In this project
- Easy to rely on temporal freq perception b/c spatial freq constant.
- Has anyone measured pure stretch adaptation? Makes a MAE?
- Our effect is orientation selective?
- someone found lack of correlation between pressure thresholds and motion (displacement) thresholds
- Konkle et al. could be multimodal integration during test rather than transfer. Or criterion shift when dunno motion, just go with other modality
Jacono M, Gori M, Sciutti A, Sandini G, Burr D, 2008, "Perception of acceleration and deceleration in visual, tactile and visuo-tactile stimuli" Perception 37 ECVP Abstract Supplement, page 49
Perception of acceleration and deceleration in visual, tactile and visuo-tactile stimuli
M Jacono, M Gori, A Sciutti, G Sandini, D Burr
Psychophysical literature suggests that the human visual system is more sensitive to speed than acceleration (the temporal derivative of velocity). However few studies consider tactile perception of acceleration and none of them analyzes the visual - tactile modality. Here we investigated visual, tactile and bimodal perception of acceleration/deceleration by measuring speed discrimination over a wide range of transient speeds (from 6.8 to 454 cm s-1). The stimuli were physical wheels etched with sinewave profile. They could be seen, felt or concurrently seen and felt. Subjects were presented sequentially with the standard stimulus, characterized by a fixed final velocity and variable accelerations and with the comparison test, which reached different final velocities with maximal acceleration. Subjects had to evaluate in 2AFC protocol which interval contained the faster movement, using only visual, only tactile or bimodal information. We found similar PSEs among visual, tactile, and bimodal tasks considering all the different accelerations. Moreover we investigated the difference between deceleration and acceleration and the integration of bimodal signals characterized by opposite direction of motion.
Gori M, Mazzilli G, Sandini G, Burr D, 2008, "A characteristic 'dipper function' for bimodal and unimodal visual and tactile motion discrimination and facilitation between modalities" Perception 37 ECVP Abstract Supplement, page 6 A characteristic 'dipper function' for bimodal and unimodal visual and tactile motion discrimination and facilitation between modalities
M Gori, G Mazzilli, G Sandini, D Burr
We measure bimodal and unimodal visual and tactile velocity discrimination thresholds over a wide range of base velocities and spatial frequencies. The stimuli were two physical wheels etched with a sinewave profile that was both seen and felt, allowing for the simultaneous presentation of visual and haptic velocities, either congruent or in conflict. Stimuli were presented in two separate intervals and subjects reported the faster motion in 2AFC using visual, tactile or bimodal information. We found an improvement in the bimodal thresholds well predicted by the maximum likelihood estimation model and not specific for direction. Interestingly, both bimodal and unimodal thresholds showed a characteristic 'dipper function', with the minimum at a given 'pedestal duration'. The 'dip' occurred over the same velocity range at all spatial frequencies and conditions. Most interestingly, a tactile pedestal facilitated a visual test and vice versa, indicating facilitation between modalities and suggesting that the thresholding of these signals occurs at high levels after crossmodal integration.
p.470 of Blake & Sekuler: in "the temporal cortex, some cells distinguish clearly between tactile stimuli that are expected and those that are not. These cells respond strongly when the skin is touched unexpectedly but fail to respond to the same touch if the individual being touched has been able to see that touch was impending (Mistlin & PErrett 1990)
Failures of tactile localisation
- absolute much worse than relative
- Weber described that two points on a part of the skin with greater acuity also are perceived to be separated by more distance (see unused tactile acuity tute slide)
- cutaneous crawling illusion
- Helmholtz said that in case of acute toothache patient is uncertain whether the pain is coming from the upper or lower jaw
- Cain (1973) focused a radiant heat source on either front or back of torso, often had no idea where on their skin heat was delivered
|Receptor||depth||skin type||Fave temp freq$||afferent||stimulation it responds to||driven by||adapts to vibration?|
|Merkel's disk||top skin layers||glabrous and hairy[a]||~1 Hz, <5Hz||SA-1||pressure, orientation||spatial period||YES|
|Meissner's corpuscle||glabrous||~10 Hz||FA-1 (RA)||flutter, some stretch (b/c very sensitive to indentation)||speed, similarly for temporal freq||YES|
|Ruffini corpuscle||glabrous and hairy?||~100 Hz||SA-2||stretching||NO |
|nail beds||nails||SA-2||fingertip force, fingertip direction|
|Pacinian corpuscle||glabrous?||~400 Hz[b]||FA-2 (PC)||vibration||speed, spatial period|
|free nerve ending||deep?||sometimes on hair,||lowww?||C,?||pain, ache, heat, cold,|
a-At high amplitude, all the mechanoreceptors respond to all freqs b-Preferred frequency may change with indentation amplitude
Check out Darian & Oke 1980, they test RA, SA, Pacinian at wide range of temporal frequencies.
when stimuli move across the receptive fields of tactile afferents, the responses are different depending on the direction of movement (Goodwin and Morley, 1987; LaMotte and Srinivasan 1987; Srinivasan et al., 1990; Edin et al., 1995). Directionality of tactile afferent responses most likely results from different strains produced at the receptor site when forces are applied in different directions. In the case of the fingertip, its geometry and composite material properties may account for widespread complex patterns of strain changes that depend on the direction of the applied force (Maeno et al., 1998). Consequently, the site of stimulation, the location of the receptor in the fingertip per se as well as in relation to the stimulation site, and possible inherent directional preferences of the end-organ attributable to its microanatomy, all could contribute to the directionality of an afferent- I. Birznieks
"Both FA-I and SA-I afferents respond to changes in the magnitude and direction of tangential torque, but differ in the relative importance of specific stimulus features. FA-I fibres discriminate the onset and magnitude of changes in torque more accurately and rapidly than SA-I fibres, but rarely distinguish clockwise from anti- clockwise rotations, or signal steady-state torques. FA-I fibres are silent during static grasp or lift actions when normal forces are constant. In contrast, SA-I fibres distinguish the applied normal force with latencies as brief as 250 ms, and also discriminate torque direction more accurately and faster than FA-I fibres. These findings suggest that FA-I fibres provide early warning signals of rotational as well as translational slips when objects held in the hand are manipulated or perturbed by external forces. The absence of tonic activity in FA-I fibres during static grasp enhances the sudden appearance of spike trains signalling object motion, aiding rapid adjustment of grip force in parallel with the onset of tangential motion over the skin (Kinoshita et al. 1997; Goodwin et al. 1998)" 
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