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Hippocampus is place of interaction between unconscious and conscious memories.

Züst MA, Colella P, Reber TP, Vuilleumier P, Hauf M, Ruch S, Henke K - PLoS ONE (2015)

Bottom Line: At test, we presented the former subliminal faces, but now supraliminally, as cues for the reactivation of the unconsciously associated occupations.We hypothesized that unconscious reactivation of the associated occupation-actor or politician-would facilitate or inhibit the subsequent conscious retrieval of a celebrity's occupation, which was also actor or politician.We assume that the unconscious reactivation has pre-activated overlapping relational representations in the hippocampus reducing the neural effort for conscious retrieval.

View Article: PubMed Central - PubMed

Affiliation: Department of Psychology, Division of Experimental Psychology and Neuropsychology, University of Bern, Bern, Switzerland; Center for Cognition, Learning and Memory, University of Bern, Bern, Switzerland.

ABSTRACT
Recent evidence suggests that humans can form and later retrieve new semantic relations unconsciously by way of hippocampus-the key structure also recruited for conscious relational (episodic) memory. If the hippocampus subserves both conscious and unconscious relational encoding/retrieval, one would expect the hippocampus to be place of unconscious-conscious interactions during memory retrieval. We tested this hypothesis in an fMRI experiment probing the interaction between the unconscious and conscious retrieval of face-associated information. For the establishment of unconscious relational memories, we presented subliminal (masked) combinations of unfamiliar faces and written occupations ("actor" or "politician"). At test, we presented the former subliminal faces, but now supraliminally, as cues for the reactivation of the unconsciously associated occupations. We hypothesized that unconscious reactivation of the associated occupation-actor or politician-would facilitate or inhibit the subsequent conscious retrieval of a celebrity's occupation, which was also actor or politician. Depending on whether the reactivated unconscious occupation was congruent or incongruent to the celebrity's occupation, we expected either quicker or delayed conscious retrieval process. Conscious retrieval was quicker in the congruent relative to a neutral baseline condition but not delayed in the incongruent condition. fMRI data collected during subliminal face-occupation encoding confirmed previous evidence that the hippocampus was interacting with neocortical storage sites of semantic knowledge to support relational encoding. fMRI data collected at test revealed that the facilitated conscious retrieval was paralleled by deactivations in the hippocampus and neocortical storage sites of semantic knowledge. We assume that the unconscious reactivation has pre-activated overlapping relational representations in the hippocampus reducing the neural effort for conscious retrieval. This finding supports the notion of synergistic interactions between conscious and unconscious relational memories in a common, cohesive hippocampal-neocortical memory space.

No MeSH data available.


Related in: MedlinePlus

Independent component analysis (ICA) on encoding time-series.The depicted component is significantly associated with the occurrence of subliminal Face-Occupation Pairs. A: Clusters within the component encompassing bilateral hippocampus, amygdala, superior temporal sulcus, and temporal pole. These brain regions are important for episodic and semantic memory. Coordinates are according to MNI space; left is left on the coronal slice and upwards is left on the transversal slice. B: The temporal coupling of this network is specific for unconscious associative encoding. The component is significantly associated with the occurrence of Faces-Occupation Pairs (Pearson’s r = -.16, ** p = .004) but not with Faces Alone (Pearson’s r = .13, p = .69). The regression fit of the component is significantly better with Face-Occupation Pairs than with Faces Alone (* p = .044, effect size r = .35). The bar plot shows β-weights of the time course modelled specifically to the associative and the baseline condition. Error bars indicate the SEM.
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pone.0122459.g003: Independent component analysis (ICA) on encoding time-series.The depicted component is significantly associated with the occurrence of subliminal Face-Occupation Pairs. A: Clusters within the component encompassing bilateral hippocampus, amygdala, superior temporal sulcus, and temporal pole. These brain regions are important for episodic and semantic memory. Coordinates are according to MNI space; left is left on the coronal slice and upwards is left on the transversal slice. B: The temporal coupling of this network is specific for unconscious associative encoding. The component is significantly associated with the occurrence of Faces-Occupation Pairs (Pearson’s r = -.16, ** p = .004) but not with Faces Alone (Pearson’s r = .13, p = .69). The regression fit of the component is significantly better with Face-Occupation Pairs than with Faces Alone (* p = .044, effect size r = .35). The bar plot shows β-weights of the time course modelled specifically to the associative and the baseline condition. Error bars indicate the SEM.

Mentions: We performed an independent component analysis (ICA) on the fMRI data acquired during the encoding fMRI time-series to explore the functional connectivity of brain regions during the subliminal processing of Face-Occupation Pairs. The subliminal presentation of Face-Occupation Pairs was associated with decreased activity in a number of functionally connected brain areas that constituted one of the obtained components (r = -.16, t(32) = -3.1, p = .004 < FDR critical p = .006) (Table 1 and Fig 3). This component included bilateral areas in the superior temporal sulcus (extending into superior and middle temporal gyrus) and temporal pole, which harbour storage sites of lexical-semantic information such as occupations [16]; bilateral hippocampus and ventromedial thalamus, required for encoding of new information [25]; and bilateral amygdala, which is considered to play an important role in face perception and evaluation. As faces convey highly significant social and emotional information, the amygdala is automatically engaged when faces are perceived [26]. Importantly, this component did not covary with the Faces Alone baseline (r = .13, t(32) = 0.4, p = .69), and the regression-fit of this component with Face-Occupation Pairs was significantly better than with Faces Alone (t(32) = -2.1, p = .044, effect size r = .35) (Fig 3B). In conclusion, we can assume that this component was specifically related to the semantic associative binding of subliminal faces with written occupations.


