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Modulation of visual cortical excitability by working memory: effect of luminance contrast of mental imagery.

Cattaneo Z, Pisoni A, Papagno C, Silvanto J - Front Psychol (2011)

Bottom Line: We manipulated luminance contrast, a stimulus property known to strongly affect the magnitude of neuronal responses in early visual areas.These results point to a strong overlap in the neuronal processes underlying visual perception and mental imagery: not only does WM maintenance selectively engage neurons which are tuned to the maintained attribute (as has previously been shown), but the extent to which those neurons are activated depends on the image contrast (as is the case with visually evoked responses).From a methodological viewpoint, these results suggest that assessment of visual cortical excitability using TMS is affected by the TMS intensity used to probe the neuronal population.

View Article: PubMed Central - PubMed

Affiliation: Department of Psychology, University of Milano-Bicocca Milano, Italy.

ABSTRACT
Although much is known about the impact of stimulus properties such as luminance contrast, spatial frequency, and orientation on visually evoked neural activity, much less is known about how they modulate neural activity when they are properties of a mental image held in working memory (WM). Here we addressed this question by investigating how a parametric manipulation of an imagined stimulus attribute affects neuronal excitability in the early visual cortex. We manipulated luminance contrast, a stimulus property known to strongly affect the magnitude of neuronal responses in early visual areas. Luminance contrast modulated neuronal excitability, as assessed by the frequency of phosphenes induced by transcranial magnetic stimulation (TMS) with the exact nature of this modulation depending on TMS intensity. These results point to a strong overlap in the neuronal processes underlying visual perception and mental imagery: not only does WM maintenance selectively engage neurons which are tuned to the maintained attribute (as has previously been shown), but the extent to which those neurons are activated depends on the image contrast (as is the case with visually evoked responses). From a methodological viewpoint, these results suggest that assessment of visual cortical excitability using TMS is affected by the TMS intensity used to probe the neuronal population.

No MeSH data available.


Related in: MedlinePlus

Mean (n = 8) proportion of “Phosphene present” judgments in Experiment 2. The measure is collapsed over the three response types which indicate that a phosphene was perceived, i.e., “weak,” “almost clear” and “absolutely clear” on the response scale rating. Error bars represent ±1 SEM. Mental imagery contrast interacted with TMS intensity. When TMS was applied at 90% of PT, significantly more phosphenes were perceived in the high and middle contrast conditions relative to the low contrast condition, indicating that an increase in luminance contrast enhances visual cortical excitability. When TMS was applied at 100% of PT, a significant difference was found between the low and middle contrast conditions, but not between the low and high contrast conditions.
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Figure 4: Mean (n = 8) proportion of “Phosphene present” judgments in Experiment 2. The measure is collapsed over the three response types which indicate that a phosphene was perceived, i.e., “weak,” “almost clear” and “absolutely clear” on the response scale rating. Error bars represent ±1 SEM. Mental imagery contrast interacted with TMS intensity. When TMS was applied at 90% of PT, significantly more phosphenes were perceived in the high and middle contrast conditions relative to the low contrast condition, indicating that an increase in luminance contrast enhances visual cortical excitability. When TMS was applied at 100% of PT, a significant difference was found between the low and middle contrast conditions, but not between the low and high contrast conditions.

Mentions: Figure 4 shows phosphene present judgments as a function of stimulus contrast and TMS intensity. Firstly, we analyzed the proportion of trials on which subjects perceived a phosphene as a function of contrast; in this analysis, the three response types (i.e., “weak”; “almost clear,” “absolutely clear”), which indicate phosphene presence, are combined. A 2 × 2 ANOVA, with contrast level (0.1, 0.5, 0.9) and TMS intensity as main factors (100% of PT, 90% of PT), revealed a significant main effect of contrast [F(1,7) = 7.9, p = 0.005], a significant main effect of TMS intensity [F(1,7) = 28.9, p = 0.001] and a significant interaction between the two [F(2,47) = 4.9, p = 0.02].


