Limits...
Investigating representations of facial identity in human ventral visual cortex with transcranial magnetic stimulation.

Gilaie-Dotan S, Silvanto J, Schwarzkopf DS, Rees G - Front Hum Neurosci (2010)

Bottom Line: Behaviorally we found a robust identity repetition effect, with shorter reaction times (RTs) when identity was repeated, regardless of the fact that the pictures were physically different.But critically, we found no effects of TMS to either area that were modulated by identity repetition.Thus, we found no evidence to suggest that OFA or LO contain neuronal representations selective for the identity of famous faces which play a causal role in identity processing.

View Article: PubMed Central - PubMed

Affiliation: Institute of Cognitive Neuroscience, University College London London, UK.

ABSTRACT
The occipital face area (OFA) is face-selective. This enhanced activation to faces could reflect either generic face and shape-related processing or high-level conceptual processing of identity. Here we examined these two possibilities using a state-dependent transcranial magnetic stimulation (TMS) paradigm. The lateral occipital (LO) cortex which is activated non-selectively by various types of objects served as a control site. We localized OFA and LO on a per-participant basis using functional MRI. We then examined whether TMS applied to either of these regions affected the ability of participants to decide whether two successively presented and physically different face images were of the same famous person or different famous people. TMS was applied during the delay between first and second face presentations to investigate whether neuronal populations in these regions played a causal role in mediating the behavioral effects of identity repetition. Behaviorally we found a robust identity repetition effect, with shorter reaction times (RTs) when identity was repeated, regardless of the fact that the pictures were physically different. Surprisingly, TMS applied over LO (but not OFA) modulated overall RTs, compared to the No-TMS condition. But critically, we found no effects of TMS to either area that were modulated by identity repetition. Thus, we found no evidence to suggest that OFA or LO contain neuronal representations selective for the identity of famous faces which play a causal role in identity processing. Instead, these brain regions may be involved in the processing of more generic features of their preferred stimulus categories.

No MeSH data available.


Accuracy levels according to trial type and TMS site. (A) No significant effects were found for either trial type or TMS site. (B) Planned comparisons of TMS conditions relative to No-TMS revealed a significant reduction in accuracy for LO-TMS, for repeated trials only. TMS over OFA did not induce significant changes in accuracy. Red – different identity trials, blue – repeated identity trials. Error bars, SEM.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC2903189&req=5

Figure 4: Accuracy levels according to trial type and TMS site. (A) No significant effects were found for either trial type or TMS site. (B) Planned comparisons of TMS conditions relative to No-TMS revealed a significant reduction in accuracy for LO-TMS, for repeated trials only. TMS over OFA did not induce significant changes in accuracy. Red – different identity trials, blue – repeated identity trials. Error bars, SEM.

Mentions: The accuracy levels of the repeated identity trials [92.8 ± 1.7% (SEM)] and the different identity trials [89.5 ± 3% (SEM)] were high and no significant differences between trial types were found [No-TMS: t(11) = 1.24, p = 0.2401; five participants were more accurate in the repeated identity trials, five participants were more accurate in the non-repeated trials, and two participants showed identical performance in the two trial types; see Figure 4A]. Accuracy levels remained high when TMS was applied to OFA (repeated identity: 89.8 ± 2.1%, different identity: 89.3 ± 2.5%) or to LO (repeated identity: 90 ± 2.4%, different identity: 89.7 ± 2.7%). To analyze the effects of TMS on accuracy we carried out a repeated measured ANOVA on accuracy levels. No main effects or interaction were significant [identity repetition: F(2,22) = 0.459, p = 0.511; TMS site: F(2,22) = 2.383, p = 0.1157; interaction F(2,22) = 0.834, p = 0.448]. However planned pair-wise dedicated comparisons revealed a significant LO-TMS effect for repeated identity trials only relative to the No-TMS condition [two-tailed paired t-test: repeated: t(11) = 2.225, p = 0.048]. As can be seen in Figures 4A,B, this was evident by the reduction in accuracy for repeated trials in LO-TMS relative to the No-TMS condition [average reduction of 2.8 ± 1.26% (SEM), which was observed in 8 out of the 12 participants]. For non-repeated trials in LO-TMS no significant change was observed relative to No-TMS condition [two-tailed paired t-test: t(11) = 0.129, p = 0.9; average change of −0.17 ± 1.29% (SEM)]. For OFA-TMS neither conditions showed significant different relative to No-TMS condition [repeated trials: t(11) = 1.6, p = 0.138, average reduction 2.97 ± 1.86% (SEM), observed in 6 of the 12 participants; non-repeated trials: t(11) = 0.167, p = 0.87, average reduction 0.17 ± 0.99% (SEM) in 4 of the 12 participants].


