Robot Therapy for Elders Affected by Dementia - IEEE Pulse

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56 Long-Term Memory Paro has the property of reinforcement learning, and it assigns values to the relationship between stimulation and behavior. It places a positive value on preferred stimulation, such as stroking, and a negative value on undesired stimulation, such as beating. Users are prevented from changing its behavior program manually; however, Paro can be gradually tuned to the preferred behavior of its owner. (Paro is not tuned to be obedient to its owner when it is beaten frequently. In such a case, Paro would be a prickly character.) In addition, Paro can memorize a frequently articulated word as its new name. The user can give Paro his or her preferred name during natural interaction. Reactive Behavior Paro reacts to sudden stimulation. For example, when it hears a sudden loud sound, Paro pays attention to it and looks in the direction of the sound. There are several patterns of combination of stimulation and reaction. These patterns emulate the unconditioned reflex of animals. Physiological Behavior Paro has a diurnal rhythm. It has several spontaneous needs, such as sleep, based on this rhythm. For investigating how people evaluate the robot, studies were conducted using questionnaires at exhibitions held in six countries: Japan, United Kingdom, Sweden, Italy, Korea, and Brunei. The results showed that the seal robot was widely accepted, regardless of cultural differences [24]–[26]. Diagnosis Method of Neuronal Dysfunction There are various methods for the assessment of cognitive function. Neuropsychological tests, such as minimental state (MMSE) and clinical dementia rating (CDR), are handy and useful [37], [38], although their sensitivity depends on the measuring procedure and their time resolution is low. Functional neuroimaging techniques [single photon emission computed tomography (SPECT), positron emission tomography (PET), and functional magnetic resonance imaging (fMRI)] are useful for the early diagnosis of dementia [39]. However, they are prohibitively expensive and require huge measuring equipment and/or injection of radioactive tracer compounds. On the other hand, electrophysiological tests, such as the EEG and event-related potential (ERP), directly measure the cortical T3 F7 100,000 (s) F3 15 Fp2 Fp2 Fp1 Fp3 Fp1 Fp3 Fz F4 F2 C3 Cz C4 T2 T3 C3 Cz C4 T2 P3 P4 T5 Pz T6 10 5 0 –5 –10 F7 F3 O1 Oz O2 O1 Oz O2 –15 activity of specific neuronal populations [40], [41] and have high time resolution. However, these methods are difficult to quantify. In addition, ERP requires a well-designed test battery. Diagnosis method of neuronal dysfunction (DIMENSION), an EEG analysis method, has high time resolution and quantifiability and does not require a test battery [42]. It can detect lack of smoothness of the scalp potential distribution due to cortical neuronal impairment by analyzing spontaneous EEG alpha components recorded with 21 electrodes. This technique is applicable for the mass screening of people with early stage dementia. When neurons within a specific cortical area are depolarized, electric currents flow perpendicularly to the cortical surface, producing a scalp potential. In a normal brain, the active current generators produce the distributions of neurons that are approximately equally activated. This activation produces 1) uniform electric current density at the cortical surface, 2) electric currents within cortical sulci that cancel each other, and 3) a uniform distribution of the resulting scalp potential [43]. However, when cortical (and possibly subcortical) damage exists, randomly oriented electric current sources arise because sulcal currents do not cancel each other, and the scalp potential becomes less uniform [44] (Figure 4). Musha et al. defined mean alpha diporality (D a)todetermine the loss of uniformity of an observed scalp EEG alpha potential distribution. D a approaches unity without cortical sulcal lesions, whereas a brain with randomly distributed cortical sulcal lesions has Da values well below unity. Especially, as shown by the results from SPECT analysis, Da has a strong correlation with a decreasing regional cerebral blood flow (RCBF), which is a particular symptom of the early stage of AD. A basic experiment showed that the rough criterion Da @ 0.95 separates normal subjects and AD patients. Reproducibility of this result was examined in normal subjects, and the error is 0.005inrepeatedmeasurements after 1 h. Therefore, positive efficacy is observed when an increment d of the D a value after treatment is larger than 0.005. Robot Therapy for Patients with Dementia As for the interaction between Paro and patients with dementia in nursing homes, behavioral improvements were observed in several cases. For example, a patient who moaned continuously was able to relax and then started to talk with the therapist [22]. Moreover, on playing with Paro, another patient who often tried to return home stopped doing so, and her wandering decreased. In this study, we aimed to investigate the neuropsy- 10 chological influence of Paro. 8 100,160 (s) Fz F4 F2 P3 P4 T5 Pz T6 (a) (b) Fig. 4. a-waves of the scalp electrical potential distribution. 6 4 2 0 –2 –4 –6 –8 –10 Methods of Robot Therapy Seal robots named Paro were used at Kimura Clinic, a cranial nerve clinic in Japan, where patients with mild to moderately severe dementia were treated. After obtaining informed consent of patients and/or their families, a 20-min robot therapy was conducted in accordance with the ethical committee of the National Institute of Advanced Industrial Science and Technology (AIST). IEEE ENGINEERING IN MEDICINE AND BIOLOGY MAGAZINE JULY/AUGUST 2008