Modulation of visual cortical excitability by working memory: effect of luminance contrast of mental imagery.

Cattaneo Z, Pisoni A, Papagno C, Silvanto J - Front Psychol (2011)

Mean (n = 8) proportion of “Phosphene present” judgments in Experiment 2. The measure is collapsed over the three response types which indicate that a phosphene was perceived, i.e., “weak,” “almost clear” and “absolutely clear” on the response scale rating. Error bars represent ±1 SEM. Mental imagery contrast interacted with TMS intensity. When TMS was applied at 90% of PT, significantly more phosphenes were perceived in the high and middle contrast conditions relative to the low contrast condition, indicating that an increase in luminance contrast enhances visual cortical excitability. When TMS was applied at 100% of PT, a significant difference was found between the low and middle contrast conditions, but not between the low and high contrast conditions.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3111229&req=5

Figure 4: Mean (n = 8) proportion of “Phosphene present” judgments in Experiment 2. The measure is collapsed over the three response types which indicate that a phosphene was perceived, i.e., “weak,” “almost clear” and “absolutely clear” on the response scale rating. Error bars represent ±1 SEM. Mental imagery contrast interacted with TMS intensity. When TMS was applied at 90% of PT, significantly more phosphenes were perceived in the high and middle contrast conditions relative to the low contrast condition, indicating that an increase in luminance contrast enhances visual cortical excitability. When TMS was applied at 100% of PT, a significant difference was found between the low and middle contrast conditions, but not between the low and high contrast conditions.
Mentions: Figure 4 shows phosphene present judgments as a function of stimulus contrast and TMS intensity. Firstly, we analyzed the proportion of trials on which subjects perceived a phosphene as a function of contrast; in this analysis, the three response types (i.e., “weak”; “almost clear,” “absolutely clear”), which indicate phosphene presence, are combined. A 2 × 2 ANOVA, with contrast level (0.1, 0.5, 0.9) and TMS intensity as main factors (100% of PT, 90% of PT), revealed a significant main effect of contrast [F(1,7) = 7.9, p = 0.005], a significant main effect of TMS intensity [F(1,7) = 28.9, p = 0.001] and a significant interaction between the two [F(2,47) = 4.9, p = 0.02].

Bottom Line: We manipulated luminance contrast, a stimulus property known to strongly affect the magnitude of neuronal responses in early visual areas.These results point to a strong overlap in the neuronal processes underlying visual perception and mental imagery: not only does WM maintenance selectively engage neurons which are tuned to the maintained attribute (as has previously been shown), but the extent to which those neurons are activated depends on the image contrast (as is the case with visually evoked responses).From a methodological viewpoint, these results suggest that assessment of visual cortical excitability using TMS is affected by the TMS intensity used to probe the neuronal population.

View Article: PubMed Central - PubMed

Affiliation: Department of Psychology, University of Milano-Bicocca Milano, Italy.

ABSTRACT
Although much is known about the impact of stimulus properties such as luminance contrast, spatial frequency, and orientation on visually evoked neural activity, much less is known about how they modulate neural activity when they are properties of a mental image held in working memory (WM). Here we addressed this question by investigating how a parametric manipulation of an imagined stimulus attribute affects neuronal excitability in the early visual cortex. We manipulated luminance contrast, a stimulus property known to strongly affect the magnitude of neuronal responses in early visual areas. Luminance contrast modulated neuronal excitability, as assessed by the frequency of phosphenes induced by transcranial magnetic stimulation (TMS) with the exact nature of this modulation depending on TMS intensity. These results point to a strong overlap in the neuronal processes underlying visual perception and mental imagery: not only does WM maintenance selectively engage neurons which are tuned to the maintained attribute (as has previously been shown), but the extent to which those neurons are activated depends on the image contrast (as is the case with visually evoked responses). From a methodological viewpoint, these results suggest that assessment of visual cortical excitability using TMS is affected by the TMS intensity used to probe the neuronal population.

No MeSH data available.


Related in: MedlinePlus