Discussion
Individuals who encoded language-based information immediately following right hand clenching (left hemisphere activation), and recalled such information immediately following left hand clenching (right hemisphere activation), demonstrated superior episodic memory compared to the other hand clenching conditions. It is noteworthy that this condition was also superior to the no hand clenching control condition, though not significantly so. This may have been due to the small sample sizes, and slightly increased variability in these two comparison groups (See Table 1). It may be that increasing sample sizes would result in a significant difference between the Renc/Lrec and NENR groups.
The other three hand clenching conditions did not differ from each other; however, left hand clenching (right hemisphere activation) pre-encoding, and right hand clenching (left hemisphere activation) pre- recall, resulted in significantly poorer memory compared to the no hand clenching condition, as did the left hand clenching (right hemisphere activation) in both the pre-encoding and pre-recall conditions. Together, this pattern of results i) supports the HERA model’s prediction of left hemisphere encoding/right hemisphere retrieval of episodic information [10], [11], and ii) suggests that it is primarily the hemisphere active at encoding that predominantly influences memory ability. This latter is indicated because, although the two pre-encoding left hand clenching (right hemisphere activation) conditions, regardless of Hand Clench Condition at pre-recall, demonstrated significantly poorer recall than the no clenching control condition, the two right hand clenching (left hemisphere activation) pre-encoding conditions did not (regardless of Hand Clench Condition at pre-recall). In fact the right clenching pre-encoding/left clench pre-recall condition was numerically greater than the no clenching condition.
It is not clear why the Hand Clench Conditions did not differ in the number of false alarms. One possibility is a floor effect in the number of falsely recalled words; future studies could increase the amount of time elapsing between encoding and recall, or by manipulating the encouragement of ‘guesses’ to further investigate this issue. Likewise, given the right hemisphere’s involvement in spatial processing, it would be useful to investigate whether the left hemisphere’s superiority at encoding would remain when information to be recalled is spatially-based.
We did not measure hemispheric activation directly in the current study. However, previous work [1], [2] demonstrating that identical hand clenching activates the contralateral prefrontal cortex suggests that this mechanism accounts for the results presented here. Future work could directly measure hemispheric activity and memory following hand clenching in order to confirm that increased hemispheric activity following hand clenching is in fact the mechanism of action for the effects. Additionally, we would like to point out that the stimuli used here were language-based. It not known whether pictorial or spatially-based stimuli would also benefit from Renc/Lrec. The HERA model predicts left hemisphere encoding, and right hemisphere retrieval, of episodic information, regardless of stimuli type. Future research could examine this hypothesis directly [10], [11].
In total, these results are striking, given that the manipulation used- a total of 90 seconds of unilateral hand clenching pre-encoding and pre-recall- is easily adaptable to a variety of experimental, clinical, and real-world situations. Additionally notable is that the sizes of the effects (d) tended to be large or very large, with only two comparisons being in the medium range, supporting the robustness of the findings. The findings presented here offer the exciting possibility that simple unilateral hand clenching can be used as a means by which the functional specialization of the cerebral hemispheres can be investigated and possibly adapted to practical situations.
ช่วยแปลภาษาอังกฤษให้ทีค่ะ กราบ
Individuals who encoded language-based information immediately following right hand clenching (left hemisphere activation), and recalled such information immediately following left hand clenching (right hemisphere activation), demonstrated superior episodic memory compared to the other hand clenching conditions. It is noteworthy that this condition was also superior to the no hand clenching control condition, though not significantly so. This may have been due to the small sample sizes, and slightly increased variability in these two comparison groups (See Table 1). It may be that increasing sample sizes would result in a significant difference between the Renc/Lrec and NENR groups.
The other three hand clenching conditions did not differ from each other; however, left hand clenching (right hemisphere activation) pre-encoding, and right hand clenching (left hemisphere activation) pre- recall, resulted in significantly poorer memory compared to the no hand clenching condition, as did the left hand clenching (right hemisphere activation) in both the pre-encoding and pre-recall conditions. Together, this pattern of results i) supports the HERA model’s prediction of left hemisphere encoding/right hemisphere retrieval of episodic information [10], [11], and ii) suggests that it is primarily the hemisphere active at encoding that predominantly influences memory ability. This latter is indicated because, although the two pre-encoding left hand clenching (right hemisphere activation) conditions, regardless of Hand Clench Condition at pre-recall, demonstrated significantly poorer recall than the no clenching control condition, the two right hand clenching (left hemisphere activation) pre-encoding conditions did not (regardless of Hand Clench Condition at pre-recall). In fact the right clenching pre-encoding/left clench pre-recall condition was numerically greater than the no clenching condition.
It is not clear why the Hand Clench Conditions did not differ in the number of false alarms. One possibility is a floor effect in the number of falsely recalled words; future studies could increase the amount of time elapsing between encoding and recall, or by manipulating the encouragement of ‘guesses’ to further investigate this issue. Likewise, given the right hemisphere’s involvement in spatial processing, it would be useful to investigate whether the left hemisphere’s superiority at encoding would remain when information to be recalled is spatially-based.
We did not measure hemispheric activation directly in the current study. However, previous work [1], [2] demonstrating that identical hand clenching activates the contralateral prefrontal cortex suggests that this mechanism accounts for the results presented here. Future work could directly measure hemispheric activity and memory following hand clenching in order to confirm that increased hemispheric activity following hand clenching is in fact the mechanism of action for the effects. Additionally, we would like to point out that the stimuli used here were language-based. It not known whether pictorial or spatially-based stimuli would also benefit from Renc/Lrec. The HERA model predicts left hemisphere encoding, and right hemisphere retrieval, of episodic information, regardless of stimuli type. Future research could examine this hypothesis directly [10], [11].
In total, these results are striking, given that the manipulation used- a total of 90 seconds of unilateral hand clenching pre-encoding and pre-recall- is easily adaptable to a variety of experimental, clinical, and real-world situations. Additionally notable is that the sizes of the effects (d) tended to be large or very large, with only two comparisons being in the medium range, supporting the robustness of the findings. The findings presented here offer the exciting possibility that simple unilateral hand clenching can be used as a means by which the functional specialization of the cerebral hemispheres can be investigated and possibly adapted to practical situations.