Brain Areas of Time-To-Contact Perception: an Awake Surgery Study

Localizing in the Brain the Areas of Time to Contact Perception During an Awake Surgery

During a brain surgery targeted to remove a brain tumor, the neurosurgeon wakes up the patient to delimit the tumor area exactly, and identify the surrounding areas, to limit the surgery damages. The present project aims at testing the patient in this awake phase to determine the brain areas implied in time to contact (TTC) perception, a function that allows determining the arrival time of moving objects and used in many tasks of our daily life.

Time to contact (TTC) estimation is a major visual function that allows an observer determining the time a moving object will take to reach him. It is however striking to note that the different brain areas supporting this function are not clearly identified, in particular the contribution of non-visual areas that are engaged in the definition of a peri-personal space for the observer. This lack could be fulfilled during a brain surgery experiment. Indeed, in such a surgery, the patient is awakened, and the surgeon apply direct cortical stimulation to de-activate specific brain areas while testing different cognitive function. The failure to succeed in the task indicates that this area is engaged in the cognitive function. The present study therefore will test different brain areas to investigate their respective contribution in the TTC estimation function.

Three groups of participants will be tested, in pre and per surgery phases. After an initial pre-surgery phase, patients for which the tumor does not interfere with the TTC estimation anility will be enrolled in the Pré-Per group, and tested during the brain surgery. Patients for which the pre-test indicates that the TTC estimation is damaged by the tumor, will be tested in pre-surgery phase only, constituting the Pré-End group. Finally, a control group, paired with the patients, will be tested as well.

For the patients, all the testing phases will be achieved during their medical process. The awake surgery is now a well-established technique, currently and usually done at the University Hospital Toulouse, and the present test in the per surgery phase only lasts a couple of minutes, no more than 5 minutes. As such, there is no additional risk carried out in the project.

Inclusion Criteria:

For the patients:

• Brain tumor that does not affect the dominant hand motricity. The patient that have a tumor in an area targeted for a cortical stimulation will be automatically enrolled within the Pre-End group.
• Who will agree with all terms and sign the experimental agreement
• Correct or corrected vision, as allowed by the surgery constraints
• With no known oculomotor abnormalities (list of exclusion in Annexe)
• Affiliated to a social security system

For the control group:

• Who will agree with all terms and sign the experimental agreement
• Correct or corrected vision
• With no known oculomotor abnormalities.
• Affiliated to a social security system

Exclusion Criteria:

For the patients:

• Brain tumor located in the occipital area
• Legally protected patient, or with unknown ability to sign the experimental agreement, as determined by the medical team.
• Medical background of neurological diseases of the central nervous system, as Parkinson, Alzheimer, stroke
• Pregnancy

For the control group:

• Legally protected patient, or with unknown ability to sign the experimental agreement, as determined by the medical team.
• Medical background of neurological diseases of the central nervous system, as Parkinson, Alzheimer, stroke
• Pregnancy