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An fMRI study on cortical responses during active self-touch and passive touch from others.

Ackerley R, Hassan E, Curran A, Wessberg J, Olausson H, McGlone F - Front Behav Neurosci (2012)

Bottom Line: Separate somatotopical palm and arm representations were found in Brodmann area (BA) 3 of the right primary somatosensory cortex (SI) and in both these areas, active stroking gave significantly higher signals than passive stroking.Active, self-touch elicited a positive BOLD signal in a network of sensorimotor cortical areas in the left hemisphere, compared to the resting baseline.In contrast, during passive touch, a significant negative BOLD signal was found in the left SI.

View Article: PubMed Central - PubMed

Affiliation: Department of Physiology, University of Gothenburg Gothenburg, Sweden.

ABSTRACT
Active, self-touch and the passive touch from an external source engage comparable afferent mechanoreceptors on the touched skin site. However, touch directed to glabrous skin compared to hairy skin will activate different types of afferent mechanoreceptors. Despite perceptual similarities between touch to different body sites, it is likely that the touch information is processed differently. In the present study, we used functional magnetic resonance imaging (fMRI) to elucidate the cortical differences in the neural signal of touch representations during active, self-touch and passive touch from another, to both glabrous (palm) and hairy (arm) skin, where a soft brush was used as the stimulus. There were two active touch conditions, where the participant used the brush in their right hand to stroke either their left palm or arm. There were two similar passive, touch conditions where the experimenter used an identical brush to stroke the same palm and arm areas on the participant. Touch on the left palm elicited a large, significant, positive blood-oxygenation level dependence (BOLD) signal in right sensorimotor areas. Less extensive activity was found for touch to the arm. Separate somatotopical palm and arm representations were found in Brodmann area (BA) 3 of the right primary somatosensory cortex (SI) and in both these areas, active stroking gave significantly higher signals than passive stroking. Active, self-touch elicited a positive BOLD signal in a network of sensorimotor cortical areas in the left hemisphere, compared to the resting baseline. In contrast, during passive touch, a significant negative BOLD signal was found in the left SI. Thus, each of the four conditions had a unique cortical signature despite similarities in afferent signaling or evoked perception. It is hypothesized that attentional mechanisms play a role in the modulation of the touch signal in the right SI, accounting for the differences found between active and passive touch.

No MeSH data available.


Related in: MedlinePlus

Overview of the main regions where positive BOLD signal changes were found for active and passive stroking on the palm and arm, compared to the resting baseline. There were clear differences between active and passive touch, as can be seen in the BOLD signal in the left SI and MI (compare the top two panels). There were also body site differences: the right SI had large regions of activity from palm stroking, whereas much less activity was found to arm stroking (see also Table 1). There was also bilateral SII activation to arm stroking, whereas bilateral activity for palm stroking was only found for passive touch (in active touch to the palm, there was only right SII activity). The maps are to neurological convention (left is left).
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Figure 1: Overview of the main regions where positive BOLD signal changes were found for active and passive stroking on the palm and arm, compared to the resting baseline. There were clear differences between active and passive touch, as can be seen in the BOLD signal in the left SI and MI (compare the top two panels). There were also body site differences: the right SI had large regions of activity from palm stroking, whereas much less activity was found to arm stroking (see also Table 1). There was also bilateral SII activation to arm stroking, whereas bilateral activity for palm stroking was only found for passive touch (in active touch to the palm, there was only right SII activity). The maps are to neurological convention (left is left).

Mentions: The results from comparing the different touch conditions showed striking differences in sensorimotor areas. From inspection of each participant's data, and as found previously (Olausson et al., 2002; Björnsdotter et al., 2009), the data from some participants (n = 4) showed less BOLD activation, due to increased head movement and also drowsiness may have played a factor. Although, these participants' data followed similar trends, they were not used in calculations. Overall in the data, there were more extensive areas showing positive BOLD signal changes for palm compared to arm stroking in the right sensorimotor cortex, irrespective of whether the stroking was active or passive (Figure 1). A somatotopical representation was found in the right SI (BA03): the palm representation was in the middle of the post-central gyrus and covered a large area (see Figure 1), whereas the arm representation was further lateral (not shown in Figure 1 due to the slice orientation; see Table 1 for details). In both of these specific body site regions in BA03, active touch gave significantly higher beta values than passive touch to the same area, respectively (p < 0.05; Figure 2). Other areas in the left sensorimotor cortex showed significant positive BOLD modulations compared to the resting baseline for touch to the palm and arm (see Table 1), however, none of these regions showed significant differences between the active and passive touch beta values.


