Dynamic cutaneous information is sufficient for precise curvature discrimination

Self Cite

In three experiments participants haptically discriminated object shape using unimanual (single hand explored two objects) and bimanual exploration (both hands were used, but each hand, left or right, explored a separate object). Such haptic exploration (one versus two hands) requires somatosensory processing in either only one or both cerebral hemispheres; previous studies related to the perception of shape/curvature found superior performance for unimanual exploration, indicating that shape comparison is more effective when only one hemisphere is utilized. The current results, obtained for naturally shaped solid objects (bell peppers, Capsicum annuum) and simple cylindrical surfaces demonstrate otherwise: bimanual haptic exploration can be as effective as unimanual exploration, showing that there is no necessary reduction in ability when haptic shape comparison requires interhemispheric communication. We found that while successive bimanual exploration produced high shape discriminability, the participants’ bimanual performance deteriorated for simultaneous shape comparisons. This outcome suggests that either interhemispheric interference or the need to attend to multiple objects simultaneously reduces shape discrimination ability. The current results also reveal a significant effect of age: older adults’ shape discrimination abilities are moderately reduced relative to younger adults, regardless of how objects are manipulated (left hand only, right hand only, or bimanual exploration).

Section: Methodsmentioning

confidence: 81%

Section: Methodsmentioning

confidence: 99%

Haptic shape discrimination and interhemispheric communication

Dowell

Norman

Moment

et al. 2018

Self Cite

“…Note however, that the segregation between serial and parallel haptic information cannot simply be due to a difference in active versus passive touch. Serial information has been shown to transfer between passive (object moving) and active (hand moving) conditions 13 , and the active component only seems to lead to increased discrimination thresholds 46 . If passive and active haptic perception do not adapt independently, why does this seem to be the case for the different modes of serial and parallel exploration?…”

Section: Discussionmentioning

confidence: 99%

Haptic adaptation to slant: No transfer between exploration modes

Dam

Plaisier

Glowania

et al. 2016

Human touch is an inherently active sense: to estimate an object’s shape humans often move their hand across its surface. This way the object is sampled both in a serial (sampling different parts of the object across time) and parallel fashion (sampling using different parts of the hand simultaneously). Both the serial (moving a single finger) and parallel (static contact with the entire hand) exploration modes provide reliable and similar global shape information, suggesting the possibility that this information is shared early in the sensory cortex. In contrast, we here show the opposite. Using an adaptation-and-transfer paradigm, a change in haptic perception was induced by slant-adaptation using either the serial or parallel exploration mode. A unified shape-based coding would predict that this would equally affect perception using other exploration modes. However, we found that adaptation-induced perceptual changes did not transfer between exploration modes. Instead, serial and parallel exploration components adapted simultaneously, but to different kinaesthetic aspects of exploration behaviour rather than object-shape per se. These results indicate that a potential combination of information from different exploration modes can only occur at down-stream cortical processing stages, at which adaptation is no longer effective.

“…In addition to object shape discrimination, we evaluated the participants' manual dexterities using a modified version of the Moberg pick-up test 8,[25][26][27][28][29] . For this task, the younger and older participants picked up 12 small metal objects (e.g., nail, paperclip, coins, flat-head screw, a key, a wing nut, etc.)…”

Section: Vol:(0123456789)mentioning

confidence: 99%

Aging and haptic shape discrimination: the effects of variations in size

Norman

Dukes

Palmore

2020

Self Cite

Seventy-two older and younger adults haptically discriminated the solid shape of natural objects (bell peppers, Capsicum annuum). Plastic copies of the original-sized fruits were used as experimental stimuli, as well as copies that were reduced in size to 1/8th and 1/27th of the original object volumes. If haptic object shape is represented in a part-based manner, then haptic shape discrimination performance should be at least partly size invariant, since changes only in scale do not affect an object’s constituent parts. On any given trial, participants sequentially explored two bell pepper replicas and were required to judge whether they possessed the same shape or had different shapes. For some participants, the objects to be discriminated possessed the same size, while for others, the two objects had different sizes. It was found that variations in scale did significantly reduce the participants’ haptic sensitivities to shape. Nevertheless, the discrimination performance obtained for large variations in size was no lower than that obtained for smaller variations in size. The results also demonstrated that increases in age modestly affect haptic shape discrimination performance: the d′ values of the older participants were 15.5% lower than those of the younger participants.