**2. fNIRS measurement**

136 Infrared Spectroscopy – Life and Biomedical Sciences

rehabilitation system is proposed which includes both muscle strength enhancement by walking rehabilitation machines and neurological rehabilitation by imaginary of walking. This system has the following most prominent advantages compared with traditional

 Early rehabilitation of cognitive functions related to walking. After falling ill (stroke et al.), surgery or injure, physical rehabilitation might not be able to performed in a certain period of time according to the patient's condition. During this period, neurological rehabilitation by imaginary of walking is considered to be an effective method to keep the brain areas related to walking active and maintain the cognitive functions related to

 Quickening walking rehabilitation. Walking is a complex cognitive task that is associated with higher-level cognitive function (Fukuyama, 1997; Riecker et al., 2003). Even routine walking is suggested to be considered as a relatively complex task that involves higher-level cognitive input (Hausdorff et al., 2005 ). In hospitals or rehabilitation facilities, physical rehabilitation time is limited due to the schedule of the physical therapist or the condition of the patients. However, there is no such limit in neurological rehabilitation. Therefore, the combination of physical rehabilitation and

However, the neural mechanism of neurological rehabilitation is yet to be elucidated and

Recently, motor imagery, as a method of neurological rehabilitation, is drawing more and more attention.Motor imagery is widely used in sport to improve performance, which raises the possibility of applying it as a rehabilitation method. The effectiveness of motor imagery training at restoring motor function after stroke has been indicated by several studies (Sharma et al., 2006; Dickstein et al., 2004). However, the underlying mechanism of motor imagery training-induced improved performance remains unexplained. Understanding the effect of rehabilitative techniques on brain plasticity is potentially important in providing a neural substrate to underpin rehabilitation and hence in developing novel rehabilitation strategies. An fMRI study has shown that premotor cortex (PM) and supplementary motor area (SMA), as shown in Fig. 3, are involved in the observation of gait and related conditions in combination with motor imagery of gait (Iseki et al., 2008; Wagner et al., 2008). However, since the MRI environment excluded real gait movement, the comparison between brain activities involved in walking and imaginary walking was still insufficient. In this chapter, we compared the activation in motor area of the brain during real walking and imaginary

neurological rehabilitation may lead to earlier recovery of walking ability.

there is no standard method to carry out neurological rehabilitation.

walking by means of fNIRS. Two experiments were conducted.

Fig. 3. Activated brain regions by mental imagery of walking (Iseki et al., 2008;).

rehabilitation methods considering only physical rehabilitation.

walking.

Regional hemodynamic changes in brain tissue were monitored using fNIRS system ETG-7100 (Hitachi Medical Corporation) (Fig. 4). This system uses two wavelengths of nearinfrared light (695 nm and 830 nm) to separate the two types of hemoglobin concentration

Fig. 4. ETG-7100 system and its shell to hold 4×4 optodes.

Comparison of Cortical Activation During Real Walking and Mental Imagery of

Walking – The Possibility of Quickening Walking Rehabilitation by Mental Imaginary of Walking 139

**1 2 3**

**456 7**

**8 9 10**

**15 16 17**

**18 19 20 21**

**11 12 13 14**

Cz

**22 23 24**

Fig. 5. Schematic placement of the emitter and detector optodes on the subject's head

(a) Real walking (b) Walking observation

in the task. During the WO task, the subjects were shown a video (Fig. 7) in which a person walks along a line at the same speed (0.3 m/s). The subjects were instructed to imagine that they were walking the same as the person in the video, especially to match their gaits to the video, while keep standing on the ground. The video was shot in a corridor against the wall.

The experiment procedure is shown in Fig. 8. During the experiment, a 20 s real walking task and a 20 s imaginary walking task were performed, with a 60 s rest period before and after each task. In order to avoid the influence by the order of the tasks, two procedures were conducted. In procedure 1, the real walking task was before the imaginary walking

Fig. 6. Experiment scene

**3.1.4 Task paradigm** 

task while in procedure 2 the order was reversed.

**Detectors**

**Emitters**

changes independently. The distance between the detector optode and emitter optode was 30 mm, which enabled cerebral blood volume measurement at a 2 to 3 cm depth from the surface of cerebral cortex (Toronov et al., 2001). The midpoints of pairs of emitter-detector optodes were regarded as the points of measurement (channels). Data were measured with a sampling rate of 10 Hz. Light emitters and detectors were alternated at an equal distance of 3 cm to give one 4×4 optode probe sets (Fig. 4). All of the transmitted intensities of the two wavelengths that left the tissue were continuously recorded over 24 channels to estimate changes in the concentrations of oxy-Hb and deoxy-Hb.

Data collection by this system is comfortable for subjects, since it requires less constrictive circumstances of measurements and fewer movement restrictions, yielding more ecologically valid conditions. The whole system is fixed on a platform installed with casters so that the system can move with the subject in moving tasks. In our study, the subjects walked in the experiment. Therefore fNIRS is more suitable for this study (Suzuki et al., 2004; Miyai et al., 2001).
