The special nervous system represents the space around the body, called the personal space (PPS)
By combining visual or auditory stimuli that occur near the body with somatosensory information.
As a behavioral agent for PPS, we measured the response time of participants to tactile stimuli at the time of the task
Unrelated auditory or visual stimuli appear at different distances from the body.
In 7 experiments, we depict the critical distance of auditory or visual stimuli that promote tactile processing of hands, faces and torso as agents for PPS expansion.
Three major findings were made.
First of all, the size of PPS varies according to the stimulating body parts, gradually increasing for the hands and faces, and gradually increasing for the torso.
Second, when approaching stimuli, tactile processing in the space is always modulated --
The way to rely, the stimulus of retreat is just for the hand.
Finally, the extension around the hands and face of PPS varies depending on their relative positioning and stimulation consistency, while the trunk PPS is constant.
These results show that there are at least three bodies.
There is a partial specific PPS representation that is different in terms of expansion and direction adjustment.
However, these different PPS expressions are not completely independent of each other, but refer to the public reference framework of the backbone.
A total of 191 subjects (
65 women with an average age of 24. 2. Scope: 18-33)
In addition to 3 method-controlled experiments, a total of 7 experiments were involved (see ).
Section 15 (
6 women, average age = 25)
Participate in experiments 1 and 16 (
6 women, average age = 24 years old)
Experiment 2 and 16 (
5 women, average age = 21)
Experiment III. eighteen (
7 women, average age
Experiment IV. 19 (
7 women, average age
Experiment five, experiment six (
18 years of age for women, and twenty (
6 women, average age = 24 years old)
Experiment 7
Please note that for all the experiments we used
In experiment 6, we used-
Subject Design, which explains the difference in sample size used in experiment 6. Twenty-seven (
10 women, average age = 23 years old)
Participants participated in 3 method-controlled experiments.
All participants reported normal, normal or corrected touch and hearingto-
Normal vision.
All participants agreed to participate in the study, which was approved by the local ethics committee-the ethics committee of the brain thinking Institute for EPFL human behavior research-and carried out in accordance with the Helsinki Declaration.
All participants were paid in Swiss francs 20.
A vibration tactile device consisting of a small vibration motor (
Precision micro drive shaft-less vibration motor, Model 312-10, 3 v, 60 ma, 9000 rpm, hz, 5g)
Used for tactile stimulation.
The surface area of the motor is 113 and the maximum speed is reached within 50 MS.
Depending on the needs of the experiment, the positions and quantities of the vibrators used vary.
A vibrating tactile device is placed on the upper chest (sternum level)
Participants in experiment 1 and experiment 4, 6 and 7 (peri-
The trunk conditions of the last three).
Two vibrating tactile devices were placed on the torso of the participant (
Chest level, front and back)
Experiment 2.
Tactile stimulation is delivered to the hand (dorsum)
In experiments 3, 4, through a single vibrating tactile device (peri-hand condition), and 5.
Finally, a vibrating tactile device was placed on the forehead of participants in experiment 6 and 7 (peri-face condition).
Tactile stimulation always lasts 100 kbps ms.
Two different settings were used to implement auditory stimulation; a 2-
Speaker settings and 16-
Set the speaker according to the experimental needs (
He Board). The 2-
Speaker settings are used in experiments 1, 3, 4 and 5. Six body-
In experiments 1, 4 and 5, the sound distance is sampled and the sound travels at a rate of 22 cuccm/s.
In Experiment 3, five distances were sampled and the sound was transmitted at a rate of 22 cuccm/s.
The distance between speakers is always 100 cm.
Like Canzoneri, the apparent sound position of 2012 is given by the non-strong between the two speakers and the relative position between each other and between the participants.
In this way, even if there are only 2 speakers, a continuous dynamic faint or backward sound is generated, so the points in the space are "sampled "(audio-
Tactile distance)
Determined by the time offset used between sound start and tactile start (e. g.
, In the case of hidden sound, the longer the difference between hearing and tactile start, the closer the sound).
Validation of this collection-
In Canzoneri, up is widely described in 2012, and the same settings are effectively used in several consecutive studies.
