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Cortical responses elicited by luminance and compound stimuli modulated by pseudo-random sequences: comparison between normal trichromats and congenital red-green color blinds.

Risuenho BB, Miquilini L, Lacerda EM, Silveira LC, Souza GS - Front Psychol (2015)

Bottom Line: Trichromats and color-blinds had similar VECP amplitude for compound pattern-reversal K1 and compound pattern-onset K2.2, as well as for all luminance conditions.The cross-correlation analysis showed high similarity between waveforms of compound pattern-onset K2.1 and pattern-reversal K2.2 as well as pattern-reversal K2.1 and K2.2.We suggest that compound pattern-reversal K2.1 is an appropriate response to study red-green color-opponent activity.

View Article: PubMed Central - PubMed

Affiliation: Instituto de Ciências Biológicas - Universidade Federal do Pará Belém, Brazil.

ABSTRACT
Conventional pattern-reversal visual evoked cortical potential (VECP) shows positivity for luminance and chromatic equiluminant stimuli while conventional pattern-onset VECP shows positivity for luminance pattern-onset and negativity for chromatic pattern-onset. We evaluated how the presentation mode affects VECPs elicited by luminance and compound (luminance plus chromatic) pseudo-random stimulation. Eleven normal trichromats and 17 red-green color-blinds were studied. Pattern-reversal and pattern-onset luminance and compound (luminance plus red-green) gratings were temporally modulated by m-sequence. We used a cross-correlation routine to extract the first order kernel (K1) and the first and second slices of the second order kernel (K2.1 and K2.2, respectively) from the VECP response. We integrated the amplitude of VECP components as a function of time in order to estimate its magnitude for each stimulus condition. We also used a normalized cross-correlation method in order to test the similarity of the VECP components. The VECP components varied with the presentation mode and the presence of red-green contrast in the stimuli. In trichromats, for compound conditions, pattern-onset K1, K2.1, and K2.2, and pattern-reversal K2.1 and K2.2 had negative-dominated waveforms at 100 ms. Small negativity or small positivity were observed in dichromats. Trichromats had larger VECP magnitude than color-blinds for compound pattern-onset K1 (with large variability across subjects), compound pattern-onset and pattern-reversal K2.1, and compound pattern-reversal K2.2. Trichromats and color-blinds had similar VECP amplitude for compound pattern-reversal K1 and compound pattern-onset K2.2, as well as for all luminance conditions. The cross-correlation analysis showed high similarity between waveforms of compound pattern-onset K2.1 and pattern-reversal K2.2 as well as pattern-reversal K2.1 and K2.2. We suggest that compound pattern-reversal K2.1 is an appropriate response to study red-green color-opponent activity.

No MeSH data available.


Visual evoked cortical potential (VECP) average waveforms obtained from normal trichromats using luminance and compound stimuli, as well as pattern-onset and pattern-reversal stimulations. Waveforms were obtained by averaging results from 11 subjects. From top to bottom are depicted waveforms corresponding to the first order kernel (K1), first slice of the second order kernel (K2.1), and second slice of the second order kernel (K2.2). The average waveforms were dominated by the presence of negativity at about 100 ms for the majority of stimulus conditions and kernels. An important exception is achromatic pattern-reversal K2.1 waveform which is dominated by a positive peak at the same latency. The gray shades represent the SD of the averaged recordings. They provide an indication of interindividual variability.
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Figure 2: Visual evoked cortical potential (VECP) average waveforms obtained from normal trichromats using luminance and compound stimuli, as well as pattern-onset and pattern-reversal stimulations. Waveforms were obtained by averaging results from 11 subjects. From top to bottom are depicted waveforms corresponding to the first order kernel (K1), first slice of the second order kernel (K2.1), and second slice of the second order kernel (K2.2). The average waveforms were dominated by the presence of negativity at about 100 ms for the majority of stimulus conditions and kernels. An important exception is achromatic pattern-reversal K2.1 waveform which is dominated by a positive peak at the same latency. The gray shades represent the SD of the averaged recordings. They provide an indication of interindividual variability.

Mentions: Visual evoked cortical potential kernel waveforms had several positive and negative components starting at about 70 ms after stimulus onset (Figures 2–4). In order to estimate the evoked response magnitude, we calculated the recording total power. The total power was taken as the numerical integration of the squared amplitude of all amplitude data in the first 500 ms of the recordings. We used Kruskal–Wallis test with Dunn’s post hoc test (α = 0.05) to compare the magnitude of the VECP components at different stimulus conditions. The p-values were corrected by Bonferroni correction.


