s on; 44 s off). Each voxel was coloredaccording to the lag value with which it correlated highest. By identifying
patterns of phase reversals in the activation displayed on the f lattenedmaps, the retinotopic visual areas (V1, V2, V3 and VP) were determinedfor each subject. This technique of delineating visual area borders issimilar to previous studies [e.g. (Sereno et al., 1995; Engel et al., 1997)].

Figure 4. Common objects stimuli and motion imagery stimuli. (A) Examples of common objects (left) and band-limited white noise patterns used as control stimuli (right).
(B) Examples of motor and visual imagery sentences.

The biological motion data were overlaid onto each subject’s f lattened
map and the visual area borders were then overlaid.
In addition to transforming the high-resolution volume anatomies to
the Talairach coordinate system (as in experiment 1), the cortical surfaces
were rendered, inf lated, and f lattened. In isolating the cortical surface,
first the skull and subcortical structures were stripped off, and theventricles filled. The gray–white matter boundary was determined by aregion growing technique and dilated to a point within gray matter(approximately beneath layer 4). A fter smoothing the border, thehemispheres were disconnected and any handles or topological errors
were removed through an automated algorithm (Kriegeskorte andGoebel, 2001). The resulting border for each hemisphere was used tocreate a three-dimensional reconstruction of the cortical sheet, which
was inf lated and then cut in five places. The surface was unfolded
outwards from the cuts. A similar unfolding technique has been reported
previously (Goebel et al., 1998).

Results
Figure 6 shows, for each subject, the activation produced by the
biological motion task (P < 0.000001) projected onto a f lattened
cortical representation with visual area borders overlaid. The
results replicate the lingual gyrus finding of experiment 1.
Voxels with the highest correlation values are located within VP(two subjects) or at the VP/V2 border (one subject).
As in experiment 1, during the biological motion task,
performance was more than 90% accurate for both biologicalmotion and control sequences, indicating that subjects wereattending to the stimuli.
Discussion
The experiment 2 results replicate those of experiment 1 — a

Cerebral Cortex Jul 2002, V 12 N 7 777

Figure 5. Average activation map for each task. The results of group analysis were overlaid on the anatomical image of one subject transformed into the Talairach coordinate system.
(A) The regions activated by the two biological motion tasks. (B) The regions activated by linear motion perception in comparison to static dots. (C) The regions activated by common
object perception in comparison to white noise patterns. (D) The regions activated by motor imagery in comparison to visual imagery.

778 Biological Motion Perception • Servos et al.

Figure 6. Activation for the biological motion with disturbance task for each subject (AD, AS and SK). The results are projected onto a flattened representation of the cortical surfaceof the right hemisphere. Overlaid on the cortical surface are also the borders of visual areas that have been identified with retinotopic methods.

Cerebral Cortex Jul 2002, V 12 N 7 779

lingual gyrus activation during the perception of biologicalmotion. Moreover, the results suggest that this lingual gyrus
activation is centered within area VP. The finding of activation
within VP is consistent with the proposal by Zeki (Zeki, 1993)
outlined in the Introduction. In addition, it refines his hypothesis
by suggesting that it is the ventral portion of area V3 (area VP)
that appears to play a special role in the perception of dynamic
form such as biological motion.

General Discussion
Our main finding is that a region of the lingual gyrus, within area
VP, is involved in biological motion processing. In experiment 1,
we observed no overlap between the biological motion sensitive
region and human area MT — the linear motion sensitive area —suggesting that our control stimuli were appropriate. The lack ofoverlap between the biological motion sensitive region and thefrontal (precentral gyrus) and parietal (superior parietal lobule)regions involved in motor imagery suggests that the neuralsubstrates of point-light body motion perception are different
from those of motor imagery. Furthermore, the findings indicatethat the neural substrates of point-light body motion perception
are different from those of action perception (Decety andGrèzes, 1999) and those of apparent human movement
perception (Stevens et al., 2000).
Although most other biological motion neuroimaging studies
do not report, or fail to emphasize, activation within the lingual
gyrus, our finding is less surprising when one considers thatseveral studies have demonstrated that the lingual gyrus appears
to be involved in more specific aspects of motion processing
than MT/MST. Orban et al. used PET to investigate the regions
activated during speed discrimination tasks in comparison withsimple motion detection tasks (Orban et al., 1998). They showedthat the right cuneus and right lingual gyrus, and to a lesser
degree the left lingual gyrus and a more anterior lingual region in
the right hemisphere, were involved in speed discrimination
tasks, whereas the MT/MST complex did not show different
activation between these tasks. Cornette et al. also showed a
far greater involvement of lingual gyrus than the MT/MST
complex in motion direction discrimination tasks than insimple detection tasks (Cornette et al., 1998). These studies
demonstrate that the same visual input and the same attribute(e.g. speed or direction of motion) produce different activationsites depending on whether or not a temporal comparison isrequired. Other studies have shown activation in the lingual
gyrus during the observation of second-order motion comparedwith first-order motion (Smith et al., 1998), and during theobser vation of motion-defined gratings, but not during theobservation of static dots or unidirectional speed (Shulman etal., 1998). These findings are consistent with the role of thelingual gyrus in such higher-level motion processing, as
form-from-motion.
The neuroimaging study having the most similar methodology
to ours is that conducted by Grossman et al. (Grossman et al.,2000). Like our study, Grossman et al. used appropriate control
stimuli (same local motion as biological motion stimuli) and an
active task. Consistent with Grossman et al. (Grossman et al.,2000), who reported STS activation in their group analyses, weobserved 5 out of 10 subjects showing STG activation in one ofour biological motion perception tasks. Unlike Grossman et al.,however, our group analysis did not result in a significant overall
STG activation during the perception of point-light biologicalmotion. Our group analysis did identif y lingual gyrus activationin both of our biological motion perception tasks. Indeed, inexperiment 1, 9 of our 10 subjects showed lingual gyrus

