Selective Attention Modulates Neural Substrates of Repetition Priming and “Implicit” Visual Memory: Suppressions and Enhancements Revealed by fMRI

Abstract

Attention can enhance processing for relevant information and suppress this for ignored stimuli. However, some residual processing may still arise without attention. Here we presented overlapping outline objects at study, with subjects attending to those in one color but not the other. Attended objects were subsequently recognized on a surprise memory test, whereas there was complete amnesia for ignored items on such direct explicit testing; yet reliable behavioral priming effects were found on indirect testing. Event-related fMRI examined neural responses to previously attended or ignored objects, now shown alone in the same or mirror-reversed orientation as before, intermixed with new items. Repetition-related decreases in fMRI responses for objects previously attended and repeated in the same orientation were found in the right posterior fusiform, lateral occipital, and left inferior frontal cortex. More anterior fusiform regions also showed some repetition decreases for ignored objects, irrespective of orientation. View-specific repetition decreases were found in the striate cortex, particularly for previously attended items. In addition, previously ignored objects produced some fMRI response increases in the bilateral lingual gyri, relative to new objects. Selective attention at exposure can thus produce several distinct long-term effects on processing of stimuli repeated later, with neural response suppression stronger for previously attended objects, and some response enhancement for previously ignored objects, with these effects arising in different brain areas. Although repetition decreases may relate to positive priming phenomena, the repetition increases for ignored objects shown here for the first time might relate to processes that can produce "negative priming" in some behavioral studies. These results reveal quantitative and qualitative differences between neural substrates of long-term repetition effects for attended versus unattended objects.

Breaking the symmetry: Mirror discrimination for single letters but not for pictures in the Visual Word Form Area

“…In support of this notion, a role for attention in left-right discrimination of non-alphabetic shapes has been evoked in behavioural and fMRI studies (Stankiewicz et al, 1998;Eger, 2004;Vuilleumier et al, 2005). The general conclusion of such studies seems to be that both view-invariant and view-dependent representations can be evoked when the subjects are attentive to the stimuli.…”

“…Monkey's single cell recordings show neurons in visual ventral cortex (IT) responding in an equivalent way to a given picture and its mirror reflected presentation (Logothetis et al, 1995;Rollenhagen and Olson, 2000). In humans, the phenomenon of fMRI repetition suppression has been used to demonstrate that pictures and their mirror images can be encoded as the same object within the ventral stream (Eger, 2004;Vuilleumier et al, 2005;Dehaene et al, 2010). Investigating if written words elicit equivalent mirror priming as pictures in the occipitotemporal cortex is of particular importance since it has been claimed that this region is a domain-general site (Priftis et al, 2003;Price et al 2006).…”

Object words modulate the activity of the mirror neuron system during action imitation

“…Specifically, the main effect of stage showed the highest activity in the observation stage relative to the imitation stage, p s < .05. The stronger activity in the observation stage and relatively weak activity in the imitation stage is somewhat analogous to the fMRI adaption effect or repetition suppression effect on the repeated presentation of specific stimulus (De Lucia et al., 2010; Press et al., 2012; Vuilleumier, Schwartz, Duhoux, Dolan, & Driver, 2005); that is, action observation increased the activity in motor preparation areas during the initial observation period, whereas the execution of the same action evoked neural suppression over the motor areas (Dinstein et al., 2007; Kable & Chatterjee, 2006; Krams, Rushworth, Deiber, Frackowiak, & Passingham, 1998; Oosterhof, Tipper, & Downing, 2013). Additionally, the Word×Stage interaction effect was significant in the left vPM ( F 6,108  = 2.567, p  <   .05), right vPM ( F 6,108  = 3.498, p  <   .01), left STS ( F 6,108  = 2.944, p  <   .05), and right STS ( F 6,108  = 2.367, p  <   .05) and marginal significant over the right aIPS ( F 6,108  = 2.158, p  =   .053), indicating that the word effect showed in the imitation stage only.…”

Neuro-imagerie et neuroscience des émotions

“…Plus récemment, en parallèle avec les théories postulant l'existence d'un nombre limité d'émotions primaires, certains chercheurs comme Jaak Panksepp [4] ont décrit sept circuits fonctionnels distincts : quatre seraient pré-mammaliens (peur, rage, recherche et désir) et trois autres seraient liés à l'expansion des régions limbiques des mammifères (maternance, jeu, panique). Ces travaux ont instauré les premiers fondements impliquée dans les processus d'orientation attentionnelle involontaires [7]. Une fonction cardinale de l'attention est d'augmenter (volontairement ou non) la « saillance » d'un percept afin de maximiser son traitement et de minimiser l'interférence par des informations non pertinentes.…”

“…Elle accroît ainsi la « saillance » du stimulus et favorise l'orientation de l'attention vers la source du danger. L'IRMf a montré que des patients ayant une lésion de l'amygdale, à l'inverse de ceux qui ont une lésion de l'hippocampe, ne montrent plus cette modulation [7]. Par ses effets sur le cortex et l'hippocampe, l'AMG influence aussi la mémorisation.…”