Cortical responses elicited by luminance and compound stimuli modulated by pseudo-random sequences: comparison between normal trichromats and congenital red-green color blinds.

Risuenho BB, Miquilini L, Lacerda EM, Silveira LC, Souza GS - Front Psychol (2015)

Visual evoked cortical potential (VECP) average waveforms obtained from normal trichromats using luminance and compound stimuli, as well as pattern-onset and pattern-reversal stimulations. Waveforms were obtained by averaging results from 11 subjects. From top to bottom are depicted waveforms corresponding to the first order kernel (K1), first slice of the second order kernel (K2.1), and second slice of the second order kernel (K2.2). The average waveforms were dominated by the presence of negativity at about 100 ms for the majority of stimulus conditions and kernels. An important exception is achromatic pattern-reversal K2.1 waveform which is dominated by a positive peak at the same latency. The gray shades represent the SD of the averaged recordings. They provide an indication of interindividual variability.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4309178&req=5

Figure 2: Visual evoked cortical potential (VECP) average waveforms obtained from normal trichromats using luminance and compound stimuli, as well as pattern-onset and pattern-reversal stimulations. Waveforms were obtained by averaging results from 11 subjects. From top to bottom are depicted waveforms corresponding to the first order kernel (K1), first slice of the second order kernel (K2.1), and second slice of the second order kernel (K2.2). The average waveforms were dominated by the presence of negativity at about 100 ms for the majority of stimulus conditions and kernels. An important exception is achromatic pattern-reversal K2.1 waveform which is dominated by a positive peak at the same latency. The gray shades represent the SD of the averaged recordings. They provide an indication of interindividual variability.
Mentions: Visual evoked cortical potential kernel waveforms had several positive and negative components starting at about 70 ms after stimulus onset (Figures 2–4). In order to estimate the evoked response magnitude, we calculated the recording total power. The total power was taken as the numerical integration of the squared amplitude of all amplitude data in the first 500 ms of the recordings. We used Kruskal–Wallis test with Dunn’s post hoc test (α = 0.05) to compare the magnitude of the VECP components at different stimulus conditions. The p-values were corrected by Bonferroni correction.

Bottom Line: Trichromats and color-blinds had similar VECP amplitude for compound pattern-reversal K1 and compound pattern-onset K2.2, as well as for all luminance conditions.The cross-correlation analysis showed high similarity between waveforms of compound pattern-onset K2.1 and pattern-reversal K2.2 as well as pattern-reversal K2.1 and K2.2.We suggest that compound pattern-reversal K2.1 is an appropriate response to study red-green color-opponent activity.

View Article: PubMed Central - PubMed

Affiliation: Instituto de Ciências Biológicas - Universidade Federal do Pará Belém, Brazil.

ABSTRACT
Conventional pattern-reversal visual evoked cortical potential (VECP) shows positivity for luminance and chromatic equiluminant stimuli while conventional pattern-onset VECP shows positivity for luminance pattern-onset and negativity for chromatic pattern-onset. We evaluated how the presentation mode affects VECPs elicited by luminance and compound (luminance plus chromatic) pseudo-random stimulation. Eleven normal trichromats and 17 red-green color-blinds were studied. Pattern-reversal and pattern-onset luminance and compound (luminance plus red-green) gratings were temporally modulated by m-sequence. We used a cross-correlation routine to extract the first order kernel (K1) and the first and second slices of the second order kernel (K2.1 and K2.2, respectively) from the VECP response. We integrated the amplitude of VECP components as a function of time in order to estimate its magnitude for each stimulus condition. We also used a normalized cross-correlation method in order to test the similarity of the VECP components. The VECP components varied with the presentation mode and the presence of red-green contrast in the stimuli. In trichromats, for compound conditions, pattern-onset K1, K2.1, and K2.2, and pattern-reversal K2.1 and K2.2 had negative-dominated waveforms at 100 ms. Small negativity or small positivity were observed in dichromats. Trichromats had larger VECP magnitude than color-blinds for compound pattern-onset K1 (with large variability across subjects), compound pattern-onset and pattern-reversal K2.1, and compound pattern-reversal K2.2. Trichromats and color-blinds had similar VECP amplitude for compound pattern-reversal K1 and compound pattern-onset K2.2, as well as for all luminance conditions. The cross-correlation analysis showed high similarity between waveforms of compound pattern-onset K2.1 and pattern-reversal K2.2 as well as pattern-reversal K2.1 and K2.2. We suggest that compound pattern-reversal K2.1 is an appropriate response to study red-green color-opponent activity.

No MeSH data available.