Processing of object selectivity across cortical layers in the inferior temporal cortex S Strokov1, J Ito2, H Tamura3, S Gruen2 |
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1Institute of Neuroscience and Medicine INM-6, Forschunszentrum Juelich, Germany |
| The inferior temporal (IT) cortex is known for object recognition since IT neurons selectively respond to specific, complex visual objects (Tanaka, 1993, Science, 262:685-688). Here we aim to test the hypothesis that object selectivity is processed within IT across the cortical layers. Therefore we recorded simultaneously the neuronal activities in form of the local field potentials (LFP) from multiple depths of IT cortex using a linear electrode array in analgesized and immobilized monkeys. The monkeys were presented with 128 complex visual objects each separately shown on a gray background for 0.5 sec. From the amplitudes of the LFPs (bandpass filtered 1.5-300 Hz) during the stimulus presentations we computed the selectivity index (SI) defined as across-stimulus response variance divided by within-stimulus variance (Kreiman et al, 2006, Neuron, 49:433-445). At about 100ms after stimulus onset we observed a negative deflection in the LFP amplitude in the granular layer which is typically not associated with high SI value. Later at 230ms after stimulus onset there was a second, strong negative deflection spanning all layers which is associated with strong selectivity also observed in all layers. This suggests a transformation of non-specific input activity to object-selective output of IT cortex. |
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