Investigating representations of facial identity in human ventral visual cortex with transcranial magnetic stimulation.

Gilaie-Dotan S, Silvanto J, Schwarzkopf DS, Rees G - Front Hum Neurosci (2010)

Accuracy levels according to trial type and TMS site. (A) No significant effects were found for either trial type or TMS site. (B) Planned comparisons of TMS conditions relative to No-TMS revealed a significant reduction in accuracy for LO-TMS, for repeated trials only. TMS over OFA did not induce significant changes in accuracy. Red – different identity trials, blue – repeated identity trials. Error bars, SEM.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2903189&req=5

Figure 4: Accuracy levels according to trial type and TMS site. (A) No significant effects were found for either trial type or TMS site. (B) Planned comparisons of TMS conditions relative to No-TMS revealed a significant reduction in accuracy for LO-TMS, for repeated trials only. TMS over OFA did not induce significant changes in accuracy. Red – different identity trials, blue – repeated identity trials. Error bars, SEM.
Mentions: The accuracy levels of the repeated identity trials [92.8 ± 1.7% (SEM)] and the different identity trials [89.5 ± 3% (SEM)] were high and no significant differences between trial types were found [No-TMS: t(11) = 1.24, p = 0.2401; five participants were more accurate in the repeated identity trials, five participants were more accurate in the non-repeated trials, and two participants showed identical performance in the two trial types; see Figure 4A]. Accuracy levels remained high when TMS was applied to OFA (repeated identity: 89.8 ± 2.1%, different identity: 89.3 ± 2.5%) or to LO (repeated identity: 90 ± 2.4%, different identity: 89.7 ± 2.7%). To analyze the effects of TMS on accuracy we carried out a repeated measured ANOVA on accuracy levels. No main effects or interaction were significant [identity repetition: F(2,22) = 0.459, p = 0.511; TMS site: F(2,22) = 2.383, p = 0.1157; interaction F(2,22) = 0.834, p = 0.448]. However planned pair-wise dedicated comparisons revealed a significant LO-TMS effect for repeated identity trials only relative to the No-TMS condition [two-tailed paired t-test: repeated: t(11) = 2.225, p = 0.048]. As can be seen in Figures 4A,B, this was evident by the reduction in accuracy for repeated trials in LO-TMS relative to the No-TMS condition [average reduction of 2.8 ± 1.26% (SEM), which was observed in 8 out of the 12 participants]. For non-repeated trials in LO-TMS no significant change was observed relative to No-TMS condition [two-tailed paired t-test: t(11) = 0.129, p = 0.9; average change of −0.17 ± 1.29% (SEM)]. For OFA-TMS neither conditions showed significant different relative to No-TMS condition [repeated trials: t(11) = 1.6, p = 0.138, average reduction 2.97 ± 1.86% (SEM), observed in 6 of the 12 participants; non-repeated trials: t(11) = 0.167, p = 0.87, average reduction 0.17 ± 0.99% (SEM) in 4 of the 12 participants].

Bottom Line: Behaviorally we found a robust identity repetition effect, with shorter reaction times (RTs) when identity was repeated, regardless of the fact that the pictures were physically different.But critically, we found no effects of TMS to either area that were modulated by identity repetition.Thus, we found no evidence to suggest that OFA or LO contain neuronal representations selective for the identity of famous faces which play a causal role in identity processing.

View Article: PubMed Central - PubMed

Affiliation: Institute of Cognitive Neuroscience, University College London London, UK.

ABSTRACT
The occipital face area (OFA) is face-selective. This enhanced activation to faces could reflect either generic face and shape-related processing or high-level conceptual processing of identity. Here we examined these two possibilities using a state-dependent transcranial magnetic stimulation (TMS) paradigm. The lateral occipital (LO) cortex which is activated non-selectively by various types of objects served as a control site. We localized OFA and LO on a per-participant basis using functional MRI. We then examined whether TMS applied to either of these regions affected the ability of participants to decide whether two successively presented and physically different face images were of the same famous person or different famous people. TMS was applied during the delay between first and second face presentations to investigate whether neuronal populations in these regions played a causal role in mediating the behavioral effects of identity repetition. Behaviorally we found a robust identity repetition effect, with shorter reaction times (RTs) when identity was repeated, regardless of the fact that the pictures were physically different. Surprisingly, TMS applied over LO (but not OFA) modulated overall RTs, compared to the No-TMS condition. But critically, we found no effects of TMS to either area that were modulated by identity repetition. Thus, we found no evidence to suggest that OFA or LO contain neuronal representations selective for the identity of famous faces which play a causal role in identity processing. Instead, these brain regions may be involved in the processing of more generic features of their preferred stimulus categories.

No MeSH data available.