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Microstimulation of inferotemporal cortex influences face categorization

A Corrigendum to this article was published on 05 October 2006


The inferior temporal cortex (IT) of primates is thought to be the final visual area in the ventral stream of cortical areas responsible for object recognition1,2. Consistent with this hypothesis, single IT neurons respond selectively to highly complex visual stimuli such as faces3,4,5,6. However, a direct causal link between the activity of face-selective neurons and face perception has not been demonstrated. In the present study of macaque monkeys, we artificially activated small clusters of IT neurons by means of electrical microstimulation while the monkeys performed a categorization task, judging whether noisy visual images belonged to ‘face’ or ‘non-face’ categories. Here we show that microstimulation of face-selective sites, but not other sites, strongly biased the monkeys' decisions towards the face category. The magnitude of the effect depended upon the degree of face selectivity of the stimulation site, the size of the stimulated cluster of face-selective neurons, and the exact timing of microstimulation. Our results establish a causal relationship between the activity of face-selective neurons and face perception.

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Figure 1: Visual stimuli and event timing.
Figure 2: Effect of microstimulation of two representative face-selective neural clusters in IT cortex.
Figure 3: Correlation between face selectivity of stimulated sites and the behavioural impact of microstimulation.
Figure 4: Effect of stimulus selectivity of neighbouring cortical sites on microstimulation results.

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We thank S.-M. Noorbakhsh for technical assistance, and Y. Najian for training one of the monkeys. We also thank W. T. Newsome, M. N. Shadlen and N. Kanwisher for comments on the manuscript.

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Correspondence to Hossein Esteky.

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Reprints and permissions information is available at The authors declare no competing financial interests.

Supplementary information

Supplementary Figure 1

Examples of shift in psychometric functions due to microstimulation. (PDF 217 kb)

Supplementary Note 1

This file contains the legend to Supplementary Figure 1. (DOC 20 kb)

Supplementary Table 1

Summary table of the fit parameters obtained from the data collected from each monkey. (DOC 32 kb)

Supplementary Note 2

This file contains the legend to Supplementary Table 1. (DOC 22 kb)

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Afraz, SR., Kiani, R. & Esteky, H. Microstimulation of inferotemporal cortex influences face categorization. Nature 442, 692–695 (2006).

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