We designed two seal robots and placed them in the center of tables. Five to ten patients were arranged around the tables (Figure 5). They interacted with the seal robots freely during the robot therapy. Before and after the robot therapy, a 5-min EEG recording was performed with the patient at rest with closed eyes. The recorded EEG was analyzed by DIMENSION. In addition, a questionnaire about their impressions of Paro was conducted after the 20-min interaction. The questionnaire consisted of four items evaluated in five grades (Table 1). All the answers to the questions were scored as follows: most positive answer ¼ 2, positive ¼ 1, no opinion ¼ 0, negative ¼ 1, and most negative ¼ 2. The impression of Paro was evaluated by the total score of the questionnaire. The examiner heard each question to the subject. Results of Robot Therapy We examined 29 patients (including 11 men, 62–90 years). Some of these patients were rejected because they were subnormal or normal according to the DIMENSION analysis. In such cases, no improvement was expected by robot therapy. In some other cases, the patients were rejected because they were unable to close their eyes during the EEG recording. The number of available subjects was reduced to 14. Their basic attributes are shown in Table 2. Figure 6 presents the results. The Y-axis, D r, denotes the standard deviation of fluctuations of D a. The fan beam area denotes the rough standard of levels of neuronal activity. Arrows indicate displacements after the 20-min robot therapy. The green arrows indicate positive displacements. The robot therapy was effective for seven patients. In particular, one patient improved from impaired to normal, and two other patients improved to subnormal. As for the questionnaire on the impressions of Paro, we were able to obtain data from 11 of the 14 available subjects. Figure 7 shows the scores of their questionnaires and changes of D a. Four patients whose total score was eight showed improvement. In contrast, no improvement was observed in patients whose score was lower than seven (except for patient B). As for their interactions with Paro, for example, patient K treated Paro like her grandchild. She hugged and spoke to it while smiling during the robot therapy (Figure 8). She felt Paro was so cute that she recommended it to a patient seated at her side. She said, ‘‘I want to sleep with Paro,’’ and ‘‘I’m never tired of Paro.’’ On the other hand, patient A did not try to interact with Paro, and said, ‘‘It seems to be alive, but it is not a real animal.’’ Fig. 5. A scene of robot therapy. Cortical neuron activity of two patients, F and G, who achieved the same total scores on the impression questionnaire, was opposite after the robot therapy. In response to the question about their lives, we found that patient F had owned pets, but G had not. Patient G felt that animals were fearful, dirty, and stinky, but commented ‘‘Paro never bit me, and it’s very clean. I want this one! I feel as if Paro is alive.’’ On the other hand, patient F said this was well made, even though she was dandling Paro on her knee during the robot therapy. To clarify the effects, we inactivated Paro so that it appeared to be a stuffed toy and applied it to subjects whose neuronal activities had been improved by Paro. We obtained data from Table 1. Questionnaire of the impression of the seal robot. 1. Is Paro cute/ugly? a) very cute b) cute c) no opinion 2. Do you like/dislike Paro? a) like it very much b) like c) no opinion 3. Is playing with Paro fun or boring? a) very fun b) fun c) no opinion 4. Do you want to play more with Paro? a) more b) a little more c) no opinion d) ugly e) very ugly d) dislike e) dislike it very much d) boring e) very boring d) not too eager Table 2. Basic attributes of the 14 subjects. e) no more Sex Male 4 Female 10 Age (avg. SD) 79.2 4.5 MMSE (avg. SD) 16.6 2.9 D σ : SD of Smoothness Fluctuation 0.0350 0.0300 0.0250 0.0200 0.0150 0.0100 0.0050 0.0000 0.8000 0.8200 Before After 0.8400 0.8600 0.8800 0.9000 0.9200 Subnormal 0.9400 0.9600 Normal 0.9800 1.0000 D α : Smoothness of Scalp Electrical Potential Distribution Fig. 6. The change of cortical neuron activity of 14 patients before and after robot therapy. IEEE ENGINEERING IN MEDICINE AND BIOLOGY MAGAZINE JULY/AUGUST 2008 57
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Robot Therapy for Elders Affected by Dementia - IEEE Pulse

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