Percevoir l'imperceptible par l'action : l'exemple du mouvement biologique

Percevoir l'imperceptible par l'action : l'exemple du mouvement biologique

Christel Ildéi-Bidet, Alan Chauvin & Yann Coello

Université Charles De Gaulle, LilleUniversité Pierre Mendès France, Grenoble

Théorie

- Visual perception of human movement is thought to involve interaction between sensory processing and motor representations (including the mirror neuron system).

- Motor representation can be viewed as a component of a predictive system, which includes a neural process that simulates the dynamic behaviour of the body in relation to the environment enabling thus to anticipate sensory, postural and/or spatial consequences (ideomotor principle, James, 1890).

Conceptually, this approach refers to the control theory based on internal model. According to the model, independently of whether a motor action is performed or not, a visual stimulus can be mapped in motor terms (inverse model) and a predictive model associated with action planning can be used to simulate the expected dynamic behaviour of the body in relation to the environment (forward model).

visualstimulus

Action planninginverse model

Action execution

Prediction of forthcomingsensory inputsForward model

Effect onenvironment

Control theory and prediction

Proprioception

Vision

True state

visualstimulus

Action planninginverse model

Action execution

Prediction of forthcomingsensory inputsForward model

Effect onenvironment

The role of the predictive model is to optimise the control of motor activity and also to provide by anticipation information about the feasibility of potential motor actions.

Proprioception

Vision

True state

visualstimulus

Action planninginverse model

Action execution

Prediction of forthcomingsensory inputsForward model

Effect onenvironment

Predicted final state

Space perception

Because it carries information about the predicted final state of anticipated action, the predictive model can be considered as being the support for spatial perception in relation to action (e.g. peripersonal space).

Proprioception

Vision

True state

Because it carries information about the predicted ongoing state of the body, the predictive model can also be considered as contributing to the understanding of movements performed by others.

visualstimulus

Action planninginverse model

Action execution

Proprioception

Vision

Prediction of forthcomingsensory inputsForward model

Effect onenvironment

Predicted final state

X

Space perception

Predicted ongoing state

Movement perception

True state

Arguments in favour of a role of motor representation in the perception of human movement

- Observed movements are easier to perceive when they belong to the observer repertoire. (Calvo-Merino et al. 2005, 2006; Casile & Giese, 2006; Cross et al. 2006)

- It is easier to recognise oneself from visual display than persons with who we have shared time before.(Loula et al., 2005)

- Preferred observed dynamical visual stimuli are those that are congruent with motor laws.

(Bidet-Ildei et al. 2006; Meary et al. 2005).

- Patients with motor deficit (dysgraphia) show deficit in movement perception (writing).(Chary et al. 2004)

- Visual exposure to biological motion improves subsequent visual perception of human action.(Daems & Verfaillie 1999; Nilsson et al. 1992; Olofsson et al. 1997; Pavlova & Sokolov 2000; Verfaillie 2000).

- fMRI studies have shown shared cortical networks in movement production and observation.(Decety et al. 1997; Hari et al. 1998; Nishitani & Hari 2000; Rizzolatti et al. 1996).

Issue:

Visual exposure to biological motion improves subsequent visual perception of human action.Is this also true for daily observed actions ?

Rational:

Activating motor representation by performing or observing a real action just before perceiving a human movement should improve perceptual performances.

Mean :

Performing or observing a real motor action just before performing the perceptual discrimination of a point light display presenting a human action (priming effect)

Task:

Discriminating a biological motion in difficult perceptual condition (visual mask).

Stimuli

Stimuli 21 masks: 0 dot … 220 dots

Step: 11 dots 600 ms

110 … 220 dots

Step: 11 dots

Chance level

Selection of 11 masks:

110 dots … 220 dots

Step: 11 dots600 ms

Prior information

MethodsTwo groups of 15 participants (Mean age = 24.8years, SD = 6.8years)

Prior visual information (running-man, neutral stimuli)

132 trials (6 trials* 11 masks* 2 directions)

Session duration: about 15 minutes

Duration 30 secondes

Specific effect of the gender in the perception of biological movement ?(Cutting & Kozlowski, 1977)

47%Prior information

Neutral: 5 Males10 Females

Running: 7 Males8 Females

50%56% 48%

47%Prior information

Neutral: 5 Males10 Females

Running: 7 Males8 Females

50%56% 48%

7 Females, 8 Males (mean age= 30 years) Judging the probability that the point-light stimulus was either a man or a woman.

55 masking dots (84% of correct perception)

52% Male - 48% FemaleNo gender effect

Prior information differenciating the gender

Prior information

MethodsThree groups of 9 females and 9 males (Mean age = 20.7years, SD = 2.7years)

Prior visual information (running-man, running-female, neutral stimuli)

132 trials (6 trials* 11 masks* 2 directions)

Session duration: about 15 minutes

Duration 30 secondes

Selection of 11 masks:

110 dots … 220 dots

Step: 11 dots

Chance level

56% 56%

Effect of prior actual activity ?

MethodsOne group of 9 females and 9 males (Mean age = 22.7 years, SD = 2.7 years)Prior motor information (running in the corridor for 30 seconds)132 trials (6 trials* 11 masks* 2 directions) Session duration: about 15 minutes

Prior motor information

Chance level

56% 56%54% 55%

Conclusion

- Performing or observing a real human action for only 30 seconds is enough to improve later visual perception of biological motion in a difficult perceptual context.

- This effect can obviously be explained by the contribution of motor representations in the visual processing of biological movement.

- The gender effect indicates furthermore that interaction between motor and sensory information depends on the observer motor repertoire which seem different for males and females.