Limits...
Direct comparisons of hand and mouth kinematics during grasping, feeding and fork-feeding actions.

Quinlan DJ, Culham JC - Front Hum Neurosci (2015)

Bottom Line: As in many past studies, we found that the hand oversized considerably larger (~11-27 mm) than the food item during grasping; moreover, the amount of oversizing scaled with food size.Surprisingly, regardless of whether the hand or fork was used to transport the food, the mouth oversized only slightly larger (~4-11 mm) than the food item during biting and the oversizing did not increase with food size.Taken together, our results show that while many aspects of kinematics share some similarity between grasping and feeding, oversizing may reflect strategies unique to the hand vs. mouth (such as the need to have the digits approach the target surface perpendicularly for grip stability during lifting) and differences in the neural substrates of grasping and feeding.

View Article: PubMed Central - PubMed

Affiliation: Brain and Mind Institute, University of Western Ontario London, ON, Canada ; Department of Psychology, Huron University College London, ON, Canada ; Graduate Program in Neuroscience, University of Western Ontario London, ON, Canada.

ABSTRACT
While a plethora of studies have examined the kinematics of human reach-to-grasp actions, few have investigated feeding, another ethologically important real-world action. Two seminal studies concluded that the kinematics of the mouth during feeding are comparable to those of the hand during grasping (Castiello, 1997; Churchill et al., 1999); however, feeding was done with a fork or spoon, not with the hand itself. Here, we directly compared grasping and feeding kinematics under equivalent conditions. Participants were presented with differently sized cubes of cheese (10-, 20- or 30-mm on each side) and asked to use the hand to grasp them or to use a fork to spear them and then bring them to the mouth to bite. We measured the apertures of the hand during grasping and the teeth during feeding, as well as reaching kinematics of the arm in both tasks. As in many past studies, we found that the hand oversized considerably larger (~11-27 mm) than the food item during grasping; moreover, the amount of oversizing scaled with food size. Surprisingly, regardless of whether the hand or fork was used to transport the food, the mouth oversized only slightly larger (~4-11 mm) than the food item during biting and the oversizing did not increase with food size. Total movement times were longer when using the fork compared to the hand, particularly when using the fork to bring food to the mouth. While reach velocity always peaked approximately halfway through the movement, relative to the reach the mouth opened more slowly than the hand, perhaps because less time was required for the smaller oversizing. Taken together, our results show that while many aspects of kinematics share some similarity between grasping and feeding, oversizing may reflect strategies unique to the hand vs. mouth (such as the need to have the digits approach the target surface perpendicularly for grip stability during lifting) and differences in the neural substrates of grasping and feeding.

No MeSH data available.


Related in: MedlinePlus

Experimental procedure. (A) Experiment 1. Participants began Hand-to-Food reaches with their right index finger and thumb in a closed pinch position, resting on their chin (i). Participants then reached out toward a cube of cheese (ii) and grasped it with a precision grip (iii). Once the food item was within the participant’s grasp, an inwardly directed reach toward the mouth (Hand-to-Mouth) was performed (iv), ending the reach with a precision bite using the upper and lower incisor teeth (v). (B) Experiment 2. Participants performed the same movement as (A) except that instead of using the index finger and thumb to capture and transport the food item, a fork was used to pierce the cheese and bring it to the mouth to bite (i–v). Zoomed views at the top of the figure show the placement of markers (infrared-emitting diodes, IREDs) on the index finger and thumb (red circles; to measure hand aperture), on the temple and lower jaw (red squares; to measure mouth aperture), and on the hand or fork (blue square and blue triangle respectively; to measure transport kinematics).
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Figure 1: Experimental procedure. (A) Experiment 1. Participants began Hand-to-Food reaches with their right index finger and thumb in a closed pinch position, resting on their chin (i). Participants then reached out toward a cube of cheese (ii) and grasped it with a precision grip (iii). Once the food item was within the participant’s grasp, an inwardly directed reach toward the mouth (Hand-to-Mouth) was performed (iv), ending the reach with a precision bite using the upper and lower incisor teeth (v). (B) Experiment 2. Participants performed the same movement as (A) except that instead of using the index finger and thumb to capture and transport the food item, a fork was used to pierce the cheese and bring it to the mouth to bite (i–v). Zoomed views at the top of the figure show the placement of markers (infrared-emitting diodes, IREDs) on the index finger and thumb (red circles; to measure hand aperture), on the temple and lower jaw (red squares; to measure mouth aperture), and on the hand or fork (blue square and blue triangle respectively; to measure transport kinematics).

