U825 and CerCo are equipped with several NeuroScan systems in practically identical configurations. The recent acquisition of several versions of the BESA (Brain Electrical Source Analysis) software enables the location of the sources at the origin of the evoked potentials obtained to be actively sought. These types of analyses have notably been used to locate the origin of the brain activity connected with cognitively complex visual processing (for faces, animals, or manufactured objects) and to approach the respective time kinetics for phonological and lexico-semantic processing, or the time kinetics of proprioceptive stimulations in patients during post-ischemic functional recovery.

EEG/ERP (U825)

Chantal Blanchard (TCE Inserm) chantal.blanchard@inserm.fr
Nicolas Chauveau (IR Inserm) nicolas.chauveau@inserm.fr
INSERM U825 has a soundproofed room, to isolate the subject properly during experiments, and EEG BIOSEMI recording equipment (http://www.biosemi.com/products.htm) with 64 channels + 8 supplementary channels (for HEOG, VEOG, Mastoids,…). This equipment is battery operated (about 3 hours' autonomy) and is connected to the acquisition PC by a USB opto-coupled link (optical fibre).

salle EEG/ERP
Stimuli are presented to the subject through the Presentation software, the stimulation PC being connected to the BIOSEMI apparatus using the parallel port (http://www.neurobs.com/)
The recordings made concern all sorts of research protocols (including the presentation of auditory, visual, motor, mixed, etc.  stimuli and the responses using a mouse,  joystick, specific keyboard, …). Recordings are made for both control subjects and subjects with specific neurological pathologies.
Apparatus measuring the 3-dimensional coordinates, Fastrak® (http://www.polhemus.com), determines the position of the electrodes on the head.

The main software packages used for processing EEG/ERP data are:

EEG/ERP and ECoG in monkeys (CerCo)

CerCo possesses two 32-channel Neuroscans and a 32-channel Nuamps (portable version of the neuroscan) devoted to experiments on humans. The two Neuroscans can be used together to make recordings on 64 channels.
A third Neuroscan is consecrated to electrocortographic recordings in monkeys.


CerCo also has a 64-channel Biosemi system.
CerCo uses the same processing software as U 825.

The EEGLAB software (interactive programme for electrophysiological data processing) was developed by one of the CerCo researchers, Arnaud Delorme, in collaboration with the Swartz Center for Computational Neuroscience. For this software development, Arnaud Delorme received the ANT "Young Scientist Award", a prize for exceptional progress in the field of EEG/MEG research.

Single-unit electrophysiology in monkeys (CerCo)

CerCo has 5 single-unit electrophysiology stations for use with non-human primates, 4 for macaques in the awake state and1 for marmosets (or macaques) with acute preparation. In the awake monkey, the activity of isolated neurones is recorded in extracellular configuration during a visual task in which stimuli are presented in their receiving field. The stimuli may be natural images or artificial stimuli, presented in 2D or 3D. Eye movements are checked by a video system (Iscan) or by the coil technique (scleral filament placed in a low-power magnetic field and giving a precision of a few minutes of arc).
                          Response of a neurone of the V4 area to two natural textures under different angles
                          of illumination: lettuce leaf (A) and white bread (B). For each texture, the left-hand column
                          shows the cell response to the original texture and the right-hand column shows a
                          random phase redistribution. In each raster, the grey rectangle corresponds to the
                         stimulus presentation time.

The possibility also exists of recording more global activity at the brain surface (near the dura mater) in the awake monkey by electrocorticography (up to 25 electrodes), which allows the evoked potentials to be measured, a frequency analysis to be performed and the synchronization to be studied from one test to another or from one electrode to another when the visual stimuli are presented. (See EEG section)
In the marmoset (or macaque) in acute preparation (anaesthesia) the unit extracellular activity is recorded in response to visual stimulations comparable to those used with the awake monkey. The activity of a neurone can be recorded over a longer time (allowing a larger number of tests), and it is then possible to investigate the modulations of its activity according to the surrounding local neuronal influence. The influence of more distant cortical areas is studied by reversibly deactivating these areas using a chemical mediator (e.g. gaba) or by cooling, a technique that can also be used with awake animals.

Single unit (blue) and multiunit (black) activity obtained in the
V1 area in the marmoset monkey in response to the presentation of a moving network