The flow of information during mental simulation

The motor system does not only enable us to make movements, it also allows us
to make mental simulations of movements without actually executing them. Mental
simulation of movements has been implicated to play a key role in a number of
cognitive processes such as the preparation and execution of movements,
understanding the intention of other people*s movements and semantic processing
of action words (Gallese & Lakoff, 2005; Wolpert & Ghahramani, 2000). When the
ability to simulate movements is hampered, this may have severe adverse effects
on everyday life.
Although mental simulations play a crucial role in our everyday lives, its
neuronal underpinnings have not been elucidated in great detail. Previous
studies have indicated the fronto-parietal circuitry as the neuronal substrate
for mental simulations. But the exact time course of the interactions between
the different subregions of the underlying neuronal network -in other words,
the flow of information- remains unclear.
This information is especially relevant for patients that undergo brain
surgery. Deficits in mental imagery may underlie hitherto unexplained
postoperative complaints of lack of concentration, reduced executive
performance or impaired thinking. If we can identify the essential nodes of the
underlying network, this information can be taken into consideration in
resections of neural tissue.


Gallese, V., & Lakoff, G. (2005). The Brain*s concepts: the role of the
Sensory-motor system in conceptual knowledge. Cognitive neuropsychology, 22(3),
455-79.

Wolpert, D M, & Ghahramani, Z. (2000). Computational principles of movement
neuroscience. Nature neuroscience, 3 Suppl(november), 1212-7

The main objective of this study is to characterize the flow of information in
the fronto-parietal network during the simulation of movements using
intracranial EEG recordings. In the characterization we will pinpoint the
neuronal (sub)regions of the underlying neuronal network and map their
interactions. Critical nodes of the network will be identified using cortical
stimulation during the task. The architecture and location of this network can
have consequences for neurosurgical strategies, especially in brain resections
for epilepsy, to avoid postoperative impairments. Therefore, a second objective
of this study is the development of a protocol to localize essential nodes in
the network for the simulation of movement.

This core of this study is the recording of intercranial EEG signals (ECoG)
while the subject is engaged in a mental simulation task. The design of the
experiment therefore is as follows:

1. Before the implantation, the patient will perform one session of the mental
simulations task and the control task This will take 20
minutes.

2. After the implantation of the ECoG electrodes the patient will remain in the
hospital for one week. During this week the patient will
perform the mental simuation task 3 times. On the last
session, we will apply cortical stimulation to identify the nodes that are
essential
for performing the task. In total, this will take 3x 20
minutes.

3. To assess the effect of the resection of the task, the patient will be
tested three times after the resection ( 48h, 1 week and 6 weeks
post-resection). On these occasions the patient will again
perform the mental simulations task and the control task. This will take 3x 20
minutes in total.

The proposed methods do not differ substantially from those used for tests that
are currently performed on these subjects as part of their clinical
investigations (language, spatial orientation, short-term memory tasks, etc.).
It is possible that the subject has an epileptic seizure during the course of
the experiment. In the case of a seizure, the medical staff at the IEMU, who
are specialized do deal with such situations, will take over immediately.
Epileptic seizure are common in these patients and are in fact used to locate
the source of the epilepsy.
The main burden for the subjects is that he/she may be exhausted by the
amount of testing. Therefore we only test the subject three times during the
hospitalication. There will be an independant nurse that monitors whether the
subject is not exhausted. The subject will only perform the task when both the
subject and the independent nurse indicate that the subject is fit enough to
participate.
To minimize the burden of the pre- and post-surgical testing we will test
the subject at times when they already have to be at the UMC Utrecht for a
clinical appointment. Therefore the subject does not need to travel to the UMC
Utrecht on a separate occasion for the purpose of the study.
We think that patients may benefit from the study. Mental simulation may
be disturbed in dyspraxia or execution disorders that may be a sequel of brain
surgery but cannot be predicted from current tests. Electrocortical stimulation
interfering with a task is a powerful predictor of the critical role of a brain
area in the execution of that task, and the subsequent loss of ability to
perform the task after resection of that area.
Therefore, this study may yield information that improves the post-surgical
functional outcome of the patient. The protocol may become part of the standard
repertoire of clinical tests that are currently performed on the ECoG patients
to predict and minimize the adverse effects of the resection.