Cognitive neuroscience and neuropsychology 913
Grasping actions remap peripersonal space
Claudio Brozzolia,b, Francesco Pavanic,d, Christian Urquizara,
Lucilla Cardinalia,b and Alessandro Farne`a,b
The portion of space that closely surrounds our body
parts is termed peripersonal space, and it has been shown
to be represented in the brain through multisensory
processing systems. Here, we tested whether voluntary
actions, such as grasping an object, may remap such
multisensory spatial representation. Participants
discriminated touches on the hand they used to grasp
an object containing task-irrelevant visual distractors.
Compared with a static condition, reach-to-grasp
movements increased the interference exerted by visual
distractors over tactile targets. This remapping of
multisensory space was triggered by action onset and
further enhanced in real time during the early action
execution phase. Additional experiments showed that
this phenomenon is hand-centred. These results provide
the first evidence of a functional link between voluntary
object-oriented actions and multisensory coding of
the space around us. NeuroReport 20:913–917 c 2009
Wolters Kluwer Health | Lippincott Williams & Wilkins.
NeuroReport 2009, 20:913–917
Keywords: bimodal neurons, cross-modal congruency effect, grasping,
kinematics, motor control, multisensory, peripersonal space
aINSERM UMR-S 864 ‘Espace et Action’, Bron, bUniversite´ Claude Bernard
Lyon I, Lyon, France, cDepartment of Cognitive Sciences and Education and
dCenter for Mind/Brain Sciences, University of Trento, Rovereto, Italy
Correspondence to Claudio Brozzoli, INSERM, 16, avenue du Doyen Le´pine,
Lyon 69002, France
Tel: + 33 472 913420; fax: + 33 472 913401;
e-mail: claudio.brozzoli@inserm.fr; alessandro.farne@inserm.fr
Received 13 March 2009 accepted 24 March 2009
Introduction
The representation of the space near the body, termed
‘peripersonal’ space (PpS) [1,2], relies on multisensory
processing, both in human and non-human primates. In
monkeys, bimodal neurons in parieto-frontal and sub-
cortical structures code for tactile events on a body part
(e.g. the hand) and visual events near that body part,
thus giving rise to body-centred representations of PpS
[3–6]. In humans, a functionally homologous coding of PpS
is largely supported by behavioural studies showing
stronger visuotactile interaction in near rather than far
space in brain-damaged [7–9] and healthy individuals
[10–13]. For example, visual events occurring in the
immediate proximity to the body induce more severe
tactile extinction than farther ones [7–9]. Recent func-
tional neuroimaging studies further support the exis-
tence of similar multisensory integrative structures in
the human brain [11–13].
Despite the large body of knowledge accumulated across
species on the multisensory properties of PpS, little is
known about its function, and this issue has never been
directly assessed in humans. By acting as an anticipatory
sensorimotor interface, PpS may serve early detection
of potential threats approaching the body to drive in-
voluntary defensive movements [3]. The same antici-
patory feature, however, may also have evolved to serve
voluntary object-oriented actions [1,2,14]. Here, we
tested the latter hypothesis by assessing the effects
of grasping objects on the multisensory coding of PpS.
In Experiment 1, we modified a cross-modal paradigm
[10], whereby participants indicate the elevation (up or
down) of a tactile target delivered to a finger (index or
thumb), while a visual distractor is presented at either
congruent or incongruent elevation (Fig. 1). We then con-
ducted three experiments in which participants were
additionally required to grasp the object in which the
visual distractors were embedded. Although the percep-
tual task was always performed on the right hand, the
motor task was performed by either the right (Experi-
ments 2 and 4) or left (Experiment 3) hand. This simple
manipulation is crucial in two respects: it equalizes
attentional demands for the target object in the sti-
mulated and the nonstimulated hand actions, and it
allows assessing whether any modulation of multisensory
processing is hand-centred.
Experimental procedures
Participants
Fifteen healthy participants (nine men, mean age 27±5
years) took part in Experiments 1, 19 (10 men, mean age
26±6 years) in Experiments 2 and 3, and 16 (8 male,
mean age 25±3) in Experiment 4. All gave their verbal
informed consent to take part in this study, approved by
the local INSERM Ethics Board.
