فرمت آماده سازی روانی اثرات مثبتی بر روی تصویرسازی حرکتی در مقایسه با اجرای حرکتی: یک مطالعه طیف سنجی مادون قرمز نزدیک کاربردی
|کد مقاله||سال انتشار||مقاله انگلیسی||ترجمه فارسی||تعداد کلمات|
|29620||2012||11 صفحه PDF||سفارش دهید||محاسبه نشده|
Publisher : Elsevier - Science Direct (الزویر - ساینس دایرکت)
Journal : Cortex, Volume 48, Issue 5, May 2012, Pages 593–603
Motor imagery (MI) is widely used to study cognitive action control. Although, the neural simulation theory assumes that MI and motor execution (ME) share many common features, the extent of similarity and whether it spreads into the preparation phase is still under investigation. Here we asked, whether an extension of physiological mental preparation has a comparable effect on MI and ME. Data were recorded using wireless functional near-infrared spectroscopy (fNIRS) in a two-stage task design where subjects were cued with or without preparatory stimuli to either execute or imagine complex sequential thumb-finger tasks. The main finding is that the extended mental preparation has a significant positive effect on oxy-hemoglobin (∆[O2Hb]) in response to MI, which is proportionally larger as that found in response to ME. Furthermore, fNIRS was capable to discriminate within each task whether it was preceded by preparatory stimuli or not. Transition from mental preparation to actual performance (ME or MI) was reflected by a dip of the fNIRS signal presumably related to underlying cortical processes changing between preparation and task performance. Statistically significant main effects of ‘Preparation’ and ‘Task’ showed that ∆[O2Hb] during preparation was preparation-specific, i.e., positively affected by the presence of preparatory stimuli, whereas during task performance ∆[O2Hb] was both preparation- and task-specific, i.e., additionally affected by the task mode. These results are particularly appealing from a practical point of view for making use of MI in neuroscientific applications. Especially neurorehabilitation and neural interfaces may benefit from utilizing positive interactions between mental preparation and MI performance.
MI has been described as the mental rehearsal of voluntary movement (Jeannerod, 2001). According to the so-called simulation hypothesis (Rizzolatti et al., 2001 and Jeannerod, 1994), MI activates a cortical network located in primary motor cortex (M1) and secondary motor areas, such as premotor cortex (PMC), supplementary motor area (SMA) and parietal cortices (Fadiga et al., 1995) which is thought to overlap with that responsible for the actual execution of the same motor action (Decety, 1996a and Lotze et al., 1999). Likewise motor execution (ME), it is suggested, that the cognitive processes underlying MI comprise two consecutive phases (Cunnington et al., 2005 and Thoenissen et al., 2002). While the first phase consists of mental preparation to set up planning for a given task, the second phase involves the actual performance of the task, e.g., execution or imagery. Though extensive evidence has been provided that MI and ME share many common features (Decety, 1996b), the extent of similarity and whether it spreads into the mental preparation phase has only recently attracted the attention of researchers.