780 Biological Motion Perception • Servos et al.

activation during biological motion perception. The lack oflingual gyrus activation in Grossman et al.’s (Grossman et al.,2000) study is somewhat puzzling since our study is quite
similar. It is possible that any lingual gyrus activation that might
have been present in their study would have been obscured by
the relatively large (FWHM of 7.5 mm) spatial filter that theyused to smooth their data.
The present findings in combination with previous worksuggest that more than one cortical region is involved in theperception of biological motion — paralleling results in the faceperception literature. As mentioned in the Introduction, in themonkey, neurons that respond selectively to faces are located inboth the inferior temporal gyrus and on the bank of the STS.
Human imaging studies also suggest involvement of two distinct
areas (STS and fusiform gyrus) in face perception, which likely
play different functional roles (Kanwisher et al., 1997; Puce etal., 1998). It is possible that the double dissociation found forface perception also holds true for biological motion perception.
For example, the STS may be involved in providing the social
meaning of biological motion stimuli [cf. (Allison et al., 2000)]
whereas the lingual gyrus (specifically area VP) may be involved
in deriving biological forms from the motion information. It isnoteworthy that the observation of meaningful hand actions has
been shown to activate the STS while meaningless hand actions
do not (Neville et al., 1998).
We did not find activation in motor related, or motor imagery
related, areas during obser vation of biological motion. Thismight be due to the nature of the biological motion perceptiontasks our subjects performed. Grèzes et al. (Grèzes et al., 1998)
showed that even when a subject is observing the same stimulus,
areas of activation will differ depending on whether subjects are
simply perceiving the stimuli or if they know that they will be
asked to imitate the action later. Grèzes et al. (Grèzes et al.,1998) found that when subjects perceived action with the aim to
reproduce it later, the dorsal pathway and premotor cortex weremore strongly activated than when they only perceived the sameactions. It is understandable that we did not find activation in
motor-related areas during the biological motion perceptiontasks because we did not require subjects to subsequently
perform these movements.
A nother area involved in the obser vation of action is theinferior frontal gyrus (Brodmann’s areas 44/45). This appears tobe the human homologue of monkey area F5 where mirror
neurons (neurons that respond both when a particular action is
performed by a monkey and when the monkey observes thesame action performed by another individual) are found (Gallese
and Goldman, 1998). Grèzes et al. (Grèzes et al., 1998) foundactivation in these areas during observation of action with nopurpose. We were unable to confirm this obser vation because
the signal around these areas was distorted due to the air in theear adjacent to these regions.
To summarize, the goal of the present study was to localize thebrain regions involved in biological motion perception. In order
to be confident that we were indeed localizing the critical brain
regions, we developed biological motion displays and related
control stimuli that had highly comparable local motion properties. We were able to identif y a region in the lingual gyrus at the
cuneus border that appears to be involved in the perception of
biological motion. Furthermore, we replicated this finding in asecond experiment that additionally determined the area to bewithin area VP. Given the findings from our study, and evidence
from the functional neuroimaging, neuropsychological andsingle-cell recording literature, there is reason to believe that
two regions are involved in biological motion perception: one

region centered around the STS and the other region centered
within the lingual gyrus. These two regions are dissociable fromcortical regions involved in the perception of linear motion,
objects, and in the generation of motor imagery. These two
spatially distinct regions may play complementary roles in theperception of biological motion. One area (lingual gyrus) may
be involved in processing motion and deriving global form
information while the other region (STG) may derive social
meaning from this form-from-motion information. Future work
will hopefully disambiguate the role of these two regions inbiological motion perception.

Notes
We thank Dr Mel Goodale of the University of Western Ontario forcontinuing encouragement; Drs M. R iley, E. Nakano of ATR-I ISD and
T. Yoshioka of ER ATO for acquisition of biological motion data; andJoe Gati of the Robarts Research Institute for fMRI technical assistance.
P.S. is supported by an NSERC operating grant and the Canada Research
Chairs program.
Address correspondence to Philip Servos, Department of Psychology,
Wilfrid Laurier University, Waterloo, ON, N2L 3C5 Canada. Email:pservos@wlu.ca.

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