Supplementary data are available at The NeuroReport Online (http://links.lww.com/
A1251; http://links.lww.com/A1250; http://links.lww.com/A1249; http://links.lww.
com/A1248; http://links.lww.com/A1247; http://links.lww.com/A1246)
0959-4965 c 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins DOI: 10.1097/WNR.0b013e32832c0b9b

Apparatus
A cylinder (7-cm height, 1.7-cm diameter) was presented
in one of four orientations (18 and 361 clockwise or
anticlockwise) 47 cm from the participant’s hand. Visual
distractors consisted of an LED flash (200ms) delivered
concurrently with the electro-cutaneous stimulation (see
below), from either the top or the bottom extremities
of the cylinder (Fig. 1). Neurology electrodes were used
to present suprathreshold (100% detection accuracy)
electro-cutaneous stimuli consisting of squared-wave
pulse (100 ms, 400 V) delivered by constant-current
stimulators (DS7A, Digitimer Ltd., Welwyn Garden City,
Hertfordshire, UK) either on the index finger (up) or
thumb (down) of the right hand. Participants discrimi-
nated tactile targets by releasing one of two foot pedals.
The participants’ eye movements (EyeLink-II, SR
Research, Mississauga, Ontario, Canada; SMI) and spatial
position of their grasping hand (Optotrak 3020, Northern
Digital Inc., Waterloo, Ontario, Canada) were recorded
online.
Design and procedure
In Experiment 1, participants performed only the
perceptual task consisting of a speeded discrimination
(up or down) of tactile stimulation regardless of the
task-irrelevant distractor (the upper or lower LED in
the cylinder). In Experiments 2, 3 and 4, participants
additionally performed a motor task that consisted
grasping the cylinder along its longitudinal axis with
the index and thumb (precision grip, for details see
movies 1–6 in supplementary data). An auditory signal
warned the participant about the start of the trial,
followed after a variable delay (1500–2200ms) by a
second auditory signal constituting the ‘go’ for the motor
task. The motor task was performed using the stimulated
(right) hand in Experiments 2 and 4, and the nonstimu-
lated (left) hand in Experiment 3. The visuotactile
stimulation could be delivered: (i) before movement
start (Static condition) or (ii) at movement onset (action
Start condition) or (iii) during the early phase of move-
ment execution (action Execution condition). These
temporal conditions were run across blocks in Experi-
ments 2 and 3, and were fully randomized in Experi-
ment 4. At the beginning of each trial, the tip of the
thumb and index finger of each hand were kept in a
closed pinch-grip posture on a start switch, whose release
triggered the visuotactile stimulation in the Start and
Execution conditions (0 and 200ms delay, respectively).
Results
Multisensory interplay without action
When action was not required (Experiment 1), partici-
pants proved faster in responding to congruent (360ms)
than incongruent [394ms; t(14)=4.99, P<0.001] trials,
thus extending the typical cross-modal congruency
effect (CCE) finding to a situation in which visual
distractors were far from the stimulated hand [10].
Hereafter, the dependent variable will be the CCE,
calculated as the (reaction times, RTs) difference
between incongruent and congruent trials, in that it
quantifies the strength of the interaction between visual
and tactile inputs (similar trends were found on
accuracy). In the absence of action, the CCE varied as
a function of object orientation with stronger visuotactile
interaction for clockwise (43ms) rather than anticlock-
wise tilted object [24ms; t(14)= 2.15, P=0.049].
Action-dependent multisensory interplay
In the Static condition of Experiment 2, before the
stimulated hand started to move, the CCE was again
stronger when the object was tilted clockwise (66ms)
than anticlockwise [51ms; F(1,18)=6.43, P=0.021].
Crucially, a modulation of the CCE was observed as soon
as the stimulated hand started the action: Fig. 2a shows
that the CCE changed on-line with action specifically
for the objects oriented anticlockwise [F(2,36)=4.37,
P=0.020]. For these orientations, the CCE was stronger
when visuotactile stimuli were delivered at action Start
Fig. 1
Experimental setup. (a) Bird’s eye view of the participant facing the
cylinder (upper inset) with both hands in a pinch-grip position (lower
inset). Electro-cutaneous targets (green zap) were delivered to the
index finger (up) or thumb (down), while a visual distractor (yellow flash)
could be presented from either the same (congruent, not shown) or
different (incongruent) elevation. Grasping the clockwise tilted object
required an inward wrist rotation of the left hand (b) but an outward
wrist rotation of the right hand (c), the opposite pattern being required
for the anticlockwise orientations.
914 NeuroReport 2009, Vol 20 No 10

(63ms) than in the Static condition (31ms; P=0.037).