Inwe reported new data, supporting the effectiveness of the manipulation implemented in terms of causing a clear sense of sound movement in space and perceived at different distances from the participant's hand or torso, for different time delays (seesection in ). The 16-
Speaker settings are used in experiment 2 and experiment 6. Fourteen body-
Sampling the sound distance in experiment 2 (
7 in the front, 7 in the back, and 7 distances were sampled in experiment 6 (
All in front of the space). The 16-
The speaker setup produced a dynamic sound of 35 cm/s in experiment 2 and a dynamic sound of 25 cm/s in experiment 6.
In Experiment 2, participants stood in the middle of the speaker array (
As for the speakers with 1 m in front and back)
While the 6 subjects in the experiment were standing at the end of the array, the farthest speaker was 2 m.
Experiments 1, 2, 3, 4, and 6 use the sound of the faint and backward, while the experiment 5 only uses the sound of the faint.
View details and validation of acoustic stimuli.
A 3D virtual ball approaching the participant's face was used in experiment 7.
The ball moved about 2 m in the virtual space at a speed of 100/s until it had a virtual contact with the participant's face.
The virtual ball is on the head.
Install display (
Virtual Research Systems Ltd.
, 1280 pixels, 1024 pixels, 60-
Diagonal View, 60Hz)
And presented in-House software (ExpyVR; ).
Vibration tactile device in the laboratory (s)
Was arranged on the participants.
According to the experimental requirements, the number of vibrators and their positions on the body of the participants are different (see above).
Subjects were told that they would feel the tactile vibration and hear the sound of approaching and/or retreating (
Or they will see a virtual ball in experiment 7).
They were told the Voice (
Or visual stimulation, experiment 7)were task-
Irrelevant, their task is to respond to tactile vibration as accurately and quickly as possible by pressing a specific button on the wireless gaming board (
XBOX 360 controller, hz sampling frequency, Microsoft, Redmond, Washington state)
They were also told that in some trials (catch trials)
Only sounds without tactile stimulation will appear, but in other trials (Baseline Test)
Will give only tactile vibration (
For a detailed breakdown of the trial, see below).
All the experiments included three types of experiments.
About 70% of the trials were experimental twin peaks where participants heard the sound (
Or see a moving ball in experiment 7)
, Or close to them, or back to them, and for a given period of time (hereafter T)
They received a vibration tactile stimulation of 100 kbps ms.
Participants should respond to the touch as soon as possible.
When the experimental double peak backward test is presented, the stimulus time dimension, I . E. e.
The delay between sound start and touch delivery, and the spatial dimension, I. e.
, When the touch is given, the distance between the sound position and the body is mapped linearly to the other party.
That is to say, tactile stimulation starts when the time delay increases (T1, T2 etc…)
Corresponding to the sound perceived when increasing the distance (hereafter D)
From the body ,(D1, D2, etc…).
On the contrary, when the subject is presented with a faint sound (
So, by definition, this has been approaching participants since a long time later)
, The time and space dimensions of the stimulus are negatively linearly mapped.
That is to say, D1 and D2 correspond to the last and penultimate time delays, and so on.
The purpose of the task is to identify the farthest distance from the body (D)
When sound or visual stimuli significantly affect tactile processing, that is, when audio-tactile RTs (or visuo-
Tactile RTs in experiment 7)
Much faster than responding to tactile stimuli alone.
This distance is considered as an agent for PPS to represent the boundary.
Therefore, we also include a single-modal tactile test of 20%, in which vibration tactile stimulation is provided without hearing (or visual)stimulation.
For the duration of the experiment, a single-mode tactile test was performed under two different time delays, corresponding to the closest and most distant equivalent time sampled in the experimental test (
See Canzoneri for a similar approach, 2012).
The single-mode tactile test is considered a baseline test and is used to show the multi-sensory promotion effect of sound presented in PPS on tactile RT compared to single-mode tactile stimulation.
RT-in audio for this purpose-
Tactile stimulation conditions were individually corrected according to baseline performance.
