Fore–aft translation aftereffects

Abstract

A general theme in sensory perception is that exposure to a stimulus makes it seem more neutral such that perception of subsequent stimuli is shifted in the opposite direction. The visual motion aftereffect (MAE) is an extensively studied example of this. Although similar effects have been described in other sensory systems, it has not previously been described in the vestibular system. Velocity storage has been extensively studied in the vestibular system and suggests a persistence of perception in the direction of the initial movement. The current study sought to determine how motion perception is influenced by prior movement in darkness. Thirteen human subjects (mean age 41, range 21–68) underwent whole-body fore–aft translation. The threshold of vestibular motion discrimination perception was measured using a single interval (1I) of motion lasting 0.5 s in which subjects identified their direction of motion as forward or backward using an adaptive staircase. The translation aftereffect (TAE) was measured in 2-interval (2I) experiments: The adapting stimulus moved 15 cm in 1.5 s (peak velocity 20 cm/s, peak acceleration 42 cm/s2). After a fixed inter-stimulus interval (ISI) of 0.5, 1.0, 1.5, or 3 s, a second stimulus lasting 0.5 s was delivered and the subject identified the perceived direction of the second test stimulus. The test stimulus was determined using an adaptive staircase. The ISI was constant within the block, but adapting stimuli directions were randomly interleaved. During the 1I condition, the response bias was near zero in all subjects. With a 2I stimulus, 8 of 13 subjects demonstrated a significant bias. At an ISI of 0.5 s, a minority of subjects demonstrated a bias in the same direction as the adapter. When the ISI was 1, 1.5, or 3 s, all subjects who demonstrated a significant TAE had one in the opposite direction of the adapter, similar to that seen for MAE. When averaged across subjects, the TAE was significant with ISIs of 1.0 s and above. These findings demonstrate that perception of vestibular stimuli depends on prior motion. This has important implications for understanding and quantifying vestibular perception.

Visual and vestibular perceptual thresholds each demonstrate better precision at specific frequencies and also exhibit optimal integration

“…Variations in threshold across frequencies indicate different filtering, i.e., that responses to different cues depend on current and past inputs being weighted differently. As with many other motion threshold studies (Benson et al 1986(Benson et al , 1989Butler et al 2010;Crane 2012a;Grabherr et al 2008;Haburcakova et al 2012;Kolev et al 1996;Roditi andCrane 2012a, 2012b;Soyka et al 2011;Valko et al 2012;Zupan and Merfeld 2008), motion stimuli were single cycles of sinusoidal acceleration with frequency f. Figure 2 shows the corresponding cosine bell velocity and sigmoidal displacement and demonstrates how the amplitudes of the three co-vary for a given frequency. While not a primary objective of this study, when compared across frequencies, this approach is sometimes used to separate the contributions of position, velocity, acceleration and higher-derivate cues.…”

The influence of head and body tilt on human fore-aft translation perception

“…This mechanical vibration likely only had a significant effect for small movements (< 5 mm) and its purpose was to provide vibration so that absence of vibration could not be used as a cue to no motion occurring. The control condition in which fore-aft translation occurred with the head fixed with no tilt (NT) was previously reported in many of the current subjects in the current laboratory in two recent studies(Crane 2012a; Crane 2013) but was also repeated in the current study.…”

“…Fore-aft motion stimuli were delivered using a 6-degree-of-freedom motion platform (Moog model 6DOF2000E) as previously described in the current laboratory for fore-aft translation perception(Crane 2012a; Roditi and Crane 2012a; Crane 2013). Subjects were seated in a platform mounted racing seat with the body held in place by four-point harness.…”

“…This motion profile contains no discontinuities in acceleration, velocity, or position, as has been previously described (Roditi and Crane 2012a). A small amount of side-to-side mechanical oscillation was delivered to every stimulus as previously described(Crane 2012a) to create a small amount of noise and vibration to minimize non-vestibular cues. This oscillation consisted of a 6 Hz sine wave.…”

Determining thresholds using adaptive procedures and psychometric fits: evaluating efficiency using theory, simulations, and human experiments

“…Motions were single cycles of sinusoidal acceleration, as in many other motion threshold studies (Benson, Hutt, and Brown 1989;Benson, Spencer, and Stott 1986;Kolev, Mergner et al 1996;Grabherr, Nicoucar, Mast, and Merfeld 2008;Zupan and Merfeld 2008;Butler, Smith, Campos, and Bulthoff 2010;Soyka, Robuffo, Beykirch, and Bulthoff 2011;Haburcakova, Lewis, and Merfeld 2012;Roditi and Crane 2012a;Roditi and Crane 2012b;Crane 2012a;Valko, Priesol, Lewis, and Merfeld 2012). In this study, motions always had a frequency f =2 Hz and were defined by the equations: $$\text{angular acceleration}\alpha false(tfalse)=A\text{sin}false(2\pi \text{italicft}false),$$ $$\text{angular velocity}\omega false(tfalse)=A/false(2\pi ffalse)false[1-\text{cos}false(2\pi \text{italicft}false)false]\text{and}$$ $$\text{displacement}\Delta \theta false(tfalse)=A/false(2\pi ffalse)false[t-1/false(2\pi ffalse)\text{sin}false(2\pi \text{italicft}false)false].$$ …”