The CCE further increased during the Execution phase
of the action (100ms; P<0.001 with respect to the
Static condition; P=0.09 with respect to the Start
condition). Importantly, when the very same grasping
action was performed by the nonstimulated hand
(Experiment 3), no modulation of the CCE was observed
(Fig. 2a), either in the Start or Execution condition
compared with the Static condition.
Experiment 4 further corroborated the finding that the
action modulates the visuotactile interaction [F(2,30)=
16.51, P<0.001]. Furthermore, in this fully inter-
leaved design, the CCE was stronger at the action Start
(55ms) than in the Static condition (22ms; P=0.026),
and in addition, this modulation emerged irrespective
of object orientation. As shown in Fig. 3, the action-
dependent modulation of the CCE was further increased
during the Execution phase (79ms), with respect to
both the Start (P=0.022) and the Static conditions
(P<0.001).
Grasping kinematics
To further establish multisensory motor relationships,
we analysed the kinematic pattern of all reach-to-grasp
movements. Comparison between Experiments 2 and 3
served the important purpose of controlling that hand-
related difference between the on-line modulations of
action over the CCE were not because of differences
between hands kinematic patterns. In addition, through
kinematic analyses, we tested for possible parallels
between the motor and perceptual performance [15].
Depending on which hand performed the grasping (left or
right), the object orientation imposed specific patterns
of wrist orientation: clockwise and anticlockwise object
orientations required, respectively, outward and inward
movements of the right hand (for details see movies 1–2
in supplementary data). The reverse was applied to the left
hand (for details see movies 4–5 in supplementary data).
Results of Experiments 2 and 3 showed an effect of
object orientation on grasping kinematics. Crucially,
however, the overall kinematic pattern proved remark-
ably similar for the two hands, both for the reaching and
grasping components. Object orientations modulated
motor RTs to the ‘go’ signal: it took more time for
participants to start the action when the object had to be
grasped with an inward (425ms) than an outward wrist
rotation [418ms; F(1,17)=6.80, P=0.018]. In addition,
as shown in Fig. 2b, deceleration peaks for both hands
Fig. 2
Multisensory perception during action(a) (b)
(c) Multisensory stimulation along grasping kinematics
Grasping kinematics
Nonstimulated hand action Nonstimulated hand action
∗ ∗
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Stimulated hand action Stimulated hand action
500 400 300 200 100 0
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Static Start Execution
Static Start Execution
Real-time modulation of visuotactile processing. (a) Bar plots (with SEM) show the modulation of cross-modal congruency effect (CCE) as a function
of grasping hand and object orientation. (b) Movement deceleration peak, similarly modulated by object orientation across hands. (c) Mean
movement trajectory of the wrist (green line) and the thumb and index fingers (purple lines). Hand position is schematically illustrated along the
trajectory at the time when the tactile stimulus (green zap) was presented. *Refers to significant differences between conditions.
Grasping remaps space Brozzoli et al. 915

were more pronounced for inward ( – 5709mm/s2) than
outward movements [ – 5474mm/s2; F(1,17)=23.19,
P=0.0002]. Irrespective of which hand performed the
task, acceleration peaks were higher when participants
grasped the object with an inward (6337mm/s2) rather
than an outward [6233mm/s2; F(1,17)=6.46, P=0.021]
movement. The same tendency was present for the
velocity peak [1267mm/s and 1274mm/s for inward
and outward movements, respectively; F(1,17)=3.75,
P=0.069]. Peak latencies were not modulated by object
orientation with the exception of the acceleration peak,
which was anticipated for inward (156ms) than outward
movements [160ms; F(1,17)= 5.81, P=0.028]. Kine-
matics of the grasping component of the movement
showed little influence of the perceptual task.
In Experiment 4, kinematics of the reaching movement
was less affected by object orientation. First, motor RTs
did not differ between inward and outward movements
(377 and 371ms, respectively). Second, the remaining
kinematic parameters were not modulated by object
orientation [except the acceleration peak, differing
between inward (8928mm/s2) and outward movement,
8690mm/s2; F(1,14)=5.15, P=0.04].
Discussion
These findings provide the first evidence that purpose-
fully acting on objects links initially separated visual
and somatosensory information, updating their inter-
action as a function of the required sensory motor
transformations. When performing an action, our brain
updates the relationship between visual and tactile
information well before the hand touches the object.