That is, for each participant, we determined the baseline condition, resulting in the fastest RT in the baseline single-modal tactile condition, and we calculated the mean original RT for that condition, this value subtracts the tactile stimulation of each audio from the average original RTtactile (or visuo-tactile)condition.
In this way, compared to the fastest single-mode tactile RT, we adopted the most conservative criteria to show the promotion of tactile RT due to sound presentation and spatial location.
Negative deviation from baseline (
Zero by definition)
Indicates the effect of multi-sensory promotion.
In order to identify the boundaries represented by PPS, we searched the space for the farthest points where sound produced a significant boost effect compared to baseline (i. e.
, The fastest single-state tactile condition)(
See also Noel, 2015 for similar methods).
Baseline trials are also useful in other ways.
First, they are used to control false modulation in reaction time due to expected effects (i. e.
In fact, if a trial has already started and does not give tactile vibration, it is increasingly possible for tactile stimulation to approach in time).
In addition, the deviation from the calculation to the single-state tactile condition allows comparison between subjects and between experiments, as it controls-
RT differences in tactile stimulation in subjects.
This method also allows the control of differences in tactile sensitivity between different body parts.
Because we always recognize PPS boundaries by comparing single-state tactile responses and audio
Touch or vision
Under tactile conditions of the same body part, we excluded that the difference in PPS extension would depend on the difference in response to touch between the body parts of the test.
Finally, about 10% of the trials were single-state auditory (
Or visual effects in experiment 7)
Trial due to mission request, thus catching up with the trial.
There is only one sound in these trials (
Or virtual ball)was presented (
Approaching or retreating to participants)
But there is no tactile stimulation.
Participants will refuse to respond.
In order to avoid cobbering of the self-driving response and to ensure that participants are concerned about the task, the catch test was included.
For each experiment, a preliminary analysis of the single-state auditory/visual capture test was performed to test the accuracy of the tactile task.
Due to the setting of tactile target stimuli, participants are always very accurate in the task, and in any experiment there is no statistical difference in response accuracy under different conditions.
Therefore, performance is always analyzed only according to RT. Accuracy data (i. e.
Percentage of correct detention response during catch test and 1-
Percentage of omissions in experimental trials)
Different experiments were reported.
The total number and combination of the tests vary depending on the sampling distance, total sampling space, and velocity.
Experiment 1 includes 240 tests ([multisensory (D1 through D6)+u2009baselines (D1 and D6)+u2009catch trials]×u20092 (
Hiding and retreating)
X 16 times).
Experiment 2 includes 372 tests ([multisensory (13 distances)
Two Sound Directions, three basic principles, two capture tests]
X repeat 12).
Experiment 3 includes 208 tests ([multisensory (D1 through D5)×u20092 (
Hiding and retreating)+u2009baselines (D1 and D5)+u2009catch trials]
X 16 times).
Experiment 4 includes 480 tests ([multisensory (D1 through D6)×u20092 (
Hiding and retreating)+u2009baselines (D1 and D6)+u2009catch trials]×u20092 (peri-hand and peri-trunk)
X 16 times).
Experiment 5 includes 432 tests ([multisensory (D1 through D6)+u2009baselines (D1 and D6)+u2009catch trials]×u2009(Near vs. Far)
X 24 times).
Experiment 6 includes 320 tests ([multisensory (D1 through D7)+u2009baselines (D1 and D7)+u2009catch trials]×u2009(
Hiding and retreating)
X 16 times).
Finally, experiment 7 includes 320 tests ([multisensory (D1 through D7)+u2009baselines (D1 and D7)+u2009catch trials]×u20092 (Trunk vs. Face)
X 16 times). Inter-
The test interval was randomly shuffled between 500-700 MS.
The experimental time never exceeded 60 minutes.
To provide a concise summary of cross-experiments (
Vary in the point of spatial sampling, the total distance of sampling, and the speed of incoming and outgoing stimuli)
The data of all 7 experiments were fitted to the sigmoidal and linear curves.
To compare the two fitting processes, the sigmoidal curve is limited to two parameters, such as Canzoneri, 2012.
The results of this fitting process are shown in the conceptual schematic diagram.