An fMRI study on cortical responses during active self-touch and passive touch from others.

Ackerley R, Hassan E, Curran A, Wessberg J, Olausson H, McGlone F - Front Behav Neurosci (2012)

Overview of the main regions where positive BOLD signal changes were found for active and passive stroking on the palm and arm, compared to the resting baseline. There were clear differences between active and passive touch, as can be seen in the BOLD signal in the left SI and MI (compare the top two panels). There were also body site differences: the right SI had large regions of activity from palm stroking, whereas much less activity was found to arm stroking (see also Table 1). There was also bilateral SII activation to arm stroking, whereas bilateral activity for palm stroking was only found for passive touch (in active touch to the palm, there was only right SII activity). The maps are to neurological convention (left is left).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3412995&req=5

Figure 1: Overview of the main regions where positive BOLD signal changes were found for active and passive stroking on the palm and arm, compared to the resting baseline. There were clear differences between active and passive touch, as can be seen in the BOLD signal in the left SI and MI (compare the top two panels). There were also body site differences: the right SI had large regions of activity from palm stroking, whereas much less activity was found to arm stroking (see also Table 1). There was also bilateral SII activation to arm stroking, whereas bilateral activity for palm stroking was only found for passive touch (in active touch to the palm, there was only right SII activity). The maps are to neurological convention (left is left).
Mentions: The results from comparing the different touch conditions showed striking differences in sensorimotor areas. From inspection of each participant's data, and as found previously (Olausson et al., 2002; Björnsdotter et al., 2009), the data from some participants (n = 4) showed less BOLD activation, due to increased head movement and also drowsiness may have played a factor. Although, these participants' data followed similar trends, they were not used in calculations. Overall in the data, there were more extensive areas showing positive BOLD signal changes for palm compared to arm stroking in the right sensorimotor cortex, irrespective of whether the stroking was active or passive (Figure 1). A somatotopical representation was found in the right SI (BA03): the palm representation was in the middle of the post-central gyrus and covered a large area (see Figure 1), whereas the arm representation was further lateral (not shown in Figure 1 due to the slice orientation; see Table 1 for details). In both of these specific body site regions in BA03, active touch gave significantly higher beta values than passive touch to the same area, respectively (p < 0.05; Figure 2). Other areas in the left sensorimotor cortex showed significant positive BOLD modulations compared to the resting baseline for touch to the palm and arm (see Table 1), however, none of these regions showed significant differences between the active and passive touch beta values.

Bottom Line: Separate somatotopical palm and arm representations were found in Brodmann area (BA) 3 of the right primary somatosensory cortex (SI) and in both these areas, active stroking gave significantly higher signals than passive stroking.Active, self-touch elicited a positive BOLD signal in a network of sensorimotor cortical areas in the left hemisphere, compared to the resting baseline.In contrast, during passive touch, a significant negative BOLD signal was found in the left SI.

View Article: PubMed Central - PubMed

Affiliation: Department of Physiology, University of Gothenburg Gothenburg, Sweden.

ABSTRACT
Active, self-touch and the passive touch from an external source engage comparable afferent mechanoreceptors on the touched skin site. However, touch directed to glabrous skin compared to hairy skin will activate different types of afferent mechanoreceptors. Despite perceptual similarities between touch to different body sites, it is likely that the touch information is processed differently. In the present study, we used functional magnetic resonance imaging (fMRI) to elucidate the cortical differences in the neural signal of touch representations during active, self-touch and passive touch from another, to both glabrous (palm) and hairy (arm) skin, where a soft brush was used as the stimulus. There were two active touch conditions, where the participant used the brush in their right hand to stroke either their left palm or arm. There were two similar passive, touch conditions where the experimenter used an identical brush to stroke the same palm and arm areas on the participant. Touch on the left palm elicited a large, significant, positive blood-oxygenation level dependence (BOLD) signal in right sensorimotor areas. Less extensive activity was found for touch to the arm. Separate somatotopical palm and arm representations were found in Brodmann area (BA) 3 of the right primary somatosensory cortex (SI) and in both these areas, active stroking gave significantly higher signals than passive stroking. Active, self-touch elicited a positive BOLD signal in a network of sensorimotor cortical areas in the left hemisphere, compared to the resting baseline. In contrast, during passive touch, a significant negative BOLD signal was found in the left SI. Thus, each of the four conditions had a unique cortical signature despite similarities in afferent signaling or evoked perception. It is hypothesized that attentional mechanisms play a role in the modulation of the touch signal in the right SI, accounting for the differences found between active and passive touch.

No MeSH data available.


Related in: MedlinePlus