Effects of force levels on error compensation in periodic bimanual isometric force control

ABSTRACT The authors examined whether force level interacts with the presence or absence of vision in bimanual force control. Participants produced periodic isometric forces such that the sum of the 2 finger forces was the target force under 4 force levels cycling between lower levels (5-40%) of maximum voluntary contraction with an interval of 1000?ms. Without vision, the correlation between the 2 finger forces was strongly positive over all force levels. However, with vision the correlation changed from negative to positive with force level. The result with vision indicated that the strategy of the bimanual force control changed from force error compensation to force coupling and the available redundancy thus decreased with an increase in force.     

Effects upon rats' responses on a running wheel of single alternation of large and small rewards and external cues

Thirty-two rats were trained to run on a running wheel for one or six pellets of food, in either single alternation (SA) or quasi-random sequences of reward magnitude and with external cues either informing or not informing the rats of the reward magnitude. Reward-magnitude discrimination was clearly shown when the informative cues were given, but without such cues the SA patterning of responding appeared only late in training. The reward-magnitude discrimination developed most quickly when internal (SA) cues and external informative cues were both present; the effects of these two classes of cues on discrimination were interactive rather than additive. Possible explanations are given for the superior discrimination under the condition where both the internal and external cues were present over the condition when only the external cues were present.     

Timing of bimanual alternating finger-tapping sequences in adolescents with mental retardation: a pilot study

We examined differences between the synchronization and self-pacing tasks using repetitive tapping with alternate hands. 9 adolescents with mental retardation made faster and more variable movements on the self-pacing task than on the synchronization task at target intervals of 400 and 800 msec. This suggests that they were able to coordinate the timing of individual responses with individual stimuli on the synchronization task but on the self-pacing task they controlled the timing by memory or generation or setting of an incorrect timer rate.     

Lateralization of bilateral transfer of visuomotor information in right-handers and left-handers

The author examined the lateralization of transfer of visuomotor information between the right and left hands during unimanual finger-tapping sequences with visual feedback. The finger-tapping task consisted of a target peak force of 2 N and a target intertap interval of 500 ms. Twenty right-handed and 10 left-handed participants performed the motor task, with 3 transfer trials following 3 practice trials. The author observed positive transfers from the left to the right hand for right-handers but the opposite direction of positive transfers for left-handers. However, left-handers showed a less variable peak force than right-handers did. The author discusses left-handers' interhemispheric information processing.     

Asymmetric control of force and symmetric control of timing in bimanual finger tapping

An experiment was conducted to examine the control of force and timing in bimanual finger tapping. Participants were trained to produce both unimanual (left or right hand) and bimanual finger-tapping sequences with a peak force of 200 g and an intertap interval (ITI) of 400 ms. During practice, visual force feedback was provided pertaining to the hand performing the unimanual tapping sequences and to either the dominant or the nondominant hand in the bimanual tapping sequences. After practice, the participants produced the learned unimanual and bimanual tapping sequences in the absence of feedback. In those trials the force produced by the dominant (right) hand was significantly larger than that produced by the nondominant (left) hand, in the absence of a significant difference between the ITIs produced by both hands. Furthermore, after unilateral feedback had been provided of the force produced by the nondominant hand, the force output of the dominant hand was significantly more variable than that of the nondominant hand. In contrast, after feedback had been provided of the force produced by the dominant hand, the variability of the force outputs of the two hands did not differ significantly. These results were discussed in the light of both neurophysiological and anatomical findings, and were interpreted to imply that the control of timing (in bimanual tasks) may be more tightly coupled in the motor system than the control of force.     

Breaking Surface Feature Continuity of Previewed Mask Reinstates Object Substitution Masking12

Perception of a briefly presented target is impaired when a sparse surrounding mask (e.g., four-dot) persists after target offset compared to when the target and mask offset together (i.e., object substitution masking [OSM]). Previous studies have reported a mask preview effect in which OSM is largely attenuated by prior presentation of the mask. Here, we investigated how breaking object continuity of the previewed mask affects the mask preview effect. Introducing an abrupt surface color change of the previewed mask at target onset disrupted the beneficial effect of mask preview, that is, OSM was reinstated (Experiment 1). The masking induced by mask color change exhibited the same two characteristics as conventional OSM: target location specificity and non-necessity of voluntary attention to the mask (Experiment 2). These results suggest that a sudden change in surface color breaks object continuity of the previewed mask and causes the mask to be represented as a new one, which triggers OSM anew.     

Contagious yawning in African painted dogs

Animal Cognition - Contagious yawning (CY), which is yawning elicited by sensing another yawning, has been observed only in social species and is considered linked to high sociality. Although this...