نتیجه گیری انگلیسی
We first analyzed the temporal profile of ∆[O2Hb] in channels 1–3 of the left hemispheres, after averaging over all subjects (Fig. 3). At the group level, we observed a hemodynamic response function that reflected the time course of the experimental trial. Both the preparation phase and the production phase were appreciably evident localized in time. Full-size image (69 K) Fig. 3. Graph plot presenting the averaged time course over all subjects (N = 15) of the whole experimental trial including preparation and production phase for mean ∆[O2Hb] changes shown over channel 1–3 for each condition (NoPrep-ME (light blue) and Prep-ME (dark blue), NoPrep-MI (light red) and Prep-MI (dark red)). After the rest phase (15 sec, white), onset of stimulation phase (green): preparation phase (S1) from 0 to 10 sec, production phase (S2) from 10 to 25 sec; two time windows are marked used for the ANOVA calculations and the bar plots shown in Fig. 5. (NoPrep = without preparatory stimuli, Prep = with preparatory stimuli, ME = motor execution, MI = motor imagery). Figure options After the onset of the preparation phase (S1) a distinct response pattern for the four conditions was found replicating the effect of preparatory stimuli: In both Prep-conditions that provided preparatory number stimuli (Prep-ME, Prep-MI) the ∆[O2Hb] response increased approximately 3 sec after the onset of the preparation phase (S1); whereas in the two other NoPrep-conditions without preparatory stimuli (NoPrep-ME, NoPrep-MI), either no or a distinctly lower increase was observed. After the onset of the production phase (S2) a second distinct response pattern became evident approximately 4 sec after S2 reflecting the effect of the task mode: In both Prep-conditions (Prep-ME, Prep-MI) larger ∆[O2Hb] responses were found as compared to the NoPrep-conditions. Although the same pattern was found in both task modes, ME elicited overall larger ∆[O2Hb] responses as compared to MI. However, the proportional ∆[O2Hb] changes, i.e., the comparative change in amplitude between NoPrep- and Prep-conditions, were proportionally larger in response to MI (preparation phase: Δ[O2Hb] in Prep-condition was 2.9 times larger than in NoPrep-condition; production phase: Δ[O2Hb] in Prep-condition was 2.3 times larger than in NoPrep-condition) as compared to ME (preparation phase: Δ[O2Hb] in Prep-condition was 2.4 times larger than in NoPrep-condition; production phase: Δ[O2Hb] in Prep-condition was 1.3 times larger than in NoPrep-condition). Additionally, this shows that in the preparation phase the changes between the NoPrep- and the Prep-∆[O2Hb] signals were slightly larger as compared to in the production phase (Table 2). As illustrated in the graph plot (Fig. 3), we observed a dip of the ∆[O2Hb] signal between the preparation and the production phase after the first 15 sec of the experimental trial. This dip appears prominent in the Prep-conditions (Prep-ME, Prep-MI) and may therefore be related to the underlying cortical processes that change between preparation and task execution. The same data are shown in a sample subject plot (Fig. 4) demonstrating that the dip is also reflected on the single subject basis. Here, likewise on the group level, the dip is prominent in the Prep-conditions (Fig. 4, top plots) as compared to the NoPrep-conditions (Fig. 4, bottom plots). Full-size image (41 K) Fig. 4. Graph plot presenting the time course of a single sample subject of mean [O2Hb] and [HHb] changes (μmol/l) for each condition; only shown for channel 1. After the rest phase (15 sec, white), onset of stimulation phase (green): preparation phase (S1) from 0 to 10 sec, production phase (S2) from 10 to 25 sec. (NoPrep = without preparatory stimuli, Prep = with preparatory stimuli, ME = motor execution, MI = motor imagery). Figure options To verify the statistical significance of these observations, we calculated for each subject the mean value during the two time windows marked in Fig. 3. Previous fNIRS studies showed that Δ[O2Hb] is more sensitive to motor-related activity changes than