Delays in using chromatic and luminance information to correct rapid reaches

Abstract

People can use feedback to make online corrections to movements but only if there is sufficient time to integrate the new information and make the correction. A key variable in this process is therefore the speed at which the new information about the target location is coded. Conduction velocities for chromatic signals are lower than for achromatic signals so it may take longer to correct reaches to chromatic stimuli. In addition to this delay, the sensorimotor system may prefer achromatic information over the chromatic information as delayed information may be less valuable when movements are made under time pressure. A down-weighting of chromatic information may result in additional latencies for chromatically directed reaches. In our study, participants made online corrections to reaches to achromatic, (L-M)-cone, and S-cone stimuli. Our chromatic stimuli were carefully adjusted to minimize stimulation of achromatic pathways, and we equated stimuli both in terms of detection thresholds and also by their estimated neural responses. Similar stimuli were used throughout the subjective adjustments and final reaching experiment. Using this paradigm, we found that responses to achromatic stimuli were only slightly faster than responses to (L-M)-cone and S-cone stimuli. We conclude that the sensorimotor system treats chromatic and achromatic information similarly and that the delayed chromatic responses primarily reflect early conduction delays.

Population receptive field (pRF) measurements of chromatic responses in human visual cortex using fMRI

“…The RMS (root mean square) contrasts used for the stimuli in the isoluminance tasks matched those used in the spatial sensitivity and pRF fMRI experiments for the same conditions: L-M = 4%, S-cone = 15%. These contrast values approximately equalize responses in primary visual cortex ( Kane et al., 2011 ), and were calculated as 3× the average contrast detection levels measured using a spatial 4-alternative-forced-choice (4AFC) method, with circular (2° diameter) white noise stimuli placed at 7° eccentricity from the central fixation mark; the luminance contrast threshold acquired with the same method yielded a 5% contrast.…”

Correction and suppression of reaching movements in the cerebral cortex: Physiological and neuropsychological aspects

“…Transmission delays sum up as information is processed at the different stages of visuo-motor pathways, starting with the processing of optic information in the retina (Kane et al, 2011;Lamme and Roelfsema, 2000;Nijhawan, 2008). Visual information is transmitted from the retina to the lateral geniculate nucleus, and from there to area V1.…”

Quantifying Variability in Oculomotor and Manual Choice Response Times

“…Oculomotor responses, which have been tested more recently due to advances in eye-tracking techniques (Yarbus, 1967) show effects of stimulus contrast (Beutter, Eckstein, & Stone, 2003;Carpenter, 2004;Liston & Krauzlis, 2003;Masson, Mestre, Blin, & Pailhous, 1994;Taylor, Carpenter, & Anderson, 2006;Wheeless, Cohen, & Boynton, 1967), luminance (Bompas & Sumner, 2008;Kane, Wade, & Ma-Wyatt, 2011;Liston, Krukowski, & Stone, 2013;Masson et al, 1994;Wheeless et al, 1967), target speed (Rashbass, 1961;Robinson, 1964Robinson, , 1965, and changes in target position (Kane et al, 2011). Similarly, manual RTs show effects of contrast (Taylor et al, 2006), luminance (Bompas & Sumner, 2008;Cattell, 1886;Kane et al, 2011), and changes in target position (Kane et al, 2011). However, paired comparisons of various motor systems show manual RTs to visual stimuli have longer latencies (Beutter et al, 2003;Bompas & Sumner, 2008;Kane et al, 2011;Stone & Krauzlis, 2003) and take longer to modify compared to oculomotor responses (Kane et al, 2011).…”

“…Similarly, manual RTs show effects of contrast (Taylor et al, 2006), luminance (Bompas & Sumner, 2008;Cattell, 1886;Kane et al, 2011), and changes in target position (Kane et al, 2011). However, paired comparisons of various motor systems show manual RTs to visual stimuli have longer latencies (Beutter et al, 2003;Bompas & Sumner, 2008;Kane et al, 2011;Stone & Krauzlis, 2003) and take longer to modify compared to oculomotor responses (Kane et al, 2011). Could this delay in RT potentially be advantageous in detecting internal changes or simply a greater source of variability?…”

“…Paired RT comparisons of various motor systems also show systematic differences in their properties (e.g., Beutter et al, 2003;Bompas & Sumner, 2008;Kane et al, 2011;Liston & Krauzlis, 2003;Masson et al, 1994), which suggests that although there are shared neural processing stages (Beutter & Stone, 2000;Krauzlis & Adler, 2001; Krauzlis & Stone, 1999;Stone & Krauzlis, 2003), manual and oculomotor responses may ultimately display different utility to detect internal changes. Indeed, when stimulus strength is high, oculomotor and manual responses are correlated on a trial-by-trial basis (Beutter & Stone, 2000;Krauzlis & Adler, 2001).…”