Mentions: While these studies of feeding actions were impressive initial forays into a new area of kinematic research, several aspects of the experiments may have artificially exaggerated the similarities between the kinematics of reach-to-bite and reach-to-grasp actions. First, the grip component was not comparable between the hand and mouth. That is, in grasping an object with a precision grip, the finger and thumb contact the sides of the object (Figure 1Aiii); whereas, in both of the feeding studies, the mouth was used not to grip the food (cheese cube or dollop of yoghurt) but to reach around the food and then pull it into the mouth. As such, in these feeding paradigms, the food served as an obstacle such that the mouth necessarily had to open larger than the food to avoid striking the teeth. Likewise, perhaps the presence of a “food obstacle” within the mouth grip aperture serves to inflate maximum aperture, much like the presence of obstacles outside the hand grip aperture cause peak aperture to become smaller (Jackson et al., 1995; Tresilian, 1998). Second, in Castiello’s (1997) study, the mouth aperture was determined by markers placed on the upper and lower lips. Alternatively, the markers could have been placed in a manner that would estimate the aperture between the teeth (or jaw). Although the aperture between the two lips would be correlated with the aperture between the teeth, the two are not always in perfect agreement because the lips are more elastic and can be moved somewhat independently of the teeth. In contrast, Churchill et al. (1999) placed markers on the forehead and chin, which would more directly reflect the aperture between the teeth because of skull and jaw anatomy. Notably, they found subtle kinematic differences between hand and mouth aperture. Lastly, both experiments had participants use a tool during the feeding actions, but compared the kinematics of the mouth to those exhibited when grasping with the hand alone. It remains a matter of debate how bodily actions are modified by tool use (e.g., Iriki et al., 1996; Cardinali et al., 2009; Gallivan et al., 2013). In fact, the introduction of a tool into reach-to-grasp actions alters some kinematic measures, such as lengthening the outward reach deceleration phase (Gentilucci et al., 2004). Taken together, these methodological differences between feeding and grasping may have affected the data and thus the conclusions; as such, it is worth re-examining how the two actions compare under conditions that are as similar as possible.


Direct comparisons of hand and mouth kinematics during grasping, feeding and fork-feeding actions.

Quinlan DJ, Culham JC - Front Hum Neurosci (2015)

Experimental procedure. (A) Experiment 1. Participants began Hand-to-Food reaches with their right index finger and thumb in a closed pinch position, resting on their chin (i). Participants then reached out toward a cube of cheese (ii) and grasped it with a precision grip (iii). Once the food item was within the participant’s grasp, an inwardly directed reach toward the mouth (Hand-to-Mouth) was performed (iv), ending the reach with a precision bite using the upper and lower incisor teeth (v). (B) Experiment 2. Participants performed the same movement as (A) except that instead of using the index finger and thumb to capture and transport the food item, a fork was used to pierce the cheese and bring it to the mouth to bite (i–v). Zoomed views at the top of the figure show the placement of markers (infrared-emitting diodes, IREDs) on the index finger and thumb (red circles; to measure hand aperture), on the temple and lower jaw (red squares; to measure mouth aperture), and on the hand or fork (blue square and blue triangle respectively; to measure transport kinematics).
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4612668&req=5

