Effect of adapter duration on repetition suppression in inferior temporal cortex

Recent evidence has suggested that the human occipito-temporal region comprises several subregions, each sensitive to a distinct processing level of visual words. To further explore the functional architecture of visual word recognition, we employed a subliminal priming method with functional magnetic resonance imaging (fMRI) during semantic judgments of words presented in two different Japanese scripts, Kanji and Kana. Each target word was preceded by a subliminal presentation of either the same or a different word, and in the same or a different script. Behaviorally, word repetition produced significant priming regardless of whether the words were presented in the same or different script. At the neural level, this cross-script priming was associated with repetition suppression in the left inferior temporal cortex anterior and dorsal to the visual word form area hypothesized for alphabetical writing systems, suggesting that cross-script convergence occurred at a semantic level. fMRI also evidenced a shared visual occipito-temporal activation for words in the two scripts, with slightly more mesial and right-predominant activation for Kanji and with greater occipital activation for Kana. These results thus allow us to separate script-specific and script-independent regions in the posterior temporal lobe, while demonstrating that both can be activated subliminally.

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Within and between hemifields generalization of repetition suppression in inferior temporal cortex.

Journal of Neurophysiology ◽

10.1152/jn.00361.2020 ◽

2020 ◽

Author(s):

Francesco Fabbrini ◽

Rufin Vogels

Keyword(s):

Test Stimulus ◽

Common Property ◽

Temporal Cortex ◽

Receptive Fields ◽

Selective Adaptation ◽

Inferior Temporal Cortex ◽

Repetition Suppression ◽

Repetition Trial ◽

End Stage ◽

Spatial Locations

The decrease in response with stimulus repetition is a common property observed in many sensory brain areas. This repetition suppression (RS) is ubiquitous in neurons of macaque inferior temporal (IT) cortex, the end-stage of the ventral visual pathway. The neural mechanisms of RS in IT are still unclear, and one possibility is that it is inherited from areas upstream to IT that show also RS. Since neurons in IT have larger receptive fields compared to earlier visual areas, we examined the inheritance hypothesis by presenting adapter and test stimuli at widely different spatial locations along both vertical and horizontal meridians, and across hemifields. RS was present for distances between adapter and test stimuli up to 22°, and when the two stimuli were presented in different hemifields. Also, we examined the position tolerance of the stimulus selectivity of adaptation by comparing the responses to a test stimulus following the same (repetition trial) or a different adapter (alternation trial) at a different position than the test stimulus. Stimulus-selective adaptation was still present and consistently stronger in the later phase of the response for distances up to 18°. Finally, we observed stimulus-selective adaptation in repetition trials even without a measurable excitatory response to the adapter stimulus. To accommodate these and previous data, we propose that at least part of the stimulus-selective adaptation in IT is based on short-term plasticity mechanisms within IT and/or reflects top-down activity from areas downstream to IT.

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GABAergic and cholinergic modulation of repetition suppression in inferior temporal cortex

Scientific Reports ◽

10.1038/s41598-018-31515-1 ◽

2018 ◽

Vol 8 (1) ◽

Cited By ~ 5

Author(s):

Pradeep Kuravi ◽

Rufin Vogels

Keyword(s):

Temporal Cortex ◽

Inferior Temporal Cortex ◽

Cholinergic Modulation ◽

Repetition Suppression

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Repetition suppression for visual actions in the macaque superior temporal sulcus

Journal of Neurophysiology ◽

10.1152/jn.00849.2015 ◽

2016 ◽

Vol 115 (3) ◽

pp. 1324-1337 ◽

Cited By ~ 2

Author(s):

Pradeep Kuravi ◽

Vittorio Caggiano ◽

Martin Giese ◽

Rufin Vogels

Keyword(s):

Mirror Neurons ◽

Temporal Cortex ◽

Event Related Potentials ◽

Superior Temporal Sulcus ◽

Inferior Temporal Cortex ◽

Repetition Suppression ◽

Related Potentials ◽

Hand Action ◽

Spiking Activity ◽

Adaptation Effects

In many brain areas, repetition of a stimulus usually weakens the neural response. This “adaptation” or repetition suppression effect has been observed with mass potential measures such as event-related potentials (ERPs), in fMRI BOLD responses, and locally with local field potentials (LFPs) and spiking activity. Recently, it has been reported that macaque F5 mirror neurons do not show repetition suppression of their spiking activity for single repetitions of hand actions, which disagrees with human fMRI adaptation studies. This finding also contrasts with numerous studies showing repetition suppression in macaque inferior temporal cortex, including the rostral superior temporal sulcus (STS). Since the latter studies employed static stimuli, we assessed here whether the use of dynamic action stimuli abolishes repetition suppression in the awake macaque STS. To assess adaptation effects in the STS, we employed the same hand action movies as used when examining adaptation in F5. The upper bank STS neurons showed repetition suppression during the approaching phase of the hand action, which corresponded to the phase of the action for which these neurons responded overall the strongest. The repetition suppression was present for the spiking activity measured in independent single-unit and multiunit recordings as well as for the LFP power at frequencies > 50 Hz. Together with previous data in F5, these findings suggest that adaptation effects differ between F5 mirror neurons and the STS neurons.

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