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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) vividness ratings of perceived phosphenes in Experiment 2 for (A) 100% PT condition; and (B) 90% PT condition. Error bars represent ±1 SEM.
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Figure 5: Mean (n = 8) vividness ratings of perceived phosphenes in Experiment 2 for (A) 100% PT condition; and (B) 90% PT condition. Error bars represent ±1 SEM.

Mentions: Post hoc (Sidak-adjusted) comparisons indicated that, when TMS was applied at 100% of PT, subjects perceived more phosphenes in the middle (0.5) contrast condition relative to the low (0.1) contrast (p < 0.01) and high (0.9) contrast (p < 0.01) conditions. There was no significant difference between the low and high contrast conditions (p = 0.89). Thus most phosphenes were induced in the middle contrast condition when TMS was applied 100% of PT. A different pattern was found for the 90% of PT condition: relative to the low (0.1) contrast condition, subjects perceived more phosphenes in the middle (0.5) contrast (p < 0.05) and high (0.9) contrast (p < 0.05) conditions. There was no significant difference between the middle and high contrast conditions (p = 0.82). Thus more phosphenes were induced in the middle and high contrast conditions relative to the low contrast condition. The vividness ratings for both TMS intensities are shown in Figure 5. As can be seen in the figure, the vast majority of phosphenes were classified as “weak.”


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) vividness ratings of perceived phosphenes in Experiment 2 for (A) 100% PT condition; and (B) 90% PT condition. Error bars represent ±1 SEM.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Figure 5: Mean (n = 8) vividness ratings of perceived phosphenes in Experiment 2 for (A) 100% PT condition; and (B) 90% PT condition. Error bars represent ±1 SEM.
Mentions: Post hoc (Sidak-adjusted) comparisons indicated that, when TMS was applied at 100% of PT, subjects perceived more phosphenes in the middle (0.5) contrast condition relative to the low (0.1) contrast (p < 0.01) and high (0.9) contrast (p < 0.01) conditions. There was no significant difference between the low and high contrast conditions (p = 0.89). Thus most phosphenes were induced in the middle contrast condition when TMS was applied 100% of PT. A different pattern was found for the 90% of PT condition: relative to the low (0.1) contrast condition, subjects perceived more phosphenes in the middle (0.5) contrast (p < 0.05) and high (0.9) contrast (p < 0.05) conditions. There was no significant difference between the middle and high contrast conditions (p = 0.82). Thus more phosphenes were induced in the middle and high contrast conditions relative to the low contrast condition. The vividness ratings for both TMS intensities are shown in Figure 5. As can be seen in the figure, the vast majority of phosphenes were classified as “weak.”

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