Δ[HHb] (Miyai et al., 2001, Hatakenaka et al., 2007 and Strangman et al., 2002). We thus focused in the following analysis on Δ[O2Hb] signals. When collapsing ∆[O2Hb] activity for each channel during these time windows, as compared with baseline (rest phase) the effects of both factors become evident. Fig. 5 shows these values for the preparation (Top) and production (Bottom) phase as the mean change ∆[O2Hb] profile in a bar plot. Full-size image (44 K) Fig. 5. Bar plots of mean ∆[O2Hb] profile (μmol/l ± standard error of the mean – SE) for the preparation phase (Top) and the production phase (Bottom) taken from the time windows (last 3 sec of preparation phase; 4th–7th sec of production phase) marked in Fig. 3; over all subjects for each condition in channels 3 (blue), 2 (green) and 1 (brown). (NoPrep = without preparatory stimuli, Prep = with preparatory stimuli, ME = motor execution, MI = motor imagery). Relevant differences between conditions calculated with paired t-test (confidence interval – CI 95%; p = .05) are highlighted with (*). Figure options Repeated three-way measure ANOVA (Table 1) showed that during the preparation phase (S1), a larger mean ∆[O2Hb] amplitude was observed when subjects were preparing for actions (ME/MI) compared to when they were not preparing it [F(1, 14) = 5.50, p = .034]. This effect of ‘Preparation’ shows that the ∆[O2Hb] signal amplitude during the preparation phase was preparation-specific, i.e., positively affected by the presence of preparatory stimuli. Paired t-test of mean ∆[O2Hb] in the preparation phase revealed a statistical significant difference between conditions NoPrep-ME and Prep-ME (t = −2.04; p = .044) as well as between NoPrep-MI and Prep-MI (t = −2.32; p = .016). There was no reliable effect of task on the preparation phase [F(1, 14) = .09, p = .775]. There was a reliable effect of channels [F(2, 28) = 5.71, p = .009] with strongest effects observed at channel 2 compared with channel 1 and 3, though the inter-channel differences were not significant. Table 1. Repeated three-way measures ANOVA for mean ∆[O2Hb] and ∆[HHb] per subject for the preparation phase (Top) and production phase (Bottom) between the paired factors ‘Task’ (ME vs MI), ‘Preparation’ (Prep vs NoPrep), and ‘Channels’ (inter-channels), p ≤ .05, Bonferroni correction. No interaction effects between these factors were observed. Significant values are highlighted with (*); dof = degrees of freedom, F-ratio and p-value. [O2Hb] [HHb] dof F-ratio p-value F-ratio p-value Preparation phase Task (ME × MI) 1, 14 .09 p = .775 .74 p = .403 Preparation (Prep × NoPrep) 1, 14 5.50 p = .034* .156 p = .698 Channels (inter-channels) 2, 28 5.71 p = .009* 1.11 p = .344 Production phase Task (ME × MI) 1, 14 5.38 p = .017* .13 p = .725 Preparation (Prep × NoPrep) 1, 14 5.93 p = .002* 2.04 p = .175 Channels (inter-channels) 2, 28 5.04 p = .023* .61 p = .550 Table options The same analysis for the production phase (S2) revealed again a larger mean ∆[O2Hb] when subjects were preparing for an action (ME/MI) compared to when they were not preparing it [F(1, 14) = 5.93, p = .002]. Paired t-test in the production phase showed only a statistical significant difference between conditions NoPrep-MI and Prep-MI (t = −2.54; p = .028), while the difference between conditions NoPrep-ME and Prep-ME (t = −1.98; p = .059) was just under the level of significance ( Fig. 5). In addition, there was also a reliable effect of task on the production phase [F(1, 14) = 5.38, p = .017] and of channels [F(2, 28) = 35.04, p = .023] with strongest effects again observed at channel 2 compared with channel 1 and 3, though the inter-channel differences were not significant. Here, the effects of ‘Preparation’ and ‘Task’ show that the ∆[O2Hb] signal amplitude during the production phase was both preparation- and task-specific, i.e., additionally affected by the task mode. No interactions between these effects were observed in either phase. Overall in channels 1–3 we found similar oxygenation values reflecting the effects of the factors ‘Preparation’ and ‘Task’ in the preparation