Figure 1: Experimental procedure. (A) Experiment 1. Participants began Hand-to-Food reaches with their right index finger and thumb in a closed pinch position, resting on their chin (i). Participants then reached out toward a cube of cheese (ii) and grasped it with a precision grip (iii). Once the food item was within the participant’s grasp, an inwardly directed reach toward the mouth (Hand-to-Mouth) was performed (iv), ending the reach with a precision bite using the upper and lower incisor teeth (v). (B) Experiment 2. Participants performed the same movement as (A) except that instead of using the index finger and thumb to capture and transport the food item, a fork was used to pierce the cheese and bring it to the mouth to bite (i–v). Zoomed views at the top of the figure show the placement of markers (infrared-emitting diodes, IREDs) on the index finger and thumb (red circles; to measure hand aperture), on the temple and lower jaw (red squares; to measure mouth aperture), and on the hand or fork (blue square and blue triangle respectively; to measure transport kinematics).
Mentions: While these studies of feeding actions were impressive initial forays into a new area of kinematic research, several aspects of the experiments may have artificially exaggerated the similarities between the kinematics of reach-to-bite and reach-to-grasp actions. First, the grip component was not comparable between the hand and mouth. That is, in grasping an object with a precision grip, the finger and thumb contact the sides of the object (Figure 1Aiii); whereas, in both of the feeding studies, the mouth was used not to grip the food (cheese cube or dollop of yoghurt) but to reach around the food and then pull it into the mouth. As such, in these feeding paradigms, the food served as an obstacle such that the mouth necessarily had to open larger than the food to avoid striking the teeth. Likewise, perhaps the presence of a “food obstacle” within the mouth grip aperture serves to inflate maximum aperture, much like the presence of obstacles outside the hand grip aperture cause peak aperture to become smaller (Jackson et al., 1995; Tresilian, 1998). Second, in Castiello’s (1997) study, the mouth aperture was determined by markers placed on the upper and lower lips. Alternatively, the markers could have been placed in a manner that would estimate the aperture between the teeth (or jaw). Although the aperture between the two lips would be correlated with the aperture between the teeth, the two are not always in perfect agreement because the lips are more elastic and can be moved somewhat independently of the teeth. In contrast, Churchill et al. (1999) placed markers on the forehead and chin, which would more directly reflect the aperture between the teeth because of skull and jaw anatomy. Notably, they found subtle kinematic differences between hand and mouth aperture. Lastly, both experiments had participants use a tool during the feeding actions, but compared the kinematics of the mouth to those exhibited when grasping with the hand alone. It remains a matter of debate how bodily actions are modified by tool use (e.g., Iriki et al., 1996; Cardinali et al., 2009; Gallivan et al., 2013). In fact, the introduction of a tool into reach-to-grasp actions alters some kinematic measures, such as lengthening the outward reach deceleration phase (Gentilucci et al., 2004). Taken together, these methodological differences between feeding and grasping may have affected the data and thus the conclusions; as such, it is worth re-examining how the two actions compare under conditions that are as similar as possible.

Bottom Line: As in many past studies, we found that the hand oversized considerably larger (~11-27 mm) than the food item during grasping; moreover, the amount of oversizing scaled with food size.Surprisingly, regardless of whether the hand or fork was used to transport the food, the mouth oversized only slightly larger (~4-11 mm) than the food item during biting and the oversizing did not increase with food size.Taken together, our results show that while many aspects of kinematics share some similarity between grasping and feeding, oversizing may reflect strategies unique to the hand vs. mouth (such as the need to have the digits approach the target surface perpendicularly for grip stability during lifting) and differences in the neural substrates of grasping and feeding.

View Article: PubMed Central - PubMed

Affiliation: Brain and Mind Institute, University of Western Ontario London, ON, Canada ; Department of Psychology, Huron University College London, ON, Canada ; Graduate Program in Neuroscience, University of Western Ontario London, ON, Canada.

ABSTRACT
While a plethora of studies have examined the kinematics of human reach-to-grasp actions, few have investigated feeding, another ethologically important real-world action. Two seminal studies concluded that the kinematics of the mouth during feeding are comparable to those of the hand during grasping (Castiello, 1997; Churchill et al., 1999); however, feeding was done with a fork or spoon, not with the hand itself. Here, we directly compared grasping and feeding kinematics under equivalent conditions. Participants were presented with differently sized cubes of cheese (10-, 20- or 30-mm on each side) and asked to use the hand to grasp them or to use a fork to spear them and then bring them to the mouth to bite. We measured the apertures of the hand during grasping and the teeth during feeding, as well as reaching kinematics of the arm in both tasks. As in many past studies, we found that the hand oversized considerably larger (~11-27 mm) than the food item during grasping; moreover, the amount of oversizing scaled with food size. Surprisingly, regardless of whether the hand or fork was used to transport the food, the mouth oversized only slightly larger (~4-11 mm) than the food item during biting and the oversizing did not increase with food size. Total movement times were longer when using the fork compared to the hand, particularly when using the fork to bring food to the mouth. While reach velocity always peaked approximately halfway through the movement, relative to the reach the mouth opened more slowly than the hand, perhaps because less time was required for the smaller oversizing. Taken together, our results show that while many aspects of kinematics share some similarity between grasping and feeding, oversizing may reflect strategies unique to the hand vs. mouth (such as the need to have the digits approach the target surface perpendicularly for grip stability during lifting) and differences in the neural substrates of grasping and feeding.

No MeSH data available.


Related in: MedlinePlus