This perceptual reweighting is already effective at the
very early stage of the action and seems to be
continuously updated as action unfolds. This is clearly
illustrated by the fact that from the very start of the
action, the task-irrelevant visual information located on
the to-be-grasped object interacts more strongly with
the tactile information delivered on the hand that will
eventually grasp the object. The specificity of such
visuotactile reweighting for a given hand while naturally
grasping an object confirms the hand-centred nature
of the PpS [16–19], and reveals that tool use is not
necessary for the human brain to remap space [19]. In
addition, it critically extends this property to ecological
and adaptive dynamic situations of voluntary manipula-
tive actions, thus pointing to a fundamental aspect of
multisensory motor control. By showing comparable
pattern of movements across the grasping hands, the
kinematics results rule out the possibility that the
effector-specific increase of the CCE could merely reflect
a difference between the motor performances of the
two hands.
The modulation of the visuotactile interaction induced
by action, limited to the objects oriented anticlockwise
in Experiment 2, was clearly present for all object
orientations in Experiment 4, thus fully supporting our
hypothesis that voluntary grasping actions affect multi-
sensory perception on-line. In addition, kinematic results
were remarkably associated with the perceptual modifi-
cations in both the experiments. In Experiment 2, in
which the perceptual reweighting was selective for
inward object orientation, the kinematic differed be-
tween inward and outward reaching movements, in a
direction that seemed reflecting more important wrist
rotation required for hand pronation [20]. In Experiment
4, the perceptual reweighting was present for all object
orientations and the associated kinematics was compar-
able across inward and outward rotations, thus paralleling,
again, the perceptual modulation of action-dependent
multisensory remapping. This parallel between move-
ment kinematics and the CCE performance strengthens
the functional link between multisensory coding of the
hand-centred space and voluntary actions.
Peripersonal multisensory space may serve involuntary
defensive reactions in response to objects approaching
the body [3,6]. However, here we considerably add to this
view by showing that such multisensory motor inter-
face may be functionally involved in voluntary control of
actions that bring the body towards objects. This fits well
with the functional properties of visuotactile neurons
documented in parieto-frontal circuits that present
spatially aligned visual and tactile receptive fields for a
Fig. 3
100
90
80
70
*
* *
*
60
50
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C
E
(m
s)
40
30
20
10
0
Static Start Execution
Grasping actions remap peripersonal space. Results from Experiment
4. Bar plots (with SEM) report the cross-modal congruency effect
(CCE) increase at action Start (55ms) and Execution (79ms)
compared with the Static condition (22ms). * Refers to significant
differences between conditions.
916 NeuroReport 2009, Vol 20 No 10

given body part [1–6,21]. This feature allows bimodal
neural systems to represent an object in a body-centred
reference frame and to be continuously updated during
bodily movements. This multisensory spatial representa-
tion has been suggested to serve involuntary defensive
movements, because electrical microstimulation of
some bimodal areas in the monkey brain [3] elicits stereo-
typed arm or face movements that are compatible
with defensive behaviour. Remarkably, however, some
bimodal neurons also respond when the arm is voluntarily
moved within reaching space [14,15,22,23], and have
been previously proposed to code goal-directed actions
[1,2,22]. Neurophysiological studies on monkeys have
shown activation in the posterior parietal cortex during
grasping, in the early phase of the action when the hand
has not yet reached the object. The activation gradually
shifts towards the somatosensory cortex when the hand
enters in contact with the object [14]. Finally, the on-line
enlargement of the visual receptive fields of bimodal
neurons in response to approaching objects [6] or tool use
[17–19,24,25] also emphasizes the dynamic nature of
their multisensory space coding, providing converging
evidence for the involvement of the bimodal system in
dynamic updating of the PpS. The multisensory motor
neural machinery acting as an anticipatory interface
between the body and nearby events may thus have
been selected throughout evolution to drive both in-
voluntary avoidance reactions and voluntary approaching
movements, with common adaptive advantages for
defensive and manipulative actions.
Conclusion
Voluntarily acting on objects triggers a hand-centred
remapping of multisensory spatial processing that paral-
lels action requirements and is regulated in real time as
action unfolds.
Acknowledgements
The authors thank A.C. Roy and N. Holmes for
thoughtful discussions and comments on an earlier
version of the manuscript. This study was supported
by the European Mobility Fellowship, the INSERM
AVENIR Grant No. R05265CS and the ANR Grants No.
JCJC06133960 and RPV08085CSA, the Galileo PHC
Grant and the PRIN Grant from the MIUR.
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