Hippocampus is place of interaction between unconscious and conscious memories.

Züst MA, Colella P, Reber TP, Vuilleumier P, Hauf M, Ruch S, Henke K - PLoS ONE (2015)

Independent component analysis (ICA) on encoding time-series.The depicted component is significantly associated with the occurrence of subliminal Face-Occupation Pairs. A: Clusters within the component encompassing bilateral hippocampus, amygdala, superior temporal sulcus, and temporal pole. These brain regions are important for episodic and semantic memory. Coordinates are according to MNI space; left is left on the coronal slice and upwards is left on the transversal slice. B: The temporal coupling of this network is specific for unconscious associative encoding. The component is significantly associated with the occurrence of Faces-Occupation Pairs (Pearson’s r = -.16, ** p = .004) but not with Faces Alone (Pearson’s r = .13, p = .69). The regression fit of the component is significantly better with Face-Occupation Pairs than with Faces Alone (* p = .044, effect size r = .35). The bar plot shows β-weights of the time course modelled specifically to the associative and the baseline condition. Error bars indicate the SEM.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4380440&req=5

pone.0122459.g003: Independent component analysis (ICA) on encoding time-series.The depicted component is significantly associated with the occurrence of subliminal Face-Occupation Pairs. A: Clusters within the component encompassing bilateral hippocampus, amygdala, superior temporal sulcus, and temporal pole. These brain regions are important for episodic and semantic memory. Coordinates are according to MNI space; left is left on the coronal slice and upwards is left on the transversal slice. B: The temporal coupling of this network is specific for unconscious associative encoding. The component is significantly associated with the occurrence of Faces-Occupation Pairs (Pearson’s r = -.16, ** p = .004) but not with Faces Alone (Pearson’s r = .13, p = .69). The regression fit of the component is significantly better with Face-Occupation Pairs than with Faces Alone (* p = .044, effect size r = .35). The bar plot shows β-weights of the time course modelled specifically to the associative and the baseline condition. Error bars indicate the SEM.
Mentions: We performed an independent component analysis (ICA) on the fMRI data acquired during the encoding fMRI time-series to explore the functional connectivity of brain regions during the subliminal processing of Face-Occupation Pairs. The subliminal presentation of Face-Occupation Pairs was associated with decreased activity in a number of functionally connected brain areas that constituted one of the obtained components (r = -.16, t(32) = -3.1, p = .004 < FDR critical p = .006) (Table 1 and Fig 3). This component included bilateral areas in the superior temporal sulcus (extending into superior and middle temporal gyrus) and temporal pole, which harbour storage sites of lexical-semantic information such as occupations [16]; bilateral hippocampus and ventromedial thalamus, required for encoding of new information [25]; and bilateral amygdala, which is considered to play an important role in face perception and evaluation. As faces convey highly significant social and emotional information, the amygdala is automatically engaged when faces are perceived [26]. Importantly, this component did not covary with the Faces Alone baseline (r = .13, t(32) = 0.4, p = .69), and the regression-fit of this component with Face-Occupation Pairs was significantly better than with Faces Alone (t(32) = -2.1, p = .044, effect size r = .35) (Fig 3B). In conclusion, we can assume that this component was specifically related to the semantic associative binding of subliminal faces with written occupations.

Bottom Line: At test, we presented the former subliminal faces, but now supraliminally, as cues for the reactivation of the unconsciously associated occupations.We hypothesized that unconscious reactivation of the associated occupation-actor or politician-would facilitate or inhibit the subsequent conscious retrieval of a celebrity's occupation, which was also actor or politician.We assume that the unconscious reactivation has pre-activated overlapping relational representations in the hippocampus reducing the neural effort for conscious retrieval.

View Article: PubMed Central - PubMed

Affiliation: Department of Psychology, Division of Experimental Psychology and Neuropsychology, University of Bern, Bern, Switzerland; Center for Cognition, Learning and Memory, University of Bern, Bern, Switzerland.

ABSTRACT
Recent evidence suggests that humans can form and later retrieve new semantic relations unconsciously by way of hippocampus-the key structure also recruited for conscious relational (episodic) memory. If the hippocampus subserves both conscious and unconscious relational encoding/retrieval, one would expect the hippocampus to be place of unconscious-conscious interactions during memory retrieval. We tested this hypothesis in an fMRI experiment probing the interaction between the unconscious and conscious retrieval of face-associated information. For the establishment of unconscious relational memories, we presented subliminal (masked) combinations of unfamiliar faces and written occupations ("actor" or "politician"). At test, we presented the former subliminal faces, but now supraliminally, as cues for the reactivation of the unconsciously associated occupations. We hypothesized that unconscious reactivation of the associated occupation-actor or politician-would facilitate or inhibit the subsequent conscious retrieval of a celebrity's occupation, which was also actor or politician. Depending on whether the reactivated unconscious occupation was congruent or incongruent to the celebrity's occupation, we expected either quicker or delayed conscious retrieval process. Conscious retrieval was quicker in the congruent relative to a neutral baseline condition but not delayed in the incongruent condition. fMRI data collected during subliminal face-occupation encoding confirmed previous evidence that the hippocampus was interacting with neocortical storage sites of semantic knowledge to support relational encoding. fMRI data collected at test revealed that the facilitated conscious retrieval was paralleled by deactivations in the hippocampus and neocortical storage sites of semantic knowledge. We assume that the unconscious reactivation has pre-activated overlapping relational representations in the hippocampus reducing the neural effort for conscious retrieval. This finding supports the notion of synergistic interactions between conscious and unconscious relational memories in a common, cohesive hippocampal-neocortical memory space.

No MeSH data available.


Related in: MedlinePlus