and production phase. In the preparation phase, the mean ∆[O2Hb] changes averaged over channels 1–3 and all subjects (Table 2) were largest in condition Prep-MI, followed by Prep-ME, NoPrep-ME and NoPrep-MI. In the production phase, the ∆[O2Hb] pattern changed with largest changes in condition Prep-ME, followed by Prep-MI, NoPrep-ME and NoPrep-MI. Intra-condition analysis of the mean amplitudes between [O2Hb]rest and [O2Hb]stim for the production phase using the paired t-test (Table 2) revealed statistical significance in all conditions, except NoPrep-MI in the preparation phase. Table 2. Mean ∆[O2Hb] and ∆[HHb] (μmol/l ± SE) and paired t-test (t-stat; p-values) between [O2Hb]rest, [HHb]rest and [O2Hb]stim, [HHb]stim for the preparation phase (Top) and production phase (Bottom) in each condition over all subjects (N = 15) and channels 1–3 of the contralateral left hemisphere during performance of ME and MI with (Prep) and without (NoPrep) preparatory stimuli. Significant values are highlighted with (*). NoPrep-ME Prep-ME NoPrep-MI Prep-MI Preparation phase Mean ∆[O2Hb] (t-stat; p-value) .099 ± .043 (t = −2.29; p = .023*) .237 ± .048 (t = −4.92; p ≤ .001*) .092 ± .057 (t = −1.59; p = .112) .271 ± .054 (t = −5.02; p ≤ .001*) Mean ∆[HHb] (t-stat; p-value) −.030 ± .011 (t = −2.84; p = .005*) −.020 ± .013 (t = −1.59; p = .114) −.036 ± .013 (t = −2.92; p = .004*) −.027 ± .011 (t = −2.57; p = .011*) Production phase Mean ∆[O2Hb] (t-stat; p-value) .301 ± .045 (t = −6.57; p ≤ .001*) .382 ± .048 (t = −7.91; p ≤ .001*) .151 ± .054 (t = −2.81; p = .006*) .352 ± .052 (t = −6.83; p ≤ .001*) Mean ∆[HHb] (t-stat; p-value) .006 ± .013 (t = −.491; p = .624) −.009 ± .013 (t = .654; p = .514) .024 ± .015 (t = −1.66; p = .098) −.013 ± .014 (t = .954; p = .341) Table options The previous results showed that, at wireless NIRS imaging is capable of discriminating between motor and imagery tasks and, within each task, whether the task was preceded by a preparatory stimuli or not. To evaluate whether the single subject level also revealed a relation between performance and signal amplitude of the production phase, we investigated the correlation between different independent measures obtained for each subject. Since none of the factors were blocked, all four conditions (ME, MI) × (NoPrep, Prep) were independent. We reasoned that if the different oxygenation profiles revealed distinct functional mechanisms, then we would expect correlations within task modes or preparatory stimuli. To quantify the correlations between preparatory stimuli and task mode, we compared the ∆[O2Hb] changes (μmol/l) of the production phase for each single subject for pairs of the tasks (NoPrep-ME vs Prep-ME and NoPrep-MI vs Prep-MI, top panels) and pairs of the preparatory stimuli (NoPrep-ME vs NoPrep-MI and Prep-ME vs Prep-MI, bottom panels) ( Fig. 6). For simplicity this is illustrated only for one channel, but the data are very similar for other channels. Consistent with the ANOVA results, two relevant findings were observed: First, when comparing MI across the preparatory stimuli, as expected the responses were positively correlated (r = .71; p < .001), i.e., larger ∆[O2Hb] signal amplitude in the Prep-condition as compared to the NoPrep-condition. The same correlation for ME was not significant (r = .17; p = .34). Second, when comparing the Prep-condition across the task modes, the responses were again positively correlated (r = .72; p < .001), i.e., subjects who showed higher ∆[O2Hb] responses during ME consistently showed high response level during MI. No correlation was found when fixing the NoPrep-condition (r = .13; p = .65). Full-size image (32 K) Fig. 6. Scatter plot of the mean [O2Hb] changes (μmol/l) for each single subject (N = 15) in channel 1 for each condition (Prep-ME, NoPrep-ME, Prep-MI, NoPrep-MI). Correlations between task modes (Top) and preparatory stimuli (Bottom) are shown for each pair. Figure options Taken together our results show that an extension of the physiological mental preparation phase has a significant positive effect on ∆[O2